Looking for a source for a low cost wave soldering or method to paste solder co
T&E Engineer
Posts: 1,396
How does one solder semi-large quantities (50-200 or possibly more) of components (DIP to start - surface mount design change later) to PCBs without spending tons of time hand soldering. Is there an outsource method or is it better to invest in equipment? What about a baking oven or wave soldering which sounds expensive. What is used for something like this - or do we just hand solder the parts on. I have about·100 or·so parts·on the main PCB and 10 or less parts on the 2 other·supporting PCBs.
Comments
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
But even through-hole PCBs can be a bear to solder by hand, one pad at a time.· Might the methods used for SMDs·(convection ovens, etc.) be equally good for through-hole stuff?· Many of us, I imagine,·have never used those methods and it's time to learn.
Surely there's some articulate expertise here on these fora.
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· -- Carl, nn5i@arrl.net
Some factories in China use a large solder bath instead of a wave-soldering machine. The unfortunate workers hold the boards in tongs and wipe them across the surface of the solder. They are highly skilled, of course, and get the speed and depth just right for reliable solder joints.
Toasting ovens work well for surface mount assembly, especially if a suitable controller is used to get something like the correct temperature profile. Embossing heat guns are popular, and work quite well. I use a Metcal system (STSS power unit and MX-500 handpiece and cartridges) for through-hole and surface mount assembly.
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
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· -- Carl, nn5i@arrl.net
Post Edited (Carl Hayes) : 1/23/2009 3:50:23 AM GMT
Add a 1/4 inch tab on the top and bottom. You load the parts on the board and then put a foam top down on top that holds all the parts to the board. It snaps in place, you flip the whole thing upside down and Solder the back side, snip off the leads and you are done.
I typically load all the smallest parts first, resistors and diodes, solder them and then do the larger parts.
So in one evening the 42 boards get done shown here.
Now remember I have run my own multi million dollar screen printing business since·I was 15 years old (it was just thousands back then though) and I am 51 today so·I know something about production.
·
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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!
Post Edited (metron9) : 1/23/2009 4:08:34 AM GMT
····1. Heat up the solder bath to the correct temp. (There are temp-controlled solder pots available in all sizes for this.)
····2. Using Kapton tape, mask off any exposed metal on the bottom of the board that should not get solder.
····3. Insert all the parts into the board.
····4. Spray adequate flux on the bottom of the board to wet it and all the leads.
····5. Hang board over a hot pancake griddle to dry the flux.
····6. Dip board into molten solder. Let it sit there a couple seconds or so, then pull it out. This step requires almost no precision. The solder is so dense and has so much surface tension, that the board will float on top if you let it.
····7. Remove the Kapton tape, clip the leads, and clean off the residual flux.
····8. If the board is panelized, snap it apart, and dress the rough edges with a file or sandpaper.
You'll be amazed at the clean solder fillets you can get — better than you could ever get by hand. 'And all this without a huge investment in wave-soldering equipment.
-Phil
Carl,
you might have a look at some of the educational videos on Sparkfun.
www.sparkfun.com/commerce/tutorials.php
Click on "Surface mount soldering tutorials."
I've been wanting/needing to learn this sort of thing, too, but.... someday maybe....
I ask again, though -- how do you affix, say, tiny SMD resistors and such to the top of a PCB before soldering?· Just set them in place?· Is the solder paste, perhaps, an adhesive before it gets melted?· They're so tiny, surely they'd blow away if they were held merely by gravity.· Even the handling necessary to place the PCB in a toaster-oven must surely require gluing them somehow.· How?· And the bigger stuff, like IC packages with zillions of tiny pins (solder tabs), must be prevented from shifting even slightly.· How?
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· -- Carl, nn5i@arrl.net
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· -- Carl, nn5i@arrl.net
The paste holds them in place long enough to zap in the toaster oven. Positioning is critical, of course, but the solder's surface tension helps to center parts that are a little off. I use a syringe for the solder paste and non-magnetic tweezers to set and nudge the parts into place. Inevitably, there are solder bridges to suck up, but copper braid makes quick work of those. For larger-than-one-off runs, Advanced Circuits will sell you a mylar paste mask that you can use to squeegie the paste onto the board. I know of one person who makes his own mask with a laser engraver.
-Phil
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· -- Carl, nn5i@arrl.net
The air flow isn't very high so the parts stay put. The solder paste helps, of course.
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
This months Nuts & Volts Magazine "Surface Mount Soldering: Using The Tools You Probably Have On Hand Already. "
www.nutsvolts.com/index.php?/magazine/
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Aka: CosmicBob
The Zephrtronics stations are $$$, but it seems to me something like that could be made DIY.
Things are much more difficult with no-Pb solder, due to the higher temperatures and lower surface tension. In my opinion, I would always send out to a professional assembly house any complex PCB that has 100 parts and where the board is to be assembled in more than prototype quantity and for sale. They have the really top notch equipment for solder stenciling, pick and place, and reflow, and also they have the experience to get uniform and reliable results when a board has differrent sizes of components and even SMT on two sides.
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Tracy Allen
www.emesystems.com
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· -- Carl, nn5i@arrl.net
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
Did your oven come with the fan, or did you add one? The reason I ask is that my little IR unit lacks a fan, and I'd like to add one. But I'm not quite sure where to find one that will survive the temps.
-Phil
The motor is not inside the oven. There is a hole that the shaft pokes through.
Where did you mount the fan, and in which direction is the airflow aimed? I typically solder really small boards and can just picture them blowing off the rack.
Thanks,
-Phil
www.homanndesigns.com/SMDToasterOvenProject.html
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Aka: CosmicBob
The fan is set up like the picture. It is a centrifugal type so there are holes in front of the fan for intake and two holes on the side that exhaust. The original design had the motor pwm'd for different food functions but shut off the motor when the coils quit. The coils have too much residual heat to allow that.
I am soldering 60mmx70mm boards without them or their parts blowing around but I think it would work running a bit slower.
Regarding through hole soldering similar to SMT practices. Yes, it is completely possible but expensive and complicated. The process is typically referred to as "Pin in Paste". You screen print paste into the holes and above the annular ring of through hole locations, place the TH parts, and reflow with a standard reflow profile for the paste in use. There are several limiting factors to this process such as process specific board design, paste volume determination, and components that must be able to withstand reflow temperatures.
For quicker TH soldering, I would focus on speeding up your current TH soldering methods. Designing custom ESD foam flip boards is ideal for your situation. Having a board with properly placed foam to hold your parts in place will allow you to load the board completely, flip it, then solder then entire board without additional part handling.
From a CM standpoint, your board would probably be run through a wave soldering process. Either a typical wave, or a selective, depending on your board and/or panel layout. Selective example from ACE Protech www.ace-protech.com/products/kiss_102.asp
As for SMT, solder pastes are rather tacky and will hold passives in place even when the board is held upside down without reflow. When parts are placed by pick-n-place machines, they are placed "into" the paste so that the tackiness of the paste will hold the parts prior to reflow. If you have ever seen a fast pick-n-place in action, you will see that the force created by the XY table movement during placement is much greater than the air movement by a small fan, embossing gun, or hot air pencil (unless you are using them improperly). (example:
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Andrew Williams
WBA Consulting
IT / Web / PCB / Audio
Post Edited (WBA Consulting) : 1/26/2009 8:41:18 AM GMT