ReflowR SMD Reflow Kit - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: October 12, 2016, 04:24:36 am
content: How controllable is this hotplate going to be?https://www.indiegogo.com/projects/modern-electronics-reflowr-stem-inspiration-kit-technology#/

author: ataradov
author_rank: Super Contributor
timestamp: October 12, 2016, 05:21:58 am
content: It is for one-off boards, so I don't think that actual stability and repeatability matters that much, as long as it can somewhat preheat and then reflow the solder.I'd actually buy one for $50, but obviously not from IGG.

author: Kean
author_rank: Unknown
timestamp: October 12, 2016, 05:40:22 am
content: I find that an aluminium hotplate works quite well for me, as long as your PCB will sit flat - some can have a bit of warp/twist, especially thinner FR4. Having one that follows a profile is obviously better than relying on manual control, even if not as good as a commercial unit. I've had more problems with an oven or IR reflower in terms of connectors getting scorched.Apart from the obvious concern with backing crowd-funding especially on IGG, he also hasn't completed his last campaign for the plastic injection moulder. He does at least address this issue (somewhat), and it is also a fixed funding campaign. He promotes it for STEM use, but I forsee too many safety issues with heat and presumably it is mains powered but not safety tested (UL, etc).I have to admit I've once walked away and forgotten about a set of boards I had cooking... but it wasn't for too long, and the manual thermostat kept things from going bad and had no problems with the result. They were also thankfully boards for in-house use, rather than a client. So I'm somewhat tempted by this, but at a minimum I really wish it had a better UI. I should probably just fabricate my own.

author: DTJ
author_rank: Super Contributor
timestamp: October 12, 2016, 06:17:21 am
content: Quote from: Kean on October 12, 2016, 05:40:22 amI pop mine on a modified electric fry pan set to about 120°C once preheated a quick pass with the hot air tool reflows them nicely. I've screwed a slab of 14mm aluminum to the pan to provide a nice flat surface.

author: Kean
author_rank: Unknown
timestamp: October 12, 2016, 06:30:58 am
content: Yep, mine is the good old Sunbeam electric frypan that we never really used - it was probably a wedding present!I have a thermocouple JB Welded to the centre bottom for monitoring, but found if I set it to 7 on the dial the ramp up & down is close enough and repeatable.I probably should add an aluminium plate with some simple hold down clamps, but 14mm thick seems like it may have too much thermal mass for PID control and ramp down purposes.I like the fact I can sit in front of it and inspect te results while still at reflow temp and prod/poke any tombstoned or misaligned parts. You can't do that in an oven, but you do need to be careful not to burn yourself on the pan.

author: ataradov
author_rank: Super Contributor
timestamp: October 12, 2016, 06:32:10 am
content: And that's why I would want one - so I don't have to mess with kitchen implements ever again

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 12, 2016, 07:58:27 am
content: I think it needs a very obvious "This is hot" light indication

author: tggzzz
author_rank: Super Contributor
timestamp: October 12, 2016, 08:48:54 am
content: Quote from: Kean on October 12, 2016, 05:40:22 amThat can easily be overcome.I successfully use a £5 glass-lidded saucepan on a gas ring, and have not bothered to use the local homebrew Hackspace's reflow oven.I have a ~5mm layer of sand in the saucepan which spreads the heat and provides a heat buffer thus avoiding scorching. I use a non-contact thermometer to monitor the temperature of the board. With the gas on 1/4 way, the temperature rises slowly through the pre-heat phase, then at ~160C I increase the gas and, when I see the solder melt, I reduce then turn off the gas.You get a few grains of sand on the underneath; I haven't tried a board with components on both sides.FFI:https://entertaininghacks.wordpress.com/2015/03/25/assembling-pcbs-with-surface-mount-components/

author: Kean
author_rank: Unknown
timestamp: October 12, 2016, 08:59:36 am
content: Quote from: tggzzz on October 12, 2016, 08:48:54 amInteresting hack.When I notice such a twist stopping the board lying flat and properly reflowing, it is usually just a matter of using a wooden stick to poke the PCB flat and it typically straightens out with the heat. I kinda want the PCB flat anyway, and forcing it flat after soldering could crack a component. I guess if the twist was to return during cooling that could also happen, but I've never seen it.

author: DTJ
author_rank: Super Contributor
timestamp: October 12, 2016, 10:27:58 am
content: Quote from: Kean on October 12, 2016, 08:59:36 amSurely you meant powdered silicon dioxide rather than sand!

author: tggzzz
author_rank: Super Contributor
timestamp: October 12, 2016, 04:06:18 pm
content: Quote from: DTJ on October 12, 2016, 10:27:58 amThat would imply some form of purity! No NaCl in the sand, though ;}

author: Holmes34
author_rank: Contributor
timestamp: October 20, 2016, 08:46:40 am
content: For the money he's asking, you are better just building one yourself. Nothing special about the product using a micro to PID a shitty flat heating element (at least I hope they're not using something silly like Nichrome for this, but I don't know of any good flat heating elements that are this cheap at this size) and filling up the rest of the program space with some buttons and knobs. At best this will be uneven, at worst it may overshoot the temp due to shitty PID and fry sensitive components.Bare in mind that PID autotuning isn't a completely trivial problem, and may decide to completely go ape if the temperature sensor isn't giving you accurate readings or if your parameters are out of whack or whatever reason. I'm wondering how even temp measurements could even be done across the board without using a relatively expensive temperature sensor array ... If someone has a cool solution I'd love to hear!

author: gamalot
author_rank: Super Contributor
timestamp: October 20, 2016, 10:40:14 am
content: A few years ago when I was in China I had a much larger one, I was not satisfied with it, so I bought a small reflow oven.