Fuel level sensor

Making the PCB

This is how a PCB is made.

Drawing the board. I use Eagle.

A positive film is printed on a semitransparent copy paper with Samsung ML-1610 laser printer.

FR4 board, precoated with positive photoresist.

My friends UV exposure unit.

It is a good idea to sand the edges of the board, so it fits tightly to the film


I use KTeaTime for timming. 2 minutes it just right

It looks like my PCB is ready for the developer

I use NaOH. A couple of drops in a 0.2l of water is enought. This one is actualy sold in stores as a chemical for cleaning pipes


Etching solution is made of 20% HCl, 20% H₂O₂, 60% water.


Etched board. It look quite OK.


Solder paste.

Solder paste can be spread evenly over the whole board. It doesn't matter where the pads are.
There is even no need to place the part precisely. The surface tension of the solder will align them.

Into the reflow oven. You can se the temperature sensor attached to the board. ( the underlaying PCB is just for support )

This is the profile that was used for soldering. Blue: set profile, Green: actual temperature in oven, Red: heater power. The suden drop in temerature( green ) was becouse I opened the door on the reflow owen.

And here we have a soldered board