On a BGA, yes, there would be little additional solder flow. On the rest of the SMT components you get quite a bit of additional wetting. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev Sent: Wednesday, June 13, 2007 10:32 AM To: [log in to unmask] Subject: Re: [TN] Nickel barrier and RF applications I'm not that sure about solder wetting larger areas after the second re-flow. On ENIG it usuallyh covers pads right away (unless the re-flow is screwed). As far as flux residue is concerne, then we don't know whether they use water soluable or non-clean one. Regards, Vladimir -----Original Message----- From: TechNet To: [log in to unmask] Sent: Wed Jun 13 11:10:33 2007 Subject: Re: [TN] Nickel barrier and RF applications As I stated in my previous response to Vladimer, you are doing both. Solder flows along the traces during the first reflow, forming an IMF with the nickel, and providing a path (more conductive path) for the signal. After the second reflow, the solder joints wet out a little further, and a very small increase in the IMF also takes place. While any of these is a very small change, the cumulative effect of reflowing all of the solder joints is usually enough to create a detectable improvement in performance of the high-RF/high-impedance circuit performance. Getting rid of additional flux also helps. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paymon Sani Sent: Wednesday, June 13, 2007 10:05 AM To: [log in to unmask] Subject: Re: [TN] Nickel barrier and RF applications This is the million $ question. The assemblies are single sided with no TH components. We simply pass them through the reflow oven for a second time without changing the reflow profile or adding paste or flux to improve the output power by 0.2 to 2 dB with majority of improvement at 0.5 dB! The question is what we are doing to the boards during the second reflow: 1- Does it evaporate some of the flux residues? 2- Does it increase the IMC thickness? The x-ray images of the before and after reflow are very similar, i.e. we are not collapsing voids or creating new voids. Paymon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev Sent: June 13, 2007 10:39 AM To: [log in to unmask] Subject: Re: [TN] Nickel barrier and RF applications I think, there is one question to ask. If ENIG (or rather the presence of Ni) is the source of the problem, then why does 2nd reflow improves the yield? Regards, Vladimir AMD -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paymon Sani Sent: Wednesday, June 13, 2007 10:34 AM To: [log in to unmask] Subject: Re: [TN] Nickel barrier and RF applications Thank you Steve, This sheds a lot of light on the current RF product failures at my company. As a matter of fact, my PCB supplier is applying ENIG on all copper surfaces before the mask application! Paul, thank you for initiating this trend. Cheers, Paymon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory Sent: June 13, 2007 10:23 AM To: [log in to unmask] Subject: Re: [TN] Nickel barrier and RF applications I just realized that the URL may have wrapped. Try this one: http://tinyurl.com/2vjenp This might be the same one that Inge was talking about.... Steve Gregory -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory Sent: Wednesday, June 13, 2007 9:00 AM To: [log in to unmask] Subject: Re: [TN] Nickel barrier and RF applications Here's an article: http://www.taconic-add.com/pdf/technicalarticles--effectsofsurfacefinish .pdf Steve Gregory -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paymon Sani Sent: Wednesday, June 13, 2007 8:57 AM To: [log in to unmask] Subject: [TN] Nickel barrier and RF applications Hello John, is it documented anywhere? Paymon -----Original Message----- From: John Burke [mailto:[log in to unmask]] Sent: June 13, 2007 9:53 AM To: 'TechNet E-Mail Forum'; Paymon Sani Subject: RE: [TN] Plating The nickel in enig is not good for frequencies above 3 - 4 GHz John Burke (408) 515 4992 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paymon Sani Sent: Wednesday, June 13, 2007 6:47 AM To: [log in to unmask] Subject: Re: [TN] Plating Hello Inge, This is very interesting! I did not make the connection between the Nickel on the PCBs and the RF application. Are there any papers that explain the sensitivity of RF applications to the Nickel barrier in ENIG PCBs? We are having trouble with a 5.8 GHz RF product right now. The assembly meets the IPC-610D requirement. However, 25% of the products fail testing. We reflow the failed assemblies for the 2nd time and 50% of them pass testing! We do not know the RC of the failures. I was suspecting the flux to be the root cause but could it be the Nickel barrier? Cheers, Paymon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar Sent: June 13, 2007 2:33 AM To: [log in to unmask] Subject: Re: [TN] Plating Paul, Lockheed Martin use a lot of platings. I'm not sure, but I have seen Boron as a barrier somewhere, just can't find it right now. Anyway, Lockheed as well as NASA use many special platings. Non-magnetic, guess you have a RF application that need low-loss lines. http://supplier.external.lmco.com/supplier/po_information/specpro2.htm I was myself looking for a non-magnetic finish once, and if I remember right, there is a difference between EN and EN. The acidous electroless nickel is not ferromagnetic, while alcaline electroless nickel is somewhat ferromagnetic. Borohydride electroless Nickel-Boron is probably non-magnetic too. However, you should contact your plating chemist to verify, it was many years since I mixed with this. (In earlier days, we had our own chemists, many of them had piles of knowhow, but then came the economist's era, and the chemists were kicked out) Inge -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Stolar, Paul W Sent: den 12 juni 2007 23:38 To: [log in to unmask] Subject: [TN] Plating We are using nickel as a barrier metal on a PC board for the pads. Are there any other barrier metals we can use which are non-magnetic. Bare copper is not an option. 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