Ralph,
Several years ago, I worked as an engineer for Bendix Engine Controls.
We did a lot of modification as you are describing, for assemblies that
were intended for critical airborne uninhabited applications. The tough part is
clipping the lead while the part is still soldered to the board. Among the
technicians there were 2 camps: those who advocated clipping while the
part was soldered down, and those who advocated removing the part,
discarding it, and putting the lead modification on a fresh part. A great
deal depended upon the skill of the technician. We experienced some
rework failures with both methods. Clipping the lead on the board risked
both lead breakage and frit seal damage, while removal of the part risked
damage to the board, and possibly the surrounding components. Given
good removal equipment, removal of the old part was considered the
more likely method to yield a reliable assembly. This does depend upon
the board technology being used, however, since some boards can not
withstand desoldering operations very well.
Arthur Kahlich
Solliday Engineering Corp.
Phone: (415)621-0616
Email: [log in to unmask]
-----Original Message-----
From: Vaughan, Ralph H [SMTP:[log in to unmask]]
Sent: Monday, June 01, 1998 5:42 AM
To: [log in to unmask]
Subject: [TN] CCA MOD
Hi Guys,
I am looking for some tidbits of info, mainly, I think, from folks in
the component (IC) fab business. We are proposing a mod to a completed
circuit card whereas we need to insert a resistor between a thru-hole
DIP lead and another part. We would like to cut the DIP lead flush to
the board on the component side, bend the lead out about 45 degrees, and
hook and solder the jumper lead to it. (There are reasons we can't get
to the back side of the board). The two concerns are lead breaking and
compromising the hermeticity of the package. I know the glass frit is
pretty tough, so do we have a good safety margin after this mod?
tia (thanks in advance)
Ralph
################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe: SUBSCRIBE TechNet <your full name>
To unsubscribe: SIGNOFF TechNet
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################
|
