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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


lead-free stencil printing

#25834

lead-free stencil printing | 25 September, 2003

hi, I am a research student in Electronics manufacturing at RIT. We are planning to assemble boards using lead free solder paste. I was wondering would there be any changes in printing in using lead-free paste"Sn-3.9Ag-0.5Cu". Thedensity of Sn-37Pb paste is 8.4 gm/cm3 and for lead free alloy the density is 7.4 gm/cm3. Would this change in density have any effect on printing. Please calrify my doubt. Thanks Mani

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RDR

#25835

lead-free stencil printing | 25 September, 2003

There isn't any difference in the printing process regarding leadfree vs. lead. The only differences are in the reflow process.

Russ

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#25850

lead-free stencil printing | 26 September, 2003

Thank you Russ for the information. One more clarification- I found that the %metal content in lead free paste is in the range of 88-89.5 whereas %metal content in Sn-Pb paste was 90% in general. What is the reason behind this reduction of %metal content for lead-free pastes. THank you Regards Mani

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#25853

lead-free stencil printing | 26 September, 2003

The metals used to replace the lead weigh less than the lead.

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