Eccobond 45 is a good adhesive for component bonding when used in harsh
environments.
Peter
"D.Terstegge" <[log in to unmask]> 13/07/2002 05:35 AM
Sent by: TechNet <[log in to unmask]>
Please respond to "TechNet E-Mail Forum."; Please respond to "D.Terstegge"
To: [log in to unmask]
cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: Re: [TN] part/pad mismatch
Hi Graham,
It'll probably be impossible to make this thing look like IPC3, and the
next best thing to worry about is the actual strength of the bonding from
the QFP to the board. I thought that perhaps you can achieve the extra
needed adhesion by using some kind of glue underneath the part (or
embedding it completely). Don't know what kind of adhesive would be best
for the job, but thought I'd propose this alternative kind of solution to
your problem.....
Daan Terstegge
http://www.smtinfo.net
----- Original Message -----
From: Graham Collins
To: [log in to unmask]
Sent: Friday, July 12, 2002 8:46 PM
Subject: Re: [TN] part/pad mismatch
Hi Steve
Interesting company! That said, I don't think I could sell this one to my
customer - this is a class 3 high rel vehicle electronics beast, and will
be seeing some serious off-road action. Their mods might stand up to
that, but proving it to my satisfaction would be tough, and my customer
would be more skeptical than I am... I've also talked with Circuit Tech
corp about replacing the pads, theoretically possible but again a tough
sell to the customer.
If I'm "lucky" this won't be a timing sensitive part, and we will end up
dead-bugging and wiring the thing. Ah well, it's only a 72 lead part...
Thanks!
- Graham
regards
Graham Collins
Process Engineer,
Northrop Grumman
Atlantic Facility of Litton Systems Canada
(902) 873-2000 ext 6215
>>> [log in to unmask] 07/12/02 02:52PM >>>
Hi Graham!
You're probably gonna have a heck of a time finding some sort of adaptor
that
will work, but I have another suggestion.
Have you ever heard of Additive Services? Go to:
http://www.additive.com/
They're a company that has a process to make wireless ECO's, meaning that
they can add conductors to printed circuit boards to make design changes
and
you don't have to add jumper wires.
I called them and explained your issue. Basically you need some longer
pads
so you can get a heel fillet on the device when soldered to the PCB. They
told me that it would be no problem. However, they can only work with bare
boards.
He asked me what the quantity would be, and I told him I didn't know.
I talked with a gentleman named Darren Cossette at (603) 889-1999, and
told
him I would give you the information...
If this sounds like something that would work, give him a call...
Hope this helps ;^)
-Steve Gregory-
> Good day Technet! It's Friday and of that I am glad.
>
> I have a new design where a part (a quad flatpack, 50 thou pitch part)
does
> not match the pads on the board. As-is, I can attach it but there will
be
> no heel fillet as the heel overhangs the end of pad by a fair bit.
>
> I have examined and discarded the three obvious options:
> - re-form the part to fit: not a good option due to the fact that I'd
have
> to straighten and then bend the leads in the opposite direction.
> - buy un-formed parts and form to fit - can do, but schedule will be
> totally in the dustbin.
> - re-spin the board to fix the pad layout - again the schedule will be
> totally out the window.
>
> So - that leaves me looking for an adaptor. Can Technetter's advise me
of
> anyone making such beasts on a quick turn basis?
>
> As always, thanks. And a good weekend wish to all.
>
> regards
>
> Graham Collins
> Process Engineer,
> Northrop Grumman
> Atlantic Facility of Litton Systems Canada
> (902) 873-2000 ext 6215
>
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