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Through hole capacitors

Hi, I had been trying to decouple the power supply of a prototype circuit with

200mhz+ fast pulses and precision timers, with a smd capacitor on a double sided pcb, but found there was still measurable noise on the gnd side of the capacitor due to stray inductance. the back side of the pcb is undisturbed ground plane with smaler gnd planes on the top side conected with vias. I didnt realy have room to route a better gnd conection for another capacitor and rather than put the capacitor on the back and disturb the gnd plane I had an inspiration and drilled a 1 mm hole and found a 10nf smd capacitor fitted through the hole perfectly, the end caps were flush on either side of the pcb and cld be soldered ok and the chips power pin put on top of the buried capacitor, therefore taking up very little space.

I had one go short circuit some time later (and it took a while to find as I had forgoten it was even there!) but then I find smd components can get upset quite quickly when reworking a prototype many times, the capacitor cheked out ok when I removed it, although it seemed low in value but increased when pressure applied, i find other capacitors can also fail simlarlarly varying capacitance with a smal flex of the pcb after being re soldered a few times.

A small array of through hole capacitors at various points solved the noise problem. I remember old tv tuners used to have square block ceramic wich went through a slot in the pcb, I was wondering if this is still considered ...

Colin =^.^=

Reply to
colin
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They are actually working on integrating the capacitor right into the PCB dielectric during board manufacture.

Reply to
Fred Bloggs

Just the one ! ?

That's your problem !

Graham

Reply to
Pooh Bear

The Pulsonix PCB software I use has that feature (Embedded Component Technology). Rs, Cs and inductors may be placed on the inner layers. I've never used it, though. 8-)

Leon

Reply to
Leon

I've heard of that technique being used on PCBs working at microwave frequencies.

Leon

Reply to
Leon

with

double

of the

undisturbed

vias. I

capacitor

plane I

capacitor

side of

the

find as I

get

capacitor

being re

noise

through

Interesting, yes I supose the next logical step would be to have ceramic instead of fr4 for one of the layers beteewn the power planes :)

The manafacturing guys would probably have kittens if they had to put capacitors inbetween layers, and what about reparing them ?

I was wondering if there are any big difference in stresses puting them through a hole like this.

we already have pcb printable resistors maybe printable capacitors are next ?

Colin =^.^=

Reply to
colin

with

double

Well I already had one or two but that wasnt enough so was trying to put one more in but kinda ran out of room, adding a leaded capacitor directly accros the supply rails didnt cut it either, eventualy had 2x 10nf 1x .1uf and 1x

1uf in one spot as close as possible (all but the 1uf buried), this cleaned up the supply rail nicely for the 100ns 1-3v ramp generator and comparator (right next to a 74vhc flip flop but with seperatly fed supplies)

I made a square wedge wich makes the 1mm hole have corners to acept the 0603 size wich is 1.1mm corner to corner, maybe they should make round capacitors just for this ? althought ive come acros round resistors and diodes, soldering is a little bit tricky.

Colin =^.^=

Reply to
colin

In article , Fred Bloggs wrote: [...]

You can already get high K PCB material so to some degree the capacitors have already been made into the material.

The some years back, Russians made circuit boards with some of the discrete parts internal to the PCB. It was done very like blind vias are done but capacitors and resistors were placed part way through the process. The result was a PCB with chips on both sides and many of the other parts hidden inside.

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kensmith@rahul.net   forging knowledge
Reply to
Ken Smith

Ken Smith skrev:

Have anyone tried this in practice? And is this technique viable for cost sensitive products? And lastly any PCB production companies offering this?

Thanks

Klaus

Reply to
Klaus Kragelund

Well the russians space folks did do they count? They were trying to sell the technology to others.

NASA thought it was too costly.

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kensmith@rahul.net   forging knowledge
Reply to
Ken Smith

Sounds more like something the NSA would do.

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JosephKK
Reply to
Joseph2k

In article , Joseph2k wrote: [....]

Some NASA payloads are NSA payloads.

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kensmith@rahul.net   forging knowledge
Reply to
Ken Smith

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