Author Topic: DIY Wave Solder Machine... how?  (Read 4581 times)

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Offline fivefish

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DIY Wave Solder Machine... how?
« on: September 02, 2015, 08:27:37 pm »
Is there a DIY Wave solder machine out there? Yes... wave solder, for soldering Through Hole parts.

I already have a convection oven toaster I use for SMD parts.  But some of my projects are still using TH parts.

I would really love to see if a DIY Wave solder machine is possible.  It doesn't need to be big... maybe 5" max-width.

Questions:

1. If I understand, there is a fountain of molten lead that touches the underside of the board as it slides over.  How is this fountain created?  I know the lead has to be molten, so somewhere we have a heater. But what creates this molten lead fountain? A pump?  What kind of pump?

2. the PCB has to crawl slowly over this molten lead. I think a stepper motor and some chain drives can do this.

3. The PCB underside has to go over flux first, right? ... then slowly move over the molten lead fountain.

4. When the machine is turned off, the solder solidifies.  Doesn't this destroy the "pump"? (If there is one?)

 

Online Gyro

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Re: DIY Wave Solder Machine... how?
« Reply #1 on: September 02, 2015, 09:28:29 pm »
To be wave soldering you're talking volume board soldering, not a few protos.

A wave soldering machine has  a molten bath of solder, this will have typically two heaters, or more, tubular heaters immersed in it, (a bit like  oven grill elements, but obviously with the end terminations above the solder level. You need two heaters - if you have only one and in fails, you are left with it embedded in a solid block!

The wave (or sometimes two) is raised by solder pumped through a channel just under the surface in the bath level. The pump is a screw type driven by a variable speed motor (to set the wave height). Obviously it's hell on bearings etc as they are running at molten solder temperature! The pump body is part of the tank so is heated at the same time and is of course not started until all the solder in the bath is molten.

Yes the conveyor is normally chain drive, moving reasonably quickly over the wave(s). Flux is applied (brush or spray) before passing over the wave. Everything is fairly critical - the solder bath needs to be big enough that the level doesn't drop too quickly as solder is used by the boards, doesn't get cooled significantly by the passage of the boards and doesn't suffer too much contamination.  The wave height is critical, it must completely contact the bottom of the board but if solder runs onto the top of the boards they're scrap.

This all sounds impractical for diy. The bath takes a long time to heat at each startup (normally kept molten) and you then need to run a large batch of boards to make it worthwhile.

Your only hope might be 'dip soldering' where you hand flux the  then dip the board onto the surface of a shallow solder bath - something like a solder pot, but of course big enough for the surface area of the board. You could maybe construct something like that with an external heater on the bottom, but even for something small you would need a fair volume of solder - enough to cause you a significant burn hazard in an accidental spill (think deep fat fryer but with 'oil' as thermally conductive as metal!).
Chris

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Offline rdl

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Re: DIY Wave Solder Machine... how?
« Reply #2 on: September 02, 2015, 10:11:38 pm »
Have you ever seen a selective solder machine? They work similar to wave soldering, except molten solder is pumped up in a small fountain which moves around the bottom of the board. I could see a machine like one of those being feasible for home use. I don't know how affordable one would be though.
 

Offline mikeselectricstuff

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Re: DIY Wave Solder Machine... how?
« Reply #3 on: September 02, 2015, 10:23:26 pm »
Have you ever seen a selective solder machine? They work similar to wave soldering, except molten solder is pumped up in a small fountain which moves around the bottom of the board. I could see a machine like one of those being feasible for home use. I don't know how affordable one would be though.
But then you need an X-Y table for postioning.

If you really need it, using a subcontractor is going to be a cheaper option once you account for all the time messing around and trashed boards.

Or buy a used machine. A few years ago there were quite a few going cheap when lead-free became popular - older models couldn't handle the higher temperatures.
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Online IconicPCB

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Re: DIY Wave Solder Machine... how?
« Reply #4 on: September 02, 2015, 11:03:37 pm »
The "fountain " is produced in one of two ways

mechanical centrifugal pump, usually made of titanium or magneto hydrodynamic pump relying on forces created by an alternating magnetic  field established within the molten metal.

Heaters are outside a typically steel solderpot. The pot is often coated with various treatments.

The solderpot needs to be able to produce a wave taller than the length of trimmed component leads.

Often the pot is covered with " oil " ( a very heavy flux type of chemistry ) to minimize formation of dross ( oxide of solder alloys ) and ensure a clean solder only hits the PCB

Nitrogen is often introduced over the pot to improve cleanliness of the wave and perhaps improve it's wetting.

The mechanical pump needs to be interlocked with a  thermocouple to ensure the pump is disabled while solder temperature rests below liquidus.
 

Offline LaserSteve

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Re: DIY Wave Solder Machine... how?
« Reply #5 on: September 02, 2015, 11:16:39 pm »
The one I saw pumped the lead between two plates up into a fountain, which hit the board at an acute angle.  Then it had a hot air "knife" to blow off the excess solder downstream. Big, hot nasty machine. 

Steve
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Offline fivefish

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Re: DIY Wave Solder Machine... how?
« Reply #6 on: September 02, 2015, 11:41:50 pm »
The dip soldering idea may work. Sounds feasible. Found a few rectangular solder pot models on eBay that are big enough to dip medium sized boards. Previously, all I can find are just round solder pots that seem only good for dipping wires.

No, this is not for one-off prototype boards. I know better than that.

Contractor outsourcing - may need to revisit this again. a few years ago, made inquiries and NONE of US-based companies were even interested or have the courtesy to reply back to my email inquiries.  Well, one US company did reply back... with a "go away stupid" price quote. I guess because I'm not a big medical or military related company.
 

Online IconicPCB

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Re: DIY Wave Solder Machine... how?
« Reply #7 on: September 03, 2015, 09:30:10 pm »
If You are interested in rolling your own machine and need a solder pot , have a look at an American manufacturer of solder pots

www.wenesco.com


I have no commercial links with them.
 

Offline mikeselectricstuff

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Re: DIY Wave Solder Machine... how?
« Reply #8 on: September 03, 2015, 09:59:25 pm »
The dip soldering idea may work. Sounds feasible. Found a few rectangular solder pot models on eBay that are big enough to dip medium sized boards. Previously, all I can find are just round solder pots that seem only good for dipping wires.

No, this is not for one-off prototype boards. I know better than that.

Contractor outsourcing - may need to revisit this again. a few years ago, made inquiries and NONE of US-based companies were even interested or have the courtesy to reply back to my email inquiries.  Well, one US company did reply back... with a "go away stupid" price quote. I guess because I'm not a big medical or military related company.
Well now that many US based subcontract assembers' customers will have moved to Chinese assembly, those that are left may be more willing to take on smaller jobs.
Like any subcontract job, it's a case of finding the right place - attitude is everything!

 
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