'Air Bath' PCB Preheaters - question - Page 1
Forum section: electronics / general

author: dicky96
author_rank: Regular Contributor
timestamp: September 10, 2018, 05:56:10 pm
content: Hey guys I recently came across this video while doing a bit of research on reworking QFP128 chips as I have a current repair where i need to do that (just waiting for the parts to arrive)Anyway I came across this quite old video and thought it looked like a good way to conduct this sort of repair while minimising the risk of PCB damage - as it works at only 150COne problem with that kit is it's a bit expensive (but not stupidly so if you make money from repair work) but the main problem is that it's really hard to get one outside of the USA and they slap a 150 dollar order surcharge on anyone with the audacity to live in some other part of the world!! Forgive me for saying that sort of attitude really p%$^sses me off straight away!So I can get some Chip Quik low melt solder at a reasonable price instead of the zephyrtronic low melt solder and I was having a look around for cheaper PCB preheaters as it's something I've needed to buy for a while now.But so far I can't find another one that used hot air to heat from beneath - it seems every other one I find on ebay or aliexpress is infra red.So... anyone used an airbath type preheater and are they really better than the infrared ones?And where can I find an alternative (cheaper) product to the zephytronic one from a supplier who doesn't deliberately go out of their way to annoy non USA buyers!!cheersRich

author: coppercone2
author_rank: Super Contributor
timestamp: September 10, 2018, 10:00:08 pm
content: i wonder if you can just stick a hot air gun into a bent copper tube with a thermocouple at the end of it. maybe put some furnace insulation tube on itthat would be like 60$. a 862d crappy station that you can modify not to be a fire hazard is only 4cfm, that thing is 10.but 500$ i dunno, i think you could get away calculating the temperature drop and just using a expensive hot air station with some kind of adapter to save money and get more utility. you can build a big pcb holder thing to solder on and make it elevatable, if you really wanna save money

author: coppercone2
author_rank: Super Contributor
timestamp: September 11, 2018, 01:45:03 am
content: the holder might be nice because its big, if you are reworking a heavy ass board that has a big heatsink on it (i.e. power drive), then the stand might be worth its weight in gold, because it might be difficult to make a nice one that can hold up a heavy big board, but you can make most of it with epoxy and aluminum flat bar, at least the edge holder, with good epoxy and clean aluminum that you sanded and prepared correctly. So long you can drill aligned holes and properly use high strength epoxy or threaded screws its not that hard to make with just a drill press thats not horribly off parallel. You can buy steel pins/rods and use those, I think the key for a nice product though would be to use some kind of brass bushings for the slide assembly, you can drill out pieces of brass and glue them into the bars. The thumbscrew might wanna use a heavy plastic bolt so you don't scratch up your slide rods easily.Reams, taps, drill press, drills, slide rods, aluminum or steel flat stock, file, polishing compound,wax, thumb screws and brass bushings will get you the PCB clamp assembly down.The high adjustment seems a bit difficult to do right, if you want it height adjustable on the fly, because using threaded rods or thumbscrews is kind of janky, you would want like a collet that tightens on each axis.. Since there are only 4 small points of contacts you will want collets that screw in, or are brazed on.If you can use threaded rods for the height adjustment, or can live with thumb screws, I think you can make the mechanical part for like 120$ using quality materials. Or much less.If you figure out how to get a bunch of the appropritely sized collets for the various rods that would be a much much higher quality product.

author: dicky96
author_rank: Regular Contributor
timestamp: September 11, 2018, 07:42:45 am
content: I think I actually found some cheap air bath ones that heat from below the PCBhttps://www.aliexpress.com/item/853B-220V-540W-preheating-station-BGA-recovery-station-for-BGA-PCB-Preheating-heating-desoldering-Hot-air/32833389729.html?spm=2114.10010108.1000014.5.3a01460aIUYxE7&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.13338.110449.000000000000000&scm_id=1007.13338.110449.000000000000000&scm-url=1007.13338.110449.000000000000000&pvid=2a03dd63-698c-4f09-9dae-1633264f8690and also this one wit ha nifty looking magnetic PCB standhttps://www.aliexpress.com/item/AOYUE-853-853B-500W-Soldering-Station-Adjustable-air-BGA-Preheating-Station-BGA-Rework-Station-For-PCB/32861534440.html?spm=2114.search0104.3.301.29102676LuWErH&ws_ab_test=searchweb0_0,searchweb201602_4_10065_10068_10547_10059_10548_10696_100031_10084_10083_10103_451_10618_5016315_452_10307_10820_10301_10821_10303_5015615,searchweb201603_56,ppcSwitch_2&algo_expid=c2a48e29-78af-4049-b50a-3aac8d57d83a-44&algo_pvid=c2a48e29-78af-4049-b50a-3aac8d57d83a&transAbTest=ae803_1&priceBeautifyAB=0These also have the option to blow hot or coldAnyone tried either of these?Separate PCB stands are actually quite easy to find anyway for not too much money

author: stmdude
author_rank: Frequent Contributor
timestamp: September 11, 2018, 09:09:26 am
content: I have an "airbath". They're not that expensive on eBay/AliExpress really.I use it _very_ rarely. Pretty much only when I need to rework something that exceeds the thermal capacity of my hot-air station.For QFP rework (as OP were intending to), I never use it. Just some flux and the hot-air station, and you're golden.For gigantic BGAs with huge groundplanes wicking out all the heat, I use it to give the hot-air a fighting chance by heating the _entire_ board to ~150C.

author: dicky96
author_rank: Regular Contributor
timestamp: September 11, 2018, 10:05:38 am
content: Thanks for your input stmdudeI don't have a problem reworking smd with my hot air station, I've not done anything as large as QFP128 before but I have successfully changed QFP48 by applying plenty of flux, using my soldering iron to add enough 60/40 solder down each side of the chip to make all the pins shorted together then using my hot air station to desolder the chip.As the 60/40 reduces the melting temperature of the lead free solder, I can do this without accidentally desoldering other components nearbyBut what got my interest is being able to desolder these components at 150C. That has got to be better for the PCB!Rich

author: dicky96
author_rank: Regular Contributor
timestamp: September 11, 2018, 10:35:32 am
content: Large PCB standhttps://www.aliexpress.com/item/New-BGA-Rework-Stand-Bracket-PCB-Clamps-Universal-Bracket-Active-Stent-Bracket-Rework-Table-Accessories-DIY/32824165888.html?spm=2114.search0604.3.96.591f4c8c7YU43p&ws_ab_test=searchweb0_0,searchweb201602_4_10065_10068_5016515_10547_10059_10548_5016715_10696_100031_10084_5016615_10083_10103_451_10618_452_10307_10820_10301_10821_5016415_10303,searchweb201603_55,ppcSwitch_7&algo_expid=05b7756b-8981-496e-89cb-3e2cd4fdd4fb-14&algo_pvid=05b7756b-8981-496e-89cb-3e2cd4fdd4fb&transAbTest=ae803_1&priceBeautifyAB=0cheap enough?

author: coppercone2
author_rank: Super Contributor
timestamp: September 11, 2018, 03:49:15 pm
content: the downside of that is that it uses ribbed reinforcements so its gonna be a pain in the ass to clean and generally not as nice as sliding round surfaces