Strain gage testing: the delta effect of thermal cycle testing
gives a direct method of describing and are not the greatest absolute differences significantly better in all categories of ap-
capturing visually the absolute forces that between two axes. This equation allows plied forces. This is due solely by changing
are interacting upon the solder joint at the one to see the delta effect over time and the component location on the board as
moment in time as it relates to tempera- temperature and thus allow one to have a it relates to adjacent component sets and
ture. A zero value indicates the stresses visual interpretation of multiple forces at their contribution to applying stresses onto
are in balance and moving equally, either work on the solder joint as experienced the board.
in compression or tension. The X and Y during thermal cycling.
maximum force charts should be used in Look at the effect of moving the conclusion: the effect of using y-X
conjunction with the Y-X delta graph to component down .500-inch in the x-axis. delta data (graph c)
determine the axis with the greatest strain The huge change in microstrain is a result Location A has a higher maximum
and what direction these forces are being of being outside the strain pathway, but tension of 851 microstrains and a maxi-
applied to determine strain pathways. In one can still see it has an impact on the mum compression of -701 microstrains as
most cases the maximum and minimum component location because of being near compared to Location B which saw 773 mi-
amplitude peaks on the X and Y graph the strain corridor. New Location A is crostrains in tension and -604 microstrains
Chart A. Chart of raw data spread by Temperature vs. Microstrain by location in the X- and Y-axis.
Time Chamber LOC-A LOC-A LOC B LOC B Time Chamber LOC-A LOC-A LOC B LOC B
Elapsed Temp (˚C) X-Axis Y-Axis X-Axis Y-Axis Elapsed Temp (˚C) X-Axis Y-Axis X-Axis Y-Axis
(µε) (µε) (µε) (µε) (µε) (µε) (µε) (µε)
0:00:00 105 -112 -774 -271 -841 1:10:00 -11 -164 627 -558 156
0:02:00 105 -116 -775 -272 -845 1:12:00 5 -139 587 -545 144
0:04:00 105 -118 -767 -254 -849 1:14:00 18 -113 553 -525 122
0:07:00 105 -110 -781 -232 -851 1:16:00 33 -81 492 -498 90
0:09:00 103 -104 -786 -240 -844 1:18:00 48 -43 415 -461 36
0:11:00 88 -100 -778 -245 -843 1:20:00 61 -18 314 -438 -24
0:13:00 71 -97 -770 -244 -839 1:22:00 66 -31 216 -428 -90
0:15:00 67 -110 -770 -267 -830 1:24:00 73 -34 110 -403 -154
0:17:00 53 -105 -753 -271 -816 1:26:00 79 -5 9 -381 -215
0:19:00 43 -90 -746 -262 -788 1:28:00 85 -1 -85 -379 -268
0:21:00 25 -69 -732 -258 -744 1:30:00 92 -7 -206 -369 -344
0:23:00 20 -51 -706 -260 -698 1:32:00 99 -3 -304 -344 -403
0:25:00 6 -46 -656 -271 -635 1:34:00 105 -12 -405 -330 -460
0:27:00 0 -34 -584 -282 -566 1:36:00 106 -57 -496 -327 -513
0:29:00 -17 -22 -468 -289 -487 1:38:00 106 -75 -571 -323 -552
0:31:00 -32 -15 -325 -304 -399 1:41:00 106 -86 -650 -318 -650
0:33:00 -39 -16 -177 -325 -311 1:44:00 106 -95 -673 -311 -694
0:35:00 -45 -26 -25 -350 -229 1:47:00 106 -80 -698 -283 -723
0:37:00 -46 -43 125 -384 -144 1:50:00 106 -108 -721 -276 -746
0:40:00 -46 -63 297 -428 -44 1:53:00 106 -97 -723 -269 -770
0:43:00 -43 -89 413 -464 25 1:56:00 106 -111 -739 -282 -797
0:46:00 -45 -114 495 -494 75 1:59:00 106 -111 -742 -267 -812
0:49:00 -46 -132 551 -521 118 2:02:00 106 -80 -760 -249 -816
0:52:00 -43 -146 593 -538 140 2:05:00 106 -122 -762 -250 -824
0:55:00 -40 -159 611 -554 155 2:08:00 105 -114 -768 -261 -836
0:58:00 -41 -171 629 -565 165 2:11:00 105 -117 -770 -265 -842
1:01:00 -43 -177 642 -574 175 2:14:00 105 -93 -772 -238 -845
1:04:00 -40 -187 650 -583 181 2:17:00 100 -116 -783 -241 -844
1:06:00 -36 -200 659 -581 192 2:19:00 85 -130 -775 -245 -843
1:08:00 -26 -188 650 -573 174 2:21:00 73 -104 -770 -244 -839
www.globalsmt.net Global SMT & Packaging – February 2009 – 15
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56