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SOD323 and SC90 bounceing parts in final PNP stages.

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SOD323 and SC90 bounceing parts in final PNP stages. | 4 March, 2012

What we have had recently is a lot of larger thin (32 thou) thickness boards that have had issues with SC90 diodes bouncing off the pads in the final PNP machine.

Our setup, universal instruments GC120 or quad beam 30 spindle lightning heads. This machine is usually placing the diodes.

GC11 or 7 spindle flexjet 3 on the front and a inline High force 4 on the back. Sometimes placing the diodes to avoid bouncing.

Quick Tool tooling in all machines (don't buy lasts less than a year).

What happens is when the flexjet head is placing parts the diodes can be seen flying off the board. No other parts are disturbed. The diodes are not being bumped by parts being placed. The tooling is holding the board very well and it is not moving.

Its like the head is smacking the board hard but we never see the board move. And this is the only part we ever have a issue with.

The parts are set for the minimum of 150 grams of force, Setting it for the slow place speed dose not help or only cuts the bouncing parts in 1/2. I created a super slow Z speed and it eliminated the problem but tripled the production time.

We use to be able to place SC90/SOD323 and not have this issue, or at least not this bad.

Is the small gull wing leads on SC90/SOD323 just prone to higher than normal failure rates?

SOD523 and all SOT's are OK.

Just this last week I had a long board and noticed that after moving a soft top button from the InLine 4 to the flexjet head the right 1/2 of the board had major SOD323 jumping issues where the left side was OK, moving the button back fixed the issue. Unfortunately there are no squishy buttons to be the cause on the other 2 boards we have issues with this part on.

I am at the moment open to any thoughts or ideas. This part is fast turning our inspection department in to a rework department, not a good thing.

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SOD323 and SC90 bounceing parts in final PNP stages. | 4 March, 2012

Are you sure that the parts are bouncing? We had similar problem where diodes were placed very closely and occasionally nozzle pushed already placed part away (due to pick-up tolerance)...

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SOD323 and SC90 bounceing parts in final PNP stages. | 4 March, 2012

What i have on the original 2 problem boards is the parts next to it are SOIC8 and placed using a 125F(.125" dia) 1 of witch is close and we have to Z zone it to place the SOIC last, the others have more than .02" clearance on all sides.

The other parts placed on these boards ,in the flexjet, are 1 or 2 .5x.25 inch white board to board connector, 3 SOIC8's a SOT-353 and a MLP 28. I'm rather sure the SOIC8's or the MLP 28's placement causing the bounce.

On the worst panel we did move all of the diodes to the flexjet But still have some bouncing.

Ile add checking that 3rd one that i z zoned to my list on Monday. It doesn't answer the others however.

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SOD323 and SC90 bounceing parts in final PNP stages. | 5 March, 2012

Three ideas for you: 1) Make sure nozzle tips are clean. 2) Check coplanarity of leads to bottom of body. If leads are above body, it could be the are not contacting paste well. 3) Investigate static charge in the parts caused by the feeder or packaging that makes the parts stick to the nozzles.

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SOD323 and SC90 bounceing parts in final PNP stages. | 9 March, 2012

Is your solder paste deposit drying out? Or if the paste deposit is small or there is insufficient paste then the tack between the device and paste will be poor so it can easily come out of the paste during its placement or placement of other parts. Check the stencil aperture and stencil thickness and then check the paste print quality on these pads.

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