Wednesday, 5 January 2011

QRP2004 Build


PLL photos with the tiny AD9835 tracks.

Note the laser was on draft 300dpi hence the slight dotty nature of the tracks I have done this as I wanted to test out the process.

Tinning will cover these. This was after just 15 minutes in tin solution.



Just to see how low you can go...this is what you get at 150 dpi printing:



I might b tempted to chase a blob of solder about these pads/tracks

3 comments:

Anonymous said...

Nice Work.
How long did those boards take you to make?
What drill do you use for the holes?
I would like to learn more about the tinning process.
I will keep watching with interest.

M1KTA said...

How long did those boards take you to make?

The whole process to make each PCB before drilling about an hour you could do all 7 in a day and that isn't dedicated to the one task either but it depends on if you can or want to do one board at a time or all at once and if the etch solution is strong enough.

I use the laser print and iron on process to produce the etch resistant boards the, some say an alternative and more efficient method is to create a transparancy then UV expose photo resist boards and etch them. It's a religious debate with some but for HF purposes iI find it works for me. Also I don't have a UV box or any photo resist boards.

To print the PCB film (or transparancy), involves (as the project group suggested) about 15 minutes messing about with sizing correctly. I used a 16 pin SMD IC and a 14 and 40 pin DIL socket to check the sizes. I have a couple DIL sockets I punch through the paper and you soon see if the pads line up or not. I ended up 107% and I was using Vista and some shareware image package. Find out what works for you. To be honest from PDF or image files the process is no where nearly as accurate or as good as if you have the PCB artwork from a design packages like Eagle, Express PCB etc... do a Google search to find them I will not discuss further here.

Then to etch (I use a strong solution of Ferric Chloride I know when fresh will etch 200 square inches of PCB in about 35 mins. I add to my homebrew tank and set the temp and timer and wait 35 mins... The the boards were as you have seen. I also use a persulfate etch on boards with small SMD (PLL board).

To 'Tin' I use 'tin salts' there are multiple names for them but it is a solution of tin that when it comes into contact with copper it deposits tin on the copper (remember those school physical classes when they mentioned things like sacrificial electrodes on ships etc to help reduce rust, or when you put an iron nail in a copper sulphate solution the nail is 'copper plated' basically the same process (I'm a chemist and could expand on it but lets keep this simple, put PCB into the solution and 15 minutes later a thin tin layer appears, wait 30 minutes and the layer is a bit thicker, there isn't much advantage keeping the boards infor more than 30 mins). I get mine from Farnell.

You REALLY do not have to tin the boards at all.

What drill do you use for the holes?

Well that depends on the component lead sizes but the drill bits range from 0.7mm to 1.5mm and to drill I use a Dremel and aDremel Pillar stand. You simply cannot do it by hand the bit will skit about all over the place. Or you could do it by hand with a hand drill but it would take ages on some boards.

P.S. Try and leave a callsign with a comment.

Anonymous said...

Many thanks for taking the time to reply in such detail.
I will keep watching your progress with great interest.
Sorry but I don't have a callsign.
Dave