[Falcon69]

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

[Bloy2004]

Thanks again!
I'll need a higher rated thermocouple. I see there is one available after March 12th: K type high temperature thermocouple for heat treatment [WRNK-191] - $18.62 : auberins.com, Temperature control solutions for home and industry



I intend to use the thermocouple on a heat treat oven for up to 2,000 degrees which only has a crude "high-low" switch, and still use the pid for the reflow oven.
I hope to be able to also use the PID to control a small "lost wax" burn-out oven which right now just has only a manual dial.

Heh, Jason, you're so proficient! A real pleasure to see your work.

[Bloy2004]

That's the toaster I'll be getting. But for my purposes, I think I'll be making up a socket to easily plug in the Pid controller connections. The SSR will be mounted in the oven but the Pid controller will have it's own case with handle to tranport between heating devices. I'm looking at the specs of the controller to see if several "setups" for different needs can be saved to make transfer easy. Otherwise just re-programing would suffice. It's not like any one oven will be running often. I'm just a dabbler.

Regarding the solder paste.... I'm not making anything to sell, and it doesn't matter to me either way, but are their restrictions for using lead based? I don't know the rules/laws on this yet.

[Falcon69]

dont know on the rules/laws either. I've heard lead free solder is hard to work with.

as far as the PID, I don't think you can save programs, but programming is pretty easy

[ackbar345]

Falcon,

I've also built the "poor man's reflow oven" using the Auber Instruments PID but I can't seem to get the PID values right and the Auto Tune doesn't seem to work worth a damn. Could you post your P I & D values? Thanks!

[Falcon69]

Those values will differ, based on which oven and PID you used. The only way to get the values correct is to play around with them with a separate probe hooked to a circuit board (placed in the center of the oven) and the data logger. Then play around with the values on the PID until you get the curve correct for the solder paste you are using.

[doorknob]

Can you use any old type K thermocouple with metal jacketed conductors, or is there something specific to look for?

Did you get the thermocouple with the PID (matched?) or would any one from eBay do the trick?

[Falcon69]

most of the ones off eBay are pretty cheap, not insulated very well. Buy one of the Auburn Instruments site. Make sure to connect it to a circuit board and place in the center of the oven, like, place the rack in the center, set the board on it, connect the type K to it, then configure the PID to the curve you need for the solder paste.

Make sure you calibrate the data logger, Depending on your data logger, you need to stick the thermocoupler in icecold water . That will set the data logger to 0 deggrees celsius.

[doorknob]

Are you actually affixing the thermocouple to the rack, or just hanging it in the center area?

I'm just getting started with surface mount soldering - I am probably going to play with an open-top skillet at first, but then move to a modified toaster oven for greater control of the temperature profile.

[ackbar345]

Those values will differ, based on which oven and PID you used. The only way to get the values correct is to play around with them with a separate probe hooked to a circuit board (placed in the center of the oven) and the data logger. Then play around with the values on the PID until you get the curve correct for the solder paste you are using.

So I used that same black & decker toaster oven from Wallyworld and the Auber Instruments SYL-2352P and one of their K type thermocouples. I think maybe I went wrong on the thermocouple, it doesn't clip to the circuit board, it is just stuck through the side wall. I insulated the sides and inside with rock wool. It seems to overshoot my 100degree //bake off chip moisture// step and then undershoot the final 480ish final step. I ruined a board yesterday

[Falcon69]

Are you actually affixing the thermocouple to the rack, or just hanging it in the center area?

I'm just getting started with surface mount soldering - I am probably going to play with an open-top skillet at first, but then move to a modified toaster oven for greater control of the temperature profile.

I hang it from the center of the oven down, but for the actual configuring of the PID to the right heating curve needed for the solder paste, i use a secondary thermocouple that works with the data logger, and using a laptop, i monitor the curve as the oven heats up. That thermocoupler is mounted to a circuit board, about 2x3 inch that's placed in the center of the oven. The reason for this, is because you want the actual temperature of the circuit board, and not the surrounding temperature of it for the solder paste heat curve. The thermocoupler that just hangs, that one is connected to the PID. Once the heat curve is data logged and you have the correct curve for your solder paste, you shouldn't ever need to readjust the PID, unless you change solder paste (lead to non-lead for example).

Ackbar345,
I did the same thing my first trial runs. I made the mistake of trusting the setting that was posted on that site for the PID, it melted my Headphone plugins on one of my boards. So I bought I data Logger and reprogrammed the PID. Give me a few minutes, and I'll grab the oven and post up the numbers, but no guarantees it will work for you. I have no idea what solder paste you are using.

Jason

[Falcon69]

Here are my step settings for my PID SYL-2325P.

C 01 -1
T 01 -1
C 02 45
T 02 1
C 03 80
T 03 1
C 04 110
T 04 1
C 05 175
T 05 1
C 06 10
T 06 1
C 07 -1
T 07 -1

Repeat C 07 and T 07 till end (should all be default at -1)

Keep in mind, that this is for the oven I've listed above, which is a 4 element (2 top, 2 bottom), convection (fan circulating air inside) and the SMT leaded solder paste I have listed above. These setting may or may not work for you. That's the reason you need to purchase a data logger or borrow one and monitor the setting on your PC or laptop. I believe you can also get an app now that you can plug a data logger directly into your smart phone.

Here's another link to check out. Dave just did this a couple months ago.

EEVblog #562 - More SMD Oven Reflow | EEVblog - The Electronics Engineering Video Blog

Jason

[ackbar345]

Jason,


You must be in Celsius. That is pretty much what my program looks like . I was more interested in your Settings. If you go into Setup mode where you tune the PID parameters there are values for P , I and D. I think you have to hold down the left button for a two count and the first setting is ALM1. If you scroll through you'll find your I, P, D (I think that is the order they show up in the menus).