DIY SMD reflow? - Page 1
Forum section: electronics / projects

author: JuKu
author_rank: Frequent Contributor
timestamp: November 25, 2011, 07:53:47 am
content: It is becoming more and more tempting to do my own SMD board builds. Thishttp://www.reflow-kit.com/rkuk/index.htmlkit just might have enough appeal to make me try. The offer is 129€ for the oven, some supplies and some stuff to practice on, another 129€ for a controller.-Do any of you have experience with this particular kit? Is is any good?-If you have your own oven, any tips in general that you can share?-Can you do double side assembly with this method? Assuming only small capacitors and resistors, is the tackiness of the paste and surface tension of the solder when melted enough to hold small chip components in place?-Does DIY SMD reflow work in the first place, how sensitive the process is to heat profile and how difficult the profile is to get good enough?Thank you for your comments! I'll share mine if I decide to go for this.

author: sub
author_rank: Regular Contributor
timestamp: November 25, 2011, 08:37:27 am
content: Sparkfun have an article on reflowing with an electric frying pan:http://www.sparkfun.com/tutorials/59

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 25, 2011, 09:37:02 am
content: I've done hundreds of boards in a standard toaster oven, which is what the one in the reflow-kit is. I don't bother with closed-loop temp control, just run it at about 50% for 3 mins or so, and boost it up a bit once solder starts melting. Once flowed, open the door and allow to cool naturally.I also have a large commercial pizza oven for large boards, which I modded with a stove glass window.A timer that goes beep after your oven's normal reflow time is essential, as you will get distracted while waiting for it to heat up Having said that, the other day I accidentally left a panel in for about 10 mins and apart from sight discolouration of the silkscreen and a couple of melted inductors, the board was fine.Obviously don't use leadfree solder- the margin between reflow and burn is much narrower, and oxidization is more of a problem at the higher temperatures.The important things about an oven are heaters top and bottom, a good clear window, and a tray that doesn't knock or bounce as the door is opened.

author: johnmx
author_rank: Frequent Contributor
timestamp: November 25, 2011, 08:12:17 pm
content: My advice is to forget the kit and the controller and buy the oven in a local store. Search for small ovens (<18liters), powerful (>1500W) and longer heaters. Check if the door opens smoothly without shaking the oven. A clear glass door helps to see what’s happening inside.Don’t waste time making a controller. Just buy a multimeter with temperature meter and use a good thermocouple.Double side boards are very easy to cook. I never have seen a component dropping during the second reflow process. But reflow first the side with smaller components.See bellow a picture of my oven (16 liters/1500W). Note the long heaters (4 way) on top and bottom.

author: IanB
author_rank: Super Contributor
timestamp: November 25, 2011, 08:31:42 pm
content: Quote from: johnmx on November 25, 2011, 08:12:17 pmDo you use a thermocouple with a high temperature insulating braid? I think many regular thermocouple assemblies are not designed for use in high temperature environments like ovens.

author: kripton2035
author_rank: Super Contributor
timestamp: November 25, 2011, 08:40:37 pm
content: Quote from: johnmx on November 25, 2011, 08:12:17 pmcan you please explain your process to cook double side board and be sure no component gets dropped ?thanks.

author: ToBeFrank
author_rank: Regular Contributor
timestamp: November 25, 2011, 09:06:22 pm
content: Quote from: JuKu on November 25, 2011, 07:53:47 amI've done several boards in my setup. I have the TechFX reflow controller (they went out of business). Their software sucks, but it works and it follows the temperature profile. As others have said, I don't think you necessarily need to have a controller. However, I do have an expensive component on one of my boards that says not to reflow it any higher than 220C so I'm glad I can set up a profile for it.QuoteI've only ever used the lead free solder paste, and I've not had any problems. Obviously I do have a controller doing profiles though.

author: johnmx
author_rank: Frequent Contributor
timestamp: November 25, 2011, 09:34:21 pm
content: Quote from: IanB on November 25, 2011, 08:31:42 pmI use the following thermocoupler (Farnell code: 4100773):http://pt.farnell.com/labfacility/xf-324-far/sensor-t-couple-k-f-g-2m-miniplug/dp/4100773?Ntt=4100773

author: johnmx
author_rank: Frequent Contributor
timestamp: November 25, 2011, 09:52:11 pm
content: Quote from: kripton2035 on November 25, 2011, 08:40:37 pmThere is nothing special about it. Just don’t let the bottom components to touch the grate. I use small pieces of rigid copper to suspend the board in the air. Surface tension is our best friendYou can find lots of videos in the internet explaining this.

