Automatic Vapor Phase Oven - Page 1
Forum section: electronics / projects

author: Lukas05
author_rank: Contributor
timestamp: January 22, 2020, 09:30:23 pm
content: Hi everyone,I would like to show you my latest project. I´ve been working on this thing together with a colleague of mine for quite some time now. The beginning (not quite though, I started posting half way in the project) can be seen in this Thread:https://www.eevblog.com/forum/manufacture/practical-diy-or-modest-cost-vapor-phase-does-it-exist-yet/150/I wanted to seperate this topic because I'm toying with the idea of taking this a step further... But more on that later.The goal of the project is to build a reflow oven that can reliably handle sensitiv BGAs, as well as heavy inductors. I use a hot air station for my current projects. This often leads to molten connectors(the reflowable kind) and plastic bases of electrolytic SMD capacitors fused to the PCBs. This isn´t an option for upcoming projects. Also I´m tired of long debugging hours only to find out that one QFN pin didn´t reflow properlyMy first idea was to go the pizza oven approach, or purchase a cheap China-Chip-Heater. Thinking about massive inductors and D2PAK packages made this route seem a bad Idea. Adding to this where some black boards from a China-Chip-Heater that weren´t supposed to be black...So I started building a vapor phase ovenAt first I were the only one of my collegues (that I share an lab space with) who actively tried to built this thing. After the first mishaps though a collegue of mine joined the project.We´ve created a soldering oven that works quiet good so far.We could actually stop at this point, since the oven does what we have designed it for. But we wont do that, because its was fun to built this thing up to this point, and because we would like to provide this machine to other electronic enthusiasts as well.This Idea was born while looking around the web for affordable small scale reflow ovens, that would be able to provide reliable and good quality soldering results.What du you think about this? We thought about starting a small kickstarter that would enable us to put together a small kit for self assembly at a reasonable price. (the Idea is so fresh in our minds that I can´t give a cost estimate at this point)Anyway back to topic, the project progress:We are optimizing the PID loop at the moment. The test-profile should look something like this:The response of the oven at the moment looks like this:For now we are using the thermal mass of the PCB as a low pass filter. We are regulating the lift height by the temperature of the surrounding vapor.I have to model the thermal behavior of the vapor phase. I already started some simulations of the liquid itself (can be seen in mentioned thread)Getting the regulator values right is one of the biggest parts of the project.The apparatus itself looks like this at the moment:https://www.flickr.com/photos/136915492@N02/49425843363/in/datepostedhttps://www.flickr.com/photos/136915492@N02/49426539762/in/photostreamWe also made a short (and blurry) video of the last test run:We also tried to improve our paste printing gamehttps://www.flickr.com/photos/136915492@N02/49425842163/in/photostreamWe want to test different solder paste and different pad geometry for passives and the most common packages for active devices.To get meaningful results we have to make sure the paste application is as good as possibile.I will post the results of there test here once we are through with them.RegardsLukas

author: Cerebus
author_rank: Super Contributor
timestamp: January 22, 2020, 11:24:44 pm
content: Nice. What are you using for the vapour phase 'solvent*'?* Not quite the right word, but I can't offhand think of a better one.

author: Lukas05
author_rank: Contributor
timestamp: January 23, 2020, 09:42:50 am
content: The medium used in vapor phase ovens is called Galden.You can get this fluid with various boiling points. We use Galden LS230, wich boils at 230°C. This is also the peak Temperature the PCB can get to.Unfortunately Galden is quiet expensive. We use ~200ml in the current design.

author: Cerebus
author_rank: Super Contributor
timestamp: January 23, 2020, 02:15:30 pm
content: Quote from: Lukas05 on January 23, 2020, 09:42:50 amYeah I knew that bit. The difficulty and expense of getting hold of the right perfluoropolyether is one of the things that has made hobbyist/SME use of vapour phase reflow look a bit out of reach.Quote from: Lukas05 on January 23, 2020, 09:42:50 amNow there's the interesting bit. That a practical oven can operate with such a small amount of fluid is very interesting. Never having seen one of these beasties 'in the flesh' I'd assumed that litres of heat transfer fluid would be involved. Suddenly that (and seeing a physical prototype in operation) makes this look less of a pipe-dream.

author: trevwhite
author_rank: Frequent Contributor
timestamp: January 27, 2020, 08:49:06 pm
content: When are you likely to have kits available?

author: Lukas05
author_rank: Contributor
timestamp: January 29, 2020, 09:56:36 am
content: I thought about starting the campaign in one month or so.I can´t tell you how long it takes until we can make a kit available.It all depends on whether or how many people are interested in such a thing.

