Doug: I have found very little in written spec's covering test related issues from any of the major organizations (IPC, etc.). Doesn't mean they're not out there, I just haven't found them yet either. You can see that what little there is out there is describing the pad-to-pad dimensioning without concern to components covering test pads or body-to-pad spacing. What I have found is that the ATE industry is abound with people who have written their own Design for Testability Guidelines (probably in self defense, as I have). This includes most of the turnkey programming and fixturing houses. If you deal with one of them for your ICT development, try giving them a call. As for probing accuracy, talk to the major pogo pin manufacturers. They have lots of info on this subject. Some, like IDI and QA, have nice write-ups on probe accuracy in their full catalogs or as hand-outs and have lots of sales people who will be happy to talk your ear off on the subject. Likewise fixturing houses should have data on their fixture kit accuracy (Everet Charles, Quality One, TTI, etc.) and should be able to describe the overall tolerence build-up. Current "standard" recommendations state a .050 probe hitting a .035 pad. (I believe the SMTA has this in writting somewhere...) Obviously, there are smaller probes available (though you have to use them manually as most ICT generation software will not take them into account) and today's fixture accuracy will typically allow hitting smaller pads (down to .025 with some consistancy). Smaller probes can be placed closer to your components, hence less air-gap. I have found the major issues affecting component body to pad location to be: 1. The mechanics: top side vs. bottom side probing (more slop required for top side), and are you next to a tall part (ie: does the fixture have to be relieved to allow fit?) 2. How well are your component body dimensions described in your CAD system? I've typically had to work with my CAD folks to correct body size dimensioning issues. I'm not a CAD guy, but I seem to remember a design rule check for pad to component outline? - -Anyway, the gist of this is that you will probably have to do your own DFT guidelines. Get your Test Engineer, CAD Engineer, Design Engineer and fixturing house together and hash it out. -- ORIGINAL MESSAGE ---- The following questions relate to ICT (In Circuit Test) of assembled rigid PWB's using conventional .050", .075" or .100" probes used in test fixtures. (Flying probes are not of interest due to volume of units built). 1) Is there an industry specification that address the air gap required from the edge of ICT test pads to SMT component body's and/or component pads? My dilemma: IPC-SM-782 section 5.7.2 states: "Test lands should be .025 minimum from mounting land areas." This does not specify the spacing from the component body nor does it seem sufficient to the land areas. Our vendors use IPC-A-610 to inspect assembled boards. If the assembly is class III and a 1206 resistor is on the board IPC-SM-782 section 5.7.2 would seem to allow a test pad to be .010" under the part. Obviously, this is not what we want. 2) Is there another industry specification such as IPC, Bellcore, etc. that addresses this issue? If so, please indicate the specification #. If you have an internal specification that addresses this issue I would be grateful if you could share what your parameters are. 3) Is there a specification that defines the probe pin accuracy or location tolerance of .050", .075" and .100" probes used in a "standard" ICT test fixture? I've been reading IPC's tech-net and design-net mail for years and there is a wealth of knowledge in this mailing list. Thanks for any help you can provide. Doug ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################