Author's personal copy
Cryogenics 48 (2008) 497–510
Contents lists available at ScienceDirect
Cryogenics
journal homepage: www.elsevier.com/locate/cryogenics
Measurement of mechanical properties of electronic materials at temperatures
down to 4.2 K
M. Fink a,*, Th. Fabing a, M. Scheerer a, E. Semerad a, B. Dunn b
a
b
ARC Seibersdorf Research GmbH, 2444 Seibersdorf, Austria
ESA/ESTEC, 2200 AG Noordwijk, The Netherlands
a r t i c l e
i n f o
Article history:
Received 30 October 2007
Received in revised form 25 June 2008
Accepted 16 July 2008
Keywords:
Solder
PCB
Conformal coating
Material characterisation
Tensile test
a b s t r a c t
Operating temperatures of spacecraft components in the ‘subzero’ range are encountered during solar
eclipse periods or when voyaging on deep-space missions. Moreover some spacecraft instruments or
parts of them, e.g. sensors, have to be cooled to obtain an improved performance, e.g. in spacecraft missions like the infrared space observatory (ISO) and CryoSat. Materials utilized in the assembly of electronic circuits can be subjected to mechanical loading at cryogenic temperatures. [Semerad E, Scholze
P, Schmidt M, Wendrinsky W. Effect of new cleaning liquids on electronic materials and parts. ESA metallurgy report no. 3275; January 2002, [1]].
Within the present work the mechanical properties of electronic materials at cryogenic temperatures
down to liquid helium temperature were analysed. Specifically the tensile properties of solders
(63Sn37Pb,
62Sn36Pb2Ag,
60Sn40Pb,
96Sn4Ag,
50In50Pb,
70Pb30In,
96.8Pb1.5Ag1.7Sn,
96.5Sn3Ag0.5Cu), PC boards (MLB polyimide glass fibre, MLB epoxy glass fibre, MLB Thermount), conformal coatings (Arathane 5750, Sylgard 184, Scotchcast 280, Solithane 113, CV-1144-0, Mapsil 213, Conathane EN4/EN11) as well as OFE Cu were characterised at room temperature, at liquid nitrogen and at
liquid helium temperature by tensile tests.
The fracture surface of tested samples was examined by means of optical microscope and if necessary
with scanning electron microscope.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
The objective of the present work was to check the reliability of
OFE Cu, solders, PC boards, and conformal coatings at low operating temperatures.
Specifically the temperature dependence from room temperature (RT) down to 4.2 K (LHe) of following materials properties
was characterised
Young’s modulus.
Proof stress.
Elongation at rupture.
Ultimate tensile strength.
OFE copper was delivered from Goodfellow GmbH [12] in form
of an as drawn rod (diameter: 12.7 mm, length: 1000 mm, purity:
better than 99.95%). The rod was cut into pieces of about 80 mm.
These specimens were machined according to ASTM-E8. The round
tensile specimen had a reduced length of 30 mm with a diameter
* Corresponding author. Tel.: +43 505503384; fax: +43 505503366.
E-mail address: markus.fi[email protected] (M. Fink).
0011-2275/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.cryogenics.2008.07.006
of 5 mm and threaded ends of M9x1.5. The single specimens were
taken arbitrarily for the tests at room temperature, at LN2- and at
LHe temperature.
The solders (except of 96.5Sn3Ag0.5Cu) delivered from JL Goslar
GmbH had a length of about 400 mm and a triangle profile. To get
samples having the same geometry like the OFE copper specimens,
the raw solder bars had to be melt to a rod with a length of at least
70 mm. The raw solder materials were squeezed to a roughly
round form that fits in glass tubes with an inner diameter of
10 mm and a length of 100 mm. To avoid hollows in the casted solder rods and to get comparable results with previous investigations [2,3], the melting process took place under vacuum (10E-2
mbar) at casting temperatures shown in Table 1. The melting temperatures of the solders are also given in this table. The parameters
for casting were chosen in accordance to previous investigations
[2] and [3] to ensure comparable results. In Fig. 1 a typical solder
rod after casting is shown.
The cast rods were cleaned, identified as well as end trimmed
and machined according to ASTM-E8. The round tensile test
specimens had a reduced length of 30 mm with a diameter of
5 mm and threaded ends of M9x1.5 like the OFE Cu samples.
The solder 96.5Sn3Ag0.5Cu was delivered in form of a bar
(48 4 2 cm3). From this bar the round tensile test samples
Author's personal copy
498
M. Fink et al. / Cryogenics 48 (2008) 497–510
Table 1
Solder
Melting range (°C)
Solid
63Sn37Pb
62Sn36Pb2Ag
60Sn40Pb
96Sn4Ag
50In50Pb
70Pb30In
96.8Pbl.5Agl.7Sn
96.5Sn3Ag0.5Cu
Casting temperature (°C)
Liquid
183
183
240
180
190
240
183
190
240
221
221
240
180
209
240
220
255
270
304
310
340
Tested in as-received condition!
Fig. 3. Taped PCB samples.
Fig. 1. Vacuum casted solder rod.
could be cut directly. Thus, a direct comparison of the measured
values of 96.5Sn3Ag0.5Cu with the other solders should be regarded carefully. In Fig. 2 a solder tensile test specimen is shown.
The tensile specimens were checked by means of ultrasonic inspection. Samples with any hollows were rejected.
The PCB’s were delivered from GPV Printca A/S. The dimensions
of all specimens were nearly identical, i.e. approx. 200 mm in
length, 20 mm in width and 1.6 mm in thickness. The core material
is 0.2 mm thick. It is pressed into a 1.6 mm sandwich (due to a real
board contain several layers). For clamping in the specimen holder
the thickness of the samples should be about 8 mm. Due to the
thickness of the samples of 1.6 mm and to assure that they are
not harmed when clamping them, their ends were taped with a
40 mm long glass fibre reinforced polymer. In Fig. 3 a sample of
every PCB material prepared for tensile test is shown.
The conformal coatings consisted of three silicones, three polyurethanes and one epoxy system, which where evaluated for
spacecraft applications in previous technical notes [4]. These conformal coatings have either an extensive usage in the fabrication
of spacecraft or are expected to pass the ESA requirements for outgassing, offgassing, toxicity and flammability. The materials delivered from ESA had a form of 20 20 cm2.
Fig. 2. Solder tensile test specimen.
Fig. 4. Conformal Coating tensile test specimen.
The samples had to be trumped by means of a special formed cutter. A photo of a Solithane 113 tensile specimen is shown in Fig. 4.
