I have been saved! Yes, I have seen the light…The little red one on the front of the Target hotplate! O.K. I haven’t lost it, let me explain. After reading the hotplate threads, I decided to take the plunge. I got the hotplate, bought some synthetic flux paste, and tried the first batch of a transceiver break out board I was making. The results were fair, and I spent about an hour reworking them. I made some board changes, etched the boards, and decided to try again.
The first of two, I hand soldered. It took nearly three hours, with the majority of the time spent soldering the 4mm 20 lead CC1100 in a QLP package! Those little leads just don’t play nice.
Next, I made the second using the paste, and since I didn’t have a template, I drew a continuous line of paste across the traces for the chip, and used an Exacto knife to separate the little globs of paste by cutting between them and wiping off the excess. I populated the rest of the board, gave it a once over, and placed it on the hotplate. Chipcon notes that their chips are moisture sensitive. I “cooked” the board at 60C for 5 mins., then brought it up to 180C for another 1.5 then turned the heat up to full until I saw the matte grey paste turn shiny on all components. Turned the hotplate off, waited another 30 seconds, and slid the board into a thin blade kitchen knife. I had two spots to rework…total elapsed time,35 minutes! Man, this is great! As a newly reborn “Hotplati” I want to thank the church’s founder Sparky.
Anyone who does a lot of SMT prototyping has got to try this method. For smaller boards, 0402 components and lead spacings under .050, it is priceless.
I have never done reflow board work, and I have a need to solder two double sided boards with SMD components on BOTH sides. I was wondering if anyone has used a hot plate/hot air approach in this situation. I’m concerned that I can’t use a hot plate to reflow both sides at the same time, and if I did one side at a time, I’m worried that I would run into problems with the side that I had previously soldered.
Any suggestions, perhaps a combination of the two approaches?
riden:
I have never done reflow board work, and I have a need to solder two double sided boards with SMD components on BOTH sides. I was wondering if anyone has used a hot plate/hot air approach in this situation. I’m concerned that I can’t use a hot plate to reflow both sides at the same time, and if I did one side at a time, I’m worried that I would run into problems with the side that I had previously soldered.
Any suggestions, perhaps a combination of the two approaches?
A hot plate would be disasterous. When the big guys do oven reflow, the bottom components are adhered in place to the underside of the board. I would reflow the side with more or PIA components, then do the other side by hand. The layout should be such that this is taken into account and all QLPs and TSSSSOPs etc. are on one side.
RonnyM:
A hot plate would be disasterous. When the big guys do oven reflow, the bottom components are adhered in place to the underside of the board…The layout should be such that this is taken into account and all QLPs and TSSSSOPs etc. are on one side.
I kinda thought that doing the hot plate thing with components on both sides would be a non-starter. These are existing board designs so I have to live with that. There aren’t any QLPs, but there are SOICs on both sides. I think I’ll pick a pick a side with the most SMD components and reflow that side and do the other by hand.
Just a little update. I put the wrong series of micro on the board when reflowing. Not wanting to lose it, I reheated the board with the same profile, and plucked it off when the solder melted. Real easy, and didn’t mess up the traces! This hotplate is so useful, I bet you could even cook with it!
For 2-sided work, a hot air solution like http://www.zeph.com will work. They’re pricey, but the kit pre-heats the board with air from the bottom, and then you use an air pencil to lift the temp on the top layer pins to reflow. The stuff on the bottom doesn’t crossover the melting point, and the lower temp is OK for longer durations.
Thank you, Richard, for the link to zeph.com. Very nice. I will definately have to look at the products if my needs extend past an occassional board for hobby use. I have to go through a budget approval process in our household. It is easy to get a few small PC boards through, but those soldering stations come in big boxes!
I have examined the boards carefully, and I have concluded that the best way for me to approach them is by reflowing one side and doing the other by hand. One of the boards has a single SOIC 16 and a couple of bypass caps (with the bulk of the SMD parts on the other side). The other board has only a few more SMD components.
I’m really getting excited about the prospects, and sense a moment of conversion coming on. The solder paste is on order and I’ll let everyone things worked out.
riden:
I have never done reflow board work, and I have a need to solder two double sided boards with SMD components on BOTH sides. I was wondering if anyone has used a hot plate/hot air approach in this situation. I’m concerned that I can’t use a hot plate to reflow both sides at the same time, and if I did one side at a time, I’m worried that I would run into problems with the side that I had previously soldered.
Any suggestions, perhaps a combination of the two approaches?
A hot plate would be disasterous. When the big guys do oven reflow, the bottom components are adhered in place to the underside of the board. I would reflow the side with more or PIA components, then do the other side by hand. The layout should be such that this is taken into account and all QLPs and TSSSSOPs etc. are on one side.
Hope this helps
Ron
Just for clarification (I’m one of them ‘Big Boys’ LOL) - typically double sided reflow parts are not glued to teh bottom side. The wetting forces from the solder keep the parts in place. In many years of convection reflow, I’ve never lost a part yet on the bottom of a two sided reflow. Of course there are parts that may come up that are candidates for hand soldering, but it’s very rare.
