Quest for the perfect prototype PCB
02-27-2010, 04:15 AM
Quest for the perfect prototype PCB
I've used quite a few prototyping PCBs and most seem to be designed by people who
don't actually use the boards. Your PB1 is really good and I'd like to make some
suggestions for improvement.
I like the symmetry of the PB1, I've used the PB4 (seems discontinued) and it was
asymmetric and the top was unlabeled due to plated through holes. You have to be
careful in layout with the PB4 since tiepoints off of the chip pads differ on the left
and right sides.
I like the edge tiepoints of the PB1, it allows you to have two row headers on the
edge of the board (for jtag/avr ports). The extra pwr buses on both sides of the
PB4 made it hard to use dual row headers since that row couldn't have DIPs or
SOICs across from the headers. I don't think the plated through holes are necessary.
The real problem with the PB1 is, of course, the size. It fills up fast. Now I realize
it's sized for some sort of mounting rail, but that size is just too small and the
rails are expensive and they really didn't catch on.
I've also used the SparkFun boards, they have a series Kangaroo, Diprotodon, etc
that are 80mmx100mm (fractional eurocard). It's a nice size, but totally braindead
to actually use since there are NO interconnected pads! WTF! You have to spot
solder jumper wires and make solder bridges. PITA!
So my suggestion is to make a PB1 style double wide in the 80x100 format. That
gives (on .1 centers) 30x38 holes. The easy way to lay out the board is to stick
two extended (30 holes long) PB1s side by side. Maybe some sort of horizontal
bus to tie the two vertical buses together, maybe room for power header & cap.
Even better might be to extend the PB1 to 38 holes long, then stick them together
eliminating some of the stuff in the middle. A brief bit of dorking with two PB1s
shows that to fit two columns 30 wide eliminates the PQR and ABC columns.
The QR and AB columns aren't really necessary in the middle of the board and
chopping the P and C columns only changes the SMT interconnection count.
Since you're selling the PB1 for about $1, the 80x100 size should be around $3.
SparkFun sells their bare (no usb/serial) for $10 and it's useless! Anyway,
thanks for listening.
And while I have your attention, maybe a few other rants on proto boards.
It might be nice if the ET-PCB TQFP44 could be mounted without shorting it out.
Or even better the digole CN337. It's really tough to use those TQFPs, the
only board I like is the vertical one sold by ebayer microinventor. Your LQFP48
board is nice with all the proto room, but face it, more interesting stuff is in
TQFP32 and TQFP44 form.
03-08-2010, 12:33 PM
RE: Quest for the perfect prototype PCB
(02-27-2010 04:15 AM)JimNarem Wrote: I like the symmetry of the PB1, I've used the PB4 (seems discontinued) and it was
Exactly! Plated through holes make it harder to prototype, because they take slightly longer to solder in the first place and they are very hard to remove part from. Single side unplated holes board seems to be the way to go.
(02-27-2010 04:15 AM)JimNarem Wrote: So my suggestion is to make a PB1 style double wide in the 80x100 format. That
Thank you. I am considering the 69 x 100mm board with 38 rows and 26 columns (4 columns for power traces). Top and bottom row will consist of separate pads with slightly larger holes for mounting headers and terminal blocks.
(02-27-2010 04:15 AM)JimNarem Wrote: It might be nice if the ET-PCB TQFP44 could be mounted without shorting it out.
The microinventor's adapter is truly ingenious, I really like it as well. Thank you for bringing it to my attention.
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