Before clamping the specimens in the sample holder, they were
taped with spare material of Solithane 113 to assure that they are
not harmed when clamping.
2. Experimental details
The tests included
Ultrasonic Inspection of the samples.
Tensile tests at room temperature as well as at cryogenic temperatures down to 4.2 K.
Visual inspection and surface analysis by optical microscope and
scanning electron microscope (SEM).
Before tensile tests started, all samples were checked with
ultrasonic inspection which was done by means of a automated
scanning ultrasonic testing facility type panametrics multiscan
with an immersion tank using a 20 MHz focused immersion transducer type: V317/188237 with a focal length of 28 mm in impulseecho mode. For scanning the transducer was placed 23 mm above
the surface of the sample – that means the focal point of the transducer was adjusted to the axis of the sample. The samples were rotated around their axis and the transducer was moved along the
axis giving a rectangular winding-up c-scan of the whole cylindrical part of the sample. To prove the detectable pore size, holes of
different diameters were drilled in the samples and the pre-damaged samples were inspected. Defects > 0.4 mm could be detected.
Samples with any failure larger than the minimum detectable size
were rejected.
The test campaigns were carried out on a class I universal testing machine. The load cells and the extensometers have been calibrated on site by the certified calibration service of Messphysik
Laborgeräte GmbH/Austria based on standards issued by BEF, the
supreme Austrian authority for standards and calibration. The calibration certificates state accuracies of ±0.5% of the selected load
Author's personal copy
M. Fink et al. / Cryogenics 48 (2008) 497–510
499
Fig. 5. Arrangement for tensile testing at 4.2 K in LHe featuring the 4 column testing machine, the LHe – cryostat containing the specimen (black cylindrical object).
range, ±0.005 mm of the machines stroke indicator and ±0.5% of
the extensometers gauge length.
Tests were performed with a constant cross-head speed of
1 mm/min and a tensile preload of 10–20 N. The extensometer
was calibrated and ‘‘zeroed” at preload level prior of each test.
The mechanical properties calculated after completion of each test
were based on the recorded signals of the load cell, the cross-head
position sensor and the extensometer. Measurements at room
temperature were performed with a video extensometer.
Tensile tests at 77 K (LN2 temperature) were performed by
means of a liquid nitrogen bath mounted in the tensile test machine. Measurements at cryogenic temperature were made with
a special low temperature extensometer.
Tensile properties at 4.2 K (LHe temperature) were measured by
means of a LHe – cryostat mounted in a mechanical testing machine (Fig. 5). The cryostat is described in detail in [5]. By means
of this experimental setup tensile measurements with a maximum
load of 200 kN at cryogenic temperatures down to 4.2 K can be per-
Fig. 6. Stress/strain diagram as recorded by means of a PC.
Fig. 7. Solder sample before and after tensile test at 4.2 K.
Author's personal copy
500
M. Fink et al. / Cryogenics 48 (2008) 497–510
3. Test results
At least 3 tensile specimens of each material and each temperature were tested. In Fig. 7 a solder sample, in Fig. 8 a PCB sample,
and in Fig. 9 a conformal coating sample mounted in sample holder
before and after tensile test at 4.2 K are shown.
The data are given in Tables 2–20. In Figs. 10–13 the average
values of the temperature dependence of Young’s modulus E, ultimate tensile strength Rm, proof stress Rp0.2, and elongation at
rupture A are plotted. An exception is the elongation at rupture
of OFE Cu at room temperature (Fig. 13). Due to fracture outside
of the extensometer of Test Nos. 24 and 26, it is expected that only
the elongation of test 147 is a valid factor. So, this value is shown in
Fig. 13. For this reason the A-values of Test Nos. 24 and 26 in Table
2 are marked with a red exclamation mark.
Before each tensile test, the samples were measured by means
of a micrometer screw (accuracy: +/ 0.01 mm). Applying the low
Table 2
OFE Cu
E (kN/
mm2)
Fmax (N)
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
RT
24
1-1
26
1-3
147
1-7
Average
Standard
deviation
108.024
109.649
108.284
108.652
0.873
7287.6
7317.0
7528.0
7377.530
131.138
388.00
381.80
389.61
386.470
4.124
386.79
381.03
388.14
385.320
3.776
0.255
0.453
15.876
5.528
8.962
77 K
50
1-4
51
1-5
52
1-6
Average
Standard
deviation
123.700
121.900
124.600
123.400
1.375
9939.0
9872.0
98200
9877.000
59.657
508.20
515.00
5124.0
511.867
3.431
456.50
464.20
452.90
457.867
5.773
16.750
11.760
12.330
13.613
2.731
4.2 K
18
1-1
19
1-2
82
1-3
Average
Standard
deviation
137.200
129.500
127.200
131.300
5237
9472.0
9315.0
11259.0
10015.333
1079.904
490.20
488.00
582.70
520.300
54.051
298.70
307.90
494.30
366.967
110.370
24.850
28.340
44.760
32.650
10.632
ChNo
E (kN/
mm2)
Fmax (N)
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
RT
32
2–3
34
2–5
35
2–6
Average
Standard
deviation
16.120
18.997
20.584
18.567
2.263
562.0
559.4
553.3
558.233
4.466
28.74
28.60
28.29
28.543
0.230
27.38
27.75
27.56
27.563
0.185
73.741
57.628
24.650
52.006
25.024
77 K
56
2–7
57
2–8
58
2–9
Average
Standard
deviation
38.820
35.970
38.930
37.907
1.678
2210.0
2179.0
1923.0
2104.000
157.515
115.80
113.30
101.60
110.233
7.580
87.85
83.08
93.36
88.030
5.151
1.083
1.189
0.408
0.893
0.424
4.2 K
21
2–1
23
2–3
87
2–5
Average
Standard
deviation
43.820
41.440
43.410
42.890
1.272
2698.0
2753.0
2497.0
2649.333
134.760
138.00
140.80
129.00
135.933
6.165
122.10
111.50
115.10
116.233
5.390
0.262
0.413
0.267
0.314
0.086
Test
no.
Fig. 8. PCB sample before and after tensile test at 4.2 K.
ChNo
Table 3
63Sn 37Pb
Test
no.
Fig. 9. Conformal Coating sample before and after tensile test at 4.2 K.
formed. A special top loading mechanism enables a quick change of
the samples. Therefore, no heating up of the cryostat between the
tests is warranted and so, the cooling down time of specimen is
less than 2 h (big samples, like PCB’s) and less than 1 h (smaller
samples, like OFE copper, solders and conformal coatings).
