In response to the selective soldering questions:
Selective Soldering machines are a good way to "finish automation" if
the design of the pcb's are conducive to the application with just a few
components to solder. You have a great start on what to look for as far
as a decision matrix for selecting a machine. I would also recommend
looking into the actual process; Flux application (overspray can be
very detrimental to cleanliness, also look for hole fill), solder level
measurement, nitrogen consumption and ppm levels (if no-clean flux
requires it), pcb recognition (fiducial or hardstop), preheating
profiles (ramp rates and peak temperature), warped pcb damage avoidance
are just some things I can think of to add to your list. In my
experience, offline programming would be a necessity to keep the machine
running. The programming would also have to be generated from a CIM
system such as CIMBridge or Technomatix to avoid teaching from gerbers
or by hand.
Also watch out for the promise of very tight spacing capabilities. For
instance, the vendor mentions they can solder through-hole leads 0.020"
next to a SM component. This may be possible if you have 0.150" on the
other side of the through-hole lead and you use the lead to wick the
solder to the hole. Not a robust process but possible if the PCB design
allows it. Some machines also require unique fixturing for each PCB
design which will further increase the cost of the machine. Selective
soldering machines are very limiting but are a good option for a very
specific application or pcb design.
Now that I've shared my experience, I'd like to share another option
that I am currently involved with. Most likely you have looked into
selective solder pallets for the same applications. Typically if the
PCB has 10-15 components (which is a lot) and your release quantities
are above 100, the cost justification for a selective soldering machine
would be very difficult. I know because I have tried to justify
selective soldering machines with a prior employer and could not get the
numbers in the same ball park. Selective solder pallets are a much
easier process to characterize in a manufacturing facility with wave
soldering capabilities. With a process engineering group driving the
design of such pallets, your
yields for wave soldering can be world class. If you would like to
talk
more about your applications, please feel free to contact myself or a
Ascentec Engineering sales associate.
Good luck, have a great Expo show
Morris Torseth
Process Engineer
Ascentec Engineering
503-925-1942
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rich Lasko
Sent: Wednesday, September 26, 2001 6:41 AM
To: [log in to unmask]
Subject: [TN] Selective Soldering
Good AM tech'ers
Next week I will be at the Assembly Tech Expo in Rosemont, IL in search
of
some selective soldering equipment. I was hoping that anyone that has
had
some previous experience with Selective Soldering could give me some
advice
on which important factors should be considered when reviewing selective
soldering equipment. (Low to medium volume releases)
Items that I am already looking for are (in no particular order):
a.) Ease of programming
b.) Maintenance costs (replacement parts)
c.) Fixture costs (pallets, etc...)
d.) Repeatability of the process
e.) Speed
f.) Set-up and change over time
Right now I am looking for options in our post wave soldering department
to
reduce the amount of labor needed for hand soldering. Some of the jobs
that
we have coming up are double sided SMT (so we reflow both sides) and
then
hand solder in the TH comps. Qtys per release may range from 100pcs -
500pcs (and there is usually 10 - 15 TH comps that need to be hand
soldered)
What does this all mean....more labor more labor more labor.
Any input would be helpful.
TIA for your input.
Rich Lasko
Badger Electronics
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