Microelectronics Reliability 46 (2006) 352–359
www.elsevier.com/locate/microrel
Advanced electrical and stability characterization
of untrimmed and variously trimmed thick-film and
LTCC resistors
Andrzej Dziedzic
a
a,*
, Andrzej Kolek b, Waleed Ehrhardt c, Heiko Thust
c
Faculty of Microsystem Electronics and Photonics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27,
50-370 Wroclaw, Poland
b
Department of Electronics Fundamentals, Rzeszow University of Technology, W. Pola 2, 35-959 Rzeszow, Poland
c
Microperipheric Group, Ilmenau Technical University, D-98684 Ilmenau, Germany
Received 11 October 2004; received in revised form 30 November 2004
Available online 21 January 2005
Abstract
As-fired thick-film resistors have the resistance tolerance within ±20% and this tolerance is increased for smaller
components. Therefore the novel trimming methods are necessary for microresistors, especially when they are embedded in LTCC substrate. This paper compares electrical (normalized temperature dependence of resistance, low frequency noise) and stability properties (relative resistance drift, changes of current noise index) of untrimmed,
voltage pulse trimmed and laser trimmed unglazed thick-film resistors after step-increased long-term thermal ageing
at 162 C, 207 C and 253 C. Moreover the effect of long term exposure (1000 h, 125 C) and thermal shocks (1000
shocks between 55 C and 125 C) is analysed for untrimmed and voltage pulse trimmed buried LTCC resistors.
2004 Elsevier Ltd. All rights reserved.
1. Introduction
Currently laser trimming is the dominant trimming
method of thick-film and LTCC (low temperature cofired ceramics) resistors. However, because of continuous trend in electronics industry for smaller, lighter,
faster and cheaper products, a significant dimension
reduction of thick-film and LTCC resistors as well as
the fabrication of buried components is noted at present.
From one side the laser trimming is insufficient for the
smallest thick-film and LTCC resistors, from the other
*
Corresponding author. Tel./fax: +48 7135 54822.
E-mail
address:
andrzej.dziedzic@pwr.wroc.pl
Dziedzic).
(A.
side the tolerance of as-fired resistors is within ±20%
and increases with reduction of dimensions. Since
approximately 10 years an intensive search has been
made for alternative trimming method. The most advanced research is connected with trimming by energy
of high voltage pulses.
In general, the susceptibility to high voltage pulses
and electrostatic discharges is very important and has
been investigated for thick-film resistors for almost 30
years [1–4]. Such investigations can be performed with
the aid of single or series of ‘‘long’’ pulses (rectangular
shape surges with 1–20 ms duration) [5,6] or by the series
of ‘‘short’’ rectangular voltage pulses (with duration
from several hundred nanoseconds up to several hundred microseconds). Tobita and Takasago [7] and then
a group from the Ilmenau Technical University [8–11]
0026-2714/$ - see front matter 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.microrel.2004.12.014
A. Dziedzic et al. / Microelectronics Reliability 46 (2006) 352–359
and a group from the Wroclaw University of Technology [12–15] tried to trim thick-film or LTCC resistors
by pulse voltage method. Very recently the Ilmenau
group has built and tested high voltage capacitor discharging generator allowing for controllable resistance
changes of low and high ohmic thick-film resistors
[16,17]. But still the quality of trimmed resistors is characterized only by drift of resistance, caused by various
long- and short-term exposures. This paper presents
electrical and stability characterization of untrimmed,
pulse voltage trimmed or laser trimmed thick-film resistors by extreme temperature stress. It compares their
electrical (normalized temperature dependence of resistance, low frequency noise) and stability properties (relative resistance drift, changes of current noise index).
Variously trimmed resistors were subjected to the stepincreased long-term thermal ageing at 162 C, 207 C
and 253 C. These investigations may give farther information for the optimization of HV-trimming process
especially for high temperature applications. Moreover
the use of such high stress temperatures could be useful
in analysis of conduction mechanism in variously
trimmed thick-film resistors – it is supposed that the applied voltage pulses lead to local changes of the network
properties due to Joule heating and local capacitor discharges. But still there is no full theory, which will fully
describe the nature of these changes. The first step in creation of such theory one can find in [18] where the
trimmed resistor was treated as the regular matrix made
of random resistors and capacitors. The various resistance changes resistance observed as a result of applied
high voltage pulse can be understood by requiring two
competing behaviours of the local elements: the decreasing and enhancement of the local resistances. The quantitative agreement between proposed model and
experiment can be obtained both in the frame of standard as well as biased percolation attempt.
by about +20% above initial resistance. In this case a
simple P-cut with a cut depth of about 15% of the resistor width was prepared. Second group of resistors were
trimmed by energy of high voltage pulses in system
shown in Fig. 1. The system consists on
• discharge circuit of HV-capacitor creating very short
pulses,
• programmable digital multimeter for resistor
measurement,
• high voltage relay to switch the connection between
either the HV-capacitor discharging circuit or the
multimeter and the sample (resistor),
• microcontroller for controlling the trimming process
[17].
