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March 2008

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From:
Ioan Tempea <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ioan Tempea <[log in to unmask]>
Date:
Thu, 20 Mar 2008 11:24:38 -0400
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The components soldered on the first side are on when populating the second side.

And no plasma available.

Thanks again,

Ioan

-----Message d'origine-----
De : Hfjord [mailto:[log in to unmask]] 
Envoyé : 20 mars 2008 11:20
Ā : 'TechNet E-Mail Forum'; Ioan Tempea
Objet : SV: [TN] Shelf life of bare copper boards

Are there components on already? Then, what do you assemble?

 Another trick could be to plasma clean  the boards, if you got such a
machine. If the copper oxide isn't too thick Argon bombardment may work.

 If you got organic contaminations on top of copper oxide, then I don't know
what to do, depending on what components you have already on the board. If
the components are not sensitive to solvents, you can clean (to remove many
organics) with ordinary cleaning methods, followed by plasma cleaning for
the oxide. 

/Inge

-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Ioan Tempea
Skickat: den 20 mars 2008 13:09
Till: [log in to unmask]
Ämne: Re: [TN] Shelf life of bare copper boards

Thanks TN for your answers!

My questions come from our ups and downs in assembling a few double sided
FR-4 boards, with exposed copper layers. We see variable batch to batch
soldering quality and believe it is the variable degree of surface oxidation
that is causing the problem.

This product is medium to high volume, so acid dipping or any other
conditioning of the surface would have a large impact on the assembly costs
and eventually on delivery dates.

Of course the double side reflow does not really help and I would hesitate
doing acid dipping when there are components and solder joints on the boards
already.

So what would help me even more would be a few ideas on the packaging we
should request and the handling of the boards. Mike named a few, are there
more suggestions out there?

Best regards and Happy Easter,

Ioan


-----Message d'origine-----
De : Hfjord [mailto:[log in to unmask]] 
Envoyé : 19 mars 2008 14:06
Ā : 'TechNet E-Mail Forum'; Ioan Tempea
Objet : SV: [TN] Shelf lif of bare copper boards

Have no idea what strange things you are doing, but an easy way to activate
the copper is to dip the boards in a weak acid solution, strength depending
on the time the boards have been exposed to the atmosphere. Rinse rigorously
in DI !
/Inge

-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Ioan Tempea
Skickat: den 19 mars 2008 13:42
Till: [log in to unmask]
Ämne: [TN] Shelf lif of bare copper boards

Dear Technos,

 

Anybody using PCbs with bare copper pads and traces, no plating, no OSP,
not even solder mask? Because I have a few questions:

 

What is their shelf life?

Are they suited for double side SMT reflow? I mean, during the first
reflow the oxidizing is accelerated...

What storing/handling procedures you use?

Does the copper require any particular specifications, in order to
perform better in soldering?

Anything else?

 

Thank you,

 

Ioan

 


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