Actually with some of the higher lead count fine pitch stuff, the forces to remove them from molten solder are quite high.
The problem with double sided reflow on a hotplate would be the danger of cooking teh bottom side parts. The hotplate will heat by conduction. To conduct the heat to the board and topside parts, the bottom side parts would have to contact the plate surface. They would have to be much hotter than the top needs to be to conduct enough energy to the top side and cause damage to them.
Best method for two sided reflow would be a forced air convection oven.
Thanks for your comments, Steve. I really value information from people who have been there and can say what works and what doesn’t. That is why I like the SparkFun forums.
I can picture my boards being cooked because of the conduction issues you described! Fortunately, these boards aren’t overly complex, and I’m going to hand solder one side as the boards only have one or two 8 or 16 pin SOIC devices which I’ve hand soldered before. I’m going to have a go with the reflow work this weekend, and can’t wait to see how it works out.
Actually the model I bought was the 60PC (for PC control) but it has been converted to manual control with 6 temperature controllers. I am very happy with it as everyting works as new and it looks great. Only thing is you really need a dedicated shot to fit the thing in.
I took a chance with this one. They listed it as possibly needing work, conveyor replacement, etc. I t was also in Chicago which is about a 14 hour drive one way. But it’s working really well - in fact seems to work as well as our 14 zone convection oven at work as far as I can tell. Just needed a good cleaning and a new top fan.
The machine I have was built in 1995 and is a single phase unit. I cannot get three phase power at home and was happy to find a unit of this size with a single phase power requirement. This one is rated at slightly over 50A though.
The more recent models are 3 phase though, but mostly the same machine.
riden:
I have never done reflow board work, and I have a need to solder two double sided boards with SMD components on BOTH sides. I was wondering if anyone has used a hot plate/hot air approach in this situation. I’m concerned that I can’t use a hot plate to reflow both sides at the same time, and if I did one side at a time, I’m worried that I would run into problems with the side that I had previously soldered.
Any suggestions, perhaps a combination of the two approaches?
A hot plate would be disasterous. When the big guys do oven reflow, the bottom components are adhered in place to the underside of the board. I would reflow the side with more or PIA components, then do the other side by hand. The layout should be such that this is taken into account and all QLPs and TSSSSOPs etc. are on one side.
Hope this helps
Ron
Just for clarification (I’m one of them ‘Big Boys’ LOL) - typically double sided reflow parts are not glued to teh bottom side. The wetting forces from the solder keep the parts in place. In many years of convection reflow, I’ve never lost a part yet on the bottom of a two sided reflow. Of course there are parts that may come up that are candidates for hand soldering, but it’s very rare.
Actually with some of the higher lead count fine pitch stuff, the forces to remove them from molten solder are quite high.
The problem with double sided reflow on a hotplate would be the danger of cooking teh bottom side parts. The hotplate will heat by conduction. To conduct the heat to the board and topside parts, the bottom side parts would have to contact the plate surface. They would have to be much hotter than the top needs to be to conduct enough energy to the top side and cause damage to them.
Best method for two sided reflow would be a forced air convection oven.
Good luck with it!
Steve
I went ahead and bought a “Cuisinart” convection oven because it had digital control and temp readout. I populated both sides, and about 6 minutes later, had a fully soldered board, top and bottom! Now this is cool! Thanks for the insight Steve!
I’m glad to see it worked well for you. Care to share what oven you purchased? The fan forced type are hard to find unless you go professional and then they cost a bundle.
I would love to see someone put together a decent batch reflow oven with process controll for the casual user.
FESCSteve:
I’m glad to see it worked well for you. Care to share what oven you purchased? The fan forced type are hard to find unless you go professional and then they cost a bundle.
I would love to see someone put together a decent batch reflow oven with process controll for the casual user.
Steve
I’m not saying it was the best unit for the job, but it was available locally and seems to work quite well. #TOB165. Cheapest I’ve seen on the web is 137.- or so. There is a delay between inputting a new temp setting manually, and the oven responding. Up to 15 seconds, but not an issue. I’ve been working with some Chipcon transceiver chips that need to be baked at 150F prior to reflowing, and it seems to work fine. I just wish I could get it to stop popping the boards up through the top when thay are done!
Actually that looks like a great candidate for reflow soldering. I had thought Cuisinart brand to be too expensive, but that’s not a bad price.
I assume that the stock temperature controller will go up to a suitable reflow temperature. I notice that it has a 7 temperature memory. Can you set them up so that you can have a preheat, soak, reflow and cooling stages and manually switch between them?
Do you know the power rating of the oven in watts? How many heating elements?
I’m really getting enthused about the reflow process. I want to extend my thanks for all the great information that has been shared. Last weekend I reflowed a couple of small boards as a prelude to my main project, testing the waters so to speak. I used a hybrid approach using a Salton coffee mug warmer to preheat the board (235F) and then used a hot air gun VERY carefully to finish the job. It worked very well and the sight of the parts aligning themselves as if by magic was awesome! I was so excited that I turned around to let my son know how well it worked and I caught the mug warmer with my leg sending the boards flying. A little rework and I was back in business!
A little rework and I was back in business!