During each tensile test a stress/strain diagram is plotted, from
which the tensile properties were evaluated. Fig. 6 shows a typical
one.
Author's personal copy
501
M. Fink et al. / Cryogenics 48 (2008) 497–510
Table 4
62Sn 36Pb 2Ag
Table 6
96Sn 4Ag
ChNo
E (kN/
mm2)
Fmax (N)
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
RT
15
3-1
16
3-2
17
3-3
Average
Standard
deviation
38.517
39.164
32.640
36.774
3.594
838.5
853.9
798.4
830.267
28.651
43.05
43.84
41.00
42.630
1.466
40.69
42.30
39.30
40.763
1.501
8.142
5.871
10.340
8.118
2.235
77 K
38
3-4
39
3-5
40
3-6
Average
Standard
deviation
41.230
38.560
38.830
39.540
1.470
2065.0
2067.0
2186.0
2106.000
69.289
105.60
105.70
112.20
107.833
3.782
80.67
83.77
87.64
84.027
3.492
4.2 K
24
3-1
25
3-2
26
3-3
Average
Standard
deviation
39.650
38.630
30.840
36.373
4.819
3187.0
2598.0
2815.0
2833.667
297.880
164.90
134.40
145.10
148.133
15.475
109.00
120.10
106.60
111.900
7.202
Test
no.
E (kN/
mm2)
Fmax (N)
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
RT
67
5-7
69
5-9
151
5-10
Average
Standard
deviation
58.346
57.020
66.432
60.599
5.095
590.6
656.2
636.0
627.590
33.593
30.94
33.83
32.52
32.430
1.447
18.97
32.51
26.73
26.070
6.794
29.830
2.011
44.326
25.389
21.504
1.024
0.522
0.682
0.743
0.256
77 K
59
5-1
60
5-2
61
5-3
Average
Standard
deviation
33.420
35.550
34.280
34.417
1.072
1477.0
1455.0
1346.0
1426.000
70.150
76.43
75.33
70.23
73.997
3.308
50.37
60.05
62.48
57.633
6.406
0.912
0.507
0.295
0.571
0.313
0.507
0.388
0.774
0.556
0.198
4.2 K
16
5-2
38
5-5
44
5-6
Average
Standard
deviation
46.480
42.380
42.600
43.820
2.306
1615.0
1563.0
1609.0
1595.667
28.449
84.24
79.61
82.27
82.040
2.324
n.a.
n.a.
n.a.
0.100
0.011
0.056
0.056
0.045
E (kN/
mm2)
Fmax (N)
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
Table 5
60Sn 40Pb
Test
no.
ChNo
Table 7
50In 50Pb
ChNo
E (kN/
mm2)
Fmax (N)
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
RT
21
4-1
22
4-2
23
4-3
Average
Standard
deviation
25.050
25.980
25.690
25.573
0.476
832.3
820.4
807.3
820.000
12.505
42.73
42.46
41.78
42.323
0.490
39.61
39.73
38.99
39.443
0.397
11.530
15.180
21.590
16.110
5.093
RT
12
6-1
14
6-3
87
6-11
Average
Standard
deviation
7.361
7.860
6.197
7.139
0.853
635.3
639.3
556.4
610.333
46.750
33.69
33.08
28.91
31.893
2.602
21.03
22.61
19.48
21.040
1.585
8.869
8.837
9.319
9.008
0.270
77 K
47
4-4
48
4-5
49
4-6
Average
Standard
deviation
42.770
40.470
38.070
40.437
2.350
2030.0
2100.0
1908.0
2012.667
97.167
105.10
109.10
99.14
104.447
5.012
75.68
74.62
81.09
77.130
3.470
1.377
2.263
1.050
1.563
0.628
77 K
42
6-7
43
6-8
153
6-12
Average
Standard
deviation
11.590
10.320
14.524
12.145
2.156
1145.0
1126.0
1142.4
1137.800
10.301
58.76
58.29
59.89
58.980
0.822
34.05
31.96
33.40
33.137
1.070
25.150
34.070
41.100
33.440
7.994
4.2 K
28
4-2
29
4-3
88
4-4
Average
Standard
deviation
42.500
42.730
44.560
43.263
1.129
2708.0
2735.0
2697.0
2713.333
19.553
143.60
144.40
139.00
142.333
2.914
119.70
108.70
115.70
114.700
5.568
0.529
0.773
0.882
0.728
0.181
4.2 K
31
6-1
33
6-3
85
6-5
Average
Standard
deviation
14.440
14.720
13.400
14.187
0.696
1329.0
1331.0
1735.0
1465.000
233.829
69.07
70.00
88.38
75.817
10.890
37.77
39.80
21.41
32.993
10.083
26.720
22.950
12.730
20.800
7.239
Test
no.
of error propagation a deviation of the measurements of +/ 5% is
roughly estimated.
The Young’s modulus of OFE Cu is superior to all other tested
materials. For the conformal coatings the lowest values were
found.
The temperature dependence of the elastic modulus is for all
tested PCB’s the same. The Young’s modulus increases at lower
temperatures. PCB 2301 MLB epoxy glass fibre has the highest
Young’s modulus of the PC boards, PCB Thermount the lowest
one at all temperatures investigated.
The Young’s modulus of the conformal coatings increases from a
few thousandth GPa at RT to a few GPa at low temperatures. An
exception is Arathane 5750 as well as Scotchcast 280. Their stiffness is at RT not so low. At 4.2 K the elastic modulus of Solithane
113 is superior to the rest of the tested conformal coatings.
The In-based solders have the lowest elastic modulus of all
tested solders.
Test
no.
ChNo
OFE Cu- and PCB-values of the ultimate tensile strength are superior to all tested solders and conformal coatings. The Sn-based solders show relative high Rm-values, accept of the Ag-doted
materials, their strength is in the range of 50In50Pb. 96.5Sn3Ag0.5Cu is an exception, probably due to the Cu-content.
At RT and at 77 K (=LN2) the strength of PCB 2301 MLB epoxy
glass fibre is the highest one of the tested PC boards, at 4.2 K PCB
2302 MLB polyimide glass fibre shows the highest ultimate tensile
strength of the 3 PCB’s. The tensile strength of PCB Thermount is at
all temperatures investigated the lowest one compared with the
other 2 PCB’s.