The results of thick-film resistor trimming using discharge circuit of HV capacitor point out the same effect
on resistance as by previously used HV burst generator
[please see eg. [11]]. This means that the low ohmic resistors increase (an effect of disconnection of some conductive paths due to the applied electrical energy) and high
ohmic ones decrease their values during trimming
(applying of HV energy to the high ohmic resistance
causes local heating at conductive region and temperature increase even above 600 C; this leads to formation
of additional conductive paths or regions and to resistance decrease).
The 100 X/sq resistors were trimmed by changing the
high voltage amplitude in the range from 200 to 700 V
but keeping the pulse duration constant and equal
to 0.8 ls; every increase of trimming voltage causes
increase in electrical energy and the value of resistance
increases as well. Larger electrical energy is necessary
Discharge
Circuit of HVCapacitor
2. Test sample fabrication and trimming
Test samples with five one-square resistive structures
(0.5 · 0.5 or 1 · 1 mm2) have been used for trimming of
thick-film resistors by energy of high voltage pulses and
for most of electrical and stability measurements. A part
of untrimmed and laser trimmed resistors have
0.25 · 0.25 mm2 planar dimensions. Commercial resistor
pastes 100 X/sq and 10 kX/sq as well as Pd–Ag based
thick-film conductors were screen printed on alumina
through 325 mesh stainless screen, then dried and fired
at 850 C in a standard firing profile. The resistance of
as-fired thick-film structures was from the range 400–
500 X/sq for 100 X/sq resistor paste and 7–9 kX/sq for
10 kX/sq one.
The Aurel NAVS-30 laser trimming system with
Nd:YAG laser crystal was used for resistor trimming
353
Sheet
resistor
Nanosecond
Switch
microcontroller
Ohm -Meter
Trimming
Data
Base
HV-Relay
Fig. 1. Concept of high voltage discharge trimming and
measuring system.
A. Dziedzic et al. / Microelectronics Reliability 46 (2006) 352–359
for high ohmic resistors trimming. Therefore during
trimming of 10 kX/sq resistors the 900 V voltage was
kept constant but the duration of discharge time changed in the range from 5 to 70 ls. Increasing of pulse
width means increase of electrical energy, which affects
the resistance of the tested component. This means that
the level of resistance changes after HV trimming was
dependent on the strength of electric field in the case
of low resistive components or the pulse duration in
the case of high resistive ones.
One should note, that in all of these investigations the
resistors were unglazed, because we wanted to investigate the microstructures before and after trimming.
LTCC resistors were buried in DP 951 Du Pont green
tape. The 2 · 1, 1 · 1 or 1 · 2 mm2 resistors with Aubased terminations were made from three different resistor ink systems with sheet resistance from 10 X/sq to
10 kX/sq and fabricated according to tape manufacturer
recommendation. Part of these resistors were subjected
to high voltage pulse trimming (the trimming conditions
were similar as for surface resistors). The trim target for
these components was a resistance change of about 25%.
0
o
162 C
o
207 C
o
253 C
-4
∆R/Ro [%]
354
-8
-12
-16 100 ohm/sq.
-20
0
S2 - 1x1 mm2
S3 - 1x1 mm2
S5 - 1x1 mm2
S10 - 0.5x0.5mm2
100
200 300
2
S11 - 0.5x0.5mm
S13 - 0.5x0.5mm2
400 500
t [h]
600
700
Fig. 2. Long-term stability of high voltage discharge trimmed
100 X/sq thick-film resistors (changes of resistance in trimming
process: S2; +12.1%, S3; +6.0%, S5; +18.0%, S10; +3.1%, S11;
+10.5%, S13; +19.0%).
high voltage pulse trimmed (HV)
162 °C
0
3. Long-term thermal ageing
207 °C
-1
253 °C
-2
∆R/ Ro [%]
Most often long-term thermal stability of thick-film
resistors is characterized by the drift of resistance. Usually such a drift is characteristic for particular resistor
systems, is dependent on ageing temperature and time
and also on trimming method. But there are contradictory information about long-term thermal stability of
high voltage trimmed resistors. Very good properties
were reported in [7,8,11] but data presented in [10] have
shown that 1 h keeping at 300 C created 3% relative
resistance changes for pulse voltage trimmed samples
and only about 0.1% for untrimmed ones. Investigations
described in [14] have shown that long-term stability of
HV exposed structures deteriorates with increase of
number of pulses and is somewhat worse in comparison
with laser trimmed or untrimmed ones. Similar conclusions were presented in [12].
