A: Today's electronic products are becoming more and more thin and low-profile, and the default wiring of PCB circuit boards is becoming more and more complicated and difficult. In addition to coordinating functionality and safety, it also needs to be producible and verifiable. The requirements for testability are hereby provided for the reference of preset wiring engineers. If you can pay attention to it, it will save a considerable amount of fixture manufacturing costs for your company and promote the reliability of inspection and the service life of the fixture.

　　LAYOUT rules

　　1. Although there are double-sided fixtures, it is best to place the measured points together. To be able to make a single-sided inspection as the key consideration.

　　If there is difficulty, the TOP SIZE needle point should be less than the BOTTON SIZE.

　　2. Priority of measuring points:

　　Ⅰ. Test pad

　　Ⅱ. Component lead

　　Ⅲ. Via hole –> but not Mask.

　　3. The distance between the two measured points or the measured point and the pre-drilled hole is not less than 1.27mm (50mil). Better than 2.54mm (100mil). Followed by 1.905mm (75mil).

　　4. The measured point should be at least 2.54mm away from its adjacent parts (those that sit on the same surface). For parts higher than 3mm, the distance should be at least 3.05mm.

　　5. The measured points should be evenly distributed on the surface of the PCB, and the density of the blocking part should be too high.

　　6. The diameter of the measured point should not be less than 0.7mm (28mil), if it is on the upper needle plate, it should not be less than 1.00mm, and the shape should be square (or round)

　　7. If the empty foot is within the allowable scale, the checkability should be considered. If there is no check point, the point must be pulled.

　　8. Locating hole requirements:

　　Ⅰ. Each PCB must have more than 2 positioning holes, and the holes cannot be tinned. (Aperture at least 3mm)

　　Ⅱ. Select the two holes farthest from the diagonal line as positioning holes. (distributed on four sides)

　　9. Whether the CAD GERBER FIELD has been converted into a CAM (FAB-MASTER) compatible program.

　　10. The margin of the screw hole is at least 6mm from the TEST-PAD.

　　11. Does each NET have TEST-PAD left?

　　12. Is the TEST-PAD SIZE tin surface 3mil?

　　13. TEST-PAD TO TEST-PAD center point distance is at least 54mil.

　　14. The TEST-PAD should be at least 5mm away from the edge of the board.

　　15. The PAD edge of the parts above SMD CHIP1206 should be at least 100mil away from the center of TEST-PAD.

　　16. The PAD edge of the parts below SMD CHIP1206 should be at least 60mil away from the TEST-PAD center.

　　17. The distance between SOIC and TEST-PAD should be at least 50mil in the horizontal direction and 35mil in the vertical direction.

　　18. The thickness of the PCB circuit board should be at least 0.62″ (1.35mm), and the PCB with a thickness less than this value is prone to bending and needs special treatment.

　　19. Inhibit to place measuring points on SMT parts. Not only the measurable area is too small to be depended on, but also easy to damage the parts.

　　20. To prevent the application of overly long part feet (greater than 0.17″; 4.3mm) or oversized hole diameter (greater than 1.5mm) as the measured point.

　　21. Fault from DEVICE UNDER TEST PADS to TEST PADS: 0.05mm

　　22. The height of the part on the CONDUCT PROBE side is within 6.5mm.

　　23. There are no through holes in the PAD.

　　24. All NET LIST must pull TEST POINT instead of VIA HOLE.

　　25. The NC of IC & CONNECTOR must pull out the TEST POINT without applying PIN.

　　26. TEST POINT cannot be laid in the part BODY and cannot be covered by other components.

　　27. If there is an advanced version, the original TEST-PAD should not be changed as much as possible, otherwise the fixture needs to be re-opened.

　　28. GUIDE PIN is 2.8∮ or 3.0∮

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