Jack,
1.    Qualify the cleaning process to what standard?  That may restrict
what you can or cannot use as a component.
2.    If you will be doing SIR testing, you have to make sure that the
component package HAS NO INTERNAL DIE, or a true mechanical dummy.  Many of
the Practical Components or TopLine dummy components are packages with
blown die, which can mess up SIR.  Both companies do have these true
dummies as available part numbers, but you may have to wait 6-8 weeks if
they have to have them made for you.  If you are doing only cleanliness
testing, such as ROSE or IC, this distinction is irrelevant.
3.    The B-36 board should come with solder mask on four points under the
LCC which should give you a 5 mil standoff.  You can have them made with
thicker solder mask for greater standoff, but your solder volume may need
to be increased, although the B-36 is not used as a solder demonstration
platform.  The PLCC is rather high in standoff.  If you can find a gull
wing with the proper I/O go for it.
4.    The issue of whether the B-36 board is an accurate representation of
product has always been a difficult one.  The standard B-36 has minimal
solder mask and exposed metal, usually bare copper, under the components.
Usually not indicative of actual product.  Who are you trying to convince
with the data?

Doug Pauls
Rockwell Collins




                      Jack Evans
                      <jack.evans@AEROF        To:       [log in to unmask]
                      LEX.COM>                 cc:       (bcc: Douglas O Pauls/CedarRapids/RockwellCollins)
                      Sent by: TechNet         Subject:  [TN] IPC Cleaning Evaluation using B-36 coupons
                      <[log in to unmask]>


                      10/29/2003 10:44
                      AM
                      Please respond to
                      "TechNet E-Mail
                      Forum."; Please
                      respond to Jack
                      Evans






Hello,
I am getting ready to qualify a new cleaning process using IPC B-36 test
coupons and I am looking for suitable components for the test. The board
was designed for the use of a 68 pin LCC or PLCC. The footprint is
about .800 mils inside pad to pad square. The pad length is apx .100 mils.
The problem with the components mentioned above are:
The PLCC from Practical Components has a standoff height of about .020 mils
and the LCC fits tight to the board with no stand off at all. If I use the
LCC I will likely fail the SIR testing because I don't think I can get
under it to clean completely. If I use the PLCC, I will clean it ok, but I
don't feel that it is a practical representation of what we see in
production. I would really like to find a QFP that would fit this footprint
and that I can form to a more realistic standoff height. Does anyone have
any suggestions?

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