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Reflow soldering of 208-RQFP-0.5mm

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#37444

Reflow soldering of 208-RQFP-0.5mm | 31 October, 2005

Hi,

I`m having some troubles with reflow soldering RQFP-208 pin IC with 0.5mm pitch. The profile is done according the solder paste supplier specs but still this RQFP is shifting in the reflow process. What could be the cause of this and what would be the remedy?

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#37450

Reflow soldering of 208-RQFP-0.5mm | 31 October, 2005

Shifting? Please describe the "Shifting". I.E. is it centering, sliding to cause shorts.....

Most 208s will self center. If it's causing shorts, first check your print to make sure it is on the pads. Next check placement. Another area to check is the board itself. Make sure there is board mask between the pads of the QFP. If not, all above parameters must be right on.

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#37454

Reflow soldering of 208-RQFP-0.5mm | 31 October, 2005

If the board is HASL you may always have trouble. Try to reduce the amount of paste by either reducing aperture size of stencil thickness. Jerry

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#37459

Reflow soldering of 208-RQFP-0.5mm | 31 October, 2005

The only problems I've ever had with 208's shifting out of alignment was with a board with too much HASL thickness. The lands had a convex profile and the parts kept slipping downslope.

We put down a glue dot and ranted at our board supplier. Both had the desired effect. I would also guess that a shakey reflow conveyor would exacerbate the problem.

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#37483

Reflow soldering of 208-RQFP-0.5mm | 31 October, 2005

If I brief shifting, I checked the component before it enter the reflow oven and saw that the IC is perfectly aligned on the pads but when it comes out from the oven the IC is floated on the pads. The floating is irregular and the IC is shifted away from the pads 2-5mm. I try to investigate the printing process for better results because the placement of the machine is perfect. Could this problem occur if the solder paste is too long kept on the PCB after printing. The specified time by paste supplier is 6 hours but the time I kept is +4hours.

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RDR

#37496

Reflow soldering of 208-RQFP-0.5mm | 1 November, 2005

Is an RQFP a Qfp with the center pad for heat dissipation? If so, you may be shifting when this center pad reflows and lifts the part.

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#37507

Reflow soldering of 208-RQFP-0.5mm | 1 November, 2005

Is this causing shorts? Or are your pads that wide?

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RDR

#37508

Reflow soldering of 208-RQFP-0.5mm | 1 November, 2005

I just noticed that you mention 2-5mm off, that is huge! It would seem to me that there is an external force here to move a part that far. Things such as a heavy air stream that for some reason is really hitting this part, something on the PCB underneath the QFP that is "erupting", something physically in the oven causing an obstrucion.

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#37510

Reflow soldering of 208-RQFP-0.5mm | 1 November, 2005

What's your pad geometry/sizes relative to lead width/length? Revisit this and my free website: http://www.moonmanondarkside.com and see some examples and download some free documents.

MoonMan

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