I have been planning to use mostly though hole parts in my designs mostly just because that's what I'm used to doing at home. I always hated screwing with tiny little surface mount parts at work. However, the thought occurred to me having holes drilled is probably more expensive then having SMT resistors and capacitors stamped on by the board maker.
Does adding on some SMT resistors significantly increase the cost of a PCA when I order it?
Same question regarding adding holes.
If It cost a ton to have resistors put on I will do it myself and so going through hole.
If it is cheap to have some SMT resistors added then I will go that way.
In general...what is the wattage on those? Can't be more then 1/8 watt? I am mostly doing LED and controlling triacs and such.
First time having a board made. Never made one myself.
That would (usually) require a pick and place machine and reflow.
Those are different machines than the ones used for making the PCB.
If you are not making a large number of board, having somebody else place the SMD parts will definitely be significantly more expensive than through hole you put yourself.
Even 0805 is not a problem for most of hobbyists, but if that's too small for you 1208 is easily soldered by hand, why not put that?
Have a look on youtube for people doing their own reflow oven or hotplate SMT
soldering. Its definitely the way to go rather than soldering iron. The tricky part
becomes applying the solderpaste and placing the components, the actual soldering
is a few minutes and gives professional looking results.
A cheap toaster oven can be converted into a reflow oven, you'll find various such
projects if you google around. A simple hot plate can be used too (but watch out
for overheating, some kind of active temperature control is useful.
I found a cheap toaster oven and it had an element on top and below. I took it
apart, moved the bottom element on top, spaced the two elements to cover the whole
area fairly evenly. I found you can solder by eye, since this oven has its own rough
temperature control that I use for the soak phase. Then crank to full power and
watch for the solderpaste melting and flowing.
jarrod0987:
I always hated screwing with tiny little surface mount parts at work.
When you learn to work with them, it is far faster to assemble a board with SMT parts, than through-hole. (No need to switch between top and bottom of the board.)
jarrod0987:
However, the thought occurred to me having holes drilled is probably more expensive then having SMT resistors and capacitors stamped on by the board maker.
There is no stamping. Boards are etched.
jarrod0987:
Does adding on some SMT resistors significantly increase the cost of a PCA when I order it?
Generally there's no additional cost to board, but it depends on the manufacturer.
Assuming an automated process, you're worried about the wrong aspect. You're worried about how the automated machines will make you a SMT or TH pad. You need to think about, who is going to insert the parts and solder them. Even if the board uses a wave soldering process, the cost to develop a die.
Drilling a few more holes generally doesn't cost anymore with the PCB houses, it's all CNC anyway.
jarrod0987:
In general...what is the wattage on those?
I've switched from preferring through-hole parts to using as much SMD as possible. The difference was discovering solder stencils. I get a stencil made for each board by OSHStencils and then it's much faster to do all the SMD soldering in one step.
The toaster oven idea looks cool but my research showed that some tall plastic components I was planning to use would work better if the board was heated from the bottom by conductive (not radiant) heat. I do my SMD soldering in a frypan on the stove. I did spend some time with a non-contact thermometer working out which settings on the stove heat up the pan at the correct rate.
Once you've got an idea of which setting to use, then do the soldering by eye - wait until every solder blob is shiney then pull it off the fire. It's fun to watch it pull the components into place by itself.
Actually, today, because of fine-pitch component leads and closely spaced board traces, the copper is ALL etched off a panel and then the copper is ADDED to the board. Etching very fine traces of copper will undercut the trace and cause open places.
Paul_KD7HB:
"There is no stamping. Boards are etched."
Actually, today, because of fine-pitch component leads and closely spaced board traces, the copper is ALL etched off a panel and then the copper is ADDED to the board. Etching very fine traces of copper will undercut the trace and cause open places.
I think you are trying to describe the semi-additive process, but that is only necessary for very fine traces i.e. < 3 mil.
Surely PCBs with 6 mil trace or greater will be using regular etching method?
Hot plates have one important limitation - you can't do surface mount on both sides of
the board, but with an oven this is doable. I find being able to place decoupling caps on
the reverse side helps get sensible layouts for the signal traces on a 2-layer board.
I tend to keep the reverse very simple though, a smattering of caps / resistors only, since
they are much less likely to fall off due to surface tension. I press the board into crumpled
foil as a heat-shield to help prevent component loss and I've never had anything drop off
the reverse side. You do the simpler side first of course.