Hi Kim!
Sorry, but I think I've given you almost all I know on the subject. Haven't used them myself because I've always managed to solve the problem other ways. If we are compressing spheres, then it stands to reason that the force vs. displacement will be parabolic, as you say, although displacing the resin will enter into the equation too.
Wayne
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Haynes, Kim
Sent: Monday, March 10, 2008 12:14 PM
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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