Filter mobo, first prototype

Publié: 9 mars 2009 dans Filter mobo

At last, I found some time to play with expoxy.

As I still cannot make a real “black” film, I’m still unable to use photo processing to print my pcb. For this reason, I used the “laser toner transfer” method. And, after several unsucsessful tests, I found the good temperature, the right paper, the good pressure, the best toothbrush (to scrub the paper)…

… And I got this. It’s my first pcb done with this process.

Phase I : printing, transfering (with a laminator), scrubing and etching

The “white dust” covering the surface is the paper left on the toner

to reach this quality, I had to sacrifice about 10 sheets of paper. Borders are absolutely clean. The only drawback of this method is that important flat surfaces are far from perfect. The toner deposit is not constant.

Phase II : cleaning the first side

After cleaning the board… it seems to be usable. I hope the irregularity of the main ground plane won’t affect too much the quality of the circuit

the following picture shows a filter daugter card and the interface described some time ago (level interface TTL to 3.3v, and Audio interface with a pair of Triad transformers). Laser transfer technique works better on small boards. The trace between the two circuits is a 0.010 inch line (0.25 mm), without any cut.

Phase III : printing the other side (ground plane and vias)


positioning the other side after drilling 6 marks

drilling the board

I broke my last 0,9 drill, which is absolutely necessary for the HE14 right angle connectors. I’ve no more 1 and 1.1 mm drill…

The first daughter card was bad (connectors where not in front of mobo’s connectors). Dimensions on the cad software are right. It’s probably a wrong printing ratio or something like that.

Next step : tinning the board to protect it against oxidation, plating the vias with silver compound… and looking for drill on ebay


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