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SM components or "chip on board"?

I am in the VERY EARLY stages of product development for a device roughly the size of a BIC pen.

I need to fit a single comparator, roughly 8 resistors, 3 transistors,

3 caps, led and possibly a 555 IC.

Now, I am new to all this, I have created the circuit that this product needs and it works, but now I'm trying to determine the best way to "shrink it". I have thought of assembling surface mount components together with wire to create an elongated ad stringy circuit that could fit into the space of a BIC pen, but even then it may be too big.

Idea 2: I think it's called "Chip on Board" - I'm referring to those black blobs you see on boards or usually in small consumer products(clocks, thermometer, etc)

Given the above listed parts, which would be a better solution?

Thank you for any suggestions, Steve

Reply to
SteveKlett
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A marker pen might be a lot easier.

Okay.

That likely won't save you any space, and causes other problems.

You can get some comparators and the 555 in micro SMD packages only about 1.5mm square (for a reasonable price, without having to buy container load of them). You can easily/cheaply get 0403 SMD resistors (including fairly precise ones) and (at a price) 0201 SMT resistors. If you can design with ceramic caps, you can get some of them that small too.

You might have to go with a (perhaps) multilayer board with parts mounted on both sides and probably pay a premium to get tiny vias-- assuming the board can only be 3 or 4 mm wide.

I've seen precision signal conditioners that fit into a 1/4" OD SS tube, so it's certainly not impossible, given your stated constraints.

Best regards, Spehro Pefhany

--
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Reply to
Spehro Pefhany

ive done simlar things with discrete components (long before tiny smd) things like to92 transistor tubular capacitors etc that just snugly fited into the pen however there was certainly no room for a pcb, i had to use thin wire to wire al the components together that only just fited past the devices, it was a fairly simple sensitive FET RF snifer probe i stil use it today, shame i cldnt get a batery to fit inside.

it wld be tricky to do it with smd devices, but maybe posible if its a very simple circuit and your good with this sort of thing. self tining enameled coper wire might be best. but wouldnt look to good if its in a transparent bic pen. you can also get flexible PCB wich are thinner, and flexible (obviously) so might be able to get it in easier.

im sure ive seen pen sized devices even with lcd on them.

Colin =^.^=

Reply to
colin

Hello Steve,

As Spehro said, regular parts might be better than bare die with a tar blob. This bare die would require individual bonding which only makes business sense at very large quantities.

With respect to chips look for TSSOP packages and the like. Maybe you could also use a dual comparator and rig the 2nd half up as a timer to get rid of the extra 555.

Traces from chips can be routed towards the inside instead of away from the chips. With 0204 and 0102 parts it is amazing what can be placed on a small strip of circuit board. My last one of these was about 7mm wide and 40mm or so long yet it contained dozens of parts including some logic chips. If I hadn't needed inductors I could have made it fit into a BIC pen.

Regards, Joerg

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Reply to
Joerg

Flexible very thin Kapton would make a nice pcb, you could get plenty of smd on that, double sided. Very thin copper wire links can be added if space for tracks is short.

If it were a one off 'lets see how ridiculously tiny we can make it' project I'd consider soldering the parts to each other directly, but that would be a non starter for production, testing, trouble shooting, or anything else involving basic reasonableness.

NT

Reply to
bigcat

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