Schlumberger-Private
________________________________________
Thank you Wayne. What measurement techniques have you used to measure the error?
Regards,
Amol
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Thursday, February 26, 2015 2:05 PM
To: [log in to unmask]
Subject: Re: [TN] Inspection for QFP Coplanarity
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
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-----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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