The temperature dependence of the tensile strength of Arathane
5750, Sylgard 284, Scotchcast 280, Solithane 113 and Conathane
EN4/EN11 shows a maximum at 77 K and a minimum at RT. This
devolution is in high gear with Conathane EN4/EN11 and not so
strong with Sylgard 184. The strength of CV-1144-0 and Mapsil
213 increases clearly at 4.2 K. For low temperatures the strength
Author's personal copy
502
M. Fink et al. / Cryogenics 48 (2008) 497–510
Table 8
70Pb 30In
Table 10
96.5Sn 3Ag 0.5Cu
ChNo
E (kN/
mm2)
Fmax (N)
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
RT
71
7-4
72
7-5
88
7-7
Average
Standard
deviation
12.170
11.063
12.663
11.965
0.819
508.0
431.0
473.0
470.667
38.553
26.29
22.30
23.99
24.193
2.003
21.50
n.a.
19.98
20.740
1.075
3.502
0.171
4.654
2.776
2.328
77 K
62
7-1
63
7-2
73
7-6
Average
Standard
deviation
20.110
19.450
17.580
19.047
1.312
528.8
727.8
865.8
707.467
169.418
27.15
37.67
44.99
36.603
8.968
21.10
26.66
25.89
24.550
3.012
4.2 K
34
7-1
35
7-2
43
7-4
Average
Standard
deviation
11.510
13.560
12.740
12.603
1.032
687.6
856.6
710.8
751.667
91.612
36.02
45.43
36.79
39.413
5.225
ChNo
E (kN/
mm2)
Fmax (N)
RT
18
8-1
20
8-3
154
8-3
Average
Standard
deviation
22.665
18.554
22.490
21.233
2.330
549.6
466.6
606.8
540.987
70.476
77 K
44
8-4
45
8-5
46
8-6
Average
Standard
deviation
37.770
38.910
35.560
37.413
1.703
1033.0
1015.0
1071.0
1039.667
28.589
52.62
52.34
54.98
53.313
1.450
19.18
17.27
16.80
17.750
1.261
11.330
12.060
25.050
16.147
7.719
4.2 K
41
8-2
42
8-3
46
8-4
Average
Standard
deviation
32.150
29.980
30.610
30.913
1.116
1405.0
1643.0
2020.0
1689.333
310.107
71.28
83.34
104.50
86.373
16.816
17.42
19.08
17.47
17.990
0.944
16.080
17.030
16.660
16.590
0.479
Test
no.
E (kN/
mm2)
Fmax (N)
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
RT
89
19-7
148
19-8
149
19-9
Average
Standard
deviation
15.484
15.207
14.626
15.106
0.438
564.2
594.1
656.3
604.837
46.962
29.20
20.38
33.29
27.623
6.598
25.92
25.35
28.51
26.593
1.684
48.270
46.875
42.245
45.797
3.154
4.531
7.130
27.060
12.907
12.326
77 K
53
19-4
54
19-5
55
19-6
Average
Standard
deviation
34.960
34.700
29.020
32.893
3.357
2440.0
2126.0
2672.0
2412.667
274.024
128.30
110.50
138.30
125.700
14.081
92.97
84.76
88.68
88.803
4.106
0.711
0.535
0.916
0.721
0.191
30.63
35.75
35.08
33.820
2.783
6.407
6.715
0.423
4.515
3.547
4.2 K
12
19-1
13
19-2
83
19-5
Average
Standard
deviation
41.770
39.730
41.590
41.030
1.129
1951.0
2892.0
3156.0
2666.333
633.404
99.36
146.10
160.70
135.387
32.043
n.a.
132.50
151.20
141.850
13.223
0.012
0.314
0.218
0.181
0.154
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
28.21
23.95
31.40
27.853
3.738
20.53
12.10
22.87
18.500
5.665
34.610
39.310
23.716
32.545
7.999
Table 9
96.8Pb 1.5Ag 1.7Sn
Test
no.
Test
no.
Table 11
PCB 2302 MLB polyimide glass fibre
Test
no.
of Solithane 113 is superior to the other conformal coatings and it
is in the range of the values found for most solders.
The proof stress of OFE Cu is superior to all other materials
tested. The Sn-based solders show similar temperature dependence. The proof stress of 96Sn4Ag was not detectable at 4.2 K because of its peculiar stress/strain diagram. The proof stress at low
temperatures, particularly at 4.2 K, of 96.5Sn3Ag0.5Cu is superior
to the rest of the solders.
The proof stress of PCB 2302 MLB polyimide glass fibre is the
same for RT and low temperatures, PCB 2301 MLB epoxy glass fibre
has the highest proof stress of the three tested PCB’s, particularly at
4.2 K. The proof stress of PCB Thermount is in the range of PCB
2302 MLB polyimide glass fibre.
The proof stress at room temperature is very low (between 0.1
and 1 MPa) for all conformal coatings tested. It has a clear maximum value at 77 K (between 41 and 83 MPa). The values found
ChNo
RT
1
4
142
Ch-No
E (kN/
mm2)
Fmax (N)
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
PCB 9/1
PCB 9/3
PCB 9/
10
23.510
22.960
22.614
8682.0
8268.0
8243.1
242.30
223.90
216.02
159.00
154.20
168.14
0.642
0.549
0.416
23.028
0.452
8397.700
246.526
227.407
13.486
160.447
7.082
0.536
0.114
25.940
25.860
25.878
15458.0
15732.0
15381.0
397.80
403.40
392.52
154.10
160.10
166.16
3.719
3.546
2.135
25.893
0.042
15523.667
184.484
397.907
5.441
160.120
6.030
3.133
0.869
30.520
31.490
28.320
30.110
1.624
14910.0
15127.0
16012.0
15349.667
583.769
398.60
413.30
417.20
409.700
9.809
158.30
165.20
158.10
160.533
4.043
1.484
1.350
1.997
1.610
0.342
Average
Standard
deviation
77 K
130
131
159
PCB 9/4
PCB 9/5
PCB 9/63
Average
Standard
deviation
4.2 K
1
PCB 9/7
2
PCB 9/8
3
PCB 9/9
Average
Standard
deviation
at 4.2 K are in between. At 4.2 K the proof stress of Solithane 113
is superior to the rest of the tested conformal coatings.
The elongation at rupture of all Sn-based solders is at low temperatures very low. OFE Cu and the Pb-based solders show a higher
elongation at rupture at cryogenic temperatures.
For the PC boards the elongation is in the range of a few p.c. At
room temperature the elongation of PCB 2301 MLB epoxy glass fibre is superior to the rest of the PCB’s. At low temperatures the
elongation of PCB 2302 MLB polyimide glass fibre is the highest
one of all tested PC boards.
