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December 1998

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Subject:
From:
"McMonagle, Michael R." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 10 Dec 1998 07:37:02 -0600
Content-Type:
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It was difficult to tell from your description which actual direction
the leads are presented to the wave. If they are crossing through the
wave individually (one after the other) with the bridge between the
middle and last lead, adding a 'thieving' or 'robber' pad should
eliminate the problem. This is a solid pad behind your last lead, the
same width as your part pad diameter and about x2 in length. The sole
purpose is to provide an additional area for the solder to 'pull away'
from the last two leads of your device which are shorting. Hopefully you
haven't bought 50,000 fabs already and can convince your design group of
the production cost savings versus the cost of rolling the fab....

Mike McMonagle
PCA Process Engineering Supervisor
K*Tec Electronics
1111 Gillingham Lane
Sugar Land, TX  77478
(281) 243-5639 Phone
(281) 243-5539 Fax
[log in to unmask]

> -----Original Message-----
> From: WM Cheng [SMTP:[log in to unmask]]
> Sent: Wednesday, December 09, 1998 10:19 PM
> To:   [log in to unmask]
> Subject:      [TN] Short solder problem of TO220
>
>         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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