Bob, Thank you for the feedback. Do you have any experience with Bi alloys used in some HASL vendors? I played with some a long time ago, spreading, temperature profile, they behaved like Pb solders. Also: What am I (or the others) missing on this flatness issue. Do you think it really is a non -issue once the boards are printed with solder paste? Thanks, Bob K. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob METCALF Sent: Thursday, June 02, 2011 11:45 AM To: [log in to unmask] Subject: Re: [TN] Best Board Finish - beyond gold Bob, As the surface for best solderability there is nothing better than a tin lead solder finish. The only problem is a lot of the OEM's we deal with are no longer accepting tin lead solder. The lead free solders in the HASL environment has not gained as wide spread acceptance as everyone thought. ENEPIG is considered a "universal finish" that is compatible with a wide range of applications so I see it gaining favor. I do agree with you; if you can use tin lead HASL then I would go for that in many applications. Regards, Bob Metcalf Western Regional Manager Atotech USA Inc 1750 Overview Drive Rock Hill, South Carolina 29730 USA Mobile: 714-334-7667 e-mail: [log in to unmask] Internet: www.atotech.com Managing Director: Kuldip Johal This e-mail and any attachments hereto are business documents of Atotech USA Inc. and may contain CONFIDENTIAL OR PROPRIETARY BUSINESS INFORMATION. Unauthorized disclosure and/or use of information contained in this e-mail are prohibited. If you are not the intended recipient, you should dispose of it and not use, disseminate or copy this message or any other files transmitted with it. . From: "Robert Kondner" <[log in to unmask]> To: "'TechNet E-Mail Forum'" <[log in to unmask]>, "'Bob METCALF'" <[log in to unmask]> Date: 06/02/2011 08:37 AM Subject: RE: [TN] Best Board Finish - beyond gold Bob, As for flatness: once a PCB has paste printed can you even tell what the finish is? I have never been able to figure out this flatness thing. As for reliability I think solderability wins every time. Are you telling me these other finishes have better solderability than, well solder, as found only in a HASL finish? Has anyone ever seen "Black Pad" with HASL? There is no Ni so the P cannot be wrong, ever. Right? I fell like a stick in the mud on my bias towards HASL, I am open to ideas here. Bob K. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob METCALF Sent: Thursday, June 02, 2011 11:18 AM To: [log in to unmask] Subject: Re: [TN] Best Board Finish - beyond gold When considering finishes, if the ultimate in reliability and surface flatness are key considerations, you must give electroless nickel, electroless palladium, immersion gold (ENEPIG) some consideration. Regards, Bob Metcalf Western Regional Manager Atotech USA Inc 1750 Overview Drive Rock Hill, South Carolina 29730 USA Mobile: 714-334-7667 e-mail: [log in to unmask] Internet: www.atotech.com Managing Director: Kuldip Johal This e-mail and any attachments hereto are business documents of Atotech USA Inc. and may contain CONFIDENTIAL OR PROPRIETARY BUSINESS INFORMATION. Unauthorized disclosure and/or use of information contained in this e-mail are prohibited. If you are not the intended recipient, you should dispose of it and not use, disseminate or copy this message or any other files transmitted with it. . From: "Stadem, Richard D." <[log in to unmask]> To: <[log in to unmask]> Date: 06/02/2011 07:46 AM Subject: Re: [TN] Best Board Finish - beyond gold Sent by: TechNet <[log in to unmask]> I agree with everything you say, Barbara. It sounds like you are now on your way to making the correct choice. Stay away from immersion tin. If you choose immersion silver, refer to both IPC 1601 and IPC 4553 for storage and handling considerations. They can be managed. The double-sided process can leave a slight reduction of solderability with immersion silver PWBs by the time you are ready to hand solder any PTH parts, making that more difficult to do, sometimes. That is why I asked. Also, if you select Immersion Silver, make sure that your PWB fabricator has a good plating product, a well controlled process and some experience with it. Ditto with ENIG. Especially with ENIG. Regarding immersion silver, it is susceptible to environments that are heavy in sulfides, such as automotive exhaust, rubber processing, or paper processing. Keep some of these things in mind both from an end-use environment standpoint and from a storage standpoint. Do not store in areas where there are open containers of soaps, fluxes, etc., nearby. From: Barbara Burcham [mailto:[log in to unmask]] Sent: Thursday, June 02, 2011 9:22 AM To: Stadem, Richard D. Cc: TechNet E-Mail Forum Subject: Re: [TN] Best Board Finish - beyond gold Thanks everyone for you imput. What a great group of people! Richard, The application will be double sided, fine pitch array components, some through hole components and going into a shock environment. I will need to connect with the assemblers to check on flux and paste compounds. Does this information help? You make an excellent point. Must have the total picture. I do not know, yet, how long boards will sit on the shelf before moving into assembly, either. I do know that shelf life will also impact this decision. I do not think that I want to use tin...that hairy growth stuff. Barbara On Thu, Jun 2, 2011 at 8:01 AM, Stadem, Richard D. <[log in to unmask]< mailto:[log in to unmask]>> wrote: Barbara, What is the application, board type, component types, etc? Immersion silver is my personal favorite, but that is completely irrelevant. You should choose a board finish dependent upon the application of the CCA, whether it has fine-pitch array components, including CSPs, whether it is double-sided with PTH parts or hand-soldered components, the environment the CCA will be used in, the flux type to be used, the alloy that is required, and several other factors that go into the decision. Without complete knowledge of all these factors, it is hard for anyone to answer that question. I can tell you that IAg beats ENIG in cost, but each finish has strengths and weaknesses. Some definitely have more or less than others. -----Original Message----- From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On Behalf Of Barbara Burcham Sent: Wednesday, June 01, 2011 8:17 PM To: [log in to unmask]<mailto:[log in to unmask]> Subject: [TN] Best Board Finish - beyond gold Hey Y'all, I am looking for a reliable bare board finish that beats the cost of gold. What experience is out there? What would you recommend? Thanks, Barbara Burcham pcb Trace Design [log in to unmask]<mailto:[log in to unmask]> ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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