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February 2004

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Subject:
From:
Edward Szpruch <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 18 Feb 2004 08:02:57 +0200
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text/plain (67 lines)
Hi Waclaw,
It sounds like famous "black pad" phenomena and it has nothing with Kapton,
but with Nickel layer.
Powodzenia
Edeward

Edward Szpruch
Eltek Ltd
P.O.Box 159 ; 49101 Petah Tikva Israel
Tel  ++972 3 9395050 , Fax  ++972 3 9309581
e-mail   [log in to unmask]

> -----Original Message-----
> From: karpinski [SMTP:[log in to unmask]]
> Sent: ã ôáøåàø 18 2004 23:15
> To:   [log in to unmask]
> Subject:      [TN] Ni/Au solderability on kapton
> 
> Recently we have solderability problems with Ni/Au kapton flex boards
> (0,1 µm Au, 3 µm Ni, 35m Cu).
> We have produced and assembled large number of boards.
> On 10 % of the boards we observe interconnection failures after final
> assembly of the pcbs. If  the suspected solder joints are lightly
> stressed , the connections are easily broken, leaving an open circuits.
>  It is  easy to peel  these parts with solder material  from the boards.
> The pads below the removed parts are discolored dark gray and are sleek .
> Some times the handsoldering of the broken joins was successful but
> after small strain the joints  broke again.
> Additional vapor phase soldering  did not improved the the strength of
> the joints.
> This is new problem for us. Does anyone have any experience with this?
> How to rework the boards? How to determine when a board should be
> reworked or
> scrapped? What about reliability issues? Latent failures?
> I would appreciate your help very much
>   regards
> 
> --
> Waclaw Karpinski
> I. Physikalisches Institut
> RWTH Aachen
> D - 52074  Aachen
> 
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