Thanks for your input Juliano.
If others have also seen this, it would be interesting to see just how widespread this issue is. IPC should have guidelines on what to do to prevent it (ENIG finish, 1/2 oz copper minimum, etc).
As I posted earlier, I have seen it happen many times at many client companies, and I am simply trying to get the word out. Many have no idea what may have happened, and be unfairly blaming the PWB fabricator.
It is a process/design issue.
dean
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Francesco Di Maio
Sent: Friday, November 18, 2016 8:12 AM
To: [log in to unmask]
Subject: Re: [TN] Immersion Tin - problems
Hello Juliano,
I think you are facing a problem of copper dissolution as Mike wrote.
This problem become more evidentemente with lead free solder alloy, also it may be presente with Sn/Pb alloy.
In our experience the use of Sn100 alloy may help to mitigate the effect of the annullar ring partial or complete dissolution if compared to
SAC305 or SAC405 alloy.
We noted this problem during solder pot (solder fountain) rework used to remove and resolder pth connector.
The selective soldering with long contact time, higher solder temperature, higher solder flow rate in my opinioni may cause the problem you noted.
Try to reduce these variables and problem should be mitigate.
Preheating the assembly before or during the selective wave soldering, may help.
Regards
Francesco Di Maio
SEM Comunicazione & Gestlabs
-------- Messaggio Inoltrato --------
Oggetto: Re: [TN] RES: [TN] RES: [TN] Immersion Tin - problems
Data: Thu, 17 Nov 2016 16:25:03 +0000
Mittente: Mike Fenner <[log in to unmask]>
Rispondi-a: TechNet E-Mail Forum <[log in to unmask]>, Mike Fenner
<[log in to unmask]>
A: [log in to unmask]
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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