Herewith we reported comparison of resistance drift
induced by long-term thermal ageing at three different
temperatures 162 C, 207 C and 253 C. The samples
were kept at every temperature for about 200 hours.
The relative resistance changes of high voltage discharge
trimmed resistors are shown in Figs. 2 and 3. Long-term
stability of untrimmed and laser-trimmed resistors is
presented in Fig. 4.
It is shown that untrimmed and laser-trimmed resistors are much more stable than voltage pulsed ones by
extreme temperature stress. Untrimmed resistors exhibit
resistance increase at all temperature levels. This increase is larger at the beginning of every temperature
step but even after keeping the samples at 253 C it does
-3 10 kohm/sq.
S2 - 1x1 mm2
S3 - 1x1 mm2
S5 - 1x1 mm2
S10 - 0.5x0.5 mm2
S12 - 0.5x0.5 mm2
S13 - 0.5x0.5 mm2
-4
-5
-6
0
100
200
300 400
t [h]
500
600
700
Fig. 3. Long-term stability of high voltage discharge trimmed
10 kX/sq thick-film resistors (changes of resistance in trimming
process: S2; 13.0%, S3; 10.3%, S5; 5.4%, S10; 3.8%,
S12; 10.5%, S13; 13.6%).
not exceed 1%. Very small laser trimmed resistors
(0.25 · 0.25 mm2) have negative resistance drift after
keeping at 207 C and 253 C but still within the range
of ±1%. Resistors trimmed by energy of high voltage
pulses show decidedly larger negative drift of resistance.
This drift is much higher for unglazed 100 X/sq than
10 kX/sq structures and it depends on trimming level.
Resistors with higher trim level are much less stable at
every investigated temperature (but for applications
up to 100 C the HV-pulse trimming method leads to
practically acceptable results [8–11]). Moreover one
should remember that this method is the only trimming
A. Dziedzic et al. / Microelectronics Reliability 46 (2006) 352–359
untrimmed (UN)
laser trimmed (L)
10 kohm/sq.
0.6
0.25x0.25 mm2 (UN)
0.25x0.25 mm2 (L)
1x1 mm 2 (UN)
1x1 mm 2 (L)
0.2
0.0
10 kohm /sq.; 1x1 mm2
1.02
R/R25
0.4
∆R/Ro [%]
1.03
o
untrimmed
laser trimmed
HV trimmed
1.01
1.00
162 C
-0.2
207 oC
253 oC
0.99
-0.4
-150 -100
-50
(a)
-0.6
0
100
355
200
300
400
500
0
50
o
T [ C]
100
150
600
t [h]
possibility for buried resistors. The explanation of this
behaviour could be, that during the thermal ageing up
to 253 C the conductive particles of high voltage trimmed
resistors could crystallize and decrease their resistance
value. More detailed structural investigations are necessary to explain completely such behaviour.
This method is the only trimming possibility for buried resistors. For applications up to 125 C the HV-pulse
trimming method leads to practically good acceptable
results [8–11].
4. Normalized temperature dependence of resistance
Resistance measurements of resistors in a wide temperature range are important for the analysis of conduction process. The temperature characteristics were
measured automatically in the range from 170 C to
130 C. The Keithley 2000 multimeter interfaced to PC
was used for data acquisition and presentation. The
examples of normalized temperature dependence of
resistance are shown in Fig. 5(a) whereas Fig. 5(b) presents differential temperature coefficient of resistance
dR
(TCRdiff ¼ RdT
) versus temperature. The results for
100 X/sq structures are qualitatively similar. In practice
there are no differences between R(T) and TCR(T) characteristics for untrimmed and laser trimmed resistors. It
should be noticed that HV-trimmed resistor has R(T)
curve with minimum of resistance shifted significantly
toward higher temperatures. The second difference appears above 100 C, where instead of expected resistance
increase a noticeable drop of R is observed.
