Mike and David, Any ideas of the possible mechanisms that can cause fractures in hand soldered through-hole parts using Sn5/Pb93.5/Ag1.5 HMP alloy? Pretty much the opposite of Bryan's Sn96/Ag4, we're lead-rich and tin-poor.... Mike -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Mike Fenner Sent: Thursday, September 16, 2004 2:51 AM To: [log in to unmask] Subject: Re: [TN] HMP Solder Joint Cracking Good thought. The slow cool down associated with larger parts will give what are effectively shrink holes (like in a solder pot) especially with Sn96. [On hand soldering parts with poor solderability operators tend to put more solder on as well which exacerbates the problem.] The solutions offer themselves, but you could also consider using a SAC alloy. The different structure of the solder on solidification should help. If nothing else the "cracks" will be more rounded. A final thought to double dot and cross the Ts and Is. In the unlikely event the turrets are brass they should have a NI or Cu barrier plate to prevent the solder sucking out Zn. This would certainly lead to a cracked appearance if not cracks. Regards Mike Fenner Indium Corporation of Europe 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 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Wednesday, September 15, 2004 11:50 PM To: [log in to unmask] Subject: Re: [TN] HMP Solder Joint Cracking Hi Bryan! One possible root cause to explore is that the "cracks" you have observed are actually shrinkage voids/cavities that intercept the solder joint surface. There have been several studies (NIST, NCMS) that have show that the high tin content solder alloys can form small shrinkage cavities that terminate at the solder joint surface. These shrinkage cavities could easily be mistaken for cracks. I recommend you microsection one of the suspect solder joints to see if you have a crack or a shrinkage cavity. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] "Kerr, Bryan" <bryan.kerr@AMSJV To: [log in to unmask] .COM> cc: Sent by: TechNet Subject: Re: [TN] HMP Solder Joint Cracking <[log in to unmask]> 09/15/2004 10:27 AM Please respond to TechNet E-Mail Forum; Please respond to "Kerr, Bryan" The cracks occur immediately on alloy solidification - I've watched it happen under a scope. Can't be sure that some don't occur later but that is a worrying thought which could affect reliability. Cheers Bryan -----Original Message----- From: Marsico, James [mailto:[log in to unmask]] Sent: 15 September 2004 16:21 To: 'Kerr, Bryan' Subject: RE: [TN] HMP Solder Joint Cracking When are the cracks occurring? Ate the assemblies thermally stressed after the terminals are soldered? Do the cracks occur after a wire is soldered to the turrets? Jim Marsico Senior Engineer Production Engineering EDO Electronics Systems Group [log in to unmask] <mailto:[log in to unmask]> 631-595-5879 -----Original Message----- From: Kerr, Bryan [SMTP:[log in to unmask]] Sent: Wednesday, September 15, 2004 11:07 AM To: 'Marsico, James'; IPC Mailing List (E-mail) Subject: RE: [TN] HMP Solder Joint Cracking Thanks Jim We are seeing some of the edge solderability issues that you mention however there is definite cracking as shown in microsections done by ourselves. Another batch of pins has better solderability at the edge however we still get cracks occurring. Cheers Bryan -----Original Message----- From: Marsico, James [mailto:[log in to unmask]] Sent: 15 September 2004 16:04 To: 'TechNet E-Mail Forum'; 'Kerr, Bryan' Subject: RE: [TN] HMP Solder Joint Cracking *** WARNING *** This mail has originated outside your organization, either from an external partner or the Global Internet. Keep this in mind if you answer this message. We've seen this problem in the past. The main culprit, in our case, was the solderability of the terminal on the corner of the swaged area. What looks like a crack may be an unsolderable line around the periphery of the swaged area. Try dipping the swaged end of a terminal into a solder pot and see if the corner edge wets. Jim Marsico Senior Engineer Production Engineering EDO Electronics Systems Group [log in to unmask] <mailto:[log in to unmask]> 631-595-5879 -----Original Message----- From: Kerr, Bryan [SMTP:[log in to unmask]] Sent: Wednesday, September 15, 2004 10:35 AM To: [log in to unmask] Subject: [TN] HMP Solder Joint Cracking Hi We are fitting a swaged turret terminal and soldering using 96% Tin 4% Silver alloy and have experienced cracks running around the edge of the swage solder joint - between the pin and the solder. Re-soldering gets rid of it in most but not all cases. I have thought that perhaps some stress relaxation is occurring in the swage area (brass base material) during soldering resulting in these cracks. Can anyone shed any light on this problem ? Cheers Bryan Kerr Principal Quality Engineer Process and Materials Laboratory AMS Hillend ::::::::::::::::::::::::::: This email, its content and any files transmitted with it are intended solely for the addressee(s) and may be legally privileged and/or confidential. If you are not the intended recipient please delete and contact the sender by return and delete the material from any computer. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. Messages sent via this medium may be subject to delays, non-delivery and unauthorized alteration. 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