author: yiancar
author_rank: Contributor
timestamp: May 18, 2020, 10:15:49 pm
content: Hello Lukas05,This is all so exciting! Do you have any max PCB dimentions for your upcoming kit? I would definitely be in for a groupbuy/kickstarter!

author: free_electron
author_rank: Super Contributor
timestamp: May 18, 2020, 10:34:57 pm
content: Try to lift the board above the basket ( or get rid of the basket and use a side-clamping system. The basket itself acts as a huge heatsink and slows down the heating and the cooling process ( as it too needs to heat up and cool down)having the board in contact with the basket creates uneven heat transfer.

author: Cerebus
author_rank: Super Contributor
timestamp: May 19, 2020, 01:23:56 pm
content: Quote from: free_electron on May 18, 2020, 10:34:57 pmThe basic physics of vapour phase heat transfer makes that last bit untrue. Think about it for a second and you'll see that. Sure, anything that gets unnecessarily heated and cooled will steal energy from the whole process, but the whole 'phase transition process' thing is what gives vapour phase its ability to provide even heating to a specific temperature (the condensing point of the heat transfer fluid) with no overheating (as long as you don't superheat the vapour).There's other reasons to think a basketper seis not the best of ideas, not least of which is the likelihood of localised pressure from a basket 'wire' displacing components on a double sided board. Also I suspect that a basket is a likely place for the build up of contaminants over time, cooked flux and the like - just look at the build up of crud at the junctions of wires in a deep fryer basket to see what I mean.

author: Marco
author_rank: Super Contributor
timestamp: May 19, 2020, 02:51:35 pm
content: Quote from: free_electron on May 18, 2020, 10:34:57 pmUnless you make the walls from something with low thermal conductivity it's not worth worrying about, those will steal more energy than the basket. If they're steel the basket is a drop in the bucket.

author: free_electron
author_rank: Super Contributor
timestamp: May 20, 2020, 05:08:07 pm
content: Quote from: Cerebus on May 19, 2020, 01:23:56 pmwatch the video : some parts the solder goes liquid before others.

author: Cerebus
author_rank: Super Contributor
timestamp: May 20, 2020, 05:36:24 pm
content: Quote from: free_electron on May 20, 2020, 05:08:07 pmThat doesn't say much, with many solders being either eutectic mixtures or close to eutectic mixtures. With a eutectic some liquefying while others don't could amount to a temperature difference on the close order of 0.1C or even less.

author: ebastler
author_rank: Super Contributor
timestamp: May 20, 2020, 06:55:07 pm
content: Has anybody seen this project surface on one of the crowdwourcing platforms or elsewhere? Lukas05, the OP, has not been back to this forum since mid-February. So either he isreallybusy with this project, or he might have abandoned it...

author: Cerebus
author_rank: Super Contributor
timestamp: May 20, 2020, 07:08:06 pm
content: Quote from: ebastler on May 20, 2020, 06:55:07 pmOr, like everybody else in the world, has had his life serious disrupted and has had more pressing matters to deal with.

author: Lukas05
author_rank: Contributor
timestamp: June 25, 2020, 06:29:28 pm
content: QuoteI'm sorry, I actually wanted to report more about the development process in this thread. Unfortunately, the past months were filled with many parallel projects, and were accordingly labor-intensive.QuoteThat's right. During development we looked at several mechanisms to hang up the board. The mesh proved to be the most uncomplicated and flexible solution. The thermal mass is also relatively low. A rail system to clamp the boards would be much more massive.QuoteThat's right. If a board is double-sided, it must be mounted on spacers. At least in our own application there was always a possibility for this. In most cases we have simply clamped the board at the edge with washers. We have placed very small PCBs in a panel for easy handling. We used the tooling holes to mount the spacers.QuoteWe have soldered many boards now with this mesh. Contaminants slowly form there after ~100 Boards . It is therefore advisable to clean the mesh after 100-150 solderingsWe went online with the campaign on Crowdsupply yesterday. We would be happy if one or the other of you would take a look at the sitehttps://www.crowdsupply.com/pcb-arts/vapor-phase-one

author: trevwhite
author_rank: Frequent Contributor
timestamp: October 01, 2020, 11:20:01 am
content: I like the product but it seems such a lot of money for the hardware. Totally out of reach for a few boards here and there which is a shame because its perfect for that environment. Also the idea of committing the cash and delivery not starting until Feb 2021 is a long time to wait.Good luck though, it seems the goal on crowdsupply has been reached so am interested to hear how people get on with this unit.Trev

