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October 2005

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Subject:
From:
Franklin D Asbell <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Franklin D Asbell <[log in to unmask]>
Date:
Wed, 12 Oct 2005 17:07:32 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (551 lines)
It's not? Then why is our HASL containing molten solder and air actuated
immersion clamps, also air actuated, plugged into the wall, doesn't that
mean current is being applied to the work, the current flows through things
we cannot see, into the molten solder, onto the work, and the clamps are
acting as cathodes...hmmmm.... (chuckle) Of course it is not plating, did I
say something dumb again and lead people to believe that I thought it was?
Sorry, must have been a momentary loss...

Franklin


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Wednesday, October 12, 2005 4:29 PM
To: [log in to unmask]
Subject: Re: [TN] Hasl

Hi Ramon & Franklin,
HASL is not a plating. It may start out as such--you co-plate tin and
lead as an etch-resist on your PWB, but after melt-fusing it, it
definietely is no longer a plating--it is now propely 'wetted' to the
underlying Cu. HASL is simply blowing away the excess solder to produce
as level a surface as posible.
Franklin is correct with all the variables and caveats listed.
Werner

-----Original Message-----
From: Dehoyos, Ramon <[log in to unmask]>
To: [log in to unmask]
Sent:         Wed, 12 Oct 2005 16:24:59 -0400
Subject: Re: [TN] Hasl

              Frank:
           At what pitch does one have to apply all these measures
listed below to avoid issues with the boards? Is it bigger than 10, or
25 or 50 mils pitch? Do you have similar problems with SSSR ( Selective
solder strip and reflow ) as with HASL plating?
           Regards,
           Ramon

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin Asbell
Sent: Wednesday, October 12, 2005 2:06 PM
To: [log in to unmask]
Subject: Re: [TN] Hasl

That's not exactly what I said, the question was " I would like to know
if HASL plating creates a planarity problem for QFPs or BGAs assembly
for some people in the industry."

I responded with yes, it creates problems!

Can HASL be correctly applied down to tight pitch features (my
definition of tight pitch is 10 mils or less), of course! But there are
many variables on both sides of the wall that should be addressed first,
for example, air/dwell time during the HASL process removing as much
solder from the flat pads but allowing just enough to remain behind as
to provide the solderable surface, possible stencil adjustments, paste
application (to adjust for minimal solder and stencil thickness
adjustments), then there may be the type solder to use (as the extreme
minimal solder on the bare board may invariably require a different
temperature setting during assembly), what type flux is being used,
would this interfere instead of enhance the fusing of the board and
paste...and the list here may be long.

The list above contains many of the variables of why it does not
work...of course...

Can it be done, sure, but the cost associated with this as well as the
potential for low yields make alternative (i.e immersion tin) finishes a
better choice.

Franklin





-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
Sent: Wednesday, October 12, 2005 12:40 PM
To: [log in to unmask]
Subject: Re: [TN] Hasl


        Frank:
                Your are telling me that HASL final plating can be used
on most components including fine pitch if they are design in properly
and the assembly is done by skilled people and six more variables are
correctly done. Is this right?
        Regards,
        Ramon


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard
Sent: Wednesday, October 12, 2005 1:29 PM
To: [log in to unmask]
Subject: Re: [TN] Hasl

Like Chinese fireworks and printed circuit boards.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin Asbell
Sent: Wednesday, October 12, 2005 12:25 PM
To: [log in to unmask]
Subject: Re: [TN] Hasl

Is that your question? The answer is yes, for some people it does, but
it cannot be blamed solely on HASL, you need to factor the HASL process,
the dimensions of components being attached, the skill level of those
people and about half a dozen other variables.

And just a not on planarity, HASL and planarity go together like Laurel
and Costello, Abbot and Hardy, Beer and Firearms...

Franklin


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
Sent: Wednesday, October 12, 2005 12:16 PM
To: [log in to unmask]
Subject: Re: [TN] Hasl



        Thanks Jeff. Is it from pad to pad or from thickest to thinnest
pad areas of the board? I would like to know if HASL plating creates a
planarity problem for QFPs or BGAs assembly for some people in the
industry.
        Regards,
        Ramon


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jeffrey Bush
Sent: Wednesday, October 12, 2005 12:00 PM
To: [log in to unmask]
Subject: Re: [TN] Hasl

We control the thickness from .2 to .9 mils - pad centers.  We use a
HSL-175 horizontal system.

