Why the requirement (or desire) for HASL at all?   <shudder, yes, I have a strong bias against>

HASL pressfit holes can be a problem if (when) some vias are undersize due to thick solder at knee of hole. That can spike insertion forces during pressfit install. If you're lucky you only z-in the pin and damage connector. If you're not so lucky you can damage the via and create a scrap circuit card assembly. For that reason, back in the day when tin/lead surface finishes on telecom infrastructure cards were still common it was preferred by many OEM's to use selective solder strip and fused tin lead.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lum Wee Mei
Sent: Monday, December 07, 2015 4:24 PM
To: [log in to unmask]
Subject: [TN] HASL and ENIG PCBs

Dear All,
I have several questions that bother me and hope some kind souls out there can enlighten and show me the way.

For VITA 46 card cage configuration, we have choices of press-fit connectors from different suppliers, each having their pros and cons. However, it was noted that some suppliers only have ENIG plating finish for backplane connector while there is an option for ENIG or tin/lead for daughter card connector.

The questions that bother me are :
If the backplane connector is ENIG plating finish, it is recommended that the connector's holes on PCB will be ENIG. Can I have the following option and what is the impact to a 3.5 - 5Gbps high-speed design :
(a) Both daughter cards and backplane will have HASL surface finish except for connectors holes with ENIG finish.
(b) Fully HASL finish daughter cards with fully ENIG finish backplane.
(c) Both daughter cards and backplane to be fully ENIG finish.

Deeply appreciate your respond.

Thanks and regards,
~wee mei~

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________