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From:
"Igoshev, Vladimir" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Igoshev, Vladimir
Date:
Thu, 17 Jan 2008 10:25:46 -0500
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Hi Dave,



I remember your original e-mail stating that it shouldn't be any solderabilty problemsa, but hen Wernber came up saying otherwise.



Therefore, I think the answer is still up in the air. That is why I tried to re-stated it in a slightly different way :-)





Regards,



Vladimir



----- Original Message -----

From: [log in to unmask] <[log in to unmask]>

To: Igoshev, Vladimir

Cc: TechNet E-Mail Forum <[log in to unmask]>

Sent: Thu Jan 17 10:05:55 2008

Subject: RE: [TN] SV: [TN] SV: [TN] Solderability of Tin-Gold Intermetallic





Hi Vlad! I thought we had answered the solderability questions. Intermetallic phases are typically as solderable as the parent metals until they become oxidized (then they are impossible to solder!). So as long as the Au/Sn IMC phases are not oxidized as a function of Bev's soldering process, there should be not issue. Both Inge's and my photos that Steve posted show that a non-oxidized Au/Sn IMC is fully integrated into the solder joint structure and I don't believe Bev's situation is any different. The gold embrittlement discussion that has streamed along is just the TechNet metallurgists having way too much fun. 



Dave 







"Igoshev, Vladimir" <[log in to unmask]> 



01/17/2008 08:56 AM 	

To

	"TechNet E-Mail Forum" <[log in to unmask]>, [log in to unmask] 

cc

	

Subject

	RE: [TN] SV: [TN] SV: [TN] Solderability of Tin-Gold Intermetallic



	









Dave and almost everyone else,



I believe we are missing the point. Bev has NEVER asked whether "his" joints can experience gold embrittlement, but whether the presence of gold/tin intermetallics can/will affect the solderability.



I think he is not the only one who would want to know the answer and so far the answer is almost unknown.



As far as I remember, Werner said that the solderability to AuSn4 is poor. Are their any papers with data? 



I think it would be great to have data on solderability of of common solders (Pb-free and PB-Sn) to Sn-Au alloys (with Au content from 30% down to 0).





Regards,



Vladimir  



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman

Sent: Thursday, January 17, 2008 8:21 AM

To: [log in to unmask]

Subject: Re: [TN] SV: [TN] SV: [TN] Solderability of Tin-Gold Intermetallic



Hi Bev - Arguably, the "magic" industry number is "3%"  for gold content. 

The AuSn4 phase formation kicks into gear around that percentage. The 

amount of gold you have is low and provided it is well distributed through 

out the solder joint (e.g. not segregated in one area) then you should not 

have any solder joint integrity issues. Some of the work done by Bester (

M. Bester, ?Metallurgical Aspects of Soldering Gold and Gold Plating?, 

InterNEPCON Proceedings, 1968) shows that 1-2% gold actually strengthens 

the solder joint a bit. I believe you have a low-to-no risk situation.



Dave







"Bev Christian" <[log in to unmask]> 

01/16/2008 04:24 PM



To

"TechNet E-Mail Forum" <[log in to unmask]>, <[log in to unmask]>

cc



Subject

RE: [TN] SV: [TN] SV: [TN] Solderability of Tin-Gold Intermetallic













Dave,

I only have 0.8 to 1.2% gold in the solder balls - as determined by XRF.

Bev



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman

Sent: Wednesday, January 16, 2008 5:06 PM

To: [log in to unmask]

Subject: Re: [TN] SV: [TN] SV: [TN] Solderability of Tin-Gold 

Intermetallic



Hi gang! Steve - I just sent you another set of photos showing a solder 

joint that has gold embrittlement. Bev - if you have a solder joint that 

contains the AuSn4 microstructure phase then you have an indication that 

your overall composition has exceeded the "magical" 4% limit.  The 

presence of the AuSn4 platelets cause the solder joint to behave in a 

brittle manner when subjected to some use environments. The formation of 

the AuSn4 phase isn't going to interfere with the formation of your solder 



joint but they do result in solder joint integrity degradation. The 

pretinning of gold plated component leads is an attempt to replace the 

gold with a solder coating and lower the overall total percentage of gold 

that would exist in the solder joint - the lower the overall solder joint 

gold content, the lower the likelihood for the AuSn4 phase to form.



Dave Hillman

Rockwell Collins

[log in to unmask]









Steve Gregory <[log in to unmask]> 

Sent by: TechNet <[log in to unmask]>

01/16/2008 03:35 PM

Please respond to

TechNet E-Mail Forum <[log in to unmask]>; Please respond to

Steve Gregory <[log in to unmask]>





To

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Subject

Re: [TN] SV: [TN] SV: [TN] Solderability of Tin-Gold Intermetallic













Hi Inge ol' pal!



I went back and looked on my pages, and am not sure if they're still 

there. But one of these might be:



http://stevezeva.homestead.com/files/fracture_bad.jpg



http://stevezeva.homestead.com/files/fracture_bad_2.jpg





Steve









-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord

Sent: Wednesday, January 16, 2008 3:09 PM

To: [log in to unmask]

Subject: [TN] SV: [TN] SV: [TN] Solderability of Tin-Gold Intermetallic



Not really true, the Scottish blood in my veines tells me to be careful 

with money, the kyrgise blood makes me crush the table, therefore, noone 

can actually be under it. 



I think there are pictures from my large AuSn platelets somewhere on 

Gregory's wall. If not, I can probably dig them up again from some old 

report. If such crystals are abundant in a solder joint, the components 

may just jump off the board when giving a mechanical shock.



/Inge



-----Ursprungligt meddelande-----

Från: TechNet [mailto:[log in to unmask]] För Werner Engelmaier /*

Skickat: den 16 januari 2008 20:30

Till: [log in to unmask]

Ämne: Re: [TN] SV: [TN] Solderability of Tin-Gold Intermetallic



Hi Inge,

As usual people are well advised not to argue with a (this) Swede; 1) he 

usually knows what he is talking about, and 2) if not, he will drink you 

under the table.

The IMCs formed by Sn/Pb, and Sn/Ag as well, are platellet-shaped crystals 



(in cross-section they may look like needles but are always plateletts), 

and I have seen no evidence that they are solderable. Solderability simply 



depends on how much Sn, or SnPb, to which you wet, is present. So the 

amount of these IMCs affect both solderability as well as 

Au/Ag-embrittlement.

Inge, how is Gerd? I sure have not heard anything about him for some time.







Werner




























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