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July 2008

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Subject:
From:
Dennis Fritz <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 8 Jul 2008 12:47:15 -0400
Content-Type:
text/plain
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IPC Specification 4554 on Immersion tin contains information and appendices that explain immersion tin - thickness measuring techniques, etc.? 

I am not sure it can tell you exactly what is wrong with your boards since they meet the 1.0 micron standard, but it may help you point to a solution.??I recommend it 

Denny Fritz
MacDermid, Inc. 


-----Original Message-----
From: Inge <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, 8 Jul 2008 12:18 pm
Subject: Re: [TN] Immersion Tin Problem


If you really want be familiar with the ImSn, this article from Atotech can be your snack during the coffee break.?
?
http://www.atotech.com/data/publications/pcb/Recommended_immersion_Tin_thickness_for_lead_free_soldering.pdf?
?
Inge?
?
----- Original Message ----- From: "Stadem, Richard D." <[log in to unmask]>?
To: <[log in to unmask]>?
Sent: Monday, July 07, 2008 12:03 PM?
Subject: Re: [TN] Immersion Tin Problem?
?
Good answer.?
?
-----Original Message-----?
From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak?
Sent: Friday, July 04, 2008 7:27 PM?
To: [log in to unmask]
Subject: Re: [TN] Immersion Tin Problem?
?
All of this makes perfect sense if you consider the mechanisms.?
?
ImSn has a shelf life, which is controlled by the spontaneous formation?
of the Tin/Copper intermetallic, which begins to form as the Tin is?
plated at the interface. When the Tin has totally converted to the?
Tin/Copper intermetallic, it can no longer be soldered.?
?
Heat accelerates the formation of the intermetallic.?
?
Your first pass is accelerating the formation of the intermetallic?
dramatically. You are likely simply converting the whole of the ImSn?
to intermetallic, and it is game over.?
?
Rudy Sedlak?
RD Chemical Company?
?
--- On Fri, 7/4/08, Rex Waygood <[log in to unmask]> wrote:?
?
> From: Rex Waygood <[log in to unmask]>?
> Subject: [TN] Immersion Tin Problem?
> To: [log in to unmask]
> Date: Friday, July 4, 2008, 2:35 AM?
> We do not usually use Immersion Tin finish boards but we have some?
> with a problem.?
> The boards are about 10-12 weeks old, stored in original packing,?
> double sided PTH and lead free processed.?
> Side 1 processed OK?
> Side 2 had some non-wet problems (Profiles and dwells etc are industry?
> 'norm')?
> Hand soldering has proved to be nigh on impossible.?
> The immersion tin is within the thickness specified (typical values?
> 1.1 to 1.2 micron)?
>?
> Should we have avoided ImSn (as we have done previously)??
>?
> Is the spec for the ImSn OK??
>?
> Has the PCB mfr done something wrong??
>?
> Have we? (apart from accepting ImSn)?
>?
> 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?
>?
>?
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