Jean Paul

I published these data in a seminar about the reliability of solder joints
in Germany at the CEM Neumuenster. The paper is in German so it doesn't
help you too much. The test I did was passive thermal cycling:-20/100°C;
2°C/min; dwell time 30min. I'll fax you a graph where the average crack
length in percent of the wetted solder length in the solder joints of a QFP
160 leads of alloy 42 after 2000 cycles is shown for some PCB materials. To
avoid more E-mail send in order to fax the graph to various people I
include the data in this mail.
In the example, the cracks perpendicular to the main direction of the
fibres where longer than those in the main direction despite the fact that
the components body is made of plastic.

Aramide 1 = Kevlar reinforced Epoxy, leads in the main direction of the fibres
Aramide 2 = Kevlar reinforced Epoxy, leads perpendicular to the main
direction of the fibres

                   PCB Material I FR 4 I CEM 1 I Aramide 1 I Aramide 2 I
Average crack length in percent I 8    I  20   I    41     I    100    I

Best regards

Guenter Grossmann


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