DIY Reflow Oven

So, you are designing your machine and hopefully going through with the building of it. But, you have decided that you want to design and build your own electronics for the machine as well. Well, there's a hard way, and an easy way to solder on your components.

If you plan on doing everything with through hole components, then you picked the hard way and you'll need to look elsewhere. Then, there's the easy way. This guide will help you make a Reflow Oven from a regular toaster oven so you can design and solder your own SMD components, making your design, and boards, MUCH smaller than those ugly looking through hole designed boards.

First of all, let me say, the best way I have found so far, is to design your boards using a program called DipTrace. You can find it Here. It's free use up to the first 300pin or pad designed boards. It will export into gerber files, which is what the circuit board manufactures need to print, drill, and mask your boards. Very user friendly and displays your products in 3D view. Pretty cool. Although the 3D libraries do not have all the designs, you can make your own from a drafting program like SolidWorks and save it into a .wrl file and DipTrace will create a 3D view of it, added to your board, so you can see what your product looks like before manufacturing. But it will only display in one color, unless you use the assembly feature of SolidWorks and make each part, assigning a color to that part, then assemble it with the other parts and save as .wrl. Then DipTrace will display your parts in 3D as color. Pretty cool stuff. Took me awhile to figure that out.

I have bought my boards from a company called Sitopway. There website can be found HERE. You can also find them on eBay under the username Sitopway, which is how I discovered them. They make the board and ship them fast. I think I got mine in like a week. They aren't bad quality, and for the price, very very good. I ordered about 2000 boards from them, 4 different designs, and the cost was about $600 bucks. Not bad. They can also make one off boards, prototypes, etc. for fairly cheap. You say you need some stainless steel stencils made as well so you can spread the solder paste across your circuit boards and get the correct amount of solder? They make and sell those too, at only $40 each. Well worth it.

The solder paste can be bought from a company called SMTSolderpaste which can be found HERE and is a distributor for Manncorp, maker of many smd/smt manufacturing equipment. They deliver pretty quickly, and the paste is shipped with cold packs, too make sure the solder paste does not go bad during shipment. When you buy the paste off eBay, they do not do that, so spend the extra money and get some quality paste.


When spreading your paste, I simply went to my neighborhood AceHardware and bought a 6 inch paint spreader thingy. The one they use for putting mud on the walls. I think I spent like $1.50 for it. It works great for spreading the solder across your stencil. Also, buy a bottle of rubbing alcohol. It works great for cleaning up the solder paste.

Okay, now onto the reflow oven. I am not tearing my reflow oven apart to show you the insides, but it's pretty easy to understand and do.

REFLOW OVEN BUILDING

The toaster oven I decided on was a Black&Decker convection toaster oven, model #T01675B. It has four heating elements, a good size (I think like 4 pieces of toast), and 1500 watts of power. It was cheap. A Total cost of just $35 at WalMart.


The first thing to do is to obviously unpack and take out your oven from the box. Throw away that manual, you won't need it anymore.

Unscrew the black metal that covers the 2 sides and the top. There are screws on the back and bottom. 2 of the screws require a star drive to get them off.

Once that is off, pop off the dials, and unscrew the parts from the front panel. Throw them away, you won't need them.

Clip the wiring for the elements; make sure to leave enough wire so you can reconnect those using butt-connectors. Use a good crimper if you have one when reconnecting wiring. The reason for clipping the wire is because they contain a set of diodes that are wired to them. You don't need those, and I spent several times unscrewing & screwing the toaster oven, trying to figure out why the thing wouldn't work. The diodes, those little suckers I didn't even know were there was the culprit.

Now, once that is done, download my free (I spent some time drawing this up) file I did in Microsoft Word ( ReflowOvenPanel2003.doc ). Find some 1/32"-1/16" aluminum sheet metal from your neighborhood Lowe's or HomeDepot, and also buy some 8-1/2x11 sheet of labels from WalMart or OfficeDepot that you can put into your printer. The design I laid out will make it easy for you to make a new panel, and also works as a guide for what you need to cut from the toaster oven to fit everything. This will make this process so much easier.

Once you have the panel made and the sheet metal of the toaster oven cut out and bent, ready for components, install the new panel, switches, and the PID Controller. The PID controller I went with is from Auber Instruments. A company here in the US. It's not cheap, at $80, but it's what is needed. The cheap ones on eBay I don't think can do the ramp and soak modes needed for the solder paste. Don't waste your money on them. You can buy the PID controller HERE, but you will need to download the manual from their site, as they don't include it with the product that is shipped. Manual is fairly easy to understand, but I will post the settings here later on what programming you need for that solder paste I provided a link for. Any other type of solder paste, you will need to configure your own settings.


Using a Data Logger, like the one from HERE, it will make it easier to tune your toaster oven for the plot graph you need for the solder paste you are using. Vernier is a company that makes a lot of the programming and testing equipment used in schools and colleges for their physics, chemistry, etc. courses. It works rather well. You will need the Go!Link adapter with the thermocouple sensor module. I think total cost was $143. It's nice, because you can get many other sensors that also work with the Go!Link and the software is included free. Simple easy data logging.


You will need a 40A Solid State Relay (SSR) and a heat sink for it. You will need Thermal Paste as well to place between the SSR and the heat sink. The 40A SSR can be purchased from eBay cheap. I used a 40A, 3-32VDC input to 24-380VAC output.


Now, once you have the new panel made, new switches, existing LED, and the PID controller installed into the new toaster oven, wire it up using this schematic.


The thermocouple should be ran from the top (under the black sheet metal, but outside oven) and drilled through into the toaster oven. Make sure it's placed in the center of the oven, and enough length so that it will sit approximately 1/2 inch above the circuit boards. Place the rack on the center grooves. The rack should sit evenly between the top and bottom elements. Placing the circuit boards too close to the top element, will melt your chips. I learned that the hard way. The thermocouple for the data logger can also be wired to the input terminals that the PID's thermocouple is wired too. You don't need two thermocouples.

Screw everything back up. Plug it in and power everything up and make sure it works properly. Take a glass of ice water, and place it inside the oven and recalibrate the data logger and the PID controller. Read the manuals that come with both products to understand how to do that.

That's it; you should now have a working homemade reflow oven, for cheap. The data logger connected to a laptop works great for tuning the PID for the different ramp and soaks that different solder pastes require, plus, it's kind of cool watching a real time graphing display move as the oven heats and cools.

I will post a picture later of my oven, and the settings I am currently using, right now, it's late.

Enjoy,
Falcon69

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• ReflowOvenPanel2003.doc‎ (101.0 KB)