5 Reasons to Specify Bulk Metal® Foil Potentiometers

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Texas Components

Corporation

COMPANY PROFILE

Texas Components Corporation is a technologically advanced

manufacturing and engineering services business located in

Houston Texas.

Since 1980, Texas Components Corporation has specialized in

advanced engineering and manufacturing processes that include

Vishay Bulk Metal¨ foil resistive products, custom

microelectronic assemblies, and systems integration that tie all of

our technologies together.

The following products and services are available to you:

PRECISION RESISTIVE PRODUCTS

_ MICROELECTRONIC PRODUCTS

Thank you for your interest in Texas Components Corporation and

we look forward to working with you in the future. If you require

any additional informationÓ or have any questions, please feel free

to give us a call.

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

MICROELECTRONICS

PRODUCTS

DIVISION

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

Microelectronics Design, Integration,

Packaging

Texas Components Corporation applies innovative approaches to

provide microelectronic designs and integration and packaging

services that are ideal for R&D projects. We excel at one-of-a-kind

designs, accelerated development projects and small to medium

quantity production runs.

At Texas Components, you have a variety of packaging options for

your design which include but not (.limited to ceramic, metal,

plastic packages (DIP, CLCC, PLCC, CPGA, MCM, PGA, ETC.),

or Chip-On-Board. Virtually any package size and shape can be

utilized.

In all assembly processes, proven techniques are used to provide a

viable solution with four distinct advantages:

NO Minimum Quantity Requirements

NO N.R.E. Charges

Accelerated Development and Production.

NO Redesign Tooling Charges

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

Texas Components Corporation can offer creative solutions for a

variety of applications. Our concepts are applicable to a wide range

of circuit designs. Designs are limited only by package and die

availability, die size, power dissipation requirements, and layout

restrictions.

The design and/or implementation of high performance

analog and mixed technology circuits are among our

specialties!

Microprocessor Multi-Chip-Modules

Memories, Communications, Amplifiers

Converters, A/D, D/A

Regulators, Gate Arrays,

Analog Multiplexers

...Etc...

Because Texas Components is an authorized Vishay Precision

Center for Bulk Metal¨ foil resistive components, it has the in

house ability to incorporate precision resistors with better than

5ppm TCR, with accuracy's to 0.002%, and ratio tracking to 2ppm/

¼C, within itÕs microelectronic designs.

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

Common Myths about Microelectronic Assemblies

Myth: Microelectronic assemblies are very expensive.

Over the past several years, improvements in manufacturing

technology (materials, equipment and processes) have substantially

reduced costs, making microelectronic pricing more attractive.

When performance, space limitations, shock and vibration,

reliability and reworkability are significant design factors,

microelectronic assemblies can be more cost effective than the

conventional surface mount or through hole approach.

Myth: Microelectronic assemblies are unreliable.

Unlike plastic encapsulated devices, microelectronic circuits are

hermetically sealed in dry nitrogen, which significantly reduces the

effects of two major problems that affect plastic components at

higher temperatures:

1. CTE (coefficients of thermal expansion) mismatches between

wire/plastic and silicon/plastic are magnified during component

soldering and exposure to high temperatures. Microelectronic wire

bonds are not physically distorted with temperature changes, thus

reducing induced mechanical stresses on the bond pad interfaces.

2. At elevated temperatures, many plastic encapsulants will outgas

ionic contaminants that degrade the wire bondsÕ reliability.

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

It is also known that both FR4 and Polyimide printed circuit boards

can experience delamination at higher operating temperatures.

Ceramic substrates do not experience such effects, having been

fired at 850¼C or more.

Texas Components Corporation's microelectronic products are

subjected to extensive screening procedures during manufacturing.

It is important to note that this screening is merely a method of

process verification. The materials selected and our advanced

manufacturing processes are responsible for superior reliability.

Reliability is not "screened in" but rather, is engineered into the

product.

Myth: Microelectronic assemblies are unrepairable.

Texas Components Corporation can de-lid and repair or modify

microelectronic products. Damaged assemblies or those needing

revision changes need not be discarded. Microelectronic products

can normally be reworked to meet their original or updated

specifications.

Texas Components Corporation provides a two-year warranty

against defects in materials and workmanship on all

Microelectronic products.

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

DIE LEVEL PROGRAMMING

Programmable Gate Arrays (PGA)

_ EPROM

EEPROM

FLASH

Texas Components Corporation has the ability to program PGA's

and most memory devices at the die level, before insertion into the

package. This procedure provides the distinct advantage of

reducing the total pin count to power and I/O only. The die's

programming pins need not be connected to the package itself

unless your design specifically requires them. PGA and memory

die can be placed in various package pin counts dependent upon

die size and I/O width. These die may be packaged in a monolithic

configuration or incorporated with other die as part of a true

microelectronic circuit.

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

DEVICE EMULATION

Texas Components Corporation has provided solutions for

customers faced with board or system redesigns due to a

discontinued semiconductor component. In most cases, a single

PGA can be used to emulate the discontinued component and then

packaged as a direct plug in replacement. For high density and

mixed signal components, PGA's in unification with additional

support circuitry can be utilized to provide a solution that requires

no redesign.

MICROELECTRONIC REPAIR

MODIFICATION

Microelectronics that have failed or need modification need not

always be discarded. Texas Components Corporation can precisely

de-lid many sealed packages, repair or modify the existing circuit,

and reseal the package to meet the original mechanical and

electrical specifications.

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

ELECTRICAL TEST & SCREENING

STANDARD

Environmental Electrical Testing From -65¡C to 200¡C

All microelectronic designs can be manufactured and tested at

commercial, industrial, and military temperature ranges.

Device Burn-In

Static or dynamic device burn-in is accomplished following MILSTD 883 procedures.

