Not so fast. While the dwell time and temperature in the selective solder process plays a huge role in determining the amount of copper leaching,  so does the finish. If the plating, such as ENIG, uses a nickel barrier, the amount of copper pad leaching away is greatly reduced. The nickel barrier protects it somewhat. In that case the IMF is formed with the nickel, not the copper.
Immersion Tin typically does not have any barrier; it is plated directly to the copper similar to OSP or immersion silver. As soon as the immersion tin is absorbed into the molten solder, the leaching of the basis copper begins. 
Not so much with ENIG or ENEPIG, both of which have the nickel barrier.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir
Sent: Thursday, November 10, 2016 12:17 PM
To: [log in to unmask]
Subject: Re: [TN] Immersion Tin - problems

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