The conformal coatings show very high elongations at RT, at low
temperatures the elongation decreases rapidly. At 77 K Mapsil 213
has the highest elongation, at 4.2 K the elongation of Arathane
5750 is superior to the rest of the conformal coatings.
Author's personal copy
503
M. Fink et al. / Cryogenics 48 (2008) 497–510
Table 12
PCB 2301 MLB epoxy glass fibre
Table 14
Arathane 5750
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
11890.0
11802.0
12403.0
12031.667
324.580
348.00
333.80
367.10
349.633
16.710
223.71
208.10
232.90
221.570
12.538
1.952
1.893
2.033
1.959
0.070
27.270
26.734
22528.0
18943.0
609.10
513.20
302.80
320.40
3.833
2.709
26.149
21359.0
563.70
311.30
1.401
Average
Standard deviation
26.718
0.561
20943.333
1828.289
562.000
47.973
311.500
8.802
2.648
1.217
4.2 K
4
5
11
PCB 10/7
PCB 10/8
PCB 10/
11
33.180
33.400
34.300
14684.0
12842.0
11755.0
398.40
352.40
319.0
304.40
331.00
314.80
0.648
0.315
0.207
Average
Standard deviation
33.627
0.593
13093.667
1480.629
356.600
39.866
316.733
13.405
0.390
0.230
Ch-No
E (kN/
mm2)
Fmax (N)
Rm (N/
mm2)
Rp0.2 (N/
mm2)
A (%)
PCB 11/1
PCB 11/2
PCB 11/3
16.090
17.080
14.870
16.013
1.107
7472.0
7825.0
8039.0
7778.667
286.326
194.70
205.80
207.40
202.633
6.917
187.20
159.90
179.10
175.400
14.021
1.439
1.559
1.670
1.556
0.116
16.210
16.200
16.750
16.387
0.315
7345.0
8553.0
8218.0
8038.667
623.648
178.30
213.20
200.10
197.200
17.630
151.90
n.a.
n.a.
151.900
1.264
1.331
0.934
1.176
0.213
PCB 11/7
PCB 11/8
PCB 11/
11
25.530
22.070
23.090
8791.0
9089.0
9000.0
223.50
225.10
225.70
194.00
193.00
203.80
0.438
0.393
0.326
Average
Standard deviation
23.563
1.778
8960.000
152.974
224.767
1.137
196.933
5.968
0.386
0.056
Test
no.
RT
5
6
7
Average
Standard
77 K
135
138
160
E (kN/
mm2)
Fmax (N)
22.629
23.350
23.818
23.266
0.599
PCB 10/5
PCB 10/
6-1
PCB 10/
6-4
Ch-No
PCB 10/1
PCB 10/2
PCB 10/3
deviation
eB (%)
rM (N/
mm2)
rS0.2 (N/
27.8
23.1
20.3
2.07
1.95
1.71
0.43
0.29
0.39
170.000
146.5000
134.500
3.000
0.000
23.753
3.807
1.910
0.183
0.368
0.074
150.333
18.058
77 K
83
12-5
84
12-6
90
12-7
Average
Standard
deviation
4.160
3.894
4.002
4.019
0.134
1723.0
1493.0
1637.0
1617.667
116.212
132.40
118.80
125.80
125.667
6.801
72.90
64.41
73.90
70.403
5.214
4.197
4.312
3.975
4.161
0.171
4.2 K
49
12-1
56
12-2
67
12-4
Average
Standard
deviation
1.830
1.983
1.786
1.866
0.103
1253.0
1085.0
670.0
1002.667
300.094
98.33
95.07
69.16
87.520
15.984
21.16
18.47
18.67
19.433
1.499
8.018
8.850
8.093
8.320
0.460
E (kN/
mm2)
Fmax (N)
rM (N/
rS0.2 (N/
mm2]
eB (%)
mm2)
RT
110
13-6
111
13-7
112
13-6
Average
Standard
deviation
0.001
0.001
0.001
0.001
0.000
19.4
21.9
19.8
20.370
1.318
2.19
2.54
2.36
2.363
0.175
0.36
0.34
0.27
0.325
0.045
100.400
103.500
102.700
102.200
1.609
77 K
80
13-3
81
13-4
82
13-5
Average
Standard
deviation
3.468
3.018
3.501
3.329
0.270
494.7
474.5
477.4
482.200
10.922
60.66
55.92
55.90
57.493
2.742
58.98
53.53
51.76
54.757
3.763
2.150
2.227
2.224
2.200
0.044
4.2 K
58
13-3
66
13-4
80
13-7
Average
Standard
deviation
2.880
2.221
3.058
2.720
0.441
429.0
499.0
467.0
465.000
35.043
49.57
53.01
53.33
51.970
2.085
20.62
17.70
14.55
17.623
3.036
3.61
4.39
2.07
3.355
1.183
Test
no.
RT
75
76
143
ChNo
E (kN/
mm2)
Fmax (N)
12-2
12-3
1211
3.000
3.000
3.000
Average
Standard
deviation
mm2)
Table 13
PCB Thermount
Test
no.
RT
8
9
10
Average
Standard
77 K
136
137
141
Average
Standard
4.2 K
6
7
8
deviation
PCB 11/4
PCB 11/5
PCB 11/6
deviation
For PCB bare materials and conformal coatings we found the
following:
In Fig. 14 the decomposition of the PCB 2302 MLB polyimide
glass fibre-sandwich in its single layers after tensile test particularly at cryogenic temperatures is shown.
PCB 2301 MLB epoxy glass fibre is by far not so decomposited,
but several cracks are found after tensile tests (Fig. 15). The fracture surface is smooth compared to PCB Thermount and looks similar at all temperatures investigated (Fig. 16).
The specimens of PCB Thermount looks similar to those of PCB
2301 MLB epoxy glass fibre after tensile tests but fewer cracks
were found. At room temperature and at 77 K the singular strings
can be seen in the fracture surfaces. At 4.2 K the fracture is a little
bit smoother, comparable with the fracture surfaces of PCB 2301
MLB epoxy glass fibre. The reason could be that the Young’s modulus of PCB Thermount is at 4.2 K in the range of PCB 2301 MLB
epoxy glass fibre, at RT and 77 K it is clearly lower.
At room temperature the fracture surface of all conformal coatings investigated is very smooth; at low temperatures it is more
Table 15
Sylgard 184
Test
no.
ChNo
and more brittle. In Fig. 17 photos taken with optical microscope
and in Fig. 18a–c SEM pictures of the fracture surface of Solithane
113 after tensile tests performed at room temperature, at 77 K and
at 4.2 K are shown.
