Ferro Electronic Material Systems Performance of LTCC...

Ferro Electronic Material Systems

Performance of LTCC Resistors in Extreme Cold Environment

Michail Moroz

IMAPS ATW on Reliability of Advanced Electronic Packages and Devices in Extreme Cold Environments

February 21-23, 2005 Pasadena, CA

Introduction (1)

• There is a growing demand for more capable extreme cold environment electronics used in such applications as defense andaerospace systems

• Many space applications like exploration missions to the outer planets, James Webb Space Telescope, earth-orbiting and deep-space probes and communications satellites, would benefit from availability of low temperature electronics

• Continuous interest in miniaturized, high performance and reliable electronic devices drives the electronic industry to develop newpackaging technologies

• In competition with alternative solutions like printed circuit board and thin film technologies, low temperature co-fired ceramic (LTCC) technology is being developed for the fabrication of high reliability, compact, low-cost electronic modules

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• Most modern electronic components are limited to low operating temperature of -40ºC to -55ºC

• Effect of extreme cold temperatures on the key characteristics of resistors, specifically resistance and temperature coefficient of resistance (TCR) was investigated

• The following requirements were set as a goal for the present work:

Resistivity: from 10 Ω/ to 100 KΩ/

Resistor size range: 15x15 to 80x80 mils and 40x40 to 400x40 mils

Temperature range: from 25°C down to –155°C

TCR: within ± 100 ppm/°C

Relative resistivity change: < ± 1%

R1 / R2 ratio change for resistor pairs: < ± 0.5%

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Introduction (2)

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• Temperature Coefficient of Resistance (TCR) – the amount of resistance change of a resistor material with temperature

• TCR is also dependent on resistor geometry, resistor thickness, trimming methods, encapsulation, and many other processing parameters

• Values are often quoted for "hot TCR" and "cold TCR"

• Commonly expressed as the average change over a certain temperature range in parts per million per degree Centigrade (ppm/°C)

TCR

TCR:)()(121

12

TTRRR−−

x 106, ppm/°C

• The standard TCR test uses only two readings at - 55°C and + 125°C with reference point 25°C

• No thick film resistive inks with specified and controlled continuous TCR curve shape for wide resistor size range are currently commercially available

Resistor Test Pattern

Resistor sizes, mils:

15x15 40x4020x20 80x4030x30 120x4040x40 200x4080x80 400x40

Pattern size: 1” x 1”

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• The TCR Test System enables computer-controlled measurement of resistance and calculation of the TCR

• The TCR Chamber door is equipped with five connectors that can accommodate up to 20 resistor samples

• The TCR Chamber is cooled by liquid nitrogen

• The operator enters a series of test temperatures and dwell time at each temperature into the system

• After the programmed dwell time at each temperature, the resistance is measured for each sample

• The TCR is calculated for each sample using the test results at a user defined reference temperature

• Test results for each test session are stored in a Microsoft Access database and accessed using a unique test file name

The TCR Test System

Relative Resistivity

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TCR vs. Resistor Size in Regular TemperatureRange from –55°C to 125°C

12

-200

-150

-100

-50

0

50

100

150

200

40x40 80x40 120x40 200x40 400x40

Temperature, °C

TCR

, ppm

/°C

Hot @ 125°C

Cold @ -55°C

Reference Point: +25C

Regular Hybrid Resistor

-100

-80

-60

-40

-20

0

20

40

60

80

100

40x40 80x40 120x40 200x40 400x40Temperature, °C

TCR

, ppm

Hot @ 125°C

Cold @ -55°C


High Precision LTCC 82-31PMG Resistor

TCR vs. Temperature in StandardTemperature Range from –55°C to 125°C

13

-100

-80

-60

-40

-20

0

20

40

60

80

100

-55 -45 -35 -25 -15 -5 0 5 45 55 65 75 85 95 105 115 125

Temperature, °C

TCR

, ppm

40x40 80x40 120x40 200x40 400x40


Reference Point: +25°C

Such feature of thick film resistive inks like specified and controlled continuous TCR curve shape for wide resistor size range is very desirable, as it provides significant design flexibility and helps to keep resistor performance precise for various circuit designs, facilitating enhanced yield during manufacturing

New High Precision LTCC Resistor

Regular Resistor < ±100 ppm°C @ -55°C

15

New High Precision LTCC Resistor

Regular Resistor < ±100 ppm°C @ -55°C

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TCR in the Temperature Range from 25°C to -155°C for 20x20 mils Resistors

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-350

-300

-250

-200

-150

-100

-50

0

50

100

25 15 5 0 -5 -15 -25 -35 -45 -55 -65 -75 -85 -95 -105

-115

-125

-135

-145

-155

Temperature, °C

TCR

, ppm

/°C

High Precision 82-51PMG Resistor

Regular ± 100 ppm/°C Resistor


20 x 20 mils Resistors

Relative Resistivity Change in the Temperature Range from 25°C to -155°C (20x20 mils size)

