I bought a convection oven TSF601 for reflow the other day.
I actually reflowed the board using this oven. I’m very comfortable with this, so let me introduce it.
Printing solder paste on a substrate
This time, the reflow is a kazzo clone that features a red substrate. In order to prevent the board from moving, it is surrounded on three sides by boards of the same thickness and fixed with tape.
Prepare the solder paste
The solder paste to be used from this time is TS391LT50 by CHIPQUIK. This solder paste is a low-temperature lead-free solder with a melting point of 138°C, made of Sn42/Bi57.6/Ag0.4. The feature of this solder paste is that it can be stored at room temperature. General solder paste must be stored in a refrigerator to prevent deterioration and must be returned to room temperature each time it is used. This solder paste can be kept at room temperature, so it can be used right away when you need it.
Stir before using. Ordinary solder paste is a little sticky, but this solder paste is soft and silky.
Print with squeegee
Put the solder paste on the back side.
With a squeegee (Martz point card), push the solder paste into the hole of the stencil and pull it toward you.
This solder paste has very good passage through the stencil. Since there is no solder paste left around the holes, the process of cleaning the stencil with alcohol, which I
used to do every time I printed several sheets, has been eliminated. In the blink of an eye, I was able to print 10 copies. This will make it easier to work.
The parts will be implemented. Because the solder paste this time was soft and less sticky, if the parts were to shift a little after being loaded, the solder paste would be wiped away by the leads of the parts, resulting in a pad that looked like a lack of solder. After placing the parts, you should try not to move them.
An electric vacuum pick, HAKKO 394, is used for mounting the parts, so that the mounting can be done quickly. You can read more about HAKKO 394 in this article. You can’t go back to tweezers with this.
The vacuum pick HAKKO 394 and the SMD feeder printed on a 3D printer make mounting of surface mount components very easy and fast.
The 10 pieces were implemented in no time. If you have good tools, work efficiency will increase.
Reflow in the oven
Well, it’s finally time for reflow.
In the past, a hot plate was used to reflow only one piece at a time due to the small size of the hot plate. However, this convection oven TSF601 has the room to bake four pieces of toast at the same time, so you can reflow four kazzo clone boards at the same time.
As for the temperature, the other day when I did an experiment with the temperature profile on an empty fire, the temperature in the oven was about 120 degrees at the 90 degree setting and 160 degrees at the 140 degree setting, so the actual temperature was higher than the setting.
However, experiments have shown that when the substrate is put in and reflowed, the temperature of the oven will be the same as the setting. For this reason, I heated it at 120 degrees for 180 seconds -> 160 degrees for 60 seconds + α.
The next time I use a discarded substrate with the board in, I’m going to look into settings that will give me a nice temperature profile like the other day.
Check the condition of the solder with a digital microscope. There was no solder bridge and it was nicely mounted. Also, I feel that there are very few solder balls. Very good solder paste.
Learn more about the ultra-useful digital microscope here.
After checking with a microscope, I connected to a PC and checked if the Nintendo Famicom（NES） cassette could be read correctly. After confirming that everything is working properly, the board is now complete.
Convection oven, very nice. This model has a detailed temperature setting, so you can set the temperature as you want. Moreover, because of its large capacity, it is possible to reflow many substrates at once.
I can’t go back to the hot plate, which is small and difficult to control. The convection oven TSF601 is very nice.
The reflowed kazzo clone can be purchased at here.