Re: Guidelines to shrink the PCB size

Start with the toughest constraint first. Housing tooling can be very costly, and case size can have sudden price jumps.

So, select a few candidate cases, and rank in order of price etc. Then, collect all your parts, and do a quick area verify. Aspect-ratio changes are relatively easy.

PCB layer count has a slight effect, other things can be more important. Double sided SMD placement can push density up a lot.

Then, start checking the Z dimension. Some cases impose height limits.

We've just done a PCB, where we jumped to a smaller case by two simple steps : a) Changes trimpots to side-adjust, from Top adjust. b) Changed SMD caps under PCB, to Thru-Hole 5mm ones, above PCB.

the PCB now fits into a smaller case.

-jg

Also try for chips that incorporate many functionality within it and also satisfies your requirement. This will lead you to having multiple functionalities with a single chip/component. Try placing components on the both the sides . Increase the Layers.

Karthik Balaguru

Many times I have been confronted by the request to get gargantuan amounts of functionality into a pico-sized box that my first question will be about the requirements for such functionality in such small spaces. There are sometimes other ways to do the job that will keep the client happy and ease your burden.

There are limits to how much you will be able to shrink the physical emanation of your design. Certainly, in my line, we have to deal with the really harsh world of high energy physics and physical hard knocks. Look at the sort of layout rules that are being placed on your design.

• Track separations to cope with high transient voltages.
• Track widths to carry the currents you expect
• Placing of circuit sections to maintain safety isolations
• The need for protection circuitry
• Room around the circuit to allow cooling airflow

The above criteria should be programmable in your CAD layout package.

Of course, you can select small physical sized components (mostly surface mount devices) and even consider things like circuit modules which incorporate part of the design on a thin-film device (these can sometimes use the chip die directly and place micro-sized additional components around to make up more of the whole system).

If you have volume, then multiple boards connected together can help (each board with some part of the functionality) but be careful with insulation separation between boards (use intermediate blank boards if necessary) and choose good quality inter-board connectors.

There many ways to shrink a design. As examples a switching power supply where you can use a controller that switches at higher frequencies to reduce magnetics size. Other aspects to consider are the use of phyiscal package like QFN anf BGA which are smaller but generally need a more expert setup for assembly. Our speciality of FPGAs are often used to shrink several digital IC's into one device saving space. When you shrink a design you will often need to use a higher technology pcb e.g. more layers or a smaller track/gap technology.

John Adair Enterpo> Hello,

Guys, thanks for your kind suggestions, let me summarize the points from 'jg' , 'Karthik Balaguru' , 'Paul E. Bennett' and 'John Adair '.

0- Start with Housing. Select a few candidate cases, and rank in order of size if price is not an issue, and if it is then rank'em with respect to size and price. 1- Draft the physical dimensions of all components.

2- Do CAD while focusing following things:

• Track separations to cope with high transient voltages.
• Track widths to carry the currents you expect
• Placing of circuit sections to maintain safety isolation
• The need for protection circuitry
• Room around the circuit to allow cooling airflow

2- Now do simple PCB with few layers. 2.0- Break the PCBs in parts to fill the empty space, connections can be done with ordinary connectors. Try to modularize the whole thing; Audio, RF, LAN, Image sensor and Power circuitry etc. But be careful with insulation separation between boards (use intermediate blank boards if necessary) and choose good quality inter- board connectors.

2.1- If the size is greater than free space then increase the layers to adjust the components. (sure, we got to keep in mind the heat emission and EMI if analog is involved)

3- Try to find components with different sizes with same specs. Or try to search a chips that incorporate many functionality to satisfy your requirement.t

4- Try SMD packages and even consider things like circuit modules which incorporate part of the design on a thin-film device (these can some times use the chip die directly and place micro-sized additional components around to make up more of the whole system).

5- Maybe you need to check ASIC, ASSP or FPGA if your design incorporates standard mcu or dsp chores . And do give a try to different packages too (QFN, BGA etc.).

6- Still in vicious cycle to fit all the thing in such a small place , so lets start from point '1' again and keep iterating unless we find the way-out of this puzzle.

//ali