Bev, we do a fair amount of PTH components still and we use our pcbs for
several different end products and to accommodate diff't component sizes we
dual what we call "dual footprinting", basically to accommodate 2 diff't
size parts we would actually have 3 holes instead of 2 elongating holes.
One hole would be for pin 1 of either component and depending on the size of
the part it either goes into pin 2 or pin 3, with pins 2 & 3 tied common
with a trace. Just another way of doing it that works well for is. good
luck. Lenny ERG www.ergpower.com
----- Original Message -----
From: "Bev Christian" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, July 16, 2007 10:43 AM
Subject: [TN] Question about rework of paste in hole solder joints
Technetters,
Good morning! We generally do not use PTH parts. As a result, we do
not do wave soldering, but use paste-in-hole or pin-in-paste, chose your
moniker. Because we buy the part in question from two different
suppliers, who make the parts with different dimensions, we have had to
use fairly large, oval holes instead of a more conventional round hole.
And the part leads do not stick out the bottom of the hole either. With
overprinting we have been able to get what is deemed adequate solder
joint strength (and reliability (Yes, I know the difference, Werner.)),
even though the hole fill is not stellar. Wetting angles are good and
proper intermetallics are formed.
Now let's say we do a rework - removing the component, dressing the
hole, inserting a new part and resoldering using hand soldering with
cored wire. The internal debate is whether we should demand hole fill
to meet normal IPC standards or whether we allow the same amount of hole
fill that is allowed for the original paste-in-hole. Opinions and/or
experiences (if you are willing to share the latter :) ) appreciated.
Thanks in advance.
Bev
RIM
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