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.
Regards,
Bob Walker
[log in to unmask] (mailto:[log in to unmask])
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