author: JuKu
author_rank: Frequent Contributor
timestamp: November 26, 2011, 07:28:36 am
content: Quote from: kripton2035 on November 25, 2011, 08:40:37 pmhttp://www.circuitmart.com/mart/50397D.shtml

author: slateraptor
author_rank: Frequent Contributor
timestamp: November 26, 2011, 10:31:04 am
content: Quote from: mikeselectricstuff on November 25, 2011, 09:37:02 amPics or it doesn't exist.I can only imagine what a tour of your workshop might be like: "And off to your right is an ESD-safe workbench, complete with oscilloscope, bench power supply, signal generator, spectrum analyzer and large commercial pizza oven."

author: Psi
author_rank: Super Contributor
timestamp: November 26, 2011, 11:26:01 am
content: It better still be able to make pizza!

author: vl400
author_rank: Regular Contributor
timestamp: November 26, 2011, 12:00:16 pm
content: Quote from: slateraptorThis handy SMD video shows it and the toaster oven ..

author: slateraptor
author_rank: Frequent Contributor
timestamp: November 26, 2011, 12:29:34 pm
content: LOL! That's great! My imagination was actually expecting some ridiculous wood-fed iron behemoth with a smoke stack and moving conveyor.

author: metalphreak
author_rank: Frequent Contributor
timestamp: November 27, 2011, 04:27:31 am
content: I use a sunbeam BT2600 "snack oven". RRP is only $64.95 AUD and you can usually get it for $50. Has 2 pairs of elements top and bottom. At the moment i'm building an external PID control box using a 1/16 DIN commercial controller, with a standard power socket on the back to plug in whatever device. K-type thermocouple jack on the back of the box goes to a thermalcouple mounted in the oven (just a hole drilled through the back panel). Like this:http://image.made-in-china.com/2f0j00qMwTgQhKASki/Thermocouple-Sensor.jpgIf you're happy to sit there and watch, you can just crank up the temperature and watch closely. The mechanical thermostat in these ovens are rubbish though. I set mine to 240 degrees and it rocketed to over 300!Also, the fabric braiding on regular temp probe leads will burn and turn brown/black, but they still work fineJust not something to use permanently.If doing double sided boards, you'll need something to prop up the board on its edges. You can actually get a specific type of glue for SMD components when doing 2 sides. Its red and comes in the same syringe tubes as solder paste/flux.

author: IanB
author_rank: Super Contributor
timestamp: November 27, 2011, 04:50:27 am
content: Quote from: metalphreak on November 27, 2011, 04:27:31 amFoodstuffs mainly don't mind that

author: Joshua
author_rank: Regular Contributor
timestamp: November 27, 2011, 06:04:12 am
content: In one of Mikes videos (tips for smd... I think?) he shows his reflow setup. I think the pizza oven is near the end.

author: slateraptor
author_rank: Frequent Contributor
timestamp: November 27, 2011, 07:03:12 am
content: Quote from: metalphreak on November 27, 2011, 04:27:31 amWhy PID as opposed to some other topology if you don't mind me asking?

author: metalphreak
author_rank: Frequent Contributor
timestamp: November 28, 2011, 12:32:02 pm
content: All the commercial temp controllers use PID. If I had the time I would have designed something microcontroller based but this way is cheap and lazyThis is the controller and solid state relay i'm using:http://www.ebay.com.au/itm/20-OFF-Digital-PID-Temperature-controller-25A-SSR-K-thermocouple-thermostat-/220888955443?pt=LH_DefaultDomain_0&hash=item336e01fa33#ht_5479wt_985

author: 8086
author_rank: Super Contributor
timestamp: November 28, 2011, 12:49:48 pm
content: If it's a toaster oven thing then theres no point using PID as the elements don't react quickly enough. A relay would actually work just as well.

author: metalphreak
author_rank: Frequent Contributor
timestamp: November 28, 2011, 01:00:53 pm
content: without PID control it *will* overshoot if you simply turn the elements off once it reaches the desired temperature. and then you end up with melted plastic components and such (found this out the hard way...) In any case, all the commercial units I could find use PID so it was the only option. Something more basic might work, but why not use PID if theres no additional cost. It certainly can't hurt.

author: johnmx
author_rank: Frequent Contributor
timestamp: November 28, 2011, 01:34:51 pm
content: Quote from: metalphreak on November 28, 2011, 01:00:53 pmThe elements response is predictable. Off course you need to shut them off before reaching the set point temperature. In my oven the temperature will raise more or less 7ºC after turning off the elements. You should turn on the oven one time before the reflow process to heat its metal case in order to get high repeatability.

author: 8086
author_rank: Super Contributor
timestamp: November 28, 2011, 01:50:04 pm
content: Quote from: metalphreak on November 28, 2011, 01:00:53 pmThere is considerable cost difference between a high current rated mechanical relay and a high current SSR.

