SMT footprint information 2

[djroseman]

Hi,

I am doing some PCB design, and I have found that the information on the dimensions of various SMT footprints is quite lacking on the Web. Is there a source somewhere of footprint drawings with dimensions of the pads + spacings, so that I can design them in my CAD package?

Thanks

Dave

 

[LionelHutz]

I've never found a single source of info. Many component manufacturers will have some type of documentation showing the recommended pad layout and solder mask layout for their components. If not, find another manufacturer using the same footprint that has the info.

The CAD program should also have a library of many of the more standard component footprints.

 

[itsmoked]

The foot prints of SMD parts are free form, meaning there are NO industry standard rules. A maker can do what ever they want. So there is no "place" to find the "standard" foot prints. When you need a specific one you check your layout tool for it. If it seems like one might be correct you must then check it! If it's not exactly what your part needs you make it yourself.

 

[Comcokid]

The general industry SMT footprint guidelines are defined in IPC-SM-782. This document provides footprints for many common surface mount packages. The document can be obtained from

http://www.ipc.org

or from the Surface Mount Technology Association

http://www.smta.org

for about $110.

Footprints from the document above are good for general SMT assembly where a board does not push the limits of SMT density, use less common packages, use fine pitch devices, use a high mix of different components, use unusual board materials, experience high thermal cycling extremes, or less common assembly processes.

However, the document does not cover all the available packages and is only a starting point for a PCB designer when dealing with a new or novel package. Additionally, many contract manufacturers have their own footprint libraries that they have optimized for their processes.

When you get into issues with fine pitch devices, BGA devices, flip-chip, and the like - then you get into the area where process engineers and PCB designers publish books and present papers at conferences.

But for 0603 passive/SO type ICs and larger devices on boards produced in low volumes even an general footprint is fine.

 

[MacGyverS2000]

Try these guys for a good start:

http://www.pcblibraries.com

Somewhere along the way I came across a site where a member posted his entire collection of SMD land data in PDF form. I want to say it was on the PCBStandards.com forum, but I can't say for sure.


Dan
Owner

http://www.Hi-TecDesigns.com

 

[djroseman]

Thank you all for your responses - fortunately I have mainly standard SMT devices in my design and for the ones which are not I will just have to continue designing in my CAD package. At least once they are stored, I won't have to draw them again !

Dave