Vapour Caper

Dawid Verwey

Issue 4, October 2017

When we learned that Dawid created a very simple vapour phase oven, for use with his non-contact soldering work, we couldn’t wait to take a look.

Vapour phase technology is a powerful way to solder surface mount devices. By heating solder just above its melting point, there is a greatly reduced risk of component damage from excess heat, which you may get from soldering.

WARNING: Dawid's oven uses electricity and liquids at very high temperatures. It has no brain, so please use your own.

How did you learn about vapour phase ovens?

I first learned about vapour phase ovens (VPO) in 2010, when I came to Australia and started working at Fine-Tech. One of my colleagues, Peter, had made his own VPO based on a design he had seen on the internet a really long time ago. When I started my little business, he loaned his oven to me and I was immediately smitten. Previously, I’d used a little bake-oven for soldering PCBs at home, but it was really painful. Peter offered to help me make my own (he’s got the coolest shed you’ve ever seen) and thus, my little oven was born. So this is basically version 2 of the oven; the only upgrade made from Peter’s one, is the use of a more sturdy, slightly bigger chamber. His oven is made from a rectangular olive oil tin, so mine can do slightly bigger boards and would, hopefully, last longer. That said, his has been going for more than a decade, so longevity is clearly not a problem!

Dawid is use to vapour-phase technology as he uses it in his workplace at Fine-tech Electronic Solutions: www.finetech.com.au
Dawid is use to vapour-phase technology as he uses it in his workplace at Fine-tech Electronic Solutions.

Yes, there’s clearly no planned obsolescence there! Your oven seems very functional - how are you heating the Galden?

The heat comes from a cheap 500W halogen lamp. The glass cover was removed and the light is bolted facing upwards, to direct as much heat as possible at the base of the chamber. The Galden is only about 8mm deep, so it is very important to ensure that the chamber is sitting level to avoid hot spots. Note: If you do decide to build one of these, I suggest grabbing a handful of spare globes, as these are a dying breed and I don’t know how long you’ll still be able to get them.

That’s about as simple as it gets! The Galden is expensive. Do you “use” much Galden in the process, or is it fully contained and re-used/re-cooled almost entirely?

I’ve been using my oven for about eight months now. I started with 300g of Galden and I’ve lost about 10g. My losses would probably have been less if I’d not been so slack and taken the Galden out after use.

The chamber of my oven doesn’t seal perfectly, so the Galden does evaporate over time. The best thing to do is to wait until everything has cooled down, and then move the Galden to a sealed container; I actually use a syringe to suck up every last drop! Just don’t do what I’ve done and leave it sitting in the chamber for weeks at a time!

Even losing a few grams in that period would hurt! Did it require any trial and error, or did it work first-go?

I did have to experiment a bit to find what works best for my oven. As the temperature is set by the Galden and the power is fixed, the only variable under user control is time. The size of the chamber, the mass of the boards in the oven, and the ambient temperature will determine how long it takes to bring the Galden to a boil. I use 230 degree celsius Galden, as it is suitable for use with both lead and lead-free solder paste. I just keep an eye on the board through the lid, and wait for the solder-paste to turn shiny. Then I give it another minute or so, just to be sure. Due to the nature of the process, you’ll be hard-pressed to burn or damage a board unless you leave it in the oven for a very long time. Lately, I’ve been running a 10-minute cycle by default, and that works fine, regardless of the other factors.

10 minutes - that’s less time than trying to solder by hand! Have you considered automating the PCB lowering/removal process, or is it too much complexity for such a simple process?

Considered – yes. Actually done something? It’s on the to-do list! As you said, it’s a very simple process; however, I’m thinking of automating it one day, just to make it a bit more convenient. Currently, the process is as follows:

  • Load the boards on the tray and lower them into the chamber.
  • Turn on the lamp and set your phone timer for 10 minutes.
  • After 10 minutes, turn off the lamp, raise the boards to the top of the chamber and wait two to three minutes for the Galden to condense and for the boards to cool down. Due to the low mass of the chamber, there is a huge temperature difference between the bottom and top of the chamber.

Automating this should be really easy, but if it ain’t broke…

That’s true... it could take many hours to finesse a basic automatic system, when it’s not really necessary. Any tips for someone who would like to build their own?

