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SMT electronics assembly manufacturing forum.


Lifted Leads on Fine pitch QFP's

Raul N.

#11892

Lifted Leads on Fine pitch QFP's | 19 April, 1999

We are currently having a field return of 25 PPM due to this problem - (open joint- in the field - FT passed when it left the factory). Our assembly line is equipped with an AOI and a X-ray machine to filter(100%) this out but still have this PPM figure.

Had coplanarity check on our IC placers but aside from it took too much time for measurement we found out that the system is not consistent ( false accept > 25 PPM)!

1. Is there a better process to solder the leads of QFP's with lifted "minute" lifted leads still having a realiable solder joints?

2. Or has anybody tried modifying solder pads and use thicker solder paste deposit to compensate for the gap to have reliable joints?

3. Anyone ever used a "hot bar" similar to being used for the PCMCIA connector soldering to correct this problem - performed after reflow soldering?

Would appreciate your comments/inputs...

Thanks,

Raul N.

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J.H.

#11893

Re: Lifted Leads on Fine pitch QFP's | 19 April, 1999

| We are currently having a field return of 25 PPM due to this problem - (open joint- in the field - FT passed when it left the factory). Our assembly line is equipped with an AOI and a X-ray machine to filter(100%) this out but still have this PPM figure. | | Had coplanarity check on our IC placers but aside from it took too much time for measurement we found out that the system is not consistent ( false accept > 25 PPM)! | | 1. Is there a better process to solder the leads of QFP's with lifted "minute" lifted leads still having a realiable solder joints? | | 2. Or has anybody tried modifying solder pads and use thicker solder paste deposit to compensate for the gap to have reliable joints? | | 3. Anyone ever used a "hot bar" similar to being used for the PCMCIA connector soldering to correct this problem - performed after reflow soldering? | | Would appreciate your comments/inputs... | | Thanks, | | Raul N. | | I HAVE SEEN THIS PROBLEM IN THE PAST. WHAT WE ENDED UP DOING TO HELP WITH THIS WAS CHANGING VENDORS ON OUT PROBLEM PARTS. WE FOUND THAT USING PARTS WITH PALLADIUM LEADS CUT THE FAILURES BY AT LEAST 75%. HOPEFULLY THIS IS A LITTLE HELP??

J.H.

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#11894

Re: Lifted Leads on Fine pitch QFP's | 19 April, 1999

| We are currently having a field return of 25 PPM due to this problem - (open joint- in the field - FT passed when it left the factory). Our assembly line is equipped with an AOI and a X-ray machine to filter(100%) this out but still have this PPM figure. | | Had coplanarity check on our IC placers but aside from it took too much time for measurement we found out that the system is not consistent ( false accept > 25 PPM)! | | 1. Is there a better process to solder the leads of QFP's with lifted "minute" lifted leads still having a realiable solder joints? | | 2. Or has anybody tried modifying solder pads and use thicker solder paste deposit to compensate for the gap to have reliable joints? | | 3. Anyone ever used a "hot bar" similar to being used for the PCMCIA connector soldering to correct this problem - performed after reflow soldering? | | Would appreciate your comments/inputs... | | Thanks, | | Raul N. | | Does this board go over the wave? You could be reflowing the joint with the wave, and it would pass all ICT and functional tests because the lead is making mechanical contact. It's not until it heats up out in the field and expands that it opens.

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Tuffty

#11895

Re: Lifted Leads on Fine pitch QFP's | 19 April, 1999

| | We are currently having a field return of 25 PPM due to this problem - (open joint- in the field - FT passed when it left the factory). Our assembly line is equipped with an AOI and a X-ray machine to filter(100%) this out but still have this PPM figure. | | | | Had coplanarity check on our IC placers but aside from it took too much time for measurement we found out that the system is not consistent ( false accept > 25 PPM)! | | | | 1. Is there a better process to solder the leads of QFP's with lifted "minute" lifted leads still having a realiable solder joints? | | | | 2. Or has anybody tried modifying solder pads and use thicker solder paste deposit to compensate for the gap to have reliable joints? | | | | 3. Anyone ever used a "hot bar" similar to being used for the PCMCIA connector soldering to correct this problem - performed after reflow soldering? | | | | Would appreciate your comments/inputs... | | | | Thanks, | | | | Raul N. | | | | I HAVE SEEN THIS PROBLEM IN THE PAST. WHAT WE ENDED UP DOING TO HELP WITH THIS WAS CHANGING VENDORS ON OUT PROBLEM PARTS. WE FOUND THAT USING PARTS WITH PALLADIUM LEADS CUT THE FAILURES BY AT LEAST 75%. | HOPEFULLY THIS IS A LITTLE HELP?? | | | J.H. | What size r ur pad's ?, we're using pad's that are typically 100 tho long to allow more solder and better toe fillets. Also using a 6 thou stencil to ensure the required paste is available. a thought tho'. If it's passing ICT u could be creating the good joint via the clamping or the Pin contacts and a similar thing in the functional.

