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August 2003

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Subject:
From:
Doug Pauls <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 12 Aug 2003 07:25:37 -0500
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Heavens yes.  You should have seen the LAST time Dave suggested something
like that.  The manufacturing floor folks were after him like villagers
from an old Frankenstein movie.  Took hours to quiet them down and weeks to
get the soot marks cleaned from all of the torches they were carrying.
Very ugly.

Doug Pauls



                                                                                                                                         
                      Dave Hillman                                                                                                       
                      <ddhillma@rockwellc        To:       [log in to unmask]                                                      
                      ollins.com>                cc:                                                                                     
                      Sent by: TechNet           Subject:  Re: [TN] Black pad                                                            
                      <[log in to unmask]                                                                                                
                      pc.org>                                                                                                            
                                                                                                                                         
                                                                                                                                         
                      08/12/2003 07:14 AM                                                                                                
                      Please respond to                                                                                                  
                      "TechNet E-Mail                                                                                                    
                      Forum."; Please                                                                                                    
                      respond to ddhillma                                                                                                
                                                                                                                                         
                                                                                                                                         




Hi Per-Erik! Yes, I have found that mechanical abrasion can be used to
restore BGA pads which have been impacted by black pad but I didn't offer
that method of restoration as a solution - the amount of collateral damage
to the soldermask around the pad sites usually results in bridging defects
during the component replacement phase. And I don't seem to be very popular
on the manufacturing floor when I suggest that we need to abrade every pad
on a +500 I/O BGA!

Dave



                      Tegehall Per-Erik

                      <per-erik.tegehal        To:
[log in to unmask]

                      [log in to unmask]>                cc:

                      Sent by: TechNet         Subject:  Re: [TN] Black pad

                      <TechNet@listserv

                      .ipc.org>



                      08/12/2003 04:27

                      AM

                      Please respond to

                      "TechNet E-Mail

                      Forum."; Please

                      respond to

                      Tegehall Per-Erik







Hi Werner and Dave,

The black colour on pads with the defect "black pad" is, in most cases, due
to an enrichment of nickel phosphide that occurs during the plating of
immersion gold. Some nickel is always etched from the surface in this
process but if the process is not under control too much nickel may be
etched away and the phosphorus in the electroless nickel will be enriched
as NiP in the interface between nickel and gold. I believe it will be very
difficult to remove it chemically. I think I have read somewhere that that
someone removed it mechanically and then soldered directly to the nickel
surface. A fresh electroless nickel surface has moderate solderability and
with the right soldering process it might be possible to solder to it.

Per-Erik Tegehall
IVF, Sweden

-----Ursprungligt meddelande-----
Från: Dave Hillman [mailto:[log in to unmask]]
Skickat: den 11 augusti 2003 21:31
Till: [log in to unmask]
Ämne: Re: [TN] Black pad


Hi Werner! We have tried to use our ROSA system to electrochemically reduce
the degraded nickel surfaces with no success (nickel oxide/corroded nickel
is tough stuff!). I have not heard of anyone being able to restore a "black
pad" surface successfully without having collateral damage to adjacent
regions of the printed wiring assembly.

Hey Rudy S.  - is there a chemical treatment potential/possibility?

Dave Hillman
Rockwell Collins
[log in to unmask]



                      Werner Engelmaier
                      <[log in to unmask]        To:
[log in to unmask]
                      OM>                      cc:
                      Sent by: TechNet         Subject:  [TN] Black pad
                      <TechNet@listserv
                      .ipc.org>


                      08/11/2003 02:09
                      PM
                      Please respond to
                      "TechNet E-Mail
                      Forum."; Please
                      respond to
                      Engelmaier






Hi All,
Are there any successful rework procedures for 'black pad'?

Werner Engelmaier

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