Full Device Screening

Complete MIL Standard Screening Procedures for microelectronics

are employed for each device produced.

CUSTOMER SPECIFIED

Texas Components will adhere to your electrical test and screening

specifications. If asked, Texas Components Corporation will offer

suggested testing protocols.

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

ENGINEERING SERVICES

At Texas Components Corporation, Our engineering staff is

available to assist you throughout the entire design cycle from

conception to completion. Our engineering services include:

Conceptual Design Discussions

Texas Components Corporation encourages pre-design conceptual

discussions with our customers. Our microelectronics experience

allows us to offer insights and pre-design suggestions.

Design Assistance

Texas Components Corporation stands ready to assist you in your

microelectronic design concerns including die availability,

environmental performance of various die manufacturers, and

manufacturing issues involving the implementation of your circuit

design into a microelectronic assembly.

Complete Turn-Key Engineering Solutions

Provide us with your functional and environmental specifications and

our engineers will evaluate, design, and produce a microelectronic

product that meets your requirements. This includes new products,

redesigns, and replacements for discontinued semiconductor

components.

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

HIGH TEMPERATURE CAPACITOR MODULES

Texas Components Corporation manufactures custom high

temperature (200¡C) capacitor modules as a superior alternative or

replacement for wet slug tantalum capacitors. These devices can be

manufactured in nearly any configuration of value, shape, size and

voltage to be defined by the customer's requirements.

Designed using ceramic chip capacitors (which have no acidic liquid

core to damage circuit board assemblies, as do wet tantalum

capacitors)

X7R temperature specifications

Solderless construction for high mechanical reliability

Configured to meet customer's electrical and mechanical

requirements (size and shape)

PRODUCT EXAMPLE

An example product would be a 36.uF, 250V, X7R, 200¡C

capacitor with physical dimensions of 2.0" X 1.5" X .5".

Capacitor values are limited only by available mounting space.

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

HONEYWELL HIGH TEMP DESIGN CENTER

Texas Components Corporation is an authorized Honeywell High

Temperature Design Center that carries the full line of Honeywell

HTMOS components on SOI (Silicon On Insulator). Designed for

use in extreme heat environments such as down hole

instrumentation, avionics and turbine engine control. These

products offer reliable operation from -55¼C to 225¼C.

Product offering:

HT1104 Quad Operational Amplifiers

HT1204 Quad Analog Switches

HT506/507 Analog Multiplexers

HT574 uP Compatible 12 bit A/D Converters

HT6256 32Kx8 Static RAM

HT83C51 Microcontrollers

HTANFET N-Channel Power FET

HTCCG Crystal Clock Generators

HTPLREG Positive Linear Regulators

HTREF05 5V Reference

HT1553 1553 Protocol Controllers

HT2000 Gate Arrays

Texas Components Corporation can incorporate Honeywell

HTMOS die products into your microelectronic designs upon

request.

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

Texas Components

Corporation

APPLICATION SPECIFIC STANDARD

PRODUCTS

Resistive Products Division

1716 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 468-3882 Fax (713) 461-2098

Microelectronic Products Division

1662 West Sam Houston Parkway North, Houston Texas 77043

Phone (713) 365-9199 Fax (713) 973-2838

www texascomponents com

5 Reasons to Specify Bulk Metal® Foil Potentiometers

Vishay Foil Resistors

VISHAY FOIL • FRANCE +33.4.93.37.28.24 FAX: +33.4.93.37.27.31

• ITALY + 39.2.300.11919 FAX: +39.2.300.11999

• SWEDEN +46.8.594.70590 FAX: +46.8.594.70581

Bulk Metal® Foil Technology

Trimming Potentiometers

1. TEMPERATURE COEFFICIENT OF RESISTANCE

2. SETTABILITY

3. SETTING STABILITY

4. LOW NOISE

5. NON-INDUCTIVE DESIGN

5 Reasons to Specify Bulk Metal® Foil Potentiometers

Vishay Foil Resistors

MILITARY

–50 PPM/°C

+50 PPM/°C

MILITARY

+10 PPM/°C

MAXIMUM CHORD

SLOPE

–10 PPM/°C

MAXIMUM CHORD

SLOPE

+25 +50 +0 –25 –50 +75 +100 +125 +150

+6250

+1250

–1250

–6250

Temperature °C

R (PPM) 0

–55°C

+4000

+800

–800

–4000

The low TCR minimizes the influence of these gradients on

resistances forming the voltage divider, preventing these

resistances from drifting apart and thereby keeping the ratio

essentially constant.

REASON 2

SETTABILITY

Vishay Trimmers are settable to within 0.1% maximum. The Bulk

Metal® Foil has a flat, smooth surface containing redundant

photo-etched current paths which provide essentially infinite

resolution and enhance settability.

REASON 3

SETTING STABILITY

A multi-fingered wiper-brush rides on the Bulk Metal® Foil element

with a preloaded force to maintain positive contact. The wiper is

driven through a 20:1 worm gear (Model 1240 for example) which

provides virtually backlash-free resistance adjustment. Together

they provide a smooth, linear, resistance-rotation characteristic

and exceptional stability when exposed to environmental stresses.

INTRODUCTION

Vishay Precision Trimmers have the Bulk Metal® Foil resistive

element which possesses a unique inherent temperature and

load-life stability. In addition, their advanced, virtually backlashfree

adjustment mechanism makes them easy to set quickly and

accurately and keeps the setting exactly on target.

REASON 1

TEMPERATURE COEFFICIENT OF

RESISTANCE (TCR)

The Maximum Temperature Coefficient of Resistance of standard

Vishay trimmers (except the 1280G & 1285G*) is + 10pm/°C from

– 55°C to + 25°C, and – 10ppm/°C from + 25°C to + 150°C, which

is five times tighter than required by MIL-PRF-39035 characteristic

*The TCR for the 1285G is ± 5ppm/°C

The TCR for the 1280G is ± 15ppm/°C

This TCR specification is the result of the combination of the Bulk

Metal® Foil and the matched substrate, which produces an

unusually low and predictable TCR.

