Opinion on a PCB, Please.

[SupeR-NovA]

hi all!
i'm making this PCB for some project (which is not relavant).
some information about the board:
the smallest lines are 0.03" (about 0.75mm)
smallest gap between two traces: 0.024" (about 0.6mm ,only under the ULN2803A)
EpressPCB .pcb file available, just ask and i'll send it.

there are some things about this board i'm not to sure about...
1) is the component density OK? i might have exaggerated a bit...
2) can i make this board at home(with no special equipment)? i will print the circuit on a HP photo glossy paper, and transfer it using an iron... fix any bad transfer with SHARPIE black markers and etch the board with ammonium persulfate.

one more thing... should i drill the holes before i etch or afterwards? and from which side (copper or component)?

thanks

 

[gerty]

Every time I try to drill a missed hole I usually end up ripping the pad/trace, so I would drill first, etch later.from copper side to keep from burring and lifting.
As far as the density, without knowing the application or space available that would be hard to answer..

 

[Russlk]

The density looks OK to me. Yes, you can make this at home, altho if you have no experience, you will make several before one comes out good enuf. I was frustrated with the iron method, but now sandwich the laser printed pattern and copper clad between two pieces of glass using clamps and felt over the paper, and heating in the oven to 400 degrees F. The only touch up I have to do is because my printer leaves small spaces where lines have been joined.
I drill after etching because the etched holes tend to help center the drill. The drill has to be sharp or the pad will heat and twist off. I use oversize pads to avoid that problem.

 

[Sebi]

Your PCB is pretty. Don't worry about density if You have enough place for PCB. But are You sure, the 6pin ribbon cable connector is available? (i never seen smaller as 10pin)

 

[SupeR-NovA]

thanks for your help!
I think i'll go for the oven method, it seems to be easier...
i guess i'll make the holes after etching becouse, as said, it helps placing the drill... especially becouse i'll use an electric hand drill.
for sebi: thanks for the compliment i guess there are no 6-pin Ribbon cable connectors... i changed it to header pins.

 

[grrr_arrghh]

If space, size of board etc. is not a problem, then print your board layout onto normal paper, push some components through it, and see if you think there is enough room for soldering, considering your own personal soldering skills (I know that mine aren't very good, so I would place the components a bit further apart...)

Just a thought.

Tim

 

[Johnson777717]

Every time I try to drill a missed hole I usually end up ripping the pad/trace, so I would drill first, etch later.from copper side to keep from burring and lifting.

I've found that using a small center punch works well for keeping the bit centered. I usually use hand pressure to make an indentation on the center of the pad keeping in mind that excessive pressure will crack the board. Then place the bit inside the indentation and drill away.

Burrs can be handled by using a larger drill bit, about twice the size of the hole. Using your fingers, gently rotate the drill bit on the top of the hole. This places a nice chamfer on the hole perimeter, and burrs will no longer be an issue. If you're finding excessive burrs, your bit may be too dull, or you are drilling through the board to rapidly. Maybe try easing off a bit to see if this helps.

Just trying to help.

 

[gerty]

I'll try the larger bit trick next time , sounds like it should work..And yes sometimes the bits aren't as sharp as they should be....

 

[kentken]

I have also used express pcb to make my designs, I then print a ps file and convert it into a picture, and change the colors to remove the grid points. This works good, but my old laser is showing its age. I have also tryed the iron on method with fair results. I am going to try the method above. I also use sodium persulphate in a ziploc bag.

Good luck to all