Hi Trikeman,

Yes, argon ion bombardment would do the same job after hours of exposure. 
Etching took seconds.
Don't understand how 'softening' the solder could make it more attractive 
for adhesives. The surface energy may increase, if that's what you mean. I 
have no experience from that.

Yes, it's 84-1LMI. The english gentleman I suggested seems to pretend he is 
innocent. Maybe he is on his yearly african safari.

By the way, do you have experience from soldering compressed glass Kovar 
Au-flash/Ni feedtrues with a heatgun. The manufacturers recommend preheating 
the nickel plated package to 150C before gunning. I apply the heat slowly so 
that there should be no heat shock. The feedtrues are  very tough, and 
according to the MIL spec, they are designed to withstand immersion 
test -55C.

Inge

----- Original Message ----- 
From: "Creswick, Steven" <[log in to unmask]>
To: "TechNet E-Mail Forum" <[log in to unmask]>; "Inge" 
<[log in to unmask]>
Sent: Wednesday, October 01, 2008 5:28 PM
Subject: RE: [TN] "Conductive" Bonding Material


Inge,

How about an agressive argon plasma etch to roughen up the surface a bit?

I also thought it had something to do with my cure temps on the order of 
150-160-175C for some adhesives, being close to the plastic region of the 
generic [old Sn/Pb] solders and essentially trying to make the adhesive bond 
to a 'moveable' surface ... :-)

What is 1LMI?

All I can think of is Ablebond 84-1LMI - a real good Ag-filled conductive 
adhesive

Steve

  _____

From: TechNet on behalf of Inge
Sent: Wed 10/1/2008 4:52 PM
To: [log in to unmask]
Subject: Re: [TN] "Conductive" Bonding Material



The problem with tin and lead is that it is so 'flat' , seen from a
nano-level. Conductive silver (or other metal) filled adhesives do not stick
to the metal part chemically, at least not on a essential basis, but rather
on a mechanical one. There are more binding mechanisms, but let's discuss
the one that is most important for succeeding for glueing to a solder. A
solder is amazingly smooth and dense, still seen microscopically, depending
on the way it solidifies. One could see that indirectly by putting a drop of
water on the solder: it forms a sphere instead of wetting and spreading.
High surface tension, with other words. The solder could not break the
droplet's surface tension. Adhesives have a liquidous part, which is
necessary for being dispensable. That ingredient is not very wetting by
nature either, and furthermore, the whole paste has a very high viscosity.
Now, we want a surface that is like a burdock, or how can I describe it, a
surface with billions of microscopic superficial voids and cavities. If the
wet phase of the glue has matching surface tension, and a low viscosity, and
you give it time, it will creep into all the microscratches and after curing
creating millions of micro'hooks'. How do we obtain such a condition with
solder then? You need both remove the always present oxide and also create
the rough surface. We found that a slight etching could do the job. We
were in a situation when we just had to fix it. Did not like it, but got a
acceptable result. I don't recommend the method, too many traps to fall
into, but thought it might be of interest to someone, who could perhaps
develop the idea on a more adequate way, the inventor of 1LMI, for
instance. Let's see if he takes the bate.

What adhesive? Don't remember exactly, think it was a 1,000 mPas light
curing epoxy, probably from Epotek, as it was named at that time. The
bonding had no requirements on being very strong, and was not either. Just
had to keep a grounded copper foil. Soldering was forbidden of a special
reason.

Inge

----- Original Message -----
From: "Douglas O. Pauls" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, October 01, 2008 12:06 PM
Subject: Re: [TN] "Conductive" Bonding Material


> Thermally conductive or electrically conductive?
>
> Doug Pauls
> Rockwell Collins
>
>
>
> "Joe Lara (Select Circuits)" <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]>
> 10/01/2008 01:03 PM
> Please respond to
> TechNet E-Mail Forum <[log in to unmask]>; Please respond to
> "Joe Lara (Select Circuits)" <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> [TN] "Conductive" Bonding Material
>
>
>
>
>
>
> Good Morning / Afternoon Tech Net Guru's,
>
> Has anyone used a "Conductive" bonding material on a ceramic circuit
> board?
> If so what material was used and what was the quality of the result.
>
>
>
> Thanks in advance!
>
> Joe
>
>
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