There could be a number of reasons. I offer the following to add to your
list of things to investigate.
The immersion tin will dissolve very rapidly into the Solder which will then
start to dissolve the Cu pad underneath to form a solder joint. If your
pads/tracks are small/thin then it is possible the Pb-free solder could
dissolve the pad entirely. Pb-free solders can be more aggressive in this
respect than Sn/Pb due to the higher tin content. The Sn is more
concentrated/less dilute compared to Sn/Pb. Processing temps are also
higher. The problem can be increase by a turbulent or fast wave.
Reducing the exposure time may help.
I suggest you might want to consider your Pb-free finish for unrelated
reasons. Immersion tin is a variable process and has a relatively short
storage life. It's hard to think of any advantages it has, save possibly for
cost.
---
Regards
Mike
www.chrisfennerfund.org
www.facebook.com/chrisfennerfund/
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Datacom - Juliano
Ribeiro
Sent: Thursday, November 17, 2016 11:46 AM
To: [log in to unmask]
Subject: [TN] RES: [TN] RES: [TN] Immersion Tin - problems
Many pads
_____________________________
Juliano Bettim Ribeiro
DATACOM
+55 (51) 8446-2135
+55 (51) 3933-3000
Ramal: 3484
-----Mensagem original-----
De: Stadem, Richard D. [mailto:[log in to unmask]]
Enviada em: sexta-feira, 11 de novembro de 2016 11:40
Para: TechNet E-Mail Forum; Datacom - Juliano Ribeiro
Assunto: RE: [TN] RES: [TN] Immersion Tin - problems
One, or many?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Datacom - Juliano
Ribeiro
Sent: Friday, November 11, 2016 5:21 AM
To: [log in to unmask]
Subject: [TN] RES: [TN] Immersion Tin - problems
Damaged = "Pad disappeared" the track has broken
_____________________________
Juliano Bettim Ribeiro
DATACOM
+55 (51) 8446-2135
+55 (51) 3933-3000
Ramal: 3484
-----Mensagem original-----
De: TechNet [mailto:[log in to unmask]] Em nome de George Wenger
Enviada em: quinta-feira, 10 de novembro de 2016 17:32
Para: [log in to unmask]
Assunto: Re: [TN] Immersion Tin - problems
What do you mean by "damaged"? Do you mean solder doesn't wet the pad or is
there physical damage?
Sent from my iPhone
> On Nov 10, 2016, at 1:16 PM, Vladimir <[log in to unmask]> wrote:
>
> Hi Juliano,
>
> The board finish most probably has nothing to do with the problem. It must
be your process.
>
> Regards,
>
> Vladimir
> SENTEC
>
> Sent from my BlackBerry 10 smartphone on the Rogers network.
> Original Message
> From: Datacom - Juliano Ribeiro
> Sent: Thursday, November 10, 2016 13:13
> To: [log in to unmask]
> Reply To: TechNet E-Mail Forum
> Subject: [TN] Immersion Tin - problems
>
> Hello to all,
>
>
>
> We recently are changing to Lead Free process to specific products and
> we need to change the finishes boards from (HAL Tin Lead) to Immersion
Tin.
>
> But during the Selective Soldering process the component pad is damaged.
>
> Are there limitation about Immersion Tin about Max. Temperature, Max.
> Reflow/Wave process, Max Soldering Contact Time, etc.???
>
> In this case the HAL Lead Free is better?
>
>
>
>
>
> Thank you
>
> Juliano Ribeiro
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