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-6.00

-5.50

-5.00

-4.50

-4.00

-3.50

-3.00

-2.50

-2.00

-1.50

-1.00

-0.50

0.00

0.50

1.00

25 15 5 0 -5 -15 -25 -35 -45 -55 -65 -75 -85 -95 -105

-115

-125

-135

-145

-155

Temperature, °C

Rel

ativ

e R

esis

tivity

Cha

nge,

%

High Precision 82-51PMG Resistor

Regular ± 100 ppm/°C Resistor


20 x 20 mils Resistors

19

-350

-300

-250

-200

-150

-100

-50

0

50

100

25 15 5 0 -5 -15 -25 -35 -45 -55 -65 -75 -85 -95 -105

-115

-125

-135

-145

-155

Temperature, °C

TCR

, ppm

/°C

40X4080X40120X40200X40400X40 Reference Point: +25°C


-100

-80

-60

-40

-20

0

20

40

60

80

100

25 15 5 0 -5 -15 -25 -35 -45 -55 -65 -75 -85 -95 -105 -115 -125 -135 -145 -155

Temperature, °CTC

R, p

pm/°

C

40X40 80X40 120X40 200X40 400X40



TCR in the Temperature Rangefrom 25°C to -155°C

For extreme temperature applications continuous TCR curve with a controlled slope is a newly introduced, but mandatory requirement

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-6.00

-5.50

-5.00

-4.50

-4.00

-3.50

-3.00

-2.50

-2.00

-1.50

-1.00

-0.50

0.00

0.50

1.00

25 15 5 0 -5 -15 -25 -35 -45 -55 -65 -75 -85 -95 -105

-115

-125

-135

-145

-155

Temperature, °C

Rel

ativ

e R

esis

tivity

Cha

nge,

%

40X40

80X40

120X40

200X40

400X40 Reference Point: +25°C


-1.00

-0.80

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

25 15 5 0 -5 -15 -25 -35 -45 -55 -65 -75 -85 -95 -105

-115

-125

-135

-145

-155

Temperature, °C

Rel

ativ

e R

esis

tivity

Cha

nge,

%40X40 80X40 120X40 200X40 400X40



Relative Resistivity Change in the Temperature Range from 25°C to -155°C

• Quite often pairs of resistors are used in circuit design when R1 / R2 ratio is even more important than their absolute values

• If two resistors with a different number of squares are used, and one resistor is changing TCR faster than the other (i.e. has a different TCR curve slope), this would be an indication the R1 / R2

ratio is not at –155°C as accurately as with the standard temperature range of –55°C

• For the pair consisting of same-width 10-square and 1-square precise regular resistors with TCR ± 100 ppm/°C at –55°C, the R1 / R2 ratio change at –155°C was as high as -2.5%

• The R1 / R2 ratio change for the specifically designed 82-series LTCC post fired resistors did not exceed ± 0.2% at -155°C for any resistor configuration

R1/R2 Ratio of Resistor Pair

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22

-1.00

-0.80

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

25 15 5 0 -5 -15 -25 -35 -45 -55 -65 -75 -85 -95 -105

-115

-125

-135

-145

-155

Temperature, °C

R1

/ R2

Cha

nge,

%

400x40 / 40x40

400x40 / 80x40

400x40 / 120x40

400x40 / 200x40



-3.00

-2.50

-2.00

-1.50

-1.00

-0.50

0.00

0.50

1.00

25 15 5 0 -5 -15 -25 -35 -45 -55 -65 -75 -85 -95 -105

-115

-125

-135

-145

-155

Temperature, °C

R1

/ R2

Cha

nge,

%

400x40 / 40x40

400x40 / 80x40

400x40 / 120x40

400x40 / 200x40



R1/R2 Ratio Change in the Temperature Range from 25°C to -155°C

• LTCC co-fired buried resistors must be stable and able to undergo several refirings with minimal performance change

• Termination ink composition effects resistivity and TCR shift after re-firing

• Co-fired buried resistors are completely surrounded by the sintering tape and tend to interact with the tape during firing and refirings resulting in unpredictable shifts in resistivity and TCR.

• TCR of the new Ferro experimental co-fired buried resistors after a first firing and third re-firing did not exceed ± 100 ppm/°C for any resistor size from 15x15 mils to 80x80 mils in the temperature range from –150°C to 300°C

Co-fired Buried LTCC Resistors

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24

-100

-75

-50

-25

0

25

50

75

100

-150

-130

-110 -90 -70 -50 -30 -10 10 75 100

125

150

175

200

225

250

275

300

Temperature, °C

TCR

, ppm

/°C

15x15 20x20 30x30 40x40 80x80

Reference Point: +25°C30 Ohm/Sq

CN33-398 100% Ag ConductorCo-fired Buried After First Firing

A6S Tape

-100

-75

-50

-25

0

25

50

75

100

-150

-130

-110 -90 -70 -50 -30 -10 10 75 100

125

150

175

200

225

250

275

300

Temperature, °C

TCR

, ppm

/°C

15x15 20x20 30x30 40x40 80x80


CN33-398 100% Ag Conductor

30 Ohm/Sq

Co-fired Buried After Third Re-Firing

A6S Tape

TCR of Co-fired Buried LTCC Resistors in the Temperature Range from -155 °C to +300°C

Summary

Ferro new LTCC resistor inks have the following:• Performance:

Resistivity from 10 Ω/ to 100 KΩ/TCR within ± 100 ppm/°C Relative resistivity change: < ±1%R1 / R2 ratio change for resistor pairs: < ± 0.5%

• Distinctive features:Resistor size ranges: 15x15 to 80x80 mils and 40x40 to 400x40 mils Minimized and specified sensitivity to firing / re-firing conditions Controllable and minimized TCR curve slope that:

Assures precise resistor performance at extreme temperature rangeIs a mandatory newly introduced resistor characteristic of thick film resistive materials designated for working at extreme temperature environments

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Future Plans

• Find an opportunity to test described resistive material system at absolute zero temperature

• Conduct testing for defining of maximum operating temperature (~400°C or higher)

• Test LTCC resistors microwave performance

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Ferro Electronic Material Systems Performance of LTCC...

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