The shift of a minimum on R(T) curve can be explained basing on the model proposed by Kozlowski
[19]. He analysed the changes of the percolation path
caused by appearing microcracks in thick-film resistors.
The occurrence of the microcracks manifests itself as
TCR [ppm/K]
Fig. 4. Long-term stability of untrimmed and laser-trimmed
10 kX/sq thick-film resistors.
2
10 kohm/sq.; 1x1 mm
100
untrimmed
laser trimmed
HV trimmed
0
- 100
- 200
- 300
-150
-100
(b)
-50
0
o
T [ C]
50
100
150
Fig. 5. Comparison of (a) normalized temperature dependence
of resistance, (b) differential temperature coefficient of resistance for untrimmed, laser-trimmed and high voltage-trimmed
10 kX/sq thick-film resistors.
removing of certain bonds, randomly chosen from the
initial critical percolation path. After such an operation
a new percolation path is found and because of slightly
different temperature dependence of a new ‘‘unit cells’’
in the percolation path the changes of the temperature
dependence of resistance are induced. Kozlowski has
shown both numerically and experimentally that the increase in density of microcracks caused a shift of the
resistance minimum to the higher temperatures i.e. in
the same manner as in Fig. 5(a). At this very moment
there is no explanation for the curve bending at about
100 C. However this temperature may be important
from the long-term stability point of view. Fig. 5(b) indicates the possibility of TCR shifting in high value
resistors which can be useful and desirable in some
applications.
5. Low-frequency noise
Current noise index (CNI) is one of the most important parameters of resistors. But the information stored
A. Dziedzic et al. / Microelectronics Reliability 46 (2006) 352–359
CNI ¼ 10ðlogðS ln 10Þ þ 12Þ
ð1Þ
An interesting observation is that the slope of logSV
versus log f plots in Fig. 6(b) increases after the resis-
10 kohm/sq.; 1x1 mm2; HV(-4,71%); before ageing
10
13.73 V
11.16 V
8.59 V
5.15 V
2.59 V
-11
-12
2
S u [V /Hz]
10
10
10
10
-13
-14
-15
1
10
(a)
100
f [H z]
10 kohm /sq.; 1x1 mm2; HV (-4,71%); after ageing
10
2
in its value, sufficient for practical applications, is not
sufficient to identify sources generating the fluctuations.
For these purposes the measurements of power spectral
density are necessary [20, and references therein]. The
standard procedure of such low frequency noise spectroscopy is to examine the product fSV of frequency f
and power spectral density SV of noise voltage. The
common 1/f noise in fSV versus f plots appears as a flat
background, whereas the features are associated with
other kind of noises.
Noise spectra of thick-film resistors usually possess a
typical 1/f shape. Recently it was proven that also polymer thick-film resistors [21] as well as LTCC resistors
both buried and surface [22] show Gaussian 1/f noise
below 1 kHz. There are also papers [e.g. 23,24] where
low-frequency noise measurements are used as a diagnostic tool for thick-film resistor evaluation. Even recently it
was shown that low-frequency noise is more sensitive to
the resistor degradation due to high-voltage pulse stressing than resistance itself [25]. However, this was shown
for the first time and the number of experimental results
is up to date not too large. In this paper we have measured and compared the low-frequency noise of untrimmed, laser trimmed and voltage trimmed 100 X/sq
and 10 kX/sq thick-film resistors with 0.5 · 0.5 mm2
and 1 · 1 mm2 planar dimensions. After the measurements the resistors were thermally aged at 162 C for
170 h and then again subjected to noise measurements.
Noise measurements were carried out by a standard
DC technique. The sample of resistance R was biased
through the ballast wire-wound resistor RB from a DC
source. The noise signal was AC-coupled to the lownoise preamplifier Unipan 233-7 (bandwidth 0.5
Hz–100 kHz). Then it was sent to the HP 35660A digital
signal analyser in which power spectral density SV of
voltage dV was calculated in the frequency range from
2 Hz to 800 Hz for several voltages biasing the sample.
After subtracting the noise background, SV=0 which
was the sum of preamplifier noise and thermal noise, it
has occurred that the spectra have 1/f shape (the line
in log–log plot has a slope of approximately 1) (Fig.