Jeffrey Bush
Director, Quality Assurance and Technical Support

VERMONT CIRCUITS INCORPORATED
  76 Technology Drive - POB 1890
    Brattleboro, Vermont 05302
      Voice: 802.257.4571.21 Fax: 802.257.0011
           http://www.vtcircuits.com


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
Sent: Wednesday, October 12, 2005 9:06 AM
To: [log in to unmask]
Subject: Re: [TN] Hasl


               Thanks for your comments Dr Lee. I would like to know
from the fabricators what is the range in thickness that they can
control on a HASL plating finish. Is it 0.1 to 0.6 mills?  From the
fabricators what is the finest part pitch that they can assemble on
PWBs.
                Thanks for your inputs.
                Ramon
                ME
                410.552.2210




  _____

From: Lee parker [mailto:[log in to unmask]]
Sent: Tuesday, October 11, 2005 8:10 PM
To: TechNet E-Mail Forum; Dehoyos, Ramon
Subject: Re: [TN] Hasl


Ramon

Normally, HASL is the less expensive alternative and thinner.
Consequently by being thinner, it may produce a smaller meniscus which
is usually an advantage. The risk here though is solderability; the
thinner the solder the more likely the occurrence of surface
intermetallics. These issues have been the focus of engineering
attention for years and have become more acute as the feature sizes
diminished. This is why the the industry is migrating from HASL to hard
metal finishes.

Best regards

Lee

J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389

        ----- Original Message -----
        From: Dehoyos, Ramon <mailto:[log in to unmask]>
        To: [log in to unmask]
        Sent: Tuesday, October 11, 2005 4:20 PM
        Subject: Re: [TN] Hasl

                Thanks Dr Parker and Richard for your inputs. Comparing
SSSR and
        HASL final plating which are made both using eutectic Tin/Lead
solder
        and other Lead free materials, the end surface is still domed in
the
        middle. So both have  weak gasketing due to their lack in
flatness.
        Setting this issue aside, what are the advantages of one versus
the
        other besides the longer shelf life of SSSR.
                Regards,
                Ramon


        -----Original Message-----
        From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem,
Richard
        Sent: Tuesday, October 11, 2005 2:03 PM
        To: [log in to unmask]
        Subject: Re: [TN] Hasl

        The idea of the flat surface finish is for both stencil
gasketing to the
        board and for placement accuracy. To form a "perfect brick" of
solder
        paste, there has to be a certain amount of pressure (a lot less
than
        most people think). To prevent squeezout of paste between
stencil and
        board, there has to be good, really good, gasketing or sealing
between
        the stencil and the board surface.
        The problem with HASL, as Dr. Parker stated below, is that the
round
        bump (meniscus) of HASL sticking up above the surface of the pad
on vias
        and on surfaces where there is no accomodating hole in the
stencil
        prevents this tight seal, and allows the paste to squeeze out.
(The
        aperture design is typically slightly smaller than the pad). It
is also
        a problem when you go back and perform pick-n-place, as now you
want to
        place the SMT components onto your perfectly formed bricks of
paste, but
        with about 50-100 grams of pressure. If the paste is not stable
to a
        flat pad, the parts slide all over the place. While some of this
is
        forgiven by the surface tension of the solder in liquidus,
bridges do
        form, components misalign, etc. This is especially critical in a
        no-clean process. If large (relatively) amounts of the solder
paste are
        not "tight to the brick" and fully registered on the pad, the
paste does
        not fully agglomerate into a single solder joint. Separated
solder paste
        does not usually conglomerate back into the central solder joint
during
        reflow. Extraneous solder balls form. This is very bad news if
you did
        not plan on washing them away.

        -----Original Message-----
        From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker
        Sent: Tuesday, October 11, 2005 12:03 PM
        To: [log in to unmask]
        Subject: Re: [TN] Hasl

        Ramon

        After reflowing a soldered surface, you will form a meniscus
which will
        interfere with SMT component placement. To avoid the problem I
suggest a
        flat metal finish such as immersion silver or flash gold (not
ENIG)

        Best regards
        Lee

        J. Lee Parker, Ph.D.
        JLP Consultants LLC
        804 779 3389
          ----- Original Message -----
          From: Dehoyos, Ramon<mailto:[log in to unmask]>
          To: [log in to unmask]<mailto:[log in to unmask]>
          Sent: Tuesday, October 11, 2005 12:52 PM
          Subject: [TN] Hasl



                      Hi technetters:
                     Is there a fine pitch limit  to the use of HASL
board
        plating
          finish due to its variation in thickness?  Does selective
solder strip
          and reflow plating, SSSR, have a significant advantage over
HASL? Any
          comments relating to platting finish would be greatly
appreciated. I
          thank you for your comments.
                  Ramon
                  ME
                  410.552.2210

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