In real life conditions of changing ambient temperature and

temperature gradients, the low TCR of Vishay trimmers plays an

important role in both application modes:

a. When the trimmer is used as a variable resistor (rheostat), it

keeps the resistance value constant and independent of the

changes in ambient temperature.

b. When the trimmer is used in a voltage divider mode, the two

parts of the trimmer’s element see different temperatures

because of temperature gradients created by heat

dissipated by the trimmer and by outside heat sources.

* The TCR for the 1285G is ±5 ppm/°C

The TCR for the 1280G is ±15 ppm/°C

Bulk Metal® Foil Technology

Trimming Potentiometers

FIGURE 1 - VISHAY TEMPERATURE COEFFICIENT OF

RESISTANCE (TCR) COMPARED TO

MILITARY STANDARDS

FIGURE 2 - 1240 TRIMMER ELEMENT

FIGURE 3 - 1202 TRIMMER ELEMENT

5 Reasons to Specify Bulk Metal® Foil Potentiometers

Vishay Foil Resistors

WIREWOUND

CERMET

Wiper Travel

Resistance

Wiper Travel

Resistance

Wiper Travel

Resistance

BULK METAL

FOIL

REASON 4

LOW NOISE

The flat smooth surface of the Bulk Metal® Foil, combined with the

metal-to-metal contact between the Bulk Metal® Foil and the multifingered

wiper, provide Vishay Trimmers with extremely low noise.

ALL VISHAY TRIMMERS ARE INSPECTED 100% For:

• Short-time overload (6.25 x rated power for 5 seconds on;

and for 30 seconds off — 3 cycles)

• Immersion

• Resistance tolerance check

• End Resistance

• Visual-Mechanical

• Dynamic tests for: Continuity, CRV

By Sample For:

• TCR

• DWV

Etched Bulk Metal® element

redundant current paths

eliminate catastrophic failure.

Sealed housing for

moisture protection

and solvent resistance.

All-welded construction

maintains connection

integrity under soldering.

Multi-fingered wiper.

Compression-fitted "O" ring

seals adjustment screw opening.

Etched Bulk Metal®

element redundant

current paths eliminate

catastrophic failure.

Sealed housing for

moisture protection

and solvent resistance.

All-welded construction

maintains connection

integrity under soldering.

Multi-fingered wiper.

Compression-fitted "O"

ring seals adjustment

screw opening.

FIGURE 4 - TYPICAL TRIMMER RESOLUTION

BY ELEMENT TYPE

2. SETTABILITY / 3. SETTING STABILITY Continued

REASON 5

NON-INDUCTIVE DESIGN

The Vishay resistive pattern design on a flat substrate provides an

essentially non-inductive component — 0.08µH typical; with a rise

time as fast as 10ns at 1K — excellent for high frequency

applications.

FIGURE 5 - 1240 CUTAWAY

FIGURE 6 - 1202 CUTAWAY

Bulk Metal® Foil Technology

Trimming Potentiometers

7 Technical Reasons to Specify Bulk Metal® Foil

Vishay Foil Resistors

Bulk Metal®

Foil Technology

Resistive Components

1. EXTREMELY LOW TEMPERATURE COEFFICIENT OF RESISTANCE (TCR)

2. EXCELLENT LOAD-LIFE STABILITY

3. TIGHT RESISTANCE TOLERANCE

4. LOW CURRENT NOISE

5. HIGH SPEED

6. LOW THERMAL EMF

7. NON-MEASURABLE VOLTAGE COEFFICIENT

– FOIL TCR CHARACTERISTICS

– DISCRETE RESISTORS

– RATIO

– ABSOLUTE

– RATIO

foilsales.israel@vishay.com • FRANCE/SWITZERLAND/SOUTHERN EUROPE: foilsales.eusouth@vishay.com • AMERICAS: foilsales.usa@vishay.com

Bulk Metal® Foil Technology

Resistive Components

“Why are extremely low TCR resistors required?” Is a proper

question when evaluating the performance and cost of a

system. The answers are as numerous as the systems in

which they are installed. The following may provide an

insight:

A remote TV transmitter that started up cold in the morning

and warmed up during the day required manual color

discrimination adjustment during the day due to the influence

of the temperature changes.

Satellites, in synchronous orbit that require stable position

and function, or one that rotates through temperature

extremes.

The solution to these problems is extremely low TCR resistors.

FOIL TCR

Two predictable and opposing physical phenomena within

the composite structure of the resistive alloy and its substrate

are the key to the low TCR capability of Bulk Metal® Foil:

1. Resistivity of the resistive alloy changes directly with

temperature. (Resistance of the foil increases when

temperature increases.)

2. The coefficient of thermal expansion of the alloy and

substrate are different resulting in a compressive stress

on the resistive alloy when temperature increases.

(Resistance of the foil decreases due to compression

caused by the temperature increases.)

The Temperature Coefficient of Vishay Bulk Metal® Foil

resistors is the result of matching the variation in resistivity of

the alloy with temperature and variation of the resistance of

the alloy with stress. These two effects occur simultaneously

with changes in temperature. The result is an unusually low

and predictable TCR.

Due to Vishay’s Bulk Metal® Foil resistor design, this TCR

characteristic is accomplished automatically, without

selection, and regardless of the resistance value or the date

of manufacture — even if years apart!

IMPROVED TCR IN BULK METAL® FOIL

RESISTORS

Foil resistor technology has continued to progress over the

years, with significant improvements in TCR having been

achieved. Figure 1 shows the nominal TCR characteristics of

the various Foil Alloys utilized by Vishay to produce Bulk Metal®

Foil Resistors.