Most of the parts I used, I picked up from my local Bunnings, so no great challenges there. The acrylic lid was laser cut by my mate, but you should come pretty close with a drill and some careful measuring. The hard part is getting hold of a small quantity of Galden – I need about 300g for my oven but I bought 500g, just to have a bit spare. The going rate for Galden is about $1500 for 5kg, and that’s the minimum quantity you can buy. You can either persuade your friends to share the costs with you, or, if you have the means, buy a jar and sell the rest in small quantities online as a service to the community.

I’m sure there’s someone doing just that! What’s the coolest project you’ve used your VPO to solder?

I used my VPO to build the controllers and LED boards that went into my LEGO Ghostbusters Ecto for Brickalaide this year (Brickalaide is Adelaide’s big LEGO show, held annually at Easter time). I watched YouTube clips to get the flashing sequences exactly correct; and 28 LEDs were driven from two 8-pin PIC12F675’s. I’ll have to work really hard to think of something cooler for next year’s Lego show.

Dawid's Ecto at Brickalaide 2017. 3 x PIC12F675s driving 44 LEDs in the Ecto traffic light combined. Watch the video on facebook: @UCSInnovation.
Dawid's Ecto at Brickalaide 2017. 3 x PIC12F675s driving 44 LEDs in the Ecto traffic light combined. Watch the video on facebook: @UCSInnovation.

We’ll be keeping an eye out to see what you come up with! Are there any circumstances when you think a traditional iron would be better suited than the VPO when using SMD? Or is the VPO really the way to go?

This little VPO uses exactly the same technology as what the big, industrial ovens use, so this is not a toy. It is ideal for volume work or for soldering fine pitch parts or parts with big ground pads. For Brickalaide I made 80 badge light boards. These have nine 0603 LEDs on the one side, and the PIC, battery holder, switches, caps and resistors on the other side. Yes, it took me a few nights and weekends to get them done, but it was still heaps faster than doing them one joint at a time; and the quality is superb. That said, I still needed my irons (two is way better than one – trust me!) to do rework on the odd tombstone. I have also found that the LEDs in particular, are very sensitive to overheating. None of them got damaged in the oven, but I did manage to melt a few with the irons, simply because they are so tiny and you can struggle to make a good thermal connection.

Sounds like it adds some valuable robustness to the process. If you were to start over and make a second one, would you change your approach using the knowledge you have now?

As I said, this is already version two. I do plan on adding some latches to the lid to get a better seal. For version three, I may look at automating it, but that’s very far down on the list.

As boring as it may seem, the printing of the paste onto a board during production is one of the most critical factors in determining the quality of your final product. Too much paste or bad alignment may result in short circuits; alternatively, not enough paste and you end up with dry joints. In the production environment, stencil design is a fine art. I ordered this small stainless steel stencil with my PCBs, and the PCB manufacturer set up the array for me and designed the stencil from my Gerbers. It didn't cost much and it's really convenient. Some PCB manufacturers even offer a service where you can have multiple PCB designs in one panel, so if you order a stencil to suit, you can cover multiple designs with the same stencil. Another option is to use a syringe to dispense paste onto the board, which I do on my little LED boards; but it does take time and practice to get right
The Final Product
The final product. You may see that the parts have drifted. This is due to poor PCB layout on my side. The molten solder tends to go towards the holes and pulls the components with it. Lucky for me, the boards still work fine, so I don’t have to discard my PCBs. Some of us need to make the mistakes for others to learn from!
The PCB Tray
The PCB tray is suspended about 15mm above the bottom of the chamber and 5mm to 7mm above the surface of the Galden. I use the screws (in the tray) as supports when loading double-sided boards.
Halogen Spotlight
The heat source is a 500w halogen spotlight with it’s glass cover removed.
PCB tray
The PCB tray slides on two linear bearings.
Oven on its base
The complete oven on its base.

Awesome. Is there another cool project you’re working on right now?

I’m preparing for the Adelaide Makerfaire in November, so the little oven will be running hard, doing production on the first batch of my new LED controller. It is 30mm x 20mm, runs off a single CR2032 and drives 6 LEDs. So far I have created flashing sequences for police cars and fire trucks, as well as a flickering flame effect. Each board comes with five different user-selectable programs, and I still have a few other ideas I want to try out; writing the software is my favourite part. Before the launch, I also need to design and build a display, write an instruction manual (my least favourite bit), and design the packaging. I plan on having my little oven and some of my production equipment at the Makerfaire for a bit of show and tell, for folks who are interested, so do pop in and say hi!

We’re sure some of our readers will do just that! Thanks for talking us through your vapour phase oven, and thanks for the very entertaining pics!