PCB Layout -- A question of style

Resist pen is only used to draw the outline of the cathedral. You should do something about that block of wood on your shoulders.

Jim

Resist pen is an outhouse foundation. You should do something about that chip on your shoulder.

And I'm glad that another "student with an attitude" won't be in my classes in the fall.

Jim

The different pads styles aren't necessarily for assembly purposes except for the engineering build that requires some hand assembly and twiddling. Think of the poor technicians that repair boards either coming off the production line or in a dimly lit, hot, humid, cramped compartment of a ship that's rocking back and forth. Sometime helicoptering in a replacement board isn't feasible, so you need to fix the problem on the spot. People who design PCBs should try fix boards in uncomfortable settings so they will understand why distinct pads and helpful silkscreens are provided, even in this day and age of SMT.

do

footprint

make

obliterated

silkscreens

'Should indicate pin1 as well'? As well as what?

This is the point I was making. Silks are used for also sorts of mumbo jumbo reasons- pretty rectangular blocks denoting dil IC's for example- whereas showing pin1 for a manually stuffed board is the utmost priority for the silk.

My irony meter just overloaded, and that's with a 40dB pad on the input.

Repairability is fast becoming a luxury. I'm sure that most designers would love to include it in their considerations, but the driving force is for smaller / cheaper and the technology is increasingly machine-only processable/testable. Just spent half a day reconnecting minute traces to DDR, opened on a PC motherboard (my own). At least the thing runs again.

This hardware was never meant to see a soldering iron, post-wave. I wonder how many similar physical faults are written off as static damage? ......" You TOUCHED it ? ! "

The board itself could be got for less than the cost of an hour's repair, but then, some of us are at sea, on dry land.

It's getting to be a very strange planet.

RL

Additionally it draws a nice schematic, compares the netlist, checks the design rules and produces Gerber files for the board house. The sorry state of the industry is because of guys like RST who cannot adopt to changes like SMD or uP. Those companies that have innovative ideas like Big Bill do quite well, in fact better than ever. And there is no style involved, just plain utility.

If you mean over-reliance on computed results, as from Spice or FEA, I'll agree with you. But PCB CAD (not autorouted) is exactly the same as manual layout- you learn nothing extra from the tape, no fundamental principles are hidden from you and taken care of by the computer.

Paul Burke

I have seen quite a few smt pcb's where the managers insistence on silk-screened reference designators made the smt boards *larger* than the thru-hole boards, where the refdes' used to sit inside the components. hilarious.

OTOH, I hardly ever use refdes' for smt parts, they are packed way too close for that. But I do make maps for techies (who really ought to be able to view the pcb layout, but usually cant) and do things like number parts based on the schematic sheet, so R1327 would be on sheet 13, R02xx on sheet 2 etc.

I also use a square pad for pin 1 of ICs, connectors and the like (it makes the tech work so much easier, as well as manual assy). I dont bother with 2-terminal devices though.

Cheers Terry