Hi Sumxp (couldn't bring myself to say hi no name....!),

What is the percentage of solder in your formulation?  And is it lead free or Sn 63?

You know the deposited volume before reflow and can calculate the volume after the heating process.  Typical numbers for 5 mil thick stencils with Sn63 are 40% of original height, and I will admit it has been a long time since I have printed 8 mils thick.

My maximum print height limit for a 5 mil thick stencil is 6 mils which yields approximately a 2.4 bump after reflow.   It is never flat so be aware of this.

The wetting characteristics and shape of the pad can raise this number as high as 3 mils in my experience.

The true height of the bump will also depend on the flux characteristics (whether or not it completely runs off the molten solder or puddles on top.

If you have a component lead sitting on the paste, this will lower the thickness of the solder below the lead due to the solder wicking up onto the lead.

Good luck,

Phil


No Name <[log in to unmask]> wrote:
Hi,
Is there any formula to calculate the after reflow solder bump height?The
land size is 123*63mils with 1:1 stencil opening and using 8mils stencil.

regards
sumxp

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