Bob: A couple of things. 1. The Polyclad 370HR as suggested by John will work well. We have used it for over a year with good results. Polyclad and ISOLA have merged so I believe you could get a high Tg/Td from ISOLA also. 2. If you are mixing lead and leadfree components you may have to run a hotter and/or longer duration reflow profile than you normally would. Make sure your leaded components are compatible with the higher temps. 3. If you are using SAC alloy BGA's they will definitely need higher time temp durations. 4. If you are using a standard tin/lead solder paste it may not be designed for the higher temps and times required. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Walker Sent: Wednesday, January 18, 2006 10:22 AM To: [log in to unmask] Subject: Re: [TN] RoHS board finish Genny, The design isn't required to be RoHS compliant. I would prefer to stay away from the lead-free components at this time, but some of the components designed in are lead-free and some aren't just yet, thus there will be a mixture on the board. Bob In a message dated 1/18/2006 1:01:44 P.M. Eastern Standard Time, [log in to unmask] writes: First suggestion is that you search the archives of the IPC LeadFree forum - you can get to them off the IPC.org site. There is tons of info on that forum. To a lesser extent, search the archives of this forum as well (Technet). You will see many heated arguments about the pros and cons of ENIG, Imm Ag, Imm Sn, and maybe even a little about OSP. Why are you using SnPb components if you are doing a design for Pb free? Talk to your board supplier about recommendations for Pb free FR4 - I'm sure they have options available. Td and Tg are the main factors to look into. If this is supposed to be RoHS compliant, you may need to verify that your soldermask is RoHS compliant as well. Good luck. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Walker Sent: 18-Jan-06 11:39 AM To: [log in to unmask] Subject: [TN] RoHS board finish Hi All, I'm doing my first PCB design that will use lead-free components and I need to change my board finish from what I've always used.....HASL. I'm looking for any recommendations or comments on the best board finish to use. The components used on the design will be a mixture of tin-lead and lead-free (SAC), so I'm not sure if there is a preferred finish to use in this type of situation. I work in a prototype environment where the boards may be reworked (BGA removal/replaced) a number of times, so I'm concerned about the ability of the finish being able to handle being reworked/reflowed a number of times. I'd also welcome any recommendations on the type of board material to use since it will see an elevated temperature of up to 260C. I've always just specified FR4 in the past. Thanx in advance for any feedback. 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