Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


0402

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rdm

#54907

0402 | 29 May, 2008

Gents,

We've been using a round 1:1 aperture for a 5 mils thickness on our stencil design on 0402 and recently, IPC guidelines recommend oblong, homeplate or reverse homeplate. I believed the PCB pad for 0402's area within the recommended size/dimensions but we have this recurring random tombstoning defects.

Any recommendations, ideas is greatly appreciated.

Thanks.

rdm

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#54912

0402 | 29 May, 2008

We've found that reverse homeplate reduces tombstoning significantly for us on 0603 and 0402 (the latter of which we hardly ever see).

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aj

#54914

0402 | 29 May, 2008

10% reduction on 5 thou.

Gap between pads is also critical with 0402's.

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#54915

0402 | 29 May, 2008

On 0402s we use 20x25 mil pads with a 15 mil gap between the pads on the pcb with ENIG finish, 5 mil stencil with a 1:1 aperture (20x25 mil) and SAC305 lead free solder paste. We very rarely see any tombstoning on 0402s using this setup.

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rdm

#54919

0402 | 30 May, 2008

Thank you very much for all the replies. Appreciate it! rdm

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