AS a matter of fact I had a patent issued on controlling ACF bonding
pressure about 4 years ago. Anyone wants to look it up it is entitled
"Anisotropic bonding system and method using dynamic feedback" under US
patent number 6,776,859 B1 - or I can send you a copy if you ping me.
Kind regards,
John
John Burke
(408) 515 4992
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Haynes, Kim
Sent: Monday, March 10, 2008 9:14 AM
To: [log in to unmask]
Subject: Re: [TN] Bonding on ENIG - correction
Morning Wayne,
How is the compression ratio controlled during the ACF process? Do you know
if the ACF material has a parabolic curve for compression vesus resistance
similar to the elastomer (MAF) socket mats? I have had a very difficult
time using elastomer sockets because of this curve and the fact that the
distance from too loose to too tight is very small.
Thanks,
Kim Haynes
Interface and Clock Products
High-Speed Serial Link Applications
Texas Instruments, Inc.
214-567-2057 Telephone
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne
Sent: Monday, March 10, 2008 10:36 AM
To: [log in to unmask]
Subject: Re: [TN] Bonding on ENIG - correction
Oh boy! That's much more "fun"!
ACF relies on conductively coated elastomeric particles for conduction. Key
to using them is the usable compression ratio: Calculate the sum of the
probability distributions of the planarity errors of the two materials being
bonded together and make sure the ACF can handle that range (obviously only
the relative planarity of the pads is important--not the dielectric between
the pads!). Problem is that to bond very tiny pads with ACF you need very
tiny conductive particles. This in turn implies higher co-planarity
requirements for the surfaces. I have heard that vendors are working on
nano-tube type structures to assist with this problem by making the useful
compression ratio very large, but I haven't seen anything on the
marketplace.
As far as plating finish goes, I would still want more than 30nm! With that
thin of a coating, I would expect Ni coming through. With a "more normal"
ENIG Au thickness of 150-200nm you are probably OK. Personally I prefer
electroplated Ni and Au since the possibility of the dreaded "black pad" is
far reduced. I would still think you would want to minimize the Cu
thickness just because thicker material is likely to have more planarity
issues.
Wayne
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Monday, March 10, 2008 8:54 AM
To: [log in to unmask]
Subject: [TN] Bonding on ENIG - correction
Inge, Wayne,
Thanks for the replies!
There is a correction I have to make and I hope you will forgive me, but I
am a complete layman when it comes to bonding.
We are talking about ACF bonding... How will this affect the surface
finishing?
Thank you,
Ioan
________________________________
De : Ioan Tempea
Envoyé : 7 mars 2008 08:06
À : 'TechNet E-Mail Forum'
Objet : Bonding on ENIG
Hi Technos,
A connector has to be bonded on 2 mil wide traces. Is ENIG suited as a
surface finish for bonding? If yes, why, if not, why and if it depends, why?
Or otherwise said, I have a PCB that will get some SMT parts on both sides
and then a couple hundred golden fingers will see bonding. I was presented
with 2 options for the PCB finish:
a) Immersion Gold : 0.03um Au over 3um Ni over 25±10um Cu
b) ElectroBonding Gold: 0.3um Au over 3um Ni over 25±10um Cu
Which one is to prefer?
Thank you,
Ioan
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