thinking of building a DIY need some advice - Page 1
Forum section: electronics / projects

author: diyaudio
author_rank: Frequent Contributor
timestamp: July 31, 2015, 09:54:19 am
content: HiI'm thinking of building a DIY SMD re-flow oven,can someone with experience in this area provide me with some tips/advice on this topic.thanks.

author: McBryce
author_rank: Super Contributor
timestamp: July 31, 2015, 10:58:48 am
content: How much of it do you intend doing yourself? The whole oven? Or will you use a commercial oven and just build your own controls? I've been considering this too, but I'm now leaning towards the PCBPool device:https://www.beta-estore.com/rkuk/order_product_details.html?wg=1&p=242with a cheap oven bought locally.Dave did a short review on this too.McBryce.

author: diyaudio
author_rank: Frequent Contributor
timestamp: July 31, 2015, 12:09:16 pm
content: Quote from: McBryce on July 31, 2015, 10:58:48 amThanks. yes, I will be taking a conventional oven and modifying it, im not sure what to expect or look out for though.

author: lapm
author_rank: Frequent Contributor
timestamp: July 31, 2015, 04:16:07 pm
content: Haven't built one myself but have read a lot...So two or three advice i feel confident to give you:First make sure it has heating resistors both top and bottom, helps even heating..Second is make sure it has enough heating power so you actually get those degrees/sec ramp ups..Third would be: This is live voltage system, so be extra careful while building and designing controls. Last thing you want to do is electrocute yourself or someone else. Temperature extremes also put some requirements on insulation materials, etc...Also see projects where people have done this already, temperature measurement done little off can ruin performance bigtime...

author: lgbeno
author_rank: Frequent Contributor
timestamp: August 03, 2015, 02:14:48 am
content: There are a few different oven controllers that you can use.Personally I have really good success using 2 ovens, the first heat to 250 degF, second 450 degF. Then when heated place to board in the 250 oven for 2:30 min directly followed by 2:00 min at 450. Works great and I've built oven a hundred boards this waySent from my iPhone using Tapatalk

author: charlespax
author_rank: Regular Contributor
timestamp: August 09, 2015, 10:56:08 am
content: Quote from: diyaudio on July 31, 2015, 09:54:19 amAre you building this for your own personal use or to sell as a product?If you want to make a product, I recommend making something that does not use wall power. The regulatory compliance and liability make it prohibitive for an individual to do.

author: Kremmen
author_rank: Super Contributor
timestamp: August 10, 2015, 10:13:49 am
content: Quote from: diyaudio on July 31, 2015, 09:54:19 amI have built 2 of those by modifying a regular pizza oven (the canonical way to do it)The first oven is a flat model (oven space is ~5 inches high). I moved all heating to the topside so as to avoid reaching liquidus on the bottom side and so enabling double sided loads on the PCBs. The original grid i replaced with a fine mesh net that avoids localized heat sinks (which Dave noted in his blog video!) Also, i added a microwave oven fan to recirculate the air for evening out the temperature. The controller in this one is a commercial sequencing PID intended for ceramics kilns. The oven has been in regular use for some 3-4 years and not a single failed reflow so far.The second one is a more conventional shape with built-in fan and botom and top heating with 2 elements each. The heating power was originally 650 + 650 W which i considered marginal. So i replaced the top elements with a single 2.2 kW sauna heater element that was a nice multiple finger shape filling the roof of the oven.The controller for this one i built DIY using an Arduino Due, a touch panel LCd and a home made SSR board and PSU. Both heaters and the fan are separately controlled by the Due. Thge oven is in final phase of controller tuning but already it is obvious that it is going to work nicely.I over implemented this one a bit just for the hell of it. The controller uses FreeRTOS as real time kernel and a touch GUI for operation and manipulating the configutration.The easiest way is to get a kiln controller that works out of the box. It will do the job but a DIY system will let you have profiles and extra functions if that is something you want.

author: diyaudio
author_rank: Frequent Contributor
timestamp: August 11, 2015, 10:57:20 am
content: Quote from: Kremmen on August 10, 2015, 10:13:49 amThanks for the input. Im afriad if I went your route I would never get done (rabbit holes)...what is a "sequencing PID" ?

author: McBryce
author_rank: Super Contributor
timestamp: August 11, 2015, 11:19:40 am
content: Picked up a tiny 650W two bar (top + bottom) grill for €3 at a local flee market. It takes 12 Minutes to get to 300°C, but I can always upgrade the bars. The tray is just big enough to take about a 250x160 board, which is all I need. I'll do some manual tests with it first and if they go well, I'll be looking at how I intend to control it.McBryce.

author: Jane
author_rank: Frequent Contributor
timestamp: August 13, 2015, 07:32:14 pm
content: You can also checkhttp://andybrown.me.uk/wk/2015/07/12/awreflow2/

author: McBryce
author_rank: Super Contributor
timestamp: September 28, 2015, 11:26:06 am
content: So I converted the 650W oven (removed/shorted the timer switch) and connected it up using the controller that I got from PCBPool. I've done a couple of test PCBs and I'm pretty happy with the results so far. Here's a small PCB with a few resistors and transistors I did (the connectors were hand soldered afterwards).McBryce.

author: fivefish
author_rank: Frequent Contributor
timestamp: September 28, 2015, 11:56:41 am
content: You need wattage... lots of wattage. If you don't have the initial wattage in the first place, no amount of controller could make your oven follow a typical Pb-free profile. You'll just be kidding yourself thinking adding a PID will make a weak oven behave correctly.Get this.http://www.kmart.com/kenmore-6-slice-black-convection-toaster-oven/p-00804206000PYou want 1400 Watts (or more), 2 heaters top, 2 heaters bottom, + convection fan.No need for PID or controller. Preheat oven (without PCB) until temp goes to 100C. Open door. Insert PCB. Turn ON oven again. It will reach within 280C in 6 minutes. Turn off. Open door. And it will cool down rapidly.

author: McBryce
author_rank: Super Contributor
timestamp: September 28, 2015, 12:01:10 pm
content: The 650W oven is easily following the profile without an issue, possibly because the volume of the oven is so small? I've tested even steeper temp ramp-ups and it can follow them too. The PID doesn't make the oven any better, it just makes the whole process more comfortable.... Put boards in oven, press start, grab a beer and wait.McBryce.

author: tggzzz
author_rank: Super Contributor
timestamp: September 28, 2015, 01:15:00 pm
content: Depending on your objectives and constraints, you might consider using the "skillet" a.k.a. frying pan method. For my purposes it works well enough that I don't bother to go 4 miles to the nearest hackspace to use their homebrew oven.

author: fivefish
author_rank: Frequent Contributor
timestamp: September 28, 2015, 01:39:34 pm
content: QuoteYeah, that's possible... but usually the small ovens don't have a fan and can have cold/hot spots. If using a small one, might be good idea to add an after-market fan.

author: McBryce
author_rank: Super Contributor
timestamp: September 28, 2015, 10:07:02 pm
content: I've heard that ovens with fans will blow the parts of the PCB. Any of the guides I've read specifically recommend disabling the fan if it has one. I've measured the temperature in every corner and the centre of the oven. It's a tiny bit colder in the front corners, but nothing significant, less than 2°C difference.McBryce.