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July 2008

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Subject:
From:
Ahne Oosterhof <[log in to unmask]>
Reply To:
Date:
Tue, 8 Jul 2008 10:16:02 -0700
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......... and there went a perfectly good coffeebreak.

Thorough piece of work!

Have fun,
Ahne 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Tuesday, 08 July, 2008 09:19
To: [log in to unmask]
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_thick
ness_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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