Through Hole vs. Surface Mount

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Try it for high impedance circuits >> 1E7 Ohms.

" snipped-for-privacy@att.bizzzzzzzzzzzz" wrote in news: snipped-for-privacy@4ax.com:

Cost,for one.

OTOH,I have a very small 7 component SMD IC project that I want to make a simple PCB for(.031 dbl clad) but don't have access to a laser printer to make the transfer(plus I don't have any CAD experience) and the IC pitch is too tiny to do it by hand.It's a power IC so it can't be breadboarded or dead-bug'd. I checked Express PCB,but their "cheap" way only does .062 and costs $51(for 3 boards). My parts only cost about $5 total for one unit.

I've heard rumors of ridiculously cheap PCB houses (e.g. under $20 for a regular ~4 x 6 board), but nobody ever gives names. I wonder if these shadow companies are only in business with the signed agreement that their customers cannot advertize them?!

For a teensy board like that, though, you might look at BatchPCB.

As for home production, I'm tempted to get photosensitive resist and inkjet transparency stock. That way I can print from my home inkjet without making a run to the library for toner copies, and that single copy will make hundreds of boards. Resolution is probably better too (plus, much less elbow grease!).

Tim

Try to get in on one of the exemptions :-)

I avoid that wherever possible. If needed it's best to work with guard rings.

If you ever do, get resistor and capacitor kits. Yeah, it'll be a few hundred bucks each but then you have over 100 parts of each value. I have clients who never buy resistors anymore for prototypes because these kits last and last.

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So do i, still, i did enough stuff at 1E8 Ohms and some much higher=20 (1E12 Ohms) to have a real respect for doing that routinely.

Ok, but that's a specialty area. There will always be specialty areas where normal design techniques aren't good enough. All I am saying is that IME No-Clean is quite ok for all the regular designs I did. And this has included some hardcore low-noise stuff.

No clean has no pb at all with low noise designs since low noise designs have pretty low impedances. That's high impedance low level that's tough.

The small sensors I'm working on have 0603 1G fb resistors plus caps, and have to works for decades at elevated temperature (possibly up to

No clean is a no-no...

Well, that _is_ specialty stuff. Other than guard-ringed input circuitry I can't remember ever having gone above 18M. Because anything above 18M can become a purchasing problem. Also, higher-Z nodes will need to be under some sort of coating or it'll all fall apart in high humidity places. Puerto Rico, for example.

So how do you clean the flux residue from underneath that 0402 then? Specially trained microbes? Watch out that they don't form a union some day :-)

That would be called a biofilm, and yes, they become just as slippery as human unions are. ;-)

Tim

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Thanks, it may work for me in ordinary applications then. Until i find=20 some specific need i will limp along on my Pb/Sn eutectic with rosin = core.

Done inhouse by my customer because the board stuffer can't get it right (no pb with this, it's specialty as you said). Several pass of US cleaning with some tricks I can't disclose.

I just bought a Brother HL-2170W for $89. It's built as cheap as the price implies but in a few seconds it will print an etch mask and all the the documentation files for the components.

Lame, but can rapidly design a small circuit- Drop all of your parts on a flatbed scanner. Flip along an axis to turn them from bottom-up to top-down. Now you can put all of these parts in Photoshop as transparent layers and draw the traces in another layer. Extract the trace layer, flip along an axis, and print to a transfer sheet.

I've been going here for PCB project parts-

Small sizes of copper-clad board in many thicknesses:

Press-n-Peel Blue for resist:

I was getting solder paste from Chip Quik but they seem to be gone.

I've seen a number of sites specifically recommend against buying Brother printers for use in toner-transfer PCB-making setups.

Allegedly, Brother uses a somewhat unusual toner formulation, which doesn't fuse / transfer well to copper.

I've already made a small circuit board and it worked well. I boosted the print density to make sure that there was enough toner laid down. The Press-n-Peel Blue turns black when the toner melts so there's no guesswork about heat and pressure.