Can't help you with solder mask, but I know the Arlon 35N is good
material. 


Denis Lefebvre, CID+
PCB Designer
Finisar Corporation
(408)542-3832
(831)449-3850

-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
David Baldwin
Sent: Thursday, April 29, 2010 9:27 AM
To: [log in to unmask]
Subject: [DC] HAST Solder Mask & Board Materials

DC Members:

I am designing a PCB for HAST (Highly Accelerated Stress Testing).  The
customers requirements are:

DLT (150C, 408 hours)
HAST (130C, 85% RH, 96 hours)
temp cycling (-65C to 150C for devices)
on a 28 bump CSP package. (.4mm pitch, .16mm lands)

The board material recommended by some fabricators is an Arlon 35N
Polyimide, due to it's stability over temp.

My questions are...

Is this the best material without going overboard on cost?

Is there a soldermask that is very durable and can withstand this
environment.  We have had problems in the past with it flaking off.

What is the tightest registration of the solder mask that I could
expect, in order to create the largest web possible between the CSP
lands.  We only have .24mm between the .16mm lands.

Has anyone done this in the past and already have the formula for a
successful project?

Thanks in advance.

David Baldwin CID+



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