In regards to the qualification of SIMMs, there are many issues which should
be considered. From a Mechanical perspective, one needs to address the
quality of the printed wiring board itself, plated through holes, plating,
size, thickness, and all other mechanical dimensioning elements.  From an
assembly perspective, one needs to address the robustness of the
manufacturing process. The implication here is what kind of solder joints
are being made, is the design ok with typical "J" Bend DRAMs or Gull Wing
TSOP, is the pad size according to published designed guidelines and is the
manufacturing process in control.  Does the manufacturing operation have the
appropriate controls in place in case something goes bad or awry.  The
reason this is important is that in the manufacturing of SIMMs the volume is
typically high, so any problems will create a multitude of defects which one
cannot afford to have.

>From a product perspective all "data" devices should be from the same
vendor, the "parity" devices if they exists can be from a different vendor
but they should also all be from the same vendor.  This is done for control
purposes, if any failure occurs in the field with any particular supplier,
then one should know which SIMMs to recall.  From a test perspective, the
devices should be qualified for speed; Are they what they are supposed to
be? Initial SIMM designs should be checked in the appropriate systems they
are being designed for, some systems may not work as well parametrically as
other due to speed or rise or fall time, so they should be checked out in
the systes.  Also, initially a thermal cycle test should be done to prove
the reliability of the product to weed out any infant mortalities.

Another issues which also becomes important is where the devices come from,
for example, distributors, manufacturers or whatever.  The reliability of
products acquired from various sources is different and sometimes
uncontrolled. This is where the most of the problems would come from, the
intermixing of devices which no reliability test were initially conducted.

Hope this helps. My background is in the Mechanical and Assembly end of the
business, perhaps some electrical folks can give some of the particulars for
the testing parameters.

Regards,

Leo Lambert
EPTAC Corp.
At 08:04 AM 10/10/96 -0600, [log in to unmask] wrote:
>We have a customer who is seeking information on the qualification of SIMM 
>style printed wiring boards.  Does anyone have suggestions on what type of 
>qualification/reliability testing would be appropriate for this type of 
>qualification.  We have surveyed some of our other customers but have not 
>received much feed-back.
>
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