6), Consequently fSV plots depend on frequency rather
weakly (Fig. 7) and so, we use the average h fSViover
the measured frequency range to estimate the frequency
independent noise level. This quantity is still bias dependent. When logh fSVi is displayed versus logV (Fig. 8)
the lines drawn through the data have the slope of
approximately 2. This means that the relation SV V2
holds and the physical origin of the noise are equilibrium resistance fluctuations. The quantitative measure
of such a noise is the ratio S = h fSVi/V2, which is related
to CNI via the relation
Su [V /Hz]
356
10
10
10
10
11.89 V
8.93 V
5.96 V
2.92 V
-10
-11
-12
-13
-14
1
(b)
10
100
f [Hz]
Fig. 6. Power spectral density of ‘‘excess’’ low-frequency noise
for high voltage trimmed 10 kX/sq thick-film resistor: (a) astrimmed (before ageing), (b) after thermal ageing (170 h,
162 C).
tors are thermally aged, and the plots in Fig. 7(b) are
no longer flat. We leave the reasons for this behaviour
for further studies. At this moment we summarize the
effects of long-term thermal ageing on resistance drift
and low frequency noise only on in a quantitative manner. This is done in Table 1. Data for low frequency are
expressed in the terms of both power spectral density
and current noise index. The changes in CNI are also
shown in Fig. 9. It is interesting that the noise index
of as-fired laser or HV-trimmed resistors is not worse
than that of untrimmed resistors. After ageing we observe some insignificant variations of CNI for untrimmed or laser trimmed resistors. For HV-trimmed
resistors, however, ageing process leads to noticeable
increase of noise index. The increase of CNI (S) is larger in case of significantly trimmed structures (it was
shown in Section 3, that HV-trimmed resistors with
higher trim level are much less thermally stable). Let
us note that while ageing the resistance of these
(i.e. HV-trimmed) resistors has decreased by around
0.5–2%.
A. Dziedzic et al. / Microelectronics Reliability 46 (2006) 352–359
2
2
10 kohm/sq.; 1x1 mm ; HV (-4,71%); before ageing
-10
2
f Su [V ]
10
-10
10
-11
B
Linear Fit of Data3_B
###
2
13.73 V
11.16 V
8.59 V
5.15 V
2.59 V
f Su [V ]
10 kohm/sq.; 1x1 mm ; HV (-4,71%); before ageing
10
357
α =1.96
-11
10
10
-12
2
-12
10
1
10
4
6
U p [V]
(a)
100
8
10 12 14
f [Hz]
(a)
2
10 kohm/sq; 1x1 mm ; HV (-4,71%); after ageing
2
10 kohm/sq.; 1x1 mm ; HV (-4,71%); after ageing
2
f Su [V ]
-9
2
-9
10
10
f Su [V ]
11.89 V
8.93 V
5.96 V
2.92 V
-8
10
10
-10
10
-11
α =1.99
-10
10
10
-11
2
4
(b)
1
(b)
10
6
Up [V]
8
10 12 14
100
f [Hz]
Fig. 7. The product of frequency and power spectral density
calculated for the data from Fig. 6(a) and (b).
6. Trim results and stability of buried LTCC resistors
Long-term stability investigations were made after
high-voltage-pulse trimming and after pre-conditioning.
The latter was intended to simulate assembly processes.
Fig. 8. The dependence of averaged product of frequency and
power spectral density on biasing voltage, fS V U aP (data for
high voltage trimmed 10 kX/sq resistors) (a) before (b) after
thermal ageing (170 h,162 C).
It contained 2· reflow soldering and next glob top
curing for 5 h at 150 C.
The final qualification tests are high temperature
storage (1000 h, 125 C) and temperature cycling (1000
cycles from 55 C to 125 C).
Table 1
The effect of trimming method and ageing process on resistance drift and changes of relative power spectral density (S) and current
noise index (CNI)
Dimension (mm2)
Exposure
Untrimmed
Untrimmed
Laser trimmed (+18.85%)
High voltage pulse trimmed (1.9%)
High voltage pulse trimmed (4.2%)
High voltage pulse trimmed (4.7%)
Unaged
Aged
Unaged
Aged
Unaged
Aged
Unaged
Aged
Unaged
Aged
Unaged
Aged
1·1
1·1
1·1
1·1
1·1
1·1
R (kX)
11.476
11.538
12.008
12.045
11.248
11.299
11.510
11.472
10.920
10.801
10.905
10.744
S(f=10 Hz)
CNI (dB)
14
2.88 · 10
4.32 · 1014
1.03 · 1013
8.07 · 1014
2.19 · 1014
1.76 · 1014
3.22 · 1014
6.03 · 1014
4.69 · 1014
2.05 · 1013
3.34 · 1014
5.50 · 1013
11.8
10.0
6.2
7.3
13.0
13.9
11.3
8.6
9.7
3.3
11.2
1.0
358
A. Dziedzic et al. / Microelectronics Reliability 46 (2006) 352–359
.
