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Date: | Mon, 18 Nov 96 08:35:00 cst |
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Hi John -
Let me throw another angle at you - the width of your conductors will
influence your solder wetting even if you have good solderability or
acceptable heat transfer! FM Hosking's paper "Parametric Study on the
Solderability of Etched PWB Copper" in the SMI 96 proceedings (page
671) might be helpful. He has done some interesting work on how
roughness, temperature, flux, etc (many variables) can impact wetting.
I'll bet that the influence of copper thickness can be pulled out of
his equations or maybe one of the listed references could be helpful.
Good Luck.
Dave Hillman
Rockwell Collins
[log in to unmask]
______________________________ Reply Separator _________________________________
Subject: ASSY: DSN: Conductor to Land ratio
Author: [log in to unmask] at ccmgw1
Date: 11/15/96 12:57 PM
Address,
We use .020 pitch devices extensively in our designs, 12mil lands with
8mil spacings. The conductors widths coming from these lands are
8mils (2.1 Cu thk; .0007 foil and .0014 plating). In addition to
other varibles, I believe the 8mil cond width is robbing much needed
heat for solderability. The 8mil cond width is out of context for
such lands and FPT devices.
Q: How much influence does the conductor really have on the wetting of
the land in reflow (No heavy copper planes in the 8 layer lay-up)?
Q: Is there a test that can be conducted to determine the amount heat
absorbed by the land.
I am in the process of convincing Hardware Design to reduce the
conductor width for the reason above, in addition to buying real
estate.
Please advise.
John Gulley
[log in to unmask]
972-578-3928
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