The original Alloy C Foil exhibits a negative parabolic response

to temperature with a positive chord slope on the cold side

and a negative chord slope on the hot side.

REASON 1

EXTREMELY LOW TEMPERATURE COEFFICIENT OF RESISTANCE (TCR)

-50 -25 0 +25 +50 +75 +100 +125

-55

C Alloy

2ppm/°C

K Alloy

1ppm/°C

Z Alloy

0.2ppm/°C

1ppm/°C

0.2ppm/°C

2ppm/°C

+150

+100

+50

-50

-100

-150

-200

(ppm)

FIGURE 1 - FOIL RESISTOR TCR

COMPARISON OF FOIL ALLOYS

NOMINAL TCR

Vishay Nominal TCR is defined as the chord slopes of the

relative change of resistance vs temperature (RT) curve, and is

expressed in ppm/°C (parts per million per degree centigrade).

Slopes are defined from 0°C to + 25°C and + 25°C to + 60°C

(Instrument Range); and from - 55°C to + 25°C and + 25°C to

+ 125°C (Military Range). These specified temperatures and

the defined nominal TCR chord slopes apply to all resistance

values including low value resistors. Note, however, that

without four terminals and Kelvin connections in low values,

allowance for lead resistance and associated TCR may have to

be made. All resistance and TCR measurements of leaded

styles are made by the factory at a gage point 1/2” from the

standoffs. Contact Applications Engineering Department for

the TCR increase to be expected for low value resistors.

Following was the Alloy K Foil which produced an opposite

hyperbolic response with temperature with a negative chord

slope on the cold side and a positive chord slope on the hot

side. In addition it provides a TCR approximately one half

that of Alloy C Foil.

The latest development is Alloy Z Foil which has a similar

hyperbolic response as the Alloy K Foil but produces TCR

characteristics an order of magnitude better than Alloy C and

five times better than Alloy K.

Extremely low TCR resistors have been developed that

provide virtually zero response to temperature. See the data

sheet for the Vishay Thermotropic VHP100, ultra performance

Z201, hermetically sealed VH102Z resistors.

These technological developments have resulted in a major

improvement in TCR characteristics compared to what is

available in any other resistor technology. Use Bulk Metal®

Foil resistors for all extremely low TCR requirements.

Current Path

After Trimming

Current Path

Before Trimming

Trimming Process

Removes this Material

from Shorting Strip Area

Changing Current Path

and Increasing

Resistance

Why do users employ tight tolerance resistors? A system or a

device or one particular circuit element must perform for a specified

period of time and at the end of that service period it must still be

performing within specification. During its useful life it may have

been subjected to some hostile service conditions and it is no

longer within purchased tolerance. One reason for specifying a

tighter purchased tolerance than the end of life error budget

tolerance is to allow room for service shifts. Another reason is that

the error budget is more economically applied to resistors than to

most other components.

FIGURE 10 - VISHAY S102C RESISTOR

ELEMENT

NOTE: Foil shown in white, etched spaces in black. NOTE: Foil shown in black, etched spaces in white.

REASON 2

TIGHT RESISTANCE TOLERANCE

The accuracy of Bulk Metal® Foil resistors can be made as precise

as 0.001% by selectively trimming various adjusting points that

have been designed into the photoetched pattern of the resistive

element. See Figure 10. They provide predictable step increases

in resistance to the desired tolerance level. Trimming the pattern

at one of these adjusting points will force the current to seek

another longer path, thus raising the resistance value of the

element by a specific percentage. In the fine adjust areas,

trimming affects the final resistance value by smaller and smaller

amounts down to 0.001% and finally 0.0005% (5ppm). This is the

trimming resolution. See Figure 11

FIGURE 11 - TRIMMING TO VALUES

(CONCEPTUAL ILLUSTRATION)

Bulk Metal® Foil Technology

Resistive Components

Why are designers concerned about stability with applied load?

Load Life stability is the characteristic most relied upon to

demonstrate a resistor's long term reliability. Military testing

requirements to 10,000 hours with limits on the amount of shift and

the number of failures results in a failure rate demonstration.

Precision Bulk Metal® Foil resistors have the tightest allowable

limits. Whether military or not, the load life stability of foil resistors

is unparalleled and long term serviceability is assured.

The reason foil resistors are so stable has to do with the materials

of construction (Bulk Metal® Foil and high alumina substrate). For

FIGURE 12 - RELATIVE RESISTANCE CHANGE

(R/R) AS A FUNCTION OF TIME,

LOAD 0.3 W, +125°C AMBIENT

200

150

100

250 500 1000 1500 2000

Hours

R/R

(ppm)

0.5W

0.3W

0.2W

0.1W

0.05W

200

150

100

250 500 1000 1500 2000

Hours

R/R

(ppm)

0.5W

0.3W

0.2W

0.1W

0.05W

200

150

100

250 500 1000 1500 2000

Hours

R/R

(ppm)

+125°C

+80°C

+25°C

200

150

100

250 500 1000 1500 2000

Hours

R/R

(ppm)

example, the S102C resistor is rated at 0.3W at 125°C with an

allowable R of 150ppm after 2000 hours under load. (See

Figures 12 and 13 for the demonstrated behavior). Conversely,

the R is reduced by decreasing the applied power which lowers

the element temperature rise in Vishay resistors. Figure 12 shows

the drift due to load life testing at rated power and Figure 13 shows

the drift due to load life testing at reduced power. Reducing the

ambient temperature has a marked effect on load life results and

Figure 14 shows the drift due to rated power at different ambient

temperatures. The combination of lower power and ambient

temperature is shown in Figure 15.

