| PURPOSE: |
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To establish a set of design rules that can be given to a customer which will improve the testability of their printed circuit boards. |
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| PREFERRED GUIDELINES: |
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All test targets will be on one side of the PCB but both top and bottom are accessible. |
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Test Target Priorities: 1) Test Pads; 2) Component Leads and: 3) Via's |
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Center to center spacing between test points or adjacent drilled locations should be as follows:
A) Two .100" probes with a minimum center to center spacing of .095"
B) One .100" probe and one .075" probe with a minimum center to center spacing of .075"
C) Two .075" probes with a minimum center to center spacing of .070".
D) One .075" probe and one .050" probe with a minimum center to center spacing of .060".
E) Two .050" probes with a minimum center to center spacing of .050". |
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Test targets should be at least .050" away from components on the side of the PCB being tested. |
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Test points are to be distributed evenly over the surface of the PCB. Areas of high probe density should be avoided. |
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The preferred size of test targets is .035" (or .040" on top -side targets). Square pads are preferred. Due to the increased target area (27%) over the round shaped targets. Targets that are less than .030" will require the probe tips to be guided to the targets. |
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Solder mask should not cover any test pads or vias. |
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Test targets should be at least .100" away from the edge of the PCB or "break-away" areas. This will allow the gasketing material to meet evenly with the board surface and create a good vacuum seal. |
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PCBs should have a minimum thickness of.062".This helps minimize board flex. |
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Tolling hole diameters should preferably be .125" The tolerances should be held at +.002/-.001 and the locations should be placed in opposite corners. |
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Tooling hole to pad tolerance should be +/- .002". |
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Avoid placing nodes on SMT devices. This can cause damage to the device and provides minimal probe contact area. |
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Avoid placing test points on excessively long leads (.170" or more). Additional machining may be required or leads of this length and probe contact is compromised due to deflection. |
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| Necessary Items for Fixture Making: |
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Layout CAD File: ex. PCADR -->* .pdf PADSR -->*.asc |
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Bare Board *1 pc. (Please consider the version and multi board) |
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Assembly Board *1 pc. |
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BOM |
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Circuit Diagram |
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