author: DaveW
author_rank: Frequent Contributor
timestamp: November 28, 2011, 01:52:59 pm
content: Quote from: 8086 on November 28, 2011, 12:49:48 pmBurst control with those heaters work very well indeed, you can get fine control with PID very easily

author: metalphreak
author_rank: Frequent Contributor
timestamp: November 28, 2011, 02:26:39 pm
content: Quote from: 8086 on November 28, 2011, 01:50:04 pmThere's plenty of different versions of these controllers, with inbuilt relays (low current), relay outputs for external relays, digital output etc. The ebay item I linked to includes a 25A SSR with the controller and a thermocouple for <$40 SSRs are not as outrageously expensive as they used to be.It makes it very easy to build something into a project box that is easily capable of 10A @ 240V, built using safe properly engineered hardware. Seeing home made stuff switching high voltage with exposed PCB traces, terminals etc makes me cringeYou can also use something like this for more than just toaster oven reflowhttp://mhkaufman.blogspot.com/2009/11/home-made-electric-smoker-with-pid.htmlhttp://www.flakshack.com/forum/index.php?topic=14079.0http://battlesnake.blogspot.com/2011/10/my-first-foray-into-modern-cooking.html

author: robrenz
author_rank: Super Contributor
timestamp: November 30, 2011, 01:10:08 am
content: I added this PID control to my old hotplate. The controler has a fuzzy logic Autotune of the PID parameters. It auto tuned in one pass and works very well with very minimal overshoot (1-2 deg. F) Manual adjustment of PID parameters is not trivial so the autotune is very valuable even if you just use it for a starting point for manual tuning.Controllerhttp://www.ebay.com/itm/350384161137?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649SSRhttp://www.ebay.com/itm/230390463312?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649Heatsinkhttp://www.ebay.com/itm/350488370748?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649Controller includes thermocouple. total cost 56.40usd + 11.95 shipping

author: slateraptor
author_rank: Frequent Contributor
timestamp: November 30, 2011, 02:30:59 am
content: Quote from: robrenz on November 30, 2011, 01:10:08 amWhat part exactly?

author: robrenz
author_rank: Super Contributor
timestamp: November 30, 2011, 02:52:30 am
content: Quote from: slateraptor on November 30, 2011, 02:30:59 amIf someone knowsnothingabout tuning a PID control and does not use instructions on the basics of how to aproach it. It will be a very frustrating experience. I understand that the fuzzy logic autotune may not give you the most aggressive parameters but it gives someone with no tuning experience a good working system.

author: IanB
author_rank: Super Contributor
timestamp: November 30, 2011, 04:49:19 am
content: Quote from: slateraptor on November 30, 2011, 02:30:59 amThere are two kinds of people in the world: people who know how to tune PID controllers and people who don't. Guess which group is the largest?

author: slateraptor
author_rank: Frequent Contributor
timestamp: November 30, 2011, 12:54:48 pm
content: Quote from: IanB on November 30, 2011, 04:49:19 amFor a second there, I thought we were discussing an EE topic on an EE forum.

author: wkb
author_rank: Super Contributor
timestamp: November 30, 2011, 01:15:52 pm
content: Quote from: slateraptor on November 30, 2011, 12:54:48 pmOh my $DEITY, we can't have that, can't we?

author: slateraptor
author_rank: Frequent Contributor
timestamp: November 30, 2011, 02:57:14 pm
content: Assuming the system is controllable:1) Approximate the open-loop xfer f'n of the system to be controlled.2) Root locus to determine closed-loop feedback gain that results in marginal stability.3) Ziegler-Nichols heuristic as a nominal starting point.4) Tweak gains until desired response achieved.or if you have the PID controller already integrated...1) Set integrator and differentiator gains to zero.2) Increase proportional gain until marginal stability is observed.3) Ziegler-Nichols heuristic as a nominal starting point.4) Tweak gains until desired response achieved."Tweak" with an understanding of the trade-offs listed here:http://en.wikipedia.org/wiki/PID_controller#Manual_tuning(I think wiki has understated the differentiator gain's affect on overshoot)Quote from: robrenz on November 30, 2011, 02:52:30 amAlternatively...1) Research PID control.1) Purchase integrated off-the-shelf sol'n.2) Press autoset.3) Hope and pray.Admittedly, a robust sol'n that gets the job done quickly.Jokes jokes. Gonna go hide in my corner now before receiving an admonishment from the resident controls expert.

author: gregariz
author_rank: Frequent Contributor
timestamp: November 30, 2011, 09:22:48 pm
content: I use a simple griddle from walmart ~$30. No controllers. I turn the temp to max and let it go. The reflow takes about 8mins or so, so its slow enough to fit into most profiles without having to worry about it or program anything. Has worked well for many many boards so far. Then turn it off and let it cool. Very painless.