For all comparison with data from literature it should be considered that the grain size of the solder influences the flow stress as
outlined in [6].
For OFE Cu and the solders investigated we found in detail:
3.1. OFE copper (after [12]: CV007960)
No thermal treatment was applied, but the variety of the
mechanical properties of drawn wires, rolled foils or galvanic
films should be considered. Aloud [12] the used Cu was
delivered in form of a drawn rod and has a purity of better than
99.95%.
Author's personal copy
504
M. Fink et al. / Cryogenics 48 (2008) 497–510
Table 16
Scotchcast 280
Table 18
CV-1144-0
rS0.2 (N/
mm2)
eB (%)
mm2)
70.7
66.8
57.6
64.997
6.728
10.00
11.02
10.69
10.570
0.520
0.74
0.73
0.83
0.769
0.057
105.500
91.660
93.810
96.990
7.448
4.239
4.053
4.932
4.408
0.463
600.4
597.0
464.1
553.833
77.730
98.46
108.80
113.60
106.953
7.737
81.74
78.02
88.87
82.877
5.514
2.900
3.090
3.198
3.063
0.151
554.1
956.0
503.0
671.033
248.107
64.56
98.59
81.50
81.550
17.015
25.33
26.83
27.39
26.517
1.065
E (kN/
mm2)
Fmax (N)
RT
113
14-4
114
14-5
115
14-6
Average
Standard
deviation
0.199
0.261
0.321
0.260
0.061
77 K
91
14-1
92
14-2
93
14-3
Average
Standard
deviation
4.2 K
51
14-1
69
14-4
81
14-5
Average
Standard
deviation
Test
no.
ChNo
rM (N/
0.39
0.46
0.58
0.477
0.096
0.11
0.12
0.18
0.137
0.038
93.860
106.400
155.100
118.453
32.350
3.050
3.574
2.792
3.139
0.398
398.5
467.8
423.4
429.00
35.104
48.26
53.69
42.70
48.217
5.495
47.49
50.70
41.04
46.410
4.920
1.765
2.026
1.983
1.925
0.140
2.376
2.394
2.754
2.508
0.213
535.9
462.7
1012.0
670.200
298.262
65.96
56.92
126.60
83.160
37.891
24.70
26.17
22.13
24.333
2.045
5.977
4.224
4.747
4.983
0.900
E (kN/
mm2)
Fmax (N)
rM (N/
rS0.2 (N/
mm2)
eB(%)
mm2)
RT
117
16-4
119
16-6
120
16-7
Average
Standard
deviation
0.001
0.001
0.001
0.001
0.000
2.718
3.220
2.659
2.866
0.0308
77 K
99
16-1
100
16-2
101
16-3
Average
Standard
deviation
2.75
2.43
2.72
2.631
0.174
4.2 K
57
16-2
65
16-3
77
16-5
Average
Standard
deviation
ChNo
rM (N/
Table 19
Mapsil 213
eB (%)
Test
no.
ChNo
rM (N/
mm2)
rS0.2(N/
13.5
16.6
14.1
14.703
1.638
1.62
1.73
1.51
1.620
0.110
0.24
0.40
0.31
0.314
0.078
61.420
65.610
54.650
60.560
5.530
RT
121
17-4
122
17-5
156
17-9
Average
Standard
deviation
0.001
0.001
0.001
0.001
0.000
9.8
11.9
7.8
9.833
2.035
1.46
1.76
0.73
1.317
0.530
0.16
0.26
0.21
0.210
0.047
169.300
199.100
82.760
150.387
60.432
4.097
4.102
4.165
4.121
0.038
1386.0
1199.0
1119.0
1234.667
137.027
161.10
146.60
132.20
146.633
14.450
94.54
59.04
61.06
71.547
19.938
5.464
5.793
5.410
5.556
0.207
77 K
102
17-1
103
17-2
104
17-3
Average
Standard
deviation
3.411
3.402
2.918
3.244
0.282
283.9
395.4
307.0
328.767
58.851
43.25
48.59
37.79
43.210
5.400
43.18
45.97
36.38
41.843
4.933
11.100
2.761
14.880
9.580
6.201
4.216
4.459
4.946
4.540
0.372
872.1
1104.0
1389.0
1121.700
258.904
84.31
111.30
100.50
98.703
13.584
41.79
46.85
43.24
43.960
2.606
6.659
6.824
3.333
5.605
1.970
4.2 K
54
17-1
71
17-3
90
17-4
Average
Standard
deviation
3.436
3.605
3.506
3.516
0.085
424.4
677.0
1007.0
702.800
292.156
61.12
70.98
107.00
79.700
24.151
21.57
20.99
20.10
20.887
0.740
2.849
2.950
3.182
2.994
0.171
E (kN/
mm2)
Fmax (N)
RT
116
15-6
127
15-7
128
15-8
Average
Standard
deviation
0.004
0.004
0.004
0.004
0.000
77 K
94
15-1
97
15-4
98
15-5
Average
Standard
deviation
4.2 K
48
15-1
62
15-2
89
15-3
Average
Standard
deviation
ChNo
3.5
4.4
4.9
4.260
0.740
Fmax (N)
Table 17
Solithane 113
Test
no.
rS0.2 (N/
mm2)
eB (%)
mm2)
E (kN/
mm2)
Test
no.
mm2)
The ultimate tensile strength continually increases at lower
temperature which is in good comparison with [13]; the proof
stress remains approximately constant with temperature with a
maximum value at 77 K. The values of the proof stress measured
at room temperature and at 77 K are in good comparison with
[13], the value measured at 4.2 K is lower. At room temperature,
we have only one valid value of the elongation at rupture. As mentioned above, fracture outside of the extensometer occurred during
Test Nos. 24 and 26. Thus, it is expected that only the elongation of
Test No. 147 is valid. The measured value of 15.9% is somewhat
lower compared with [13] and somewhat higher compared with
[3]. The elastic modulus measured at room temperature
(109 GPa) is lower compared with [3] (154.7 GPa). The E-Modulus
measured at 77 K (123.4 GPa) is also lower than the value measured in [3] (158.6 GPa). The E-Modulus measured at 4.2 K
(131.3 GPa) is higher compared with [3] (109.5 GPa). It has to be
considered that with pure Cu a continuous increase of the Young’s
Modulus with decreasing temperature is expected. The strength
and elasticity is superior to all solders at all temperatures. The
material shows ductile behaviour down to 4.2 K, the measured
elongation even increases at low temperatures.
