WM Cheng,

Changing the orientation of component package likely will
eleminate shorting of leads.  Rotate all TO220 pkg so that the
row of 3-leads hit the solder wave in parallel.  Or you may add a
robbing pad at the trailing end of component pads.

regards
Matthew Park
NII-Norsat International Inc.

>>> WM Cheng <[log in to unmask]> December 9,
1998  8:19 pm >>>
        Dear Technetters,

        Recently one of our customer request us to further
        improve the wave solder ppm (target 200ppm), the major
        defect found is the TO220 package component which
        contribute over 80% of the total failure, the component
        is not preformed and is inserted to the PCB with all the
        three leads lie in straight line parallel to the wave
        soldering direction, the defect symptom is short solder
        between the middle and the last lead.  My question is :

        1. Will shorten the leads help? Current lead extension
        from the bottom of PCB is 2 to 2.5mm .

        2. What hole and land size/pattern should be used? Does
        any IPC standard mention about this?

        3. What is/are the process parameter (wave soldering
        process) contribute the problem and what should be
        changed to improve this?

        Hope someone can help.

        Thanks,
        WM Cheng
        E-mail : [log in to unmask]

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