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
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
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!
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!
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
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
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