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Friday, 31 December 2010

QRP2004 Build day 1

Here starts the log for the build today easy first day.

I'm creating the PCB and my process is to use press and peel film (Maplin AB15Rso I use the REVERSED images of the CU layer you can obtain either from the qrp2004 project team website ( the yahoo group ( Printer is a laser doesn't work with an inkjet printer, Samsung ML-2240 and I am printing 1200x1200 dpi and as DARK as I can get it.
Make sure you check the print size is right. I used a 40pin DIL socket and couple 8 pin DIL sockets to check the sizes. Mine I had to print at 107% size. Print to normal paper until you get the size right.

Anyway I have 7 nice pieces of blue film ready to use.

It is still cold out so doing the rest of this in doors.... (except the etching)

1. Cut out 7 pieces of PCB sized to fit. Mine are slightly oversized.
2. Clean them of all grease and finger prints (I use Acetone and then fine wire wool and emery paper in a circular pattern). You end up with 7 shinny pieces of PCB. Now clean all the wire wool or emery paper remnants away
3. Iron on or feed the sheets and PCB through a laminator (I will be testing the later option on another build).
4. Allow to cool, peel off the film.
5. I use black marker (permanent) on the top ground plane side, you can use close fitting tape etc... your choice.

Outside now in shack...

6. Etch. You do not need a tank but I home-brewed one from a fish tank heater and aerator pump. I use either Ferric Chloride or some clear etchant. The home-brew tank I set the solution to 35degrees C and let it bubble away for about 35 mins and the boards are usually fine. Wash the boards with water and allow to dry.
7. You have a choice: either remove the etch resist pattern off the boards now or wait until after drilling the boards. I will tin mine (you do not need to) so will remove the etch resist and the tape or pen from the other side and I use a dip solution, you can tin too by chasing a bead of solder around the board (hint this is much easier when NOT drilled!). If not tinning and if you remove the resist the copper will tarnish quickly so you might want to use a flux spray like KS10.

Now the boring bit... drilling c900 holes! This might take a while.
I use a Dremel in a stand (the task is hopeless if not in a stand) with 0.7mm drill bit. Note some holes will need to be enlarged will cover those in later posts.
Drill all the 3mm holes for the mounting and the other 4-5mm holes for the TO220 and other transistors.

I think the drilling holes is why so many home-brewers have moved over to SMD...

I'll post some photos later.

You can use a photo resist and print the CU layer images to sheets and expose and develop etc... but I have not done it that way but many other homebrewers do.


G0PVN said...

Hi Dom,

Following this with great interest!

Happy New Year

Chris G0PVN

Anonymous said...

Hi Dom, thanks for this. Now i know what to do with the blue sheets :-) 72/3 de Steve G0XAR

M1KTA said...

Steve make sure the sheets are reverse images :-) Are the words on the pcb images reversed. I might have printed off few that were not, in words of Simpson chap...Doh!
If not don't use them...

BTW anyone connect a PC instead of the audio stage to the I/Q in/out and use SDR s/w instead?