The 30 /70 has a liquidus of 235C but the solidus is still 183C, so the
solder will have no strength as it will be a pastey sludge at the moulding
temperatures you require. This being the case then it suggests that a SAC
alloy will be OK.
To go over 232C Pb-free and still be financially solvent you could look at
Sn/Sb [235C] and possibly Sn/Sb/Ag [233C].
OF other Pb-free alloys Sn/Cu at 227C is higher than SAC, but would not
appear to buy you anything except low cost as it will be molten. IF you are
using from large solder pots though that might be the clincher.
Regards
Mike Fenner
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
Pb-free: www.Pb-Free.com
Mark Mayer wrote:
>Anyone have experience with replacing high lead content solder with
lead-free? We use a Sn30/Pb70 alloy (melts at 245C)for a part that is
overmolded with polyurethane. We need the high melt temperature because the
injection temperature of the polyurethane is 232C. Most of the lead-free
alloys I've seen melt between 217C and 227C which may be a problem for us in
the molding process.
>
>Mark Mayer, PE
>Senior RF Engineer
>Centurion Wireless Technologies
>3425 N. 44th St.
>Lincoln NE 68504
>(402) 325-3262 (direct)
>(402) 325-3200 (main)
>www.centurion.com
>
>
>-----Original Message-----
>From: Hilty, Robert D [mailto:[log in to unmask]]
>Sent: Thursday, August 26, 2004 6:43 AM
>To: [log in to unmask]
>Subject: [LF] High Lead Solders with SAC
>
>
>Is anyone aware of any reliability studies performed on high melt
>temperature high lead content solders (85-90%Pb) in conjunction with
>tin-silver-copper coatings or PCB finishes? I suspect that the tin rich
>coating will decrease the solidus and liquidus temps of the resulting
solder
>volume, but I don't know the reliability effect of that reduction or if
>there are confounding issues with silver or copper contamination.
>
>Cheers,
>
>Bob Hilty
>Tyco Electronics
>
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