Based on the emails below, it sounds like the ZIF connector is incompatible with any flex application where it will be mated more than once.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Wednesday, April 06, 2016 9:22 AM
To: [log in to unmask]
Subject: Re: [TN] ENIG on flexi PCBs

Hi team - a data point for the conversation: the EN plating has 1%-3% elongation so its not very robust to bending stresses.

Dave

On Wed, Apr 6, 2016 at 10:19 AM, Vladimir <[log in to unmask]>
wrote:

> According to the best flex‎ guru I know any bending with ENIG is excessive.
>
> Regards,
>
> Vladimir
>
> SENTEC
>
> Sent from my BlackBerry 10 smartphone on the Rogers network.
>   Original Message
> From: Stadem, Richard D.
> Sent: Wednesday, April 6, 2016 10:13
> To: TechNet E-Mail Forum; Vladimir
> Subject: RE: [TN] ENIG on flexi PCBs
>
> What is the limit, and how do you define that?
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir
> Sent: Wednesday, April 06, 2016 9:10 AM
> To: [log in to unmask]
> Subject: Re: [TN] ENIG on flexi PCBs
>
> I don't think E-Ni thickness has anything to do with the issue. Most 
> probably the flex was bend over the limit. That's what we normally see 
> from our customers.
>
> Regards,
>
> Vladimir
>
> ‎SENTEC
>
> Sent from my BlackBerry 10 smartphone on the Rogers network.
>   Original Message
> From: Mumtaz Bora
> Sent: Wednesday, April 6, 2016 10:05
> To: [log in to unmask]
> Reply To: TechNet E-Mail Forum
> Subject: Re: [TN] ENIG on flexi PCBs
>
> Hello Nigel, Cracking issues in flex can also occur based on the type 
> of copper used for the traces. Is your supplier using rolled annealed 
> copper or ED( electro deposited ) copper. Rolled annealed copper is 
> preferred for flex circuits.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Nigel Burtt
> Sent: Wednesday, April 06, 2016 2:10 AM
> To: [log in to unmask]
> Subject: [TN] ENIG on flexi PCBs
>
> IPC-4552 requires 3-6um nickel, but does not appear to distinguish 
> between rigid FR4 PCBs and flexible PCBs.
>
> A flexible interconnect PCB using ENIG with ZIF end connectors has 
> been shown to be prone to track cracking near the ZIF ends. The 
> supplier has suggested a lower thickness of nickel 1-3um rather than 
> the IPC spec to would be beneficial to resolve this and tests on 
> samples seem to bear this out.
>
> Does anyone have any experience of such a suggested modification of 
> ENIG spec and that thinner nickel improves the resistance to 
> stress-cracking for flexi tracks?
>
> In this specific application as there are no component soldering 
> requirements so the thinner nickel under the gold does not lead to 
> solderability concerns, but what would be the likely consequence on 
> other flexi/flex-rigid designs with flexi ZIF connector ends and SMT 
> components if a 1-3um thickness was imposed more generally? Increased 
> likelihood of black-pad type defects?
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