Hi Bill, used to work with an airknife system years ago. The original intent
of the product was to remove any solder which had not adhered to the basis
material and to also remove excessive solder if it was webbed between
component leads i.e solder shorts. If the solder had not wetted to the pads
or was webbed between the component leads, then the molten metal would have
little or no adhesive forces to the product to secure the molten solder to
the joint and it would be removed by the air flow of the hot air knife. One
of the advantages of the air knife at that time was the thought that it
could inspect the solder joints as they were being created. By removing any
excess solder from the solder joints, one could determine whether or not the
intermetallic had been created. The intermetallic compound creates an
adhesive force between the molten tin and the basis copper material and the
air knife should not be able to remove this material.
I know that if the angle of the air knife is set incorrectly or the pressure
is too high, then any and all solder can be blown off any surface. So
assuming the angle and pressures are set correctly the results should be
solder joints that are created with just the correct amount of solder. This
is the type of solder joint which has wetted to the base material, leads and
boards, and any excess solder has been removed from the joint.
What should the joint look like? You mention insufficient solder? This is a
true catch all phrase in the industry. Provided the solder joints look meet
the requirements set forth, for example IPC-A-610, then you should have no
problem. If the process is blowing out the solder from the PTH then take a
look at the pressure and air flow of the system to verify its correctness.
Hope this helps, if not call me at 1 800 643-7822 or reach me offline at
[log in to unmask] and we can talk about it some more.
Regards, Leo Lambert
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bill Raymond
Sent: Wednesday, February 13, 2002 1:32 PM
To: [log in to unmask]
Subject: [TN] Inspecting Wavesoldered bottom-side SMD joints
Hi all,
I'm using a wave solder system with a hot air knife... the knife
reduces solder shorts just fine, however, the inspectors are finding "more"
insufficient solder joints. I've read articles _somewhere_, that when
using a hot air knife system, the joints will tend to look different and
that inspectors will need to be retrained as to what to look for. Can
anyone point me to a source of information??
Thanks, Bill...
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