Last time I designed the substrate using KiCad and ordered the PCB from JLCPCB. Now that the PCB has arrived, we want to mount the components.
Printing solder paste
Preparation of PCB
Here’s the PCB and the stencil I received.
The PCB is placed on a thick piece of cardboard. Place the same PCB in the back and front.
Place the stencil and insert the pushpins into the pre-drilled holes in the four corners. The PCB and stencil alignment is now perfect.
Printing solder paste
Stir the solder paste in advance. When the paste are soft, place them on the back of the stencil. I use CHIPQUIK’s TS391LT50, a low-temperature lead-free solder paste that can be stored at room temperature. It’s very convenient because it’s ready to use when you want to use it. You can also buy them at “Digi-Key”.
Using a credit card or similar device (I use “Marutsu Parts” membership card), I print the solder paste I just placed on it while pulling it toward me.
Positioning is perfect. Solder paste can be printed neatly on 0.4mm pitch CPLD and IC pads. CHIPQUIK’s “TS391LT50” has fine particles, and it seems that it can print neatly even at a narrow pitch.
I use an electric vacuum pick instead of tweezers to mount the parts.
In the case of tweezers, you need to open the tips of the tweezers to release the parts after you place them. For this reason, it is necessary to design the PCB with a certain amount of space between components. In the case of suction tweezers, the parts are absorbed from the top of the parts, so you can be mounted without any problems, even if the space between the parts is narrow, allowing for a tighter placement of the parts.
Thanks to the electric vacuum pick, the part mounting was completed smoothly.
For details on the electric vacuum pick, see this page for more information.
Reflow in a convection oven that allows hot air to circulate in the oven to bake evenly.
It takes 2 minutes at 100℃, 1 or 2 minutes at 140℃, and about 1 minute at 160℃ to reflow nicely with low temperature lead-free solder.
I was able to reflow it nicely.
Completed mounting on the PCB
Remove the excess part and the PCB is complete.
Next time, I’d like to test the operation.
2020.6.2 added Continued here.
End of addition