This is an it depends question. With respect to the board only I would be thinking on these lines: When soldering HASL you are really reflowing a pre-made joint, so the solder on the board just has to coalesce with the solder in the paste. When you are soldering ENIG the gold has dissolve as you say and then you have to wet the nickel. The energy time required to do this is more/longer than a simple coalescence (and more than for soldering to copper). So the "it depends" comes in when considering how much margin there is in your existing profile/paste or combination. If the profile is just enough for HASL you might have to up it a bit for ENIG. Overall: you are also making joints to component leads as well, and these will have a variety of finishes which your profile will be accommodating so the picture is not quite as clear cut, what you have done for those will likely encompass to a greater or lesser extent the ENIG. You need to be aware anyway, that even if you don't have to change anything, your operating window closes a little from HASL to ENIG Regards Mike Fenner Applications Engineer, European Operations Indium Corporation T: + 44 1908 580 400 M: + 44 7810 526 317 F: + 44 1908 580 411 E: [log in to unmask] W: www.indium.com Leadfree: www.Pb-Free.com -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of [log in to unmask] Sent: Tuesday, May 13, 2003 1:14 AM To: [log in to unmask] Subject: Re: [TN] ENIG reflow profile vs HASL Hi, Chris, Not sure how you've arrived at your information that ENIG boards require higher temperatures than HASL boards - after all, it's the solder you're melting, not the plated finish. The profile used by our CEM takes board temp up to 208 C for both HASL and ENIG. Peter Chris Murphy <[log in to unmask]> 13/05/2003 07:32 AM Sent by: TechNet <[log in to unmask]> Please respond to "TechNet E-Mail Forum."; Please respond to Chris Murphy To: [log in to unmask] cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group) Subject: [TN] ENIG reflow profile vs HASL Hi Technetters, looking through the Technet archives on the differences between HASL and ENIG boards, I notice that higher temeperatures are required for soldering ENIG boards. Presumably this is because the gold layer firstly has to be dissolved, and we are dealing with a Ni/Sn intermetallic rather than a Cu/Sn intermetallic. Does anyone have any recommendations on what differences have to be made to the reflow profile (e.g. different times above 183 deg C or 200 deg C)? Or can the same profile be used for the same board regardless of whether it is HASL or ENIG? Thanks in advance for any replies. 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