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January 2007

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Subject:
From:
"Burtt, Nigel" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Burtt, Nigel
Date:
Mon, 8 Jan 2007 09:58:59 -0000
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Very common for SnPb solder paste over here to be the 2% silver loaded

variety ("brighter joints", slightly lower melt point at 179C, etc, etc)



________________________________



From: John Burke [mailto:[log in to unmask]] 

Sent: 05 January 2007 18:28

To: 'TechNet E-Mail Forum'; Burtt, Nigel

Subject: RE: [TN] Qualification of ROHS Components with tin/lead Solder







Interesting  - I note in the conclusions in the opening paragraph that

they state on the QFP failures:



" Failures in Sn-plated QFP components were probably due to batch

related solderability issues."



If you look at the "batch" you will find that this was:



4.3.5 QFP Electrical Testing

No electrical test failures occurred in any of the following

combinations:

- Batch A (SAC solder with SnPb QFPs)

- Batch B (SnPbAg solder with SnPb QFPs)

- Batch D (SnPbAg solder with Sn QFPs)

- Batches E2, E3, E4 and E5 (Contaminated solder with Sn QFPs)

Electrical failures occurred only in the following batch between 1000

and 2000 thermal

cycles

- Batch E1, 4 failures (SAC solder with Sn QFPs)





Since in any experiment of this sort all other variables are removed,

such as component batch, reflow profile, solder batch et al to avoid

skewing the results I draw the conclusion by looking at this data that

the "batch" they are referring to is actually a tin finish component

with SAC alloy combination, and that anyone using this combo is in for

an interesting time unless he is right in the "sweet spot" of a reflow

profile.





I find it extraordinary and very Interesting that they actually did not

use any 63/37 for the BGA trials (or any of the other testing given it's

market share historically) - I wonder why that would have been - anyone

know??







John









John Burke



(408) 515 4992



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

From: TechNet [mailto:[log in to unmask] <mailto:[log in to unmask]> ] On

Behalf Of N Burtt

Sent: Friday, January 05, 2007 8:01 AM

To: [log in to unmask]

Subject: Re: [TN] Qualification of ROHS Components with tin/lead Solder



THE NPL project report



"Measuring the reliability of electronics assemblies during the

transition period to lead-free soldering."



can be downloded free at



http://tinyurl.com/t6vlt <http://tinyurl.com/t6vlt> 



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