Hi Daan,
IMO time between the etch and Flux is not acceptable, the process itself is
a trouble maker for BGA's and process window is very narrow and inconsistant
as it is nearly impossible to have the same results every day.. moreover on
both side .... the variables are varying too much and maintenance is a key
for success... it's ok for some jobs but really it costs more at the assy
than alternative processes...
In order to have a good status you need to start from Solder Mask UV
exposure, SM development and curing, then prep and flux, then maintenance,
controls, etc.. etc..
Solder pot temp seems to be too low at 255°C.. with an output of 700 panels
a day.. hummm.. strange... Of course it depends also of the mass of the PCBs
. as high count ML will require more heating, dip time, the level of solder,
etc..
Also, it would be interesting to know how many PCB manufacturers had their
shop in fire because of this particular process and the share of Quicksilver
.. whish you to keep your supplier..
You definitely need to move toward a new alternative process which
definitively cost less for everyone.
Very Best Regards - Roland
www.PCBspecialist.com
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-------Message original-------
De : TechNet E-Mail Forum.; d. terstegge
Date : jeudi, 31. octobre 2002 16:05:23
A : [log in to unmask]
Sujet : [TN] HASL process OK or not ?
Hi Technet,
Yesterday I visited one of our bare board manufacturers and had a close
look at their HASL-process. The reason for the visit was solderability
problems on BGA-pads, which sometimes look thin and dull. Occasionally
copper seems to be visible through the tinlead.
In general I think this is a very professional boardshop, but (being
not an expert) I don't know what to think about their HASL-process. I
hope someone on this great forum is willing to give me some input on my
findings, in terms of good or bad, or possibilities for improvement:
Machine: Quicksilver SM, vertical HASL, 250 kg solderpot, no preheat
Time between microetch (drying) and fluxing can be up to two hours
Solder pot temperature set to 255 °C
Leveling is done is such a way that the solder is as flat as possible,
although the design of the airknives causes a big difference betweeen
the two boardsides. With XRF we measured a thickness of only 0.4 microns
on BGA-pads, with about 3 microns on similar pads on the other
boardside.
Water-based flux from an open tank, without any composition control,
but tank is replaced every 24 hours.
Solder is replaced every 6 months, but except for copper contamination
no composition-check is ever done.
When copper is above 0.3 % the dross is skimmed off to assure that
copper content stays below 0.35 %.
Throughput of the machine is about 700 panels per day.
Daan Terstegge
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net
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