REASON 3

EXCELLENT LOAD-LIFE STABILITY

FIGURE 13 - R/R = F (TIME), LOADS 0.05

TO 0.5 W, +125°C AMBIENT

FIGURE 14 - R/R = F (TIME), LOAD 0.3W,

DIFFERENT AMBIENT TEMPERATURES

FIGURE 15 - R/R = F (TIME), LOADS 0.05 TO

0.5 W, +25°C AMBIENT

Bulk Metal® Foil Technology

Resistive Components

The two parameters which must be mentioned together, power

rating and ambient temperature, can be joined into one single

parameter for a given style of resistor. If the steady state

temperature rise can be established, it can be added to the

ambient temperature, and the sum will represent the combined

(load induced + ambient) temperature. For instance the Vishay

S102C resistor has a temperature rise of 9°C per 0.1W of

applied power. It leads to the following sample calculations:

If T = 75°C, P = 0.2 Watts, and t = 2,000 hrs.;

Then self heating = 9°C x 2 = 18°C.

18°C rise + 75°C ambient = 93°C total.

Rmax = 80ppm from the curve of Figure 16.

Figure 16 shows, for a given duration of load life test, how the

drift increases with the level of the applied combined

temperature. As explained above, the combined temperature

comprises the effect of power induced temperature rise and the

ambient temperature. The curve shows maximum drift.

FIGURE 16 - MAXIMUM RESISTANCE

SHIFTS AFTER 2,000 HRS. OF LOAD LIFE

TEST UNDER THERMAL STRESSES*

240

200

160

120

Combined Temperature (°C)

R/R

(ppm)

60 80 100 120 140 160 180

Maximum for 100%

of Tested Resistors

EXCELLENT LOAD-LIFE STABILITY Continued

This information is based on product taken off the line without any

screen testing or burn in. Further drift reduction is available by

factory burn in. Consult Applications Engineering for this and other

screening tests that are available.

*Combined temperature– ambient and temperature rise due to applied

power.

Bulk Metal® Foil Technology

Resistive Components

REASON 4

HIGH SPEED

FIGURE 19 - BULK METAL® FOIL

PLANAR DESIGN

Inter-loop capacitance increases

with number of loops or spirals

Current in adjacent loops travels

in the same direction increasing

inductance by mutual fields.

The equivalent circuit of a resistor, as shown in Figure 17,

combines a resistor in series with an inductance and in parallel

with a capacitance. Resistors can perform like an R/C circuit or

filter or inductor depending on their geometry. In spiraled and

wirewound resistors these reactances are created by the loops

and spaces formed by the spirals or turns of wire. Figure 18 shows

how the capacitance and inductance increase as the resistance

value increases due to continually increasing the number of

spirals or turns.

In planar resistors such as the Vishay Bulk Metal® Foil resistors,

the geometry of the lines of the resistor patterns are intentionally

designed to counteract these reactances. Figure 19 shows a

typical serpentine pattern of a planar resistor. The opposing

directions of current prevents the build-up of mutual inductance

and reduces the capacitive effects by placing the inter-conductor

capacitances in series.

In pulse applications, these reactive distortions result in a poor

replication of the input. Figure 20 shows the current response to

a voltage pulse comparing a fast Bulk Metal® Foil resistor to a

slower wirewound. Here a pulse width of one nanosecond would

have been completely missed by the wirewound resistor while the

foil resistor achieves full replication in the time allotted.

In frequency applications these reactive distortions also cause

changes in apparent resistance (impedance) with changes in

frequency. Figure 21 shows a family of curves relating the AC

resistance to the DC resistance in Bulk Metal® Foil resistors. Very

good response is seen in the 100ohm range out to 100 MHz and

all values have good response out to 1MHz. The performance

curves for other types of resistors can be expected to show

considerably more distortion (particularly wirewounds).

r2 XL1 r1 XL2

Lead1

R XL

Lead2 Resistor

0 5 10 15 20

Time (nanoseconds)

Response to Input

Step Input Function

Precision Wirewound

Vishay Resistors

0.1 1 10 100 1000

Frequency, MHz

Æ / R0 (Resistance AC / Resistance DC)

100K 10K

160

100

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

FIGURE 20 - COMPARISON OF RESPONSE

TO A PULSE

FIGURE 21 - EFFECT OF OPERATION AT

FREQUENCY

FIGURE 18 - CAPACITANCE AND

INDUCTANCE IN A WOUND

OR SPIRALED RESISTOR

FIGURE 17 - THE EQUIVALENT CIRCUIT

OF A RESISTOR

Bulk Metal® Foil Technology

Resistive Components

Mutual Inductance

Reduces

Due To Change in

Current

Direction

Inter-Loop

Capacitance

Reduces

In Series

FIGURE 22 - SEGMENT OF

A FUNDAMENTAL CURVE

FIGURE 23 - SIGNAL WITH

ADDED RESISTOR NOISE

FIGURE 24 - SIGNAL WITH

A "NOISE FREE" RESISTOR

Courtesy of LeCroy

Noise generation is minimal when current

flow is through multiple paths as exists in

Bulk Metal® Foil resistive alloy.

Noise generation is maximum when current

flow is through point to point contacts as

shown in a particle to particle matrix.

As measurement instrumentation and circuitry become more

demanding, noise or unwanted signals, superimposed upon the

fundamental signal become troublesome. Measurement

instrumentation based on low level signal inputs and high gain

amplification cannot tolerate microvolt level background noise

when the signal being measured is itself in the microvolt range.

Although audio circuitry, when signal purity is of utmost concern,

is the most obvious use of noise free components, other industries

and technologies are equally concerned with this characteristic.

Resistors, depending on construction, can be a source of noise.

This unintended signal addition is measurable and independent of

the presence of a fundamental signal. Figures 23 and 24 below

illustrate the effects of resistor noise on a fundamental signal.

