The old way of checking was with a front-silvered mirror. Any broken flatbed 
scanner usually has a bunch of 'em, but you can also purchase. The mirror is 
very flat and doubles the error, so it makes the visual easy, but hard to get 
numbers off of, so it's just a quick check for a knowledgeable operator. If it 
looks bad, then do measurements and figure out how that happened.

Re-bending is definitely an option. Most newer QFPs bend easily (that's how 
they got out of plane to start with!). The manufacturers went to malleable 
lead frames because the extra stiff leadframes put too much stress on the 
solder joints and they would fail thermal cycling (biggest market mess was PC 
memory boards).

So if the leads are easy to bend, you can certainly bend them back without 
risking damage to the package seals.

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vargas, Stephen M
Sent: Thursday, February 26, 2015 11:44 AM
To: [log in to unmask]
Subject: Re: [TN] Inspection for QFP Coplanarity

Amol:

     Check with your flexible placement machine supplier, many offer vision 
coplanarity checkers that can be retrofitted to your machine. Fuji has an 
excellent system. I'm curious to find out what other have to say about your 
second topic, we've sent parts out to an outside supplier to straighten leads 
with limited success.

Regards,
Steve Vargas

If you don't have time to do it right, when will you have time to do it over?
John Wooden

Polaris Contract Mfg Inc
15 Barnabas Rd
Marion, MA 02738
774-553-6192
[log in to unmask]

P Please consider the environment before printing this e-mail

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Amol Kane
Sent: Thursday, February 26, 2015 11:24 AM
To: [log in to unmask]
Subject: EXTERNAL: [TN] Inspection for QFP Coplanarity

Schlumberger-Private
________________________________
Dear Technetters,
What are people using to inspect co-planarity of gull wing devices (fine pitch 
QFPs and SOICs) prior and post soldering? I am especially interested in 
techniques that can detect small differences in z axis causing the lead to 
just "sit" on solder after assembly and cause premature failure or 
intermittent operation. I was looking on line and found some inspection 
mirrors for pre-soldering inspection but not a whole lot else. I would be 
grateful if you can share your experiences regarding what other techniques 
work.

On a related topic; what is the general feeling about correcting coplanarity 
issues by using reworking templates to push the leads back to their intended 
position. I do not like it as it may damage the seal around the lead and the 
body depending on the extent of rework. Can you point me to any studies done 
on this topic that highlight the failure modes resulting from this practice?

Thanks,
Amol


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