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 *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************