Resistors made of conductive particles in a non-conductive binder

are the most likely to generate noise. In carbon composition and

thick film resistors, conduction takes place at points of contact

between the conductive particles within the binder matrix. Where

these point to point contacts are made constitutes a high resistance

conduction site which is the source for noise. These sites are

REASON 5

LOW NOISE

sensitive to any distortion resulting from expansion mismatch,

moisture swelling, mechanical strain and voltage input levels. The

response to these outside influences is an unwanted signal as the

current finds its way through the matrix. Figure 25 illustrates this

current path.

Resistors made of metal alloys, such as the Vishay Bulk Metal®

Foil resistor are the least likely to be noise sources. Here the

conduction is across the inter-granular boundaries of the alloy.

The inter-granular current path from one or more metal crystals to

another involves multiple and long current paths through the

boundaries reducing the chance for noise generation. Figure 26

illustrates this current path.

In addition, the photo lithography and fabrication techniques

employed in the manufacture of Bulk Metal® Foil resistors results

in more uniform current paths than found in some other resistor

constructions. Spiraled resistors, for example, have more

geometric variations that contribute to insertion of noise signals.

Bulk Metal® Foil resistors have the lowest noise of any resistor

technology, with the noise level being essentially immeasurable.

FIGURE 25 - THE CURRENT PATH IN A

PARTICLE TO PARTICLE MATRIX

FIGURE 26 - THE CURRENT PATH IN A

RESISTIVE ALLOY

Bulk Metal® Foil Technology

Resistive Components

7 Technical Reasons to Specify Bulk Metal® Foil

Vishay Foil Resistors

REASON 6

LOW THERMAL EMF

The thermoelectric effect, which is negligible in ordinary resistors,

may become a significant source of drift or instability in highprecision

resistors. Known as the seeback effect, it occurs when

the following two conditions are present at the same time:

1. An electrical circuit is made from two different conducting

materials (metals M1 and M2), which are soldered at their

ends, A and B.

2. A temperature difference T2 - T1 exists between A and B.

When a junction is formed by two dissimilar metals, and is heated,

a voltage is generated due to the different levels of molecular

activity within these metals. This electromotive force, induced by

temperature, is called Thermal EMF and is usually measured in

microvolts. A useful purpose of this Thermal EMF is the

measurement of temperature using a thermocouple and microvolt

meter.

In resistors, this Thermal EMF is considered a parasitic effect

interfering with pure resistance. It is often caused by the dissimilarity

of the materials used in the resistor construction especially at the

junction of the resistor element and the lead materials. The

Thermal EMF performance of a resistor can be degraded by

external temperature variations, dissymmetry of power distribution

within the element, and the dissimilarity of the molecular activity

of the metals involved.

A key feature of the Vishay Bulk Metal® Foil resistor is its low

Thermal EMF design. The flattened paddle leads make intimate

contact with the chip thereby maximizing heat transfer and

minimizing temperature variations. The resistor element is

designed to uniformly dissipate power without creating hot spots

and the lead material is compatible with the element material.

These design factors result in a very low Thermal EMF resistor.

The combination of ruggedized leads and molded case plus the highly efficient heat-transfer characteristics of the unique assembly and the ceramic substrate

results in a high reliability resistor with excellent moisture resistance, high temperature and load-life capabilities. These also afford a very low thermal EMF.

Flattened "paddles" are wrapped around the resistance element structure and welded directly to the resistance alloy – thus there is only one weld per lead. The

closely related thermal characteristics of the selected materials, combined with the unique "paddle" lead design, produce a resistor with extremely low thermal

EMF.

REASON 7

NON-MEASURABLE VOLTAGE COEFFICIENT

CONCLUSION

ALL IN ONE RESISTOR

The seven reasons to specify Vishay Bulk Metal® Foil resistors are inherent in the design and are not a function of manufacturing

variables or a selection process. This combination of parameters is not available in any other resistor technology.

Vishay Bulk Metal® Foil technology resistors provide a unique, inherent combination of performance characteristics resulting in

unmatched performance and high reliability satisfying the needs of today’s expanding requirements.

SPECIAL ORDER

As mentioned earlier in our section on resistor noise, resistors can change value due to applied voltage. The term used to describe the

rate of change of resistance with changing voltage is known as voltage coefficient.

Resistors of different constructions have noticeably different voltage coefficients. In the extreme case the effect in a carbon composition

resistor is so noticeable that the resistance value varies greatly as a function of the applied voltage.

Vishay Bulk Metal® Foil resistor elements are insensitive to voltage variation and the designer can count on foil resistors having the same

resistance under varying circuit voltage level conditions. The inherent bulk property of the metal alloy provides a non-measurable voltage

coefficient.

Silicone Rubber Encapsulation Provides a cushioning layer which isolates the resistive element from external stresses.

Vishay® Metal Foil Etched resistive element.

Molded Standoffs Allow easy PC board cleaning.

Ceramic Substrate

One-Piece Transfer Molded Case

Affords maximum protection against all environmental conditions.

Polymerized Moisture Protection Layer

Paddle Leads with Welded Terminations– No Ribbons Only two welds, both remote from the lead-to-case point-of-entry,

the best arrangement for maximum reliability. Excellent moisture resistance, high temperature and load-life capabilities, low thermal EMF.

FIGURE 27 - RUGGEDIZED CONSTRUCTION

Bulk Metal® Foil Technology

Resistive Components

Texas Components - Data Sheet

AN004 DESCRIPTION and CHARACTERISTICS of the

TX53G1 HIGH PERFORMANCE GEOPHONE

REV A

08/30/99

The TX53G1 is an extremely rugged, low distortion, wide dynamic range sensor.

The proof, or moving,

mass of the TX53G1

is a rod magnet

positioned within a

cylindrical cavity filled

with a suspending

fluid. In addition, a

rod magnet installed

within an external

mounting provides an

opposing force to that

of gravity and centers

the proof mass within

the housing cavity.

