Hi Dale-

I've responded with a different subject name because that is how TechNet keeps track of the threads.

I think you're doomed without a process engineer, because I don't believe there is a fixed answer to your query.  The simple approach is to "try" a thicker stencil, but frequently that makes no difference with a big heavy part having only 2 leads.  So you may have to put something underneath to get a required joint height.  That's really complex because it would be simple to put something beneath there that destroys reliability.  Someone used to make a spacer for apps like that which dissolved in the post-soldering cleaning process, but I haven't used them in the last 20 years, so I can't tell you where to find them.

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dale Hart
Sent: Monday, March 28, 2011 8:36 AM
To: [log in to unmask]
Subject: [TN]

Technet Folks

 I'm not a process engineer, sooo how would one go about increasing the solder
joint height (G dimension) under a component.  The company's components
generally have a height of 10 -20 um.  The screen thickness is 6 mils.  The
solder is 62Sn 36Pb 2Ag not sure about the flux, particle size, storage time
between printing, pick and place, and convection reflow, if that is important.
The chip resistors are about 2012, caps 3225, with SOP16 (copper lead frames).
Didn't actually measure the pad size but visually they appear properly sized for
the various components.  The pick n place machine is an older type that uses a
spring loaded head and they program each component height into the machine.

Dale Hart
Universal Technology Corporation

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