3.2. 63Sn37Pb (inspection certificate: DIN 50049/EN 10204-3.1)
There is an increase of the ultimate tensile strength, the Young’s
modulus and the stress at the limit of proportionality at low temperatures. The temperature dependence of these values is in good
comparison with previous investigations [2,3].
At 4.2 K and 77 K the solder is brittle, with low elongation. For
high temperatures the highest ductility of all tested solders was
found. Also a large reduction in the cross sectional area was found
at RT.
Author's personal copy
M. Fink et al. / Cryogenics 48 (2008) 497–510
505
Table 20
Conathane EN4/EN11
E (kN/
mm2)
Fmax (N)
rM (N/
mm2)
rS0.2 (N/
mm2)
eB(%)
RT
124
18-4
125
18-5
126
18-6
Average
Standard
deviation
0.003
0.003
0.003
0.003
0.000
22.6
16.9
13.7
17.749
4.485
2.88
2.37
2.07
2.440
0.410
0.49
0.36
0.42
0.423
0.065
259.400
184.200
161.400
201.667
51.282
77 K
105
18-1
106
18-2
107
18-3
Average
Standard
deviation
4.100
4.046
3.955
4.034
0.073
894.0
790.4
947.8
877.400
80.002
114.80
114.90
113.70
114.467
0.666
80.91
92.18
69.83
80.973
11.175
5.475
5.505
5.027
5.336
0.268
4.2 K
55
18-1
61
18-2
79
18-3
Average
Standard
deviation
1.708
1.648
1.546
1.634
0.082
794.2
179.9
232.0
402.033
340.624
85.96
18.28
28.60
44.280
36.463
6.74
6.93
7.78
7.148
0.559
6.121
1.459
2.077
3.219
2.532
Test
no.
ChNo
3.3. 62Sn36Pb2Ag (inspection certificate: DIN 50049/EN 10204-3.1)
The silver content improves the strength of the solder with respect to 63Sn37Pb for a little bit. The temperature dependence is
similar to 63Sn37Pb. Also for 4.2 K and 77 K a brittle fracture with
low elongation and for RT dimple fracture with higher elongation
was found.
Compared with data of [3] the values of Young’s modulus
are about the same. Those of the ultimate tensile strength,
the proof stress as well as the total elongation are a little bit
lower.
3.4. 60Sn40Pb (inspection certificate: DIN 50049/EN 10204-3.1)
Generally the tensile properties are similar to those of the eutectic composition 63Sn37Pb. Small elongations and brittle fractures are obtained at 4.2 K and 77 K. At higher temperatures the
solder is ductile with high elongation ratios.
Compared with [7] the proof stress, the ultimate tensile
strength and the elongation at rupture are somewhat lower at
cryogenic temperature. Compared with [8] and [9] the ultimate
tensile strength is somewhat lower at room temperature and same
at cryogenic temperatures. The elongation is lower at cryogenic
temperature; nevertheless this is in good comparison with previous investigations [2,3].
3.5. 96Sn4Ag (inspection certificate: DIN 50049/EN 10204-3.1)
At room temperature the modulus of elasticity is superior to the
rest of the solders. The proof stress is at RT and at 77 K somewhat
lower than the values found for the rest of the Sn-based solders. At
4.2 K no proof stress could be found because of its peculiar stress/
strain diagram.
The fracture of the solder is brittle at low temperatures with
low elongations. At RT the solder is ductile and the fracture shows
a high reduction in area.
3.6. 50In50Pb (inspection certificate: DIN 50049/EN 10204-3.1)
At 4.2 K the solder remains extremely soft with a very
low Young’s modulus and high ductility compared with the other
Fig. 10. Elastic Modulus at room temperature, 77 K and 4.2 K.
solders. The fracture surfaces of this ductile solder are shown in
Fig. 19 (photos taken after tensile test at different temperatures).
3.7. 70Pb30In (inspection certificate: DIN 50049/EN 10204-3.1)
Generally, this solder shows similar strength and elastic properties as the 50Pb 50In solder. The elongation is somewhat lower
compared with the 50Pb 50In solder. The fracture shows a little
reduction area at RT, at low temperatures the fracture is not so
brittle compared with the other tested solders.
Author's personal copy
506
M. Fink et al. / Cryogenics 48 (2008) 497–510
Fig. 11. Ultimate tensile strength at room temperature, 77 K and 4.2 K.
3.8. 96.8Pb1.5Ag1.7Sn (inspection certificate: DIN 50049/EN 102043.1)
Beside the high melting point which makes the solder suitable
for sequential soldering the solder shows interesting mechanical
properties. The stiffness lies in between the Sn-based and In/Pb
solders. The ultimate tensile strength is in the area of the In/Pb sol-
Fig. 12. Proof stress at room temperature, 77 K and 4.2 K.
ders, at 4.2 K somewhat higher. Compared with [10,11] the measured values are lower. The proof stress is the lowest one of all
solders investigated at all temperatures. The elongation is the
highest one beside 50In50Pb at low temperatures. It is in good
comparison with [10,11] at room temperature, at cryogenic temperature the elongation is lower. The fracture shows a high reduction area at RT and at 77 K, at 4.2 K the fracture shows also a
reduction.
Author's personal copy
M. Fink et al. / Cryogenics 48 (2008) 497–510
507
Fig. 14. PCB 2302 MLB polyimide glass fibre - samples after tensile test at room
temperature, 77 K, 4.2 K.
Fig. 15. PCB 2301 MLB epoxy glass fibre - samples after tensile test at room
temperature, 77 K, 4.2 K.
this brittle solder are shown in Fig. 20 (photos taken after tensile
test at different temperatures).
As mentioned above, this solder could be tested in the as-received condition. Thus, a direct comparison of the measured values
with the other solders should be regarded carefully.
4. Conclusions
4.1. Solder alloys
Fig. 13. Elongation at rupture at room temperature, 77 K and 4.2 K.
3.9. 96.5Sn3Ag0.5Cu (inspection certificate: DIN 50049/EN 10204-3.1)
The temperature dependence of the ultimate tensile strength is
similar to the other Sn-based solders, except of 96Sn4Ag. The stress
at the limit of proportionality is superior to the rest of the solders
at 4.2 K. The temperature dependence of the Young’s modulus as
well as of the elongation is similar to 63Sn37Pb. In the cross sectional area a reduction was found. For 4.2 K and 77 K brittle fracture with low elongation were found. The fracture surfaces of
The measurements of the tensile properties of bulk solder depend greatly on conditions of casting (getting pore-free samples).