N Magnetic Proof Mass S

COIL 1 COIL 2

suspending

Fluid

OUT +

OUT -

COM

TX53G1 Geophone Schematic - U.S. Patent 5756896

S Levitation Mag N

<<< Earth

The combination of the magnetic fields sets the mechanical sensitivity and

spring rate constant of the sensor. This arrangement overcomes all of the

problems associated with mechanical springs as well as enhancing the

survivability of the unit during high shock loads. Additionally, the mechanical

dimensions of the internal components were selected so as to reduce brownian

noise to an absolute minimum. Motion of the proof mass is sensed by an

external, center tapped, coil around the cavity and is designed to be interfaced

to a high common mode rejection, differential, amplifier with the center tap

providing bias current return for the amplifier inputs. What follows will describe

the performance characteristics of this device and the test procedures employed.

TX53G1 Specifications :

Resonance Frequency 6 Hz ± 10.0%

Damping + 3dB peak at Resonance ( ± 0.5 dB )

Response 4 Hz to Greater than 1KHz

Distortion < 0.0012%

Sensitivity 14.0 V/M/S

Spurious Frequencies None with lateral inputs < 0.4 In / Sec

Moving Mass 3.5 G

Excursion ± 4.2 MM

Operating Temp -45 C° to +85 C°

Coil DC Resistance 10K W ( 5K / 5K )

Shock Survival > 6000 G in any Axis

Weight 130 grams ( assembled with spike )

The TX53G1 geophone is an extremely rugged device which can actually be

hammered into the ground. The coil is molded of high impact ABS and is

vacuum impregnated to resist moisture absorption. The transducer core and

spike are fabricated of high strength, corrosion resistant, stainless steel.

All elements of the TX53G1, from one TX53G1 to another, are interchangeable

allowing easy repair in the field or shop.

5.295“

0.405“

2.680“

1.805“

0.405“

1.100“

TX53G1 Geophone Assembly

Resonant ( Natural ) Frequency, ‘Q’ and Damping Considerations

Resonant frequency is that frequency at which a mechanical system prefers to

absorb periodic energy. In general, it is a function of moving mass Vs

restraining spring rate. ‘Q’ is generally a measure of the ratio of response at

resonance Vs the response at frequencies several octaves away from

resonance. The larger the ‘Q’ , the larger the amplitude peak at resonance due

to the more efficient transduction of energy at this frequency. Damping is a

measure of forced, or artificial, amplitude reduction Vs frequency to achieve

specific device frequency or transient response characteristics.

A common, and effective, technique to reduce the amplitude response at

resonance of low impedance, moving coil or moving mass transducers is to

shunt the sensing coil with an external resistance. This is effective because it

forces the transducer to input more energy, at resonance, to energy levels more

consistent with other frequencies. The downside to this technique is that it

requires that the transducer deliver increased power to a load which can

increase the total harmonic distortion of the device.

The TX53G1 is a ‘springless’ implementation of a moving magnetic mass

transducer. It was designed to be transduced by a high impedance sensing coil

such that under no conditions would the device be required to deliver any

significant power to a load. This keeps the distortion of the device to an

absolute minimum regardless of resistive load. However, this means that

damping must be achieved solely by the kinematic viscosity of the suspending

fluid. Considering the large number of variables affected by the fluid, the best

damping compromise results in a 3 dB to 4 dB peak at resonance.

Resonant Frequency Damping vs Temperature

Frequency - Hz

0 5 10 15 20 25

Relative Output - dB

-10

-5

-45C

+25C

+85C

Distortion Performance and Measurement Procedures

In general, the best technique for measuring distortion in moving coil, or moving

mass, transducers is to apply a steady-state sine wave to the device under test

through a high value resistor. The voltage impressed across the device causes

the coil, or mass, to deflect above and below it’s nominal at rest position and any

non-linearity of movement by the proof mass will modify the voltage across the

device. This voltage can be digitized by a high resolution data acquisition

system and a resultant FFT plot can be examined for harmonic distortion.

Since all elements of this test setup can generate distortion, it is best to acquire

data from two identical channels :

One channel will digitize data from the generator + device under test + digitizer

and the other will digitize data only from the generator + digitizer.

Differential analysis of the two plots will eliminate distortion components from the

generator + digitizer, what remains is the distortion of the geophone under test.

Such a test setup is shown below. Amplitudes shown are equivalent to outputs

generated by the TX53G1 at 0.7 In / Sec @ 12 Hz

Geophone Distortion Test Setup

24 Bit A/D System

Sine Wave Generator

Khron Hite 4400A

200K

Geophone

under test

20K

X10 X10

360 Mv P-P

input to A/D

11.0 V P-P

output from

generator @ 12 Hz ADJ for

Equal Amplitudes

The FFT plots on the following page illustrate the results of such a test. Data

was taken at night to minimize the effect of traffic and human activity on ground

noise.

The isolation system appears to be fairly effective, although not perfect. However, notice

that the noise floor of both plots > 30 Hz is about the same, indicating low device self noise.

