PCB Mechanical Design Guidelines

[efortin]

I'm a mechanical engineer and have the job of "designing" the mechanical characteristics of a PCB.

Question: Where can I find some guidelines about that matters, ie suggested minimum distance between connectors, distance between assy screws, type of screws to use, number of screws to use, placement of these screws, prefered PCB sizes by manufacturer, etc, etc, etc...

Thanks,

Etienne Fortin
Sensio

 

[buzzp]

Alot of your questions depends on your design. Screw placement, etc is all determined by you. How much vibration is this exposed too? How big is it? The answers to these will determine how many screws and where they are located. If this product will be UL listed or CE marked (or any others) then the screw spacing and connector spacing, etc, may be driven by the test house since these are conductors. They will have some potential on them (even if they are at ground potential) and will require spacing guidelines to be followed. This usually is not a big deal unless you will screws spaced closer than a couple of inches (your electrical guy should be handling this part of it). The other info will depend on what board house you use to manufacture this. Some have a preference as far as board thickness, copper thickness, etc. Contact them and I am sure they will furnish you some guidelines on the items that are important to them. In addition, there is much information to be found on the internet. Use a search engine, such as google.com, and type in "PCB mechanical" or "PWB mechanical" (older people still use PWB for printed wiring board). Good luck.

 

[sreid]

Only one suggestion on mounting holes; it is less expensive to have the board designer put copper pads around the mounting holes and have the holes plated through. If you don't want the mounting holes plated the holes must be filled before pannel plate-an extra expense.

 

[gnewt]

IPC 2220 Series of documents provide a good source of info for design guidelines. They have tables for conductor sizes and spacing based on voltage and current, as well as general guidelines in regards to building for vibration robustness.

These documents won't give you all the answers- they are merely guidelines and will most likely point you in the right direction. Much of it is still left up to you, the designer, to work out.

 

[tomirvine]

I recommend the following book if the PCB is to be subjected to shock and vibration environments:

D. Steinberg, Vibration Analysis for Electronic Equipment.

Tom Irvine

http://www.vibrationdata.com