With decreasing temperature, Sn-based solders show a strong
increase in tensile strength (Rm 135–149 MPa) and proof stress
(Rp0.2 112–142 MPa), they are brittle with small elongations.
Among them 96.5Sn3Ag0.5Cu shows the highest proof stress. For
77 K and 4.2 K this solders are brittle with small elongations
(A 0.2–1.5 p.c.).
Comparing the Cu-content solder with 96Sn4Ag, for room
temperature nearly the same tensile strength and proof stress
are found. The elongation is clearly higher; the Young’s modulus
is clearly lower. For low temperatures the elongation is
nearly the same. The values found for the tensile strength and
Author's personal copy
508
M. Fink et al. / Cryogenics 48 (2008) 497–510
Fig. 16. PCB Thermount fracture surfaces after tensile test at room temperature, 77 K, 4.2 K.
Fig. 17. Fracture surfaces of Solithane 113 - samples after tensile test at room temperature, 77 K, 4.2 K.
the proof stress are clearly higher. The proof stress of 96Sn4Ag at
4.2 K could not be investigated. The Young’s modulus is somewhat
lower.
In/Pb solders remain soft (E 12–14 GPa) and ductile (A 4.5–
20 p.c.) at 4.2 K, but they have low strength (Rm 29–76 MPa) and
low proof stress (Rp0.2 33 MPa).
The Pb-based solder combines medium strength with good
stiffness at superior ductility, but low proof stress.
At room temperature the fracture surface of all investigated
conformal coatings is very smooth with extremely high elongation
(up to 200 p.c. for Conathane EN4/EN11), at low temperatures it is
brittle, the elongation decreases to less than 10 p.c. At 4.2 K the
elongation of Arathane 5750 (8.3 p.c.) is superior to the rest of
the conformal coatings.
4.2. PCB–bare materials
At cryogenic temperatures the proof stress, the elasticity and
the ductility of OFE Cu is superior to all other materials tested.
At 4.2 K the elasticity (E 33 GPa) and the proof stress
(Rp0.2 317 MPa) of PCB 2301 MLB epoxy glass fibre are superior
to the other tested PCB’s. PCB Thermount has the lowest elasticity
and strength, its elongation is at low temperatures the smallest one
of the tested PCB’s.
4.3. Conformal coatings
At cryogenic temperatures all tested conformal coatings show a
strong increase of strength, proof stress and elasticity, their elongation decreases very strong. An exception is Arathane 5750 which
has a high elasticity at all temperatures. The Young’s modulus,
the strength and the proof stress of Solithane 113 is superior to
the other tested conformal coatings.
4.4. OFE copper
4.5. Overall findings
The selection of a solder for use at cryogenic temperatures will
depend on its mechanical properties, fatigue and the specific application like soldering temperature, possible dissolution of Au or Ag
from plated components or wires, etc. The mechanical properties
of the tested solders offer a wide range from stiff and brittle to soft
and ductile materials. The differences in the strength and stiffness
of the solders increase at low temperatures so the mechanical
properties should be considered carefully for the selection of one
material.
The elasticity of all PCB materials is for all temperatures from
the same order of magnitude like the values found for the solders.
Author's personal copy
M. Fink et al. / Cryogenics 48 (2008) 497–510
Fig. 18. Solithane 113 fracture surfaces (SEM).
Strength and proof stress of the PCB materials is always higher
than those of the solders. Generally, at room temperature the elongation of solders is higher than the elongation of PC boards, at 4.2 K
only the elongation of the In/Pb as well as the Pb-based solders is
higher.
For all temperatures the modulus of elasticity, the strength and
the proof stress of PCB materials is higher compared with the
values found for conformal coatings. At all temperatures the
elongation of the conformal coatings is superior to the elongation
509
Fig. 19. Fracture surfaces of ductile solder (50In50Pb) performed with optical
microscope.
of the PCB’s, but the relative differences diminish with respect to
4.2 K.
At 77 K the tensile strength of Solithane 113 exceeds those of
the solders; at 4.2 K it is lower. The stiffness of most conformal
coatings increases relatively to the solders (typically 1/20 at
4.2 K, 1/5000 at room temperature). In combination with the large
thermal expansion of the conformal coating the coating will impose considerable loads to the solder joints and have to be avoided
at cryogenic temperatures. An exception is Arathane 5750, its stiffness is at all temperatures investigated in the same order of magnitude (1.9–4 GPa).
Author's personal copy
510
M. Fink et al. / Cryogenics 48 (2008) 497–510
References
[1] Semerad E, Scholze P, Schmidt M, Wendrinsky W. Effect of new cleaning
liquids on electronic materials and parts. ESA metallurgy report no 3275;
January 2002.
[2] Dunn BD. The properties of near-eutectic tin/lead solder alloys tested between
+70 and 60 °C and the use of such alloys in spacecraft electronics. ESA TM162 1975.
[3] Semerad E, Reithmayr P, Hahn P, Scholze P. Mechanical testing at cryogenic
temperatures. WO 1990;7(July).
[4] Dunn BD, Desplat P. Evaluation of conformal coatings for future spacecraft
applications. ESA SP-1173 1994. August.
[5] Tschegg E, Kubasta E, Steiner W. A top loading 200 kN tensile testing cryostat.
Cryogenics 1979. May.
[6] Rack HJ, Maurin JK. Mechanical properties of const tin-lead solder. J Test
Evaluat 1974;2(5):351–3. September.
[7] Fast RW, Craddock WW, Kobayashi M, Mruzek MT. Electrical and mechanical
properties of lead/tin solders and splices for superconducting cables.
Cryogenics 1988;28(1):7–9.
[8] Metals handbook, vol. 9, American Society for Metals; 1985.
[9] C. Lea. A scientific guide to surface mount technology, Electrochemical
Publications Ltd., 1988 Referenced: M.H. Manko; ‘‘Solders and soldering”.
New York: McGraw-Hill; 1979.
[10] Ainsworth PA. The formation and properties of soft soldered joints. Metals and
Materials 1979:374–9.
[11] Ainsworth PA. Soft Soldering Gold Coated Surfaces, ITRI; 1971. pp. 1–4.
[12] <www.goodfellow.com>.
[13] Material data sheet of ‘‘Deutsches Kupferinstitut e.V., Am Bonneshof 5, D40474 Düsseldorf”: <http://www.kupfer-institut.de/front_frame/pdf/Cu-OFE.
pdf>.
Fig. 20. Fracture surfaces of brittle solder (96.5Sn3Ag0.5Cu) performed with optical
microscope.