Injection molded LCP materials generally have a high filler content. This
filler may be materials such as CaCO3, and other minerals, or quartz, and
fused silica for semiconductor grade materials. When molded, a very thin
pure LCP skin is generally present across the entire surface of the molded
unit. This material is very inert since it is so highly aligned
('crystalline'), so there is little opportunity for any chemical bonding to
a subsequently applied layer. This layer has a fine microstructure that is
essentially a single 'phase', so there is very little opportunity for
adhesion due to mechanical mechanisms. Adhesion of plated metals and many
polymer materials requires some good know-how. Often this outer LCP skin
needs to be etched/removed to expose some filler material, creating a
rougher surface with mechanical locking features for either a plated metal
or another resin system. When done well, the metal can adhere as well as
copper traces on a typical build-up HDI substrate/PCB, but it may not adhere
as well as copper traces from oxidized Cu sheets laminated to a Cu prepreg.
Done inadequately, the adhesion will be poor. LCP is largely insoluble in
typical solvents and etchants. Plasma treatment may be helpful in
roughening the surface. Fluorinated plasmas are known to leave the surface
of a polymer enriched with fluorine, as reported for such processing of
polyimide passivation on IC wafers. Such fluorination has been shown to
result in difficult in achieving adhesion to some subsequently applied
materials. I do not know if this type of processing would result with
fluorinated LCP with adhesion capability even further reduced.
Consequently, if one were to try a plasma, I would suggest a nonfluorinated
plasma.
Best regards,
Leo
Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas 78704
ph 512-383-4593
fx 512-383-1590
[log in to unmask]
www.asat.com
The information contained in this electronic message is CUSTOMER/SUPPLIER
PRIVILEGED AND CONFIDENTIAL INFORMATION intended only for the use of the
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-----Original Message-----
From: Eric CHRISTISON [mailto:[log in to unmask]]
Sent: Wednesday, March 16, 2005 5:41 AM
To: [log in to unmask]
Subject: [TN] Plating LCP - delamination
There may be some board manufacturers out there who can help me.
I'm currently trying to put an EMC shield on an component moulded in LCP. I
find that I can use a vapour deposition to do this but I get adhesion
failures because small areas of the top layer of the polymer delaminate from
the bulk of the moulding.
When LCP is plated in PCB substrates does the same problem occur or is the
delamination being caused by the deposition process damaging the substrate?
What is the normal plating recipe in the PCB industry for LCP anyway and
what adhesion test would be specified?
Regards,
Eric Christison
Mechanical Engineer
Consumer & Micro Group - Imaging Division
STMicroelectronics
33 Pinkhill
Edinburgh
EH12 7BF
Tel: +44 (0)131 336 6165
Fax: +44 (0)131 336 6001
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