Rex,

Do you have a link to this paper?

Ben 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rex Waygood
Sent: Thursday, May 01, 2008 10:01 AM
To: [log in to unmask]
Subject: Re: [TN] Pb-Free BGAs on a SnPb board

We run a profile that is known to achieve a full melt of the lead free
BGA balls (by section). The melting point of the ball is influenced by
the lead in the molten solder so the temperature required to achieve a
complete melt is lower than you might expect. On our boards the slight
increase in temperature is regarded as safe for the remaining
components. The boards have subsequently been through qualification
without failure. Our customer was involved fully with the investigation
and decision.
There is an NPL paper which also demonstrates this produces a reliable
BGA joint, under the conditions they checked :-).
Rex  


Rex Waygood
Technical Manager
 
PartnerTech Poole Ltd
Benson Road
Poole
Dorset BH17 0RY
United Kingdom
 
Tel: +44 (0)1202 674333
Fax: +44 (0)1202 678028
DDI: +44 (0)1202 338222
Mob: +44 (0)7887 997403
 
[log in to unmask]
www.PartnerTech.co.uk

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Craig Sullivan
Sent: 01 May 2008 14:30
To: [log in to unmask]
Subject: [TN] Pb-Free BGAs on a SnPb board

Good Morning, 

We are seeing an increased number of our customers that specify a
Pb-Free BGA when the rest of the board assembly is SnPb. Of course when
we reflow at the SnPb profiles, we don't always get a properly collapsed
BGA. So we end up reworking the BGA. We don't run a Pb-Free profile
because we don't want to risk damaging the SnPb components.

I am sure we aren't the only ones that are experiencing this. So, I have
a question or two:

What is everyone else doing when a customer requires a Pb-Free BGA on a
SnPb assembly? Many of the jobs I refer to are consignment, so it's not
like we can order the SnPb part from the get go.

What reliability issues do you see?

Are there any extra steps that your company takes to ensure the Pb-Free
BGAs collapse properly? 

Is there a "special" profile anyone uses for the best of both worlds?

What are the advantages, if any, to use a Pb-Free BGA on a SnPb
assembly?

Thanks for any and all input.
Craig Sullivan
Manufacturing Engineer
MPL Incorporated
P: 607.266.0480
F: 607.266.0482
[log in to unmask]

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