Hi Ron,
SJs in non-supported holes are by their very design non-robust. Further, by
putting them in CEM-1, a material which not only has a large CTE but which
also swells significantly with the aborption of moisture, you set up the SJs
for significant loading in the direction perpendicular to the PWB.
Problems with SJs with this situation are almost always caused by the design,
lack of strain relief, and/or mishandling. A very similar problem resulting
in windshield wiper failure caused NTSHA to have 2-years worth of SUVs
recalled from one of the Detroit Three.
"Problem #1: The customer's process then requires that the flat cable be
flexed around and under the board in order for the assembly to be connected
to another assembly."---This sure puts unacceptable loading on SJs in
non-supported holes.
"Problem #2: If the unsupported pins (5) are slightly skewed, and if the
assemblers adjust the pins so that they are perpendicular to the edge of the
PCB, over a period of time (3-months) we have experienced a concentric
fracture of the solder fillet."---This sure puts unacceptable loading on SJs
in non-supported holes.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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