Board defect? Purple spotGlen:

In IPC-R-700, there is a procedure 4.2.10.1, Deleting Internal Conductors or
Shorts by Drilling or Machining that outlines this process. Typically this
kind of repair is only done with customer approval. It should not be done as
a standard process by the board fabricator on their own.

I have performed this procedure in the past for customers who have a short
designed in and needed it removed on expensive boards.

As far as the color is concerned, I would think that they used a quick set
epoxy that was colored, or worse it picked up coloring from some of the
chemistry it saw after the repair was performed.

If you have multiple boards with the defect in the same location it would
tend to make me think they had a film defect and performed the repair to
salvage the parts rather then start them over and make them correctly.

Bob
  -----Original Message-----
  From: Pelkey, Glenn [mailto:[log in to unmask]]
  Sent: Thursday, May 16, 2002 1:54 PM
  To: [log in to unmask]; 'TechNet E-Mail Forum.'; Pelkey, Glenn
  Subject: RE: [TN] Board defect? Purple spot


  Hi Robert,

  Yep, multilayer for BGA application.  Is that standard practice?  Nobody
here has seen it before, and right now we're rejecting them.  Why would
anybody choose purple?

  Glenn
    -----Original Message-----
    From: Robert B. Denbo [mailto:[log in to unmask]]
    Sent: Thursday, May 16, 2002 10:54 AM
    To: 'TechNet E-Mail Forum.'; 'Pelkey, Glenn'
    Subject: RE: [TN] Board defect? Purple spot


    Glen:

    It sounds like someone put an extra hole in the board and filled it with
a purple epoxy. Is it a multilayer board where they might have been drilling
out an internal short?

    Robert B. Denbo
    Engineering Manager
    Midwest Printed Circuit Services, Inc.
    http://www.midwestpcb.com
    mailto:[log in to unmask]
    847.740.4120
    847.740.4187 Fax

      -----Original Message-----
      From: TechNet [mailto:[log in to unmask]]On Behalf Of Pelkey, Glenn
      Sent: Thursday, May 16, 2002 12:14 PM
      To: [log in to unmask]
      Subject: [TN] Board defect? Purple spot


      Hi all,

              We just spotted a new board level defect, or is it?  It is a
small, about 25 mil diameter circle that is bright purple in color.  We dug
one out and found it goes all the way through the board.  Definitely no
glass fiber in this spot, and it shows some peeling on the edge where it
meets the top of the soldermask.

              So, we have our guess at what it is, but have any of you seen
this before?

      Thanks in advance for any input.

      Glenn