author: electrolust
author_rank: Unknown
timestamp: October 03, 2020, 12:59:20 am
content: Very interesting project!!QuoteBut why is fine pitch particularly challengingwrt vapor phase? Isn't the challenge in the placement? If you were hand soldering with a hot air pencil I could understand the challenge. Why is .35mm BGA a challenge for vapor phase? Once you've got the paste on and the part placed, which must be done regardless of process technology, where is the challenge vs eg SOT parts?On the campaign page where you have the comparisons, you should also note operating cost per 100 boards. Since one of your benefits is preservation of solvent. Have you done testing on the lifetime of the seal? It would be good to understand that.You should also list whether the product is produced by a company with other products and a history of maintenance, or whether it's made as a hobby device with low guarantee of support.

author: electrolust
author_rank: Unknown
timestamp: October 03, 2020, 01:03:35 am
content: Quote from: trevwhite on October 01, 2020, 11:20:01 amConsidering that the funding amount supports the build of only 12 of these ... where is the manufacturing lead time? Definitely not the type of project I would back!But I can't wait to see it delivered. I would definitely buy this if you can simply order it and if there are some reviews out there. I've been avoiding hot air / oven processes for so long but can't any more (can't avoid QFN and BGA in my recent works). I so don't want to get a tabletop chinese oven ...Open source is the icing on the cake.

author: coppercone2
author_rank: Super Contributor
timestamp: October 03, 2020, 07:40:36 pm
content: something to know about galden : it leaks like crazy, the surface tension is low, it is difficult to keep confined without good craftsmanshipAlso, inhaling the fumes will give you a massive headache. Don't stand over that potMost likely the reason why its so expensive is because the seams are precise and I bet as much forming was done as possible on the design to prevent leaks.I think the elevator built into the design is a good idea to minimize peoples exposure to galden and to minimize evaporation. You can do without it but you will likely have splashing, fume exposure, etc. I do fair bit of deep frying and I have no trouble with the cheapest of baskets going into the dishwasher or being exposed to sodium hydroxide.If the basket is stainless steel, then you can clean it with oven cleaner spray easily.

author: electrolust
author_rank: Unknown
timestamp: October 05, 2020, 08:16:07 pm
content: All my instincts tell me to not back this, but it's hard to resist. When will pre-orders close?@Lukas05, please show some photos of the cooling. Do you simply provide 2 ports and it's up to the user to provide either a closed-loop system or maybe circulating tap water than just runs down the drain? What about corrosion for the latter? In either type of system it seems that there has to be some control for the cooling, otherwise you have to babysit it. Is it possible to run it without any cooling (with much longer cycle times of course)?

author: Lukas05
author_rank: Contributor
timestamp: December 05, 2020, 11:00:19 pm
content: Hello everyone,it has been a long time since I´ve updated this thread unfortunately.I would like to show you what we have been up to lately with this project. As some of you already noted we hit our campaign goalWe are currently working together with a local partner who will assemble the devices. (https://www.assemblify.de/)There are still some (many) DFM optimizations we have to do at the current stage. We have decided to completely ditch the idea of a extrusion profile based housing. There are just too many single parts involved that drive up the necessary assembly time and cost. Using easy customizable profiles was a nice approach for a prototype that also worked really well, but for a production environment this isn´t the way to go, at least in our case. We designed a stainless steel sheet metal enclosure for the vapor phase oven. This is not only cheaper to assemble than the profile based approach, it also will look much better 😊 The prototypes are on their way, I will post some pictures once they arrived.We also Increased the heater surface area a lot. Up until now we regulated the heater surface temperature. The high power density of our heater caused it´s temperature to rise above the boiling point of the Galden due to the Leidenfrost effect. This means the average power Input to our heater was limited by the temperature regulation loop. With the new heater we don´t have this effect and can drive the heater with 100% duty cycle. This allows for shorter process cycles.After many tests we also settled on a closed cooling loop. This helps to control corrosion within the loop. The user will still have access to the cooling medium tank from outside the housing for refill or a complete medium change.Here are some screenshots of the CAD, I will post some pictures of the prototypes soon:QuoteI should have been a bite more precise with the description in that case. It´s not really the fact that these components are fine pitch that are the challenge, it´s rather a problem of the packages the fine pitch components come with. We soldered a lot "mirror finish" WLCSP parts in the past with a infrared oven. They not only reflect in the visible part of the spectrum. We had several cases where all transfer mold parts where correctly soldered while the solder paste in the middle of some WLCSP footprints hasn´t melted yet. It´s a similar story with the plastic of the connectors, just the other way around.QuoteYou are right, we will update the comparison. We did measure our galden loss with 0.49 ml (about $0.16) per cycle. (We measured the loss over twenty cycles so extrapolating that number should result in a large error)Concerning the seal we got some inspiration of products that are on the market for a long time now and added some of our own testing. The lifetime should be good, but we will definitely have spare parts ready.QuoteThe cooling cycle of the vapor phase is a closed loop. We use two radiators internally to dissipate the heat to the environment. The cooling medium tank can be accessed from the outside of the enclosure though. We monitor the cooling water temperature to prevent overheating. The firmware warns the user if starting a reflow cycle would trigger a overtemperature condition of the cooling water somewhere during the process and inhibits the start until the cooling medium is at a right temperature.That´s it for now, I will post an update with pictures soon!

