Electronics > Manufacturing & Assembly

Beta Layout reflow kit, first try


I decided to get my own reflow facilities. I bought:
Beta Reflow Kit: http://www.beta-estore.com/rkuk/order_product_details.html?p=13

The controller for it: http://www.beta-estore.com/rkuk/order_product_details.html?p=242

and a vacuum pick-up tool: http://www.pcb-soldering.co.uk/aoyue-932-vacuum-pick-up-station.html

I bought some leaded solder paste, too. In my lab, I like to work on lower temperatures. Besides, I think a 300€ SMD line might not be as tightly controlled as the factories I'm used in the past, so it is good to have some leeway here.

First the vacuum: Ok for the price, but sucks too much. The local aquarium store sold me a magnetic valve and the local electronic store a footswitch, so less than 100€ and some work I have tool that ready-made would have cost me about 500€. I'm happy with that, even though I needed to file the end of the suction needle to fit my hand angle and squeeze it to third of the original size so it does not eat 0603 parts.

The oven and controller should be seen as one unit. The controller can be programmed with several soldering profiles and you can tune the parameters. And you should, the oven does not heat or cool very fast, therefore the set times are not very accurate, even though there is a "learn" feature on the controller. The "kit" adds some experimental boards, a stencil, some parts, paste etc. My first real board board will be fairly complex with 200€ worth of parts on it. I didn't want that to be the first try, so I bought the kit.

I haven't done a teardown nor do I plan to. The build quality of the oven is what you expect from a sub-50 pizza oven. But it works, good enough. The controller is  just as you see, a plastic box. The packaging and instructions is fine, so there is some care put in to the product. I connected the supplied multimeter, my Extech and the controller temperature sensors to a scrap board and run some tests. all the meters appear to show similar temperatures and the controller sensor seems to react the fastest. After I came to this conclusion, I used the controller temperature readings.

It took me several tries to get the profile close to paste manufacturer specification. But there were no issues, the controller is able to log the temperatures to serial port in a format that excel has no trouble plotting curves, so it only took a couple of hours before I was ready to try a board. (The oven needs to cool between cycles.) Buying the kit was a good idea, I feel confident about my work flow now. (For example, I realized the vacuum would suck in 0603 components only at this stage...)

If you search beta reflow on YouTube, you'll find some videos about the kit and how to put paste on the sample board. I did just that and baked the board. Most of joints were perfect. The SOIC part did not sink in to the solder as much as I would have liked; maybe my profile is not perfect yet? More soak time? More reflow time? A bit higher reflow temperature? We'll see; I'm sure I'll get it perfect after a few real boards. The test result was good enough that I'll do a real board tomorrow.

There was also some small loose solder balls. I think there was too much paste on some of the pads, but it looked that way to me from the beginning. I would not have put that big pads on 0805 or 1206 parts.

Bottom line: about the cheapest SMD system you can buy, so it is not perfect. But value for the money is excellent. The purchase pays for itself tomorrow when I build first real board with it. That board is complex enough that I would not do it by hand. Without this system, I would have paid more that the price of the kit for assembly of thes one board alone. This is perfect for my few boards per year.

Update: First real board turned out to be perfect, as far as soldering goes. No touch up required, other than for one poorly placed resistor. I wouldn't have noticed anything unusual if I would have got that board back from a real factory. Very happy! :)

Excellent write-up, thanks for sharing your experiences.

How do you do your stencils? Do you order them or fabricate them some DIY way?

I some short time i will be trying to fabricate a stencil with my CNC mill. I'm just wondering about the material, because i'm pretty limited to plastics, wood derivatives and aluminum, did't test brass or bronze yet. Steel is a definite 'NO'...

You can get polyester stencils cheaply from the net. I first placed an order to http://www.smtstencil.co.uk/, but his printer broke. I was getting in a bit hurry, so I ended up getting the first stencil from the same place where I got the PCB, http://www.eurocircuits.com/, 49€ for a 195 x 140mm steel stencil. With that kind of prices and the small amount of boards I do, DIY stencils are not worth the effort for me, especially as I get my "I knew I could do it" satisfaction elsewhere.  :)

I would be surprised if a CNC mill could do a usable traditional stencil. You want the stencil to be very thin and likely, to have square corners. I would expect much tearing. On the other hand, maybe a drilled stencil with round blobs of paste but thicker than with a real stencil would work just as well. After all, you end up with a molten blob of solder; maybe it doesn't matter that much which shape the solder started with. On rectangular pads, you likely need two or three holes, which implies some software work. Then, you just need to be more careful in placing the parts, so that they end up on the paste. Interesting, let us know if you succeed!


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