Bah! double Bah! Utaaktoomuutch! Wonder who is sleeping when he could
instead sail in the sky, take aerial pics and present for us all.

We have not used CCs for 20 years. Last project was a ceramic board 4x6
inches packed with so many CCs as possible, primarily 28 I/Os.  We tried
some adhesive recommended by the gluelover nr 1 on this planet, you know
who. Did not work, temp change -40/+80 C caused lots of intermittent
failures or even opens. Worst of all: repair was critical, because you had
to remove all old glue before you mounted a fresh CC, whereby many pads
were damaged. Furthermore, if any of the CCs were the littlest moved during
the transport from the printer to the oven, it became frozen in that
misaligned state. In opposition to soldering, as you know.So >>>>waste bin.
Since that, noone has ever proposed superseding solder with epoxy.

Mandrake never sleeps

Inge

On 13 March 2012 15:58, Steven Creswick <[log in to unmask]> wrote:

> Blair,
>
> My tests were 'worst case', without CC.  Being a 'hybrid house' I really
> didn't have CC'ing ability anyway ...  Yes, fun stuff!  Thoroughly enjoyed
> the activities!
>
> I typically saw two failure modes WRT adhesive bonding of passives on
> PWB's.
>
> 1 - bare copper would oxidize under the adhesive, causing the device [with
> adhesive attached] to come off the board.  Typically, VERY easily.
>
> 2 - Adhesive would cleanly let go from device [or PWB], if solder coated.
>
> I would imagine the CC would delay things somewhat, but would expect the
> same results in the end.
>
> It seemed that 85/85 would kill just about anything, but can still
> envision things working 'okay' in a very benign shock and temp/humidity
> environment.
>
> Only did testing on passives.  Could have done actives too, but all had
> soldered [tinned] leads and that typically was a big nail in the coffin to
> begin with.  Was more than capable of handling 510µm [20 mil] line and
> space, even at that time.  Also with little or no heel/toe fillets, I could
> not imagine them to be very robust.
>
> Would one use this approach in a cell phone?  I know that when cutting
> wood, my cell phone gets very 'humid' when in my shirt pocket, but it uses
> soldered assy.
>
> I still believe the concept has merit, but really needs to be on an
> application by application basis.
>
> Comments Joyce?
>
> Let's see if Inge has comment.  He is probably sleeping in today, you know
> how those retired folks are  :-)
>
> Steve
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair Hogg
> Sent: Tuesday, March 13, 2012 10:09 AM
> To: [log in to unmask]
> Subject: Re: [TN] Assembling with conductive adhesive
>
> Steve,
>
> You will get that hour back in November....
>
> In a prior company we used conductive adhesives for die attach to thick
> film ceramic substrates for hermetically sealed hybrid devices. Wire bonds
> for the rest of the connections. Fun stuff.
>
> Saw the other comments on the stuff not holding up in non hermetic
> applications.
>
> I wonder if conformal coating ove rit would help?
>
> Blair
>
> On Mon, 12 Mar 2012 11:39:16 -0400, Steve Gregory <[log in to unmask]>
> wrote:
>
> >Hey all,
> >
> >
> >
> >Wish I hadn't lost that hour of sleep this weekend, I'll try to find it
> >tonight. :o)
> >
> >
> >
> >Anyways, have any of you thought of trying to replace solder with a
> >conductive adhesive for PCB assembly? There's a few out there (Henkel,
> >Cookson, Ellsworth, etc.) that are touting them as solder replacements.
> >
> >
> >
> >When I read the technical datasheets, I'm thinking to myself, why isn't
> >this stuff more widely used? There must be a reason.
> >
> >
> >
> >I do know it's pretty expensive almost all of them are silver filled,
> >and I have read that the mechanical strength and thermal conductivity
> >is not as good as solder, but what other reasons are out there not to use
> it?
> >
> >
> >
> >Steve
> >
> >
>
>
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