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April 2009

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Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Thu, 9 Apr 2009 12:41:49 -0500
Content-Type:
text/plain
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text/plain (175 lines)
Of the Loctite epoxies, Red Loctite 3621 will provide the best adhesion
to tin-plated copper, but it still won't be very good adhesion. It is
good initially, but fades after a few thermal cycles due to the delta
CTE. The Loctite 3621 adheres better to 99% tin coating, but not so well
to Sn63Pb37 (lead is very dense compared with tin). The epoxy that works
best from an adhesion standpoint to tinned or soldered copper is Zymet
TC201 P, however that is a thermally conductive epoxy, and I don't know
if that matters to you. But it adheres well enough to the point that if
you attempt to peel off the copper foil after it is cured, some of the
FR-4 will come up with it.
The key is for both the foil and the FR-4 or other substrate to be very,
very clean.
By the way, neither of the epoxies I mentioned is a two-part epoxy.
If it has to be a two-part, I would go with Armstrong C7 hardener W.
Cure schedules are critical to the amount of adhesion you will achieve,
at least from a lap shear standpoint.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of bob wettermann
Sent: Thursday, April 09, 2009 12:08 PM
To: [log in to unmask]
Subject: Re: [TN] Friday Theorizing

All:

The copper is 1 oz copper used in PCB fab. The tin is plated onto both
sides.

The adhesive system is a 2part epoxy-resin system (Loctite). 

I am trying to precict which system will provide better adhesion???

Thanks

 Bob Wettermann
PH 847-767-5745




________________________________
From: Inge <[log in to unmask]>
To: [log in to unmask]
Sent: Thursday, April 9, 2009 11:15:28 AM
Subject: Re: [TN] Friday Theorizing

The correct name of  the (vintage) machine is Sebastian stud tester.
It's probably followed by a number of more modern ones. From Dage, for
instance.
Inge


----- Original Message ----- From: "Inge" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, April 09, 2009 6:01 PM
Subject: Re: [TN] Friday Theorizing


> Bob,
> 
> why so thin Tin?  And no barrier? What's the purpose? And what do you
mean with a 'carrier' ?
> When testing conductor adhesion, we simple make a board sample with a
number of copper traces, then cut it so we get a large number of square
pieces approx. 1x1 inch. Next, we apply a solder paste dot on the center
of each square, size about 2 mm. This is followed by soldering kind of
needles with a round plate to each square sample. Vapour phase or oven
soldered. Finally, the samples are placed in a Sebastian pulling
machine's chuck and depress 'pull'. The machine increases the pull force
until the plate headed needle separates from the FR4 matrix and the
value is presented on the display. Years ago, we did this test
frequently on board coupons, but there is little interest in doing it
today, because adhesion problems are very rare.
> 
> Inge
> 
> 
> ----- Original Message ----- From: "bob wettermann"
<[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, April 09, 2009 5:17 PM
> Subject: [TN] Friday Theorizing
> 
> 
>> Dear Technetters:
>> 
>> Has anyone done any adhesion testing of a 2um tin-electrocoated
surface (copper carrier) to FR-4? How about a 0.100um tin electrocoated
surface? Can someone theorize on which might give better adhesion using
a 2-part epoxy?
>> 
>> Regards
>> 
>> Bob Wettermann
>> BEST
>> PH 847-767-5745
>> 
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