Steve, I concur with what you've said. We also had accept/reject issues with the palladium solder joints. The demarcation line along the side is unsettling to some inspectors. We answered the great majority of those questions by distributing to QA, a bulletin, with inspection criteria and photographs of acceptable joints. Overall, we get good results with these parts. If I'm evaluating solderability problems on a board where the palladium parts soldered decently, I take it as a general indicator that the profile is probably OK. Bruce Tostevin Benchmark Electronics Inc. Hudson, NH ______________________________ Reply Separator _________________________________ Subject: Re: [TN] Parts Solderability (2) Author: SteveZeva <[log in to unmask]> at 0UTG0ING Date: 3/27/98 12:21 PM TGIF Ya'll! The "peanut gallery" here is gonna throw his two-cents out in this discussion, because it is something that really can be a pain sometimes, especially if you're in a process engineering or quality postion. I've seen a lot of time and energy burned over this issue in some instances... The biggest difference I've seen between a tin/lead and a palladium coated lead, is solder joint appearance. What I noticed mainly is that the solder does not seem to flow as readily to a palladium coated lead as it does with a tin/lead coated lead. When you look at a palladium coated lead solder joint under a microscope, it will tend to have a very strong demarcation line where the solder stops and the lead begins. Many inspectors see that as the solder appearing to not have wet very good. A tin/lead plated lead will have the solder wet and flow over top of the foot making the overall joint look kind of rounded and smooth...many times when you have that kind of variances in solder joint appearance, the inspectors tend to excessively reject the palladium joints. In my opinion, when they put a defect arrow on it, and have it reworked, all it is accomplishing is making all the solder joints look the same, and nothing more. A little higher than normal peak temperature in your profile helps things a little, but don't cook your boards! This helps the appearance some, but I really don't think it's necessary. I feel the joints are good, the plating was designed to be a drop-in replacement for tin/lead. Sure, the joints will look a little different, but that's okay. From everything that I've been taught and read, the most critical area of a solder joint is the interface between the bottom of the foot of a lead and the the top surface of the pad, next in importance would be the heel, and I've always observed completely acceptable wetting in those two areas on palladium coated leads. Side and toe fillets don't add a whole lot to the joint as far as mechanical strength goes from every stress testing graph I've read. Don't get me wrong, they do add a little to the equation, but not as much as you might think... I spoke with somebody from T.I. back when I first noticed it about 5-years ago... (that's right, they've been doing it for 5-years). The biggest reason they switched I was told, was that the solder plating operation was the messiest, low yielding process that they had. Once they switched to palladium they saw at least a 50% increase in yields...plus, they eliminated using lead completely. Something that most of us are probably going to have to face sometime in the future. (even though some of us aren't really looking forward to it...) So unless I'm really missing something, from what I see, the only problem with palladium coated leads is getting everybody to agree on what the appearance of an acceptable solder joint should be. Have a great weekend everybody! -Steve Gregory- ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################