.
.
.
frequency noise) and stability (relative resistance drift,
changes of current noise index after ageing) properties
of untrimmed, laser trimmed as well as high voltage
trimmed thick film resistors. Moreover they were correlated with additional resistor high temperature ageing
after trimming process. According to our knowledge this
is the first so wide comparison of various trimming method.
During these investigations the following was found:
Fig. 9. Changes of current noise index of 10 kX/sq as a function
of trimming method and ageing process.
After pre-conditioning the first results of trim stability were obtained. Contrary to components on alumina
trimmed buried LTCC resistors drifted always in the
trimming direction i.e. they showed the positive drift if
resistance increased after trimming increase and the negative drift if resistance decreased after this process. One
candidate (A-100) changed values of more than 5%. Two
other pastes, having mean deviations of about 1%, had
one or two group members exceeding this value up to
6%. The control groups showed very low deviations.
Table 2 shows that some of the used resistor systems
are suitable for high voltage trimming. Some of them
(C-10k, B-10k, C-100) have a deviation < 1% after
preconditions and thermal ageing and others (A-10,
A-100, A-1k) have a drift up to 6%. This observation
points out that the trimming stability after thermal ageing is depended on resistor paste.
7. Conclusions
In this paper we presented wide spectrum of electrical
(normalized temperature dependence of resistance, low
• There is distinct difference in long-term thermal stability of investigated components. The drift of
untrimmed and laser trimmed resistors is similar.
But structures trimmed by series of voltage pulses
after extreme temperature stress have stability worse
by about one order of magnitude. The drift is larger
for resistors more trimmed by pulses (having larger
resistance difference before and after trimming).
• The temperature dependences of resistance in a wide
temperature range are similar for untrimmed and
laser trimmed components. However the minimum
of resistance in HV-trimmed resistors is shifted to
the higher temperatures. Moreover unexpected
change of R(T) curve shape appears near 100 C.
• The noise with a typical 1/f shape caused by an equilibrium resistance fluctuations is dominant in the
low frequency range independently of the trimming
method. The initial (i.e. before ageing) noise intensity
is comparable for all resistors made of the same ink
and of identical planar dimensions. After long-term
thermal ageing the current noise index of HV-trimmed
resistors noticeably increases in spite of simultaneous
slight decrease of resistance. The increase of CNI is
larger in case of strongly trimmed structures. On the
other hand the noise level of untrimmed and laser
trimmed resistors does not undergo changes after ageing process (similarly as resistance).
• Trimming of unglazed resistors by energy of high
voltage pulses induces other ageing mechanisms than
those, which are predominant in untrimmed or laser
trimmed resistors, which is essential for high temperature load. Such trimming method is useful in many
standard applications where the temperature of resistors do not exceed 100 C.
Table 2
Long-term stability of LTCC resistors versus applied resistive ink
Paste
Rsq after three
refirings and tolerance
Trim range and direction
of resistance changes
A-10
A-100
C-100
A-1k
B-10k
C-10k
50 X/sq ±50%
40 X/sq ±50%
80 X/sq ±20%
130 X/sq ±20%
2.3 kX/sq ±25%
3 kX/sq ±30%
>25%
>25%
>25%
>25%
<20%
<10%
a
"
"
"
"
#
#
Drift after precond. and direction
of resistance changes after ageinga
Long term stabilitya of untrimmed
resistors after pre-conditioning
typ. 1.3% "(max: 6%)
>5% "
typ. 1% "
typ. 0.7% "(max: 6%)
<1% #
<0.8% #
<0.5% #
<0.5%
<0.3% #
<0.2%
<0.1%
<0.05%
Long term stability estimated after 1000 h exposure at 125 C and subsequent 1000 thermal cycles between 55 C and 125 C.
A. Dziedzic et al. / Microelectronics Reliability 46 (2006) 352–359
• Further stability investigations of overglazed resistors are necessary for the extension of application
range of high voltage trimming method.
• The HV-trimmed buried (hermetic) LTCC resistors
have been exposed to more gentle ageing conditions
but it seems they have better long term stability in
comparison with unglazed thick-film ones made on
alumina substrate. The trimming of commercial
SMD resistors and buried LTCC resistors currently
investigated in more detail.
[12]
[13]
[14]
References
[1] Seager CH, Pike GE. Electrical field induced changes in
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