layout / component packages

[metebalci]

Hi,

For passive parts (resistors, capacitors etc.), do you design packages by yourself or use the existing package definitions in the layout program (e.g. Eagle) ? For semiconductors (diodes, transistors, ICs) packages are obvious, but for passives I could not get any standard procedure. Any help ?

Thanks in advance..

MB

[Jan Dupont]

That depends of what you (I) got in my library...
I design many of my component layouts (also if they allready are in my lib., so that they match precisely the actual component I'm going to use...

By the way, I use Easy-PC

[metebalci]

Hi,

What is the standard package names for 1/4, 1/2 and 1W through-hole resistors ? Is there any standard of packages for resistors, capacitors etc. like TO-220 for semiconductors or manufacturers put their own package sizes ?

Thanks so much.

MB

[FredM]

Hi - As far as I know, there is no universal naming for 'standard' component footprints within EDA packages.. I have used many EDA packages (Orcad,Protel,Target,EWB to name a few) and each time I must use different software and their 'standard' component libraries, I am forced to examine the footprints. Worse - Even defined packages are often different between libraries from EDA vendors - and trying to get data on 'standard' footprints is not as easy as it should be..
One useful site:
http://www.pcbstandards.com/SiteIndex2.php
Another:
http://www.pcbstandards.com/downloads/
and loads of PCB data here:
http://www.visionics.a.se/
;
I now tend to select and construct footprints for a project, naming/renaming these as required, and saving them to a seperate (meaningful) library - but it is a pain in the RS!

[jcarr]

I design a custom footprint for every component that I intend to use, both passive and active. Even for something as commonplace as a TO-92, the outline and lead construction frequently vary according to the individual manufacturer.

I start designing each footprint from the drawings in the manufacturer's data sheet, but I will also measure about a couple of hundred samples with a caliper before finalizing the footprint. The actual shape of the component is often different from that suggested in the manufacturer's drawings, and given sample-to-sample variations, it is also invaluable to know the median, standard deviations and what percentage will be _really_ off.

I design fairly complex boards (4-layer, smd mixed with leaded components, P2P air dielectric interspersed with normal traces and power planes), and I find most "standard" footprints to be hopeless for this type of work - about as useful as the autorouter function.

My pcb layout environment is Protel 98.

hth, jonathan carr

[peranders]

I do exactly the same. First get hold of drawings. I also strive to make the outline exactly as the part. By that it's much help when the pcb is tight. I also make markings visible after the part is soldered. This can be a great help when trouble shooting is necessary.