It's a long time since I HASL'd but 2 hours between microetch & flux seems
too long, especially if the atmosphere is as bad as some shops I've seen. It
doesn't take long for a micro etched surface to oxidise. Maybe the micro
etch has an anti-tarnish added to it?
255 °C seems hot for the pot. 240 °C is what I remember, but maybe a higher
temperature means it's easier to blow more off and get flatter pads.
Geoff Layhe
-----Original Message-----
From: d. terstegge [mailto:[log in to unmask]]
Sent: 31 October 2002 14:32
To: [log in to unmask]
Subject: Re: [TN] HASL process OK or not ?
Hi Mike,
Yes this was prior to assembly, it's not localised areas of bare copper
but several pads having a dull appearence and a color somewhere between
brown, green, and solder. There's no solder dome, it's very flat.
Daan Terstegge
Unclassified mail
>>> [log in to unmask] 10/31/02 02:23pm >>>
Was there Cu exposed on the bare PWB you inspected, prior to assembly
/
soldering?
-----Original Message-----
From: d. terstegge [mailto:[log in to unmask]]
Sent: Thursday, October 31, 2002 6:00 AM
To: [log in to unmask]
Subject: [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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