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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


OSP surface finish.

AF Ng

#3999

OSP surface finish. | 24 May, 2000

Could someone help to let me know when we are doing stencil printing of solder paste on board with OSP surface finish on the land, the stencil is resting on the solder mask or the land itself. If it is resting on the solder mask, then, the actual paste thickness should be higher than the stencil thickness. Pls explain. Thank you.

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#4000

Re: OSP surface finish. | 24 May, 2000

Bill,

I would assume that the stencil rests on the soldermask especially when you use a metallblade. If you know the difference in height between soldermask and land you could take that into your volume calculation when figuring out your desired stencil thickness. But I think that�s only marginal compared to other printing variables that influence the deposited amount of paste.

M2C

Wolfgang

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AF Ng

#4001

Re: OSP surface finish. | 25 May, 2000

Hi,Wolfgang Busko,

Thank you for your help. Still need some advice. If the OSP board having stencil rest on the solder mask, then, would it has more gasketing effect( solder paste squeezed out to the underside of the stencil), as compared to the HASL board whereby the stencil is resting on the land itself ?.

Thank you Bill Ng

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#4002

Re: OSP surface finish. | 25 May, 2000

Bill: I'd expect better gasketing on a nice flat solder mask surface rather than the edge of the stencil opening mashed down on a irregular shaped hunk of solder attached to a pad.

Stop thinking and get printing Dave F

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