Toater oven as reflow ove - Page 1
Forum section: electronics / general

author: evracp
author_rank: Newbie
timestamp: May 16, 2014, 01:35:00 pm
content: Dear Sir,I am making my own soldering reflow oven using existing toaster oven. That reflow oven is not having heat circulating fan.I tried it with metal core PCB(for power leds). At 90-120 degree celcius, the LEDs soldered. I asked my soldering paste vendor, he told at 180 degree celcius only it should be soldered. But at 90-120 degree celcius, the led was soldered and it is working perfectly.In the next project, I tried L clad Copper Board,but when it was 90-100 degree celcius, it was burnt backside,moddle portion only, and the top side is phenolic coated(white), started to produce bubbles. Can you give me any suggestions to improve the oven?

author: zapta
author_rank: Super Contributor
timestamp: May 16, 2014, 02:22:06 pm
content: How do you measure the temperature, directly on the board?

author: evracp
author_rank: Newbie
timestamp: May 17, 2014, 08:20:54 am
content: Hi,I am measuring the temperature using PT100 fixed in the Oven. It is controlled by PLC (with the soldering profile)

author: hamster_nz
author_rank: Super Contributor
timestamp: May 17, 2014, 10:49:26 am
content: The air in the oven does not do the bulk of the heating. It is done through infrared from the elements. (simple proof of this is that things still get quite hot with the door open).I found it essential that the thermocouple be in the same conditions as the components on the board. I tape my bare thermocouple to the surface of a scrap PCB of the same colour and thickness with a bit of kapton (heat resistant) tape - but do not put tape over the actual junction!A reflective probe, held in free air in the oven will be at a far lower temperature than the PCB will be at - likewise a dark PCB should heat a lot faster than a lightly coloured one.

author: marshallh
author_rank: Unknown
timestamp: May 17, 2014, 11:23:46 pm
content: 1. Convection (VERY important)2. Insulation around all air egress points3. Isotropic IR susceptorAll three help to avoid hotspots.

author: mjkuwp
author_rank: Unknown
timestamp: May 19, 2014, 12:05:43 pm
content: I found really good results by using an extra-high temp solder to connect the thermocouple directly to the pcb. I made a proper plated thu-hole in the ground plane. watching the reflow through the oven the displayed and controlled temperature measured this way matches within a few CHowever, doing that for each board is way too hard.as userhamster_nzdoes, I have recently been using a sacrificial bare board next to the target board. Results may vary but in my case the temp difference is around 10C. I have real-time plotting so I just mentally take the offset and open the door at a different temperature (230C instead of 220C for example for Pb solder)Another method I have heard is to put a big sheet of copper in the oven and put the board on that. This can only work for pure surface mount boards. the reflectivity of the copper will be an issue. I have not tried this way yet but I have the copper sheet on hand.these ovens are so amusing. All of them do the same thing and are pretty much done the same way - yet different. Everyone prefers to do their own thing it seems.mine is here, nearly fully documented including the PID constants and units, web code, etc.http://mjkuwp94.tumblr.com/ReflowOven