The TX53G1 is installed in a bucket of sand, using it's spike, and isolated from ambient

ground noise by suspending the bucket using two springs ( of different rates ) and a

bungy cord in series. The total deflection of the suspension system at 10 lb mass is 38"

Expanded Frequency Plot

Power Spectrum - V2 / Hz

-120

-100

-116 dB Rel ( 0.00016% )

( 0.00006% ) -124 dB Rel

( 0.0002% ) -114 dB Rel

Expanded view of

2nd and 3rd harmonics

24 Hz

36 Hz

-102 dB Rel ( 0.00079% )

FFT Frequency Plot @ 0.7 In / Sec Equivalent Excitation

Hz 10 20 30 40 50

Power Spectrum - V2 / Hz - dB

-120

-100

-80

-60

-40

-20

Plot of Generator + Digitizer + Geophone

THD = -101.7 dB ( 0.00081% )

Plot of Generator + Digitizer

THD = -115.4 dB ( 0.00017% )

THD of Geophone = -103.9 db ( 0.00064% )

+10 dB

Sensitivity

Sensitivity is measured with the test fixture shown below. The basic layout

consists of 4 linear motors driven by an audio amplifier. These motors are

coupled to a moving plate on which the device under test and the velocity

standard are mounted. This amplifier input is generated by a calibration card

within a 24 bit data acquisition system and is usually a random binary signal of

appropriate amplitude. Data from both the device under test and the velocity

standard are digitized simultaneously and a coherence plot generated to

determine both sensitivity and frequency response. Sensitivity of the velocity

standard is 18 V / m / sec and is flat to approximately 0.5 Hz.

Linear Motor Linear Motor

Base Plate

Geophone under Test

Spurious Frequency Generation and Sensitivity

Spurious frequency generation is generally the result of failure of the suspension

system to reject motion inputs in the non-sensitive axis. Because the radial

springs used in modern geophones are stiff in the lateral axis, any component

not completely rejected is translated into a vertical component at a fairly high

frequency. The TX53G1 utilizes a suspending fluid to center the proof mass

inside the device housing. Lateral force inputs are completely rejected up to a

specific lateral velocity input. This force is not linear and becomes stronger as

the proof mass approaches the wall and as such is difficult to characterize in

theory.1 However, preliminary tests indicate that lateral velocity inputs in the

range of 0.4 In / Sec should be completely rejected.

1 Texas Components is, as of 08/30/99, in the process of constructing a test fixture to determine

actual lateral rejection velocity.

Application Thoughts

The TX53G1 geophone pickup coil ( see drawing below ) is designed to reject

EMI inputs completely in the direction of motion and perpendicular to the

direction of motion because of the phasing of the two individual coils. Pickup

in any other direction is a delta sine vector function and for most field

applications would be very low. Rejection is better if the device is used with a

differential amplifier but is still very good when used in a single ended

configuration providing cable lengths are kept to a reasonable length and low

capacitance cable is used.

Traditionally, increasing geophone sensitivity for low level physical inputs has

involved stringing a number of phones in series. This has the advantage of

increasing the signal output from the string.

The disadvantages include :

· More phones results in an increase in weight and wiring complexity.

· Increased potential for string failure, as well as increased cost.

· Inherent blurring of the electrical data from the actual data point.

Because of the low noise, low distortion and large mechanical travel of the

TX53G1 geophone, using only one per data point should result in even lower

cost than a conventional string of phones while providing enhanced data.

Texas Components has considerable expertise in high performance analog

electronics. This expertise could be utilized to produce a dramatic improvement

in data quality by combining the TX53G1 with our highly integrated data

acquisition products, such as our TX5400 instrumentation amplifier or one of our

24 bit digitizing systems like our TX5300 series products.

FEATURES

• Very low distortion : better than - 90 dB

• Wide frequency response : 4 Hz to > 1500 Hz

• No spurious frequencies

• Low resonance : 5.5 Hz typ

• Very high survival shock : > 5000 g

• One piece molded coil assembly

• Consists of only three, interchangable, components

• Very long excursion : > ±0.20”

• Low total mass : 130 grams assembled with spike

• Center tapped coil permits fully differential use

• 10 Volt / Meter / Second sensitivity ( No load )

DESCRIPTION

The TX53G1 geophone is an extremely rugged

seismic transducer which may be hammered into

the ground without degrading performance.

The coil assembly is molded of high impact ABS

and is vacuum impregnated to resist moisture

absorption. The coil is center tapped to permit

fully differential connection to the acquisition

system in order to reduce common mode noise.

The transducer core and spike are fabricated of

high strength, hard anodized aluminum.

All elements of the TX53G1, from one TX53G1 to

another, are interchangeable, allowing easy repair

in the field or shop.

( See application note AN004 for more details )

APPLICATIONS

• High performance Seismic Exploration systems

• Earth Science systems

• Nuclear Treaty monitoring systems

• Underwater Seismic systems

• Down-hole seismic applications

• High performance industrial applications

FFT Distortion Plot @ 0.7 In / Sec Equivalent Excitation

Hz 10 20 30 40 50

-120

-100

-80

-60

-40

-20

Plot of Generator + Digitizer + Geophone

THD = -101.7 dB ( 0.00081% )

Plot of Generator + Digitizer

THD = -115.4 dB ( 0.00017% )

THD of Geophone = -103.9 db ( 0.00064% )

+10 dB

12/12/2004 Texas Components Corporation www.texascomponents.com

5.295“

0.405“

2.680“

1.805“

0.405“

1.100“

TX53G1 Geophone Assembly

Texas Components Corporation TX53G1

Very High Performance, Low Distortion, Extremely Rugged Geophone

TX53G1 Geophone -- Specifications

Frequency

Natural frequency (fn) 5.5 Hz

Tolerance ±5%

Spurious frequencies None

Distortion

Distortion with 0.7 in/s p-p 0.0033% max

Distortion measurement frequency 12 Hz

Maximum tilt angle for specification 15°

Pickup Coil

Type Dual center tapped

Resistance 1735Ù / 1735Ù

Tolerance ±5%

Damping 0.8 (unaffected by load)

Sensitivity

Open circuit sensitivity 10 V/M/S

Tolerance ±5%

Moving mass 5.2 Grams

Maximum proof mass excursion ±0.20 Inches

Physical Characteristics

Diameter 1.1 Inches (excluding cable exit)

Height (assembled) 4.89 Inches

Weight (total) 130 Grams

Operating temperature range -40C° to +100C°

Survival shock >5000 G x 2 ms (any direction)