Is a Reflow Oven what I need? - Page 1
Forum section: electronics / general

author: Kolman
author_rank: Newbie
timestamp: August 20, 2024, 08:54:23 pm
content: I am an EE student working as a university researcher. I am in charge of designing and assembling a PCB prototype. I am on my second revision of it and for the first one it was a real hassle to assemble the entire prototype with hot air. The main issue is that there are very large copper pours of 2 oz copper connected to each of the pads of the main devices I need to solder. I utilized an IR heating plate for my first prototype but even though I set it to 140 C the boards only reached 80C at the pads of the components. Although my first thought was to just raise the temperature and continue to heat up the board with a hot air gun, the components are very fragile and the manufacturer recommends heating it up with a hot air gun for only 30 seconds (which was not enough to fully melt the low temp solder I am using).Although it was fine for the first prototype this new one I am working on contains a lot more of the same components and they are all within very close proximity of each other, and I am worried of damaging the components while applying hot air to all of them.To me it looks like I need a way to heat up all components at once in order to fully solder them without damaging them. Upon some research I learned that a reflow oven can help with this issue but I want to make sure before spending this amount of money.Is a reflow oven the right tool for the job?PD: The reason we cannot send them out to a manufacturer is because during testing we have experienced issues that damage the components and we need to quickly swap them out.

author: stretchyman
author_rank: Regular Contributor
timestamp: August 20, 2024, 09:12:14 pm
content: Vapour phase reflow is far superior the heat being contained in a gas heating all areas evenly.Seen in used, most impressive.J.

author: fourfathom
author_rank: Super Contributor
timestamp: August 20, 2024, 10:13:35 pm
content: Quote from: Kolman on August 20, 2024, 08:54:23 pmPerhaps not all that much money?Many of us are using a modified toaster-oven for small-board reflow. In my case the modification to the oven consisted of drilling a small hole in the back for my thermocouple leads, building an external Solid State Relay control for the 110VAC power, and buying an inexpensive controller from Unexpected Maker (https://reflowmasterpro.com/). Other people add insulation to the oven, but I haven't found that to be necessary. Originally I used a controller of my own design, and that worked well until I broke it. Some people just monitor the temperature visually, but I prefer having the controller manage things.

author: thm_w
author_rank: Super Contributor
timestamp: August 20, 2024, 10:25:34 pm
content: You have two issues here:- Assembling the board- Repairing the board after components were damagedAssembly is better done by someone else, just a question of paying them, if you have the budget.Repairing and swapping out the parts is better done by you.What is the model of the IR preheater and hot air gun you are using?It should be fine to set the preheater to a high temperature, unless you have components on the bottom side of the board you are worried about.edit: you said you are already using low-temp solder, is it bismuth or lead? It should be really easy to solder bismuth paste.

author: Aspartame
author_rank: Contributor
timestamp: August 20, 2024, 10:31:47 pm
content: If all your components are on the top side, all you need is a hot plate.

author: aeg
author_rank: Regular Contributor
timestamp: August 20, 2024, 10:50:25 pm
content: What's the component?

author: Jackster
author_rank: Frequent Contributor
timestamp: August 21, 2024, 12:00:25 am
content: Quote from: Aspartame on August 20, 2024, 10:31:47 pmThis plus low melt solder of around 170-180c.Set the plate to 180, leave it on until the solder reflows and then remove from the plate.FR4 does break down with this sort of direct heat, expect the board to go darker. But it will be fine. Just don't leave it there for 10 mins..

author: Kolman
author_rank: Newbie
timestamp: August 21, 2024, 03:11:22 am
content: Yeah I have seen different open source products for modifying a regular toaster-oven. But I do think my professor will have a heart attack if I bring this into his lab.

author: SMTech
author_rank: Frequent Contributor
timestamp: August 21, 2024, 08:52:19 am
content: I have to say I find it surprising that a modern day University that offers electronics as a course doesn't have at least a mini lab style production facility to handle SMT. The days when you could easily avoid using SMT for most parts is long behind us and manufacturing knowledge is as much a skill students need as running Spice. Such a thing would after all probably cost less then they spend on software from one vendor.

author: newto
author_rank: Regular Contributor
timestamp: August 21, 2024, 03:28:37 pm
content: Honestly you don't even need a modified toaster oven. A 20$ amazon thermocouple kapton taped to a blank pcb, with the cable shoved through the door of a second hand toaster oven is fine if you're just doing a couple boards.You won't get optimal heating times, but you can even do a soak period once the thermocouple hits the target tempt by turning off the element, and then turning them back on after however many seconds your paste datasheet recommends. It will take a bit longer than a modified oven with added insulation and extra elements, and you'll need to sit in front of it for a few minutes watching, but it's more than good enough for a couple prototype boards.

author: Accu-Sembly
author_rank: Contributor
timestamp: August 22, 2024, 04:49:52 pm
content: Make friends with your local assembly house!Seriously though, we give tours annually for some local Colleges/Universities (and would be willing to do more). If a student wanted to show up and run a board through our ovens, I would have zero issues with that. When their future product takes off and production levels rise, I hope they remember us.