author: robrenz
author_rank: Super Contributor
timestamp: December 01, 2011, 12:47:38 pm
content: I got a nice Black & Decker toaster oven with a convection fan at a thanksgiving weekend sale. Normaly 69.99usd on sale for 29.99usd. Unbelievable! 4 heating elements with perforated shrouding to cut down on the direct infrared and reflectors to focus more heat to the inside. Fan is gentle its not going to blow any parts off. Perfect!

author: mobbarley
author_rank: Regular Contributor
timestamp: December 01, 2011, 01:13:59 pm
content: This my baby:Even rewired from 15A down to 10A she goes from heat soak to FR4 fire in a few minutes. Definitely needs better temperature control as the dials are either a pie warming heat or full on.I needed something to do large ~A4 sized boards - this thing is big, the entry is something like 60cm wide.

author: slateraptor
author_rank: Frequent Contributor
timestamp: December 01, 2011, 08:05:06 pm
content: Quote from: mobbarley on December 01, 2011, 01:13:59 pmFrom your pic, I can't tell if it's countertop or industrial size.

author: Time
author_rank: Frequent Contributor
timestamp: December 01, 2011, 08:38:20 pm
content: Having a precisely controllable oven has never seemed necessary for me. There are so many threads on this forum and many other forums that pertain to customizing ovens.For the first time you use an oven and dont have a feel for yet, just preheat the oven up 200C or so and let the temp stabilize there. put your board in and let it "soak" for awhile. The board and the whole oven should be at 200C at this point. Then turn up the heat little by little until you see it flow. Do this a few times and youll know how to work your oven with melting stuff.

author: robrenz
author_rank: Super Contributor
timestamp: December 01, 2011, 08:54:13 pm
content: Quote from: Time on December 01, 2011, 08:38:20 pmI thought the same way until I put a pid controller on my hotplate. It is nice to be able to just set 200 degrees and walk away and have it hit 200 and stay there without overshoot. Then turn it up to whatever you want to and know it will go to that temp and stay there without overshoot. Yes, it is not necessary but it shure is nice and saves a lot of babysitting time.

author: mobbarley
author_rank: Regular Contributor
timestamp: December 01, 2011, 11:04:09 pm
content: Quote from: Time on December 01, 2011, 08:38:20 pmthe white board is an itead 10x10cm.

author: JimmyM
author_rank: Regular Contributor
timestamp: December 07, 2011, 10:31:36 pm
content: I love reflow oven threads. I like to see how everyone struggles with the same problems as I have. Meaning I'm not just crazy or obtuse.My oven started off as a Bella Cucina 1500W convection oven from Macy's ($30 on one day sale). But it ramped too slowly. I got a second oven for its heaters and added them to the first. That plus insulation means it ramps and hold temp nicely. But the damn thing overshoots so badly using my TechFX reflow controller that I'm on the verge of scrapping it and building my own. Below is a pic of the oven just before completion. I have actually routed the thermocouple properly.

author: djsb
author_rank: Super Contributor
timestamp: December 11, 2011, 04:32:57 pm
content: Would this 900W Argos oven be OK?http://www.argos.co.uk/webapp/wcs/stores/servlet/Search?storeId=10001&catalogId=1500002901&langId=-1&searchTerms=TOASTER+OVEN#pdpProductReviewsAny other UK models I should consider? What are you using (if you live in the UK)?David.

author: IanB
author_rank: Super Contributor
timestamp: December 11, 2011, 05:13:03 pm
content: Quote from: djsb on December 11, 2011, 04:32:57 pmBased on earlier comments in this thread about ramp up time and circulation fan, this slightly more expensive model might be better?http://www.argos.co.uk/static/Product/partNumber/4234834.htmBut unfortunately I have no experience to go on here.

author: Jimmy
author_rank: Regular Contributor
timestamp: December 12, 2011, 03:26:03 am
content: mikeselectricstuffI took your advice an just jammed board in toster oven with a temp probe on my fluke. Worked a treat however I may stick in a PID controler with relay to turn off becase I probably would start forgetting them too.

author: wkb
author_rank: Super Contributor
timestamp: December 12, 2011, 07:30:40 am
content: Quote from: Jimmy on December 12, 2011, 03:26:03 amHow about using one of these 'oven timers' that the missus uses to ensure she does not forget to get the cake out of the oven?Simple & cheap I'd say.

author: hisense999
author_rank: Contributor
timestamp: December 19, 2011, 10:59:02 pm
content: And in attached pictures is my way of DIY reflow.Going with standard steps don't exist any chance for overheating, working perfect with ROHS soldering paste, solder time just about 10-20seconds, after short explain even baby can solder using this without damage, cheap chinese SMD connectors which in normal reflow way cannot survive ROHS temperature here are good.Equipement from wal-martquality of soldering industrial grade A+ cuz heat is transfered not only with the air.