author: coppercone2
author_rank: Super Contributor
timestamp: December 05, 2020, 11:30:41 pm
content: hmm if you are heating the galden in a loop a plumbing leak might cause a dangerous pressurized spray, with the tubing being routed near a ventare you sure its necessary to have that grate there over the plumbing? You might also want to put a drip tray under the unit with it standing above it to collect any hot leaks, I imagine if you are sitting at a table with that on, having galden flow on your lap is bad (the temperatures here are excessive compared to what you can expect in most fluid equipment).What you are supposed to do is puncture the plumbing and see what it does in the worst cases you can think of in your prototypealso make sure the elevator cannot decide to go too fast with the control system malfunctioning and splash people (not sure what the best is, counterbalance, damper, etc)

author: Lukas05
author_rank: Contributor
timestamp: December 05, 2020, 11:43:54 pm
content: I´m not sure if I get what you mean. We don´t heat galden in a loop. What you see in the second picture attached in my previous post are immersion heaters that heat the galden in the bottom of the soldering chamber. The heat transfer medium never leaves this chamber.QuoteThe speed of the two elevators are hardware limited. They can´t go over a certain velocity which is limited by the gear ratio and the max. voltage of the drive motors. We also have a software independent current limit for these motors in case someone puts his finger in the wrong spot while closing the lid.

author: wraper
author_rank: Unknown
timestamp: December 05, 2020, 11:50:23 pm
content: Immersion heaters will require a lot of galden, thus will make it expensive. Also it will reduce heating/cooling speed since you will need to heat/cool a lot of galden. Heating from underneath of the vessel is more econimical and requires less powerful heater. And you will need only a few mm of galden to cover the bottom.

author: Lukas05
author_rank: Contributor
timestamp: December 06, 2020, 12:20:54 am
content: We are using 500ml Galden at the moment. This isn´t a huge cost factor considering how many cycles you can do with that amount. (and the price of the oven) The nice thing using immersion heaters especially when they are covered only a few millimeters with medium is, that you can get the galden to locally boil before all the medium is heated above boiling. The convection currents which would transport colder medium to the heater surface can´t develop very well in a relatively thin layer of medium.But you are nonetheless right - a heater with low thermal mass underneath the vessel has advantages when it comes to cooling/heating times.There are other factors though with drove the decision to not go that route. One problem is mounting that heater. With huge thermal stresses this can be tricky, especially when using a thin wall stainless steel vessel. You can´t weld on these thin walls, and also can´t (or shouldn´t) drill holes in the bottom which you have to highly reliably seal in the next step. Manufacturers like asscon kind of work around that by using mikanit heaters sandwiched on the bottom of their vessels. They use a welded process chamber with comparatively thick walls which also has thermal an mechanical implications as you can certainly imagine.Considering all one has to keep in mind that this is a small batch process oven not meant for high volume production, so we choose the easy and reliable route with some tradeoff in cycle time.

author: coppercone2
author_rank: Super Contributor
timestamp: December 06, 2020, 03:46:47 am
content: oh I see you put wires in a tube, I thought it was fluid heat exchanger

author: wraper
author_rank: Unknown
timestamp: December 06, 2020, 04:11:12 am
content: Quote from: Lukas05 on December 06, 2020, 12:20:54 amThe issue is you basically have an unusable amount for technical needs which just stays there as ballast.QuoteIt's a wrong type of heater for such effect. Asks for heater used in steam cookers.

author: coppercone2
author_rank: Super Contributor
timestamp: December 07, 2020, 05:21:13 am
content: you need to decrease the watt density of immersion heaters when used with galden because the thermal conductivity is poor compared to water