good luck

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Dean

#11896

Re: Lifted Leads on Fine pitch QFP's | 19 April, 1999

| We are currently having a field return of 25 PPM due to this problem - (open joint- in the field - FT passed when it left the factory). Our assembly line is equipped with an AOI and a X-ray machine to filter(100%) this out but still have this PPM figure. | | Had coplanarity check on our IC placers but aside from it took too much time for measurement we found out that the system is not consistent ( false accept > 25 PPM)! | | 1. Is there a better process to solder the leads of QFP's with lifted "minute" lifted leads still having a realiable solder joints? | | 2. Or has anybody tried modifying solder pads and use thicker solder paste deposit to compensate for the gap to have reliable joints? | | 3. Anyone ever used a "hot bar" similar to being used for the PCMCIA connector soldering to correct this problem - performed after reflow soldering? | | Would appreciate your comments/inputs... | | Thanks, | | Raul N. | | What is the plating on your fab? HASL, OSP, Gold? What is the lead width and pitch? What is the thickness of your stencil? Need more info. to help diagnose your process. Regards, Dean

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KEVIN SIMPSON

#11897

Re: Lifted Leads on Fine pitch QFP's | 20 April, 1999

| We are currently having a field return of 25 PPM due to this problem - (open joint- in the field - FT passed when it left the factory). Our assembly line is equipped with an AOI and a X-ray machine to filter(100%) this out but still have this PPM figure. | | Had coplanarity check on our IC placers but aside from it took too much time for measurement we found out that the system is not consistent ( false accept > 25 PPM)! | | 1. Is there a better process to solder the leads of QFP's with lifted "minute" lifted leads still having a realiable solder joints? | | 2. Or has anybody tried modifying solder pads and use thicker solder paste deposit to compensate for the gap to have reliable joints? | | 3. Anyone ever used a "hot bar" similar to being used for the PCMCIA connector soldering to correct this problem - performed after reflow soldering? | | Would appreciate your comments/inputs... | | Thanks, | | Raul N. | | 1. what machine ,or coplanarity system are you using? 2 .Have you tried increasing stencil mil/ aperature sizing? 3. Alot of problems with bent /lifted leads etc. that we had at one time , was poor process handling of parts. If you are not going to use a coplanarity check before placement you will have to have some other control over what is put down.

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Raul N.

#11898

Re: Lifted Leads on Fine pitch QFP's | 21 April, 1999

| | We are currently having a field return of 25 PPM due to this problem - (open joint- in the field - FT passed when it left the factory). Our assembly line is equipped with an AOI and a X-ray machine to filter(100%) this out but still have this PPM figure. | | | | Had coplanarity check on our IC placers but aside from it took too much time for measurement we found out that the system is not consistent ( false accept > 25 PPM)! | | | | 1. Is there a better process to solder the leads of QFP's with lifted "minute" lifted leads still having a realiable solder joints? | | | | 2. Or has anybody tried modifying solder pads and use thicker solder paste deposit to compensate for the gap to have reliable joints? | | | | 3. Anyone ever used a "hot bar" similar to being used for the PCMCIA connector soldering to correct this problem - performed after reflow soldering? | | | | Would appreciate your comments/inputs... | | | | Thanks, | | | | Raul N. | | | | | 1. what machine ,or coplanarity system are you using? | 2 .Have you tried increasing stencil mil/ aperature sizing? | 3. Alot of problems with bent /lifted leads etc. that we had | at one time , was poor process handling of parts. If you are not going to use a coplanarity check before placement you will have to have some other control over what is put down. Here: 1. FUJI @ QP242. 2. Yes.To the extent that no solder bridging will not occur. 3. I agree it is a handling problem. My point is, is there a better way or a better process/technology to still process "minute" or "marginal" lifted leads that are "hard to find" even in the x-ray and AOI - than fnding it out in the field aside from 100% run-in/burn-in?

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Raul N.

#11899

Re: Lifted Leads on Fine pitch QFP's | 21 April, 1999

Thanks for all your inputs....

Raul

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