Actually, studies by Lucent have highlighted some quality issues with
immersion gold. "Random" infant mortality due to brittle fracture has been
seen, at a failure rate between 50 to 1000 ppm. Root-causes have been
speculated, but not conclusively determined.

Craig


  -----Original Message-----
  From: TechNet [mailto:[log in to unmask]]On Behalf Of Mark Simmons
  Sent: Thursday, November 16, 2000 12:01 PM
  To: [log in to unmask]
  Subject: Re: [TN] Is HASL board a better choice compare to immersion gold?


  Jacob,  all responsible engineering involves trade offs.  the trick is not
throwing out the baby with the bath water, eh?  If things are working well
with the immersion AU, why switch?  While it's true that "nothing solders
like solder", your motives to switch should require more than a claim.  Your
particular design may or may not lend itself to the HASL process.  If it
does, the cost savings could be significant.  But, be prepared for some
flexability in the quality area, as the acceptability criteria will be less
cut and dried than AU.  We have seen specs from "coverage" to one mil.
depending on design and process compatability.  Don't forget that the "real"
issue is Solderability. One size does not fit all and your mileage may vary.
  Mark Simmons, V-Score Central

  "" wrote:


    Technetter,

    Recently, we're asked to change our boards finishing from immersion gold
to HASL due to to some claims that HASL finishing is better in sense of
joint adhesion for the BGA & QFP component. How true is that?

    To my knowledge, HASL boards is troublesome too as it has surface
coplanarity issue.

    Is it right to say that the coplanarity of the solder is measured using
the solder thickness measurement from 250 microinch to 750 microinch.

    Regards,

    JACOB PAO KING HING
    Supplier Quality Engineer,