I'm a little confused by some of the process steps. Image and gold plate (assuming also nickel underplate). Is the entire circuit pattern gold or just the bond sites? If the entire pattern is gold , then why cover with resist? I would think the application of resist over gold and subsequent stripping would contribute to contamination. Also, look into eliminating the silk-screen, if possible. No telling what's being re-deposited on the gold when you cure the legend ink. Another thought, what are you applying the Entek 56 to? If the pads are gold and the circuits covered with soldermask, what purpose does the Entek serve? LPISM may be a factor as well. Have seen excellent success with Taiyo and Enthone masks. We don't do Probimer here, so it's hard to offer advice. As to ET pins, they'll cause some failure with respect to bond sites, but they aren't contributing to the orange stain. Have your customer identify critical bond area, then test to an area of the pad outside of that critical area. Judging by the dimensions of the pad, they ought to be able to accomplish this. Regards, Tom ______________________________ Reply Separator _________________________________ Subject: FAB: organic contam. on wire-bond gold Author: [log in to unmask] at INTERNET_GATEWAY Date: 11/27/96 3:11 PM HELP - What's the secret to making wire-bondable gold? Our ppm failure rate on wire bond sites is a little too high for our customer. Smallest wire-bond pad is about .014"x .050" and wire mat'l is Al (generally higher failure rates on smaller pads). The highest percentage culprit has been described as an [arguably] visible "orange stain" - very thin with a Carbon/Oxygen signature. Board is double-sided with the following route: Drill, panel plate Cu, image & plate gold (DuPont 9020), strip resist (RR3), image (cover gold), cupric etch circuitry, pumice w/brushes, LPISM (Probimer-65), solvent develop, bake & UV cure, legend, ET, Entek 56. Gold parameters: 83-85 knoop, Ni content: 30-40ppm, As,Cu,Pb,Co, all less than 3 ppm, Gold conc. is on low side: Au strike: 0.15-0.25 tr.oz./gal, Au Plate: 0.4-0.6 tr.oz./gal @ ~2 ASF. Questions: - What are the most common contributors to wire-bond failures? - Is LPISM residue one of them? - Are aqueous developable LPISMs generally more successful? - What are the, say, 3 most critical parameters to control at deep gold? - How critical is gold surface topography (roughness)? - Are ET pin dents a failure cause? - Can pumice operations be detrimental to the gold surface? - Is low Au concentration necessarily a liability? Any input will be greatly appreciated. J.Felts PC World, Toronto *************************************************************************** * 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. * ***************************************************************************