PCB News - What are the requirements for PCB circuit board test points

What are the requirements for PCB circuit board test points

Critical components need to preset check points on the PCB circuit board . The pads used for soldering surface mount components are not allowed to be used as inspection points. It is necessary to preset other dedicated inspection pads to ensure that solder joint inspection and production debugging are carried out. The pads used for inspection are arranged on one side of the PCB circuit board as much as possible, even if it is used for inspection, it is helpful to reduce the cost of inspection.
1. Process preset requirements
(1) The distance between inspection points PCB circuit board edge must be greater than 5mm;
(2) The inspection point cannot be covered by solder mask or text ink;
(3) The size, distance and layout of the inspection point pads should also match the relevant requirements of the inspection equipment used;
(4) The inspection point must be placed 1mm away from the component to prevent the probe and component from hitting;
(5) The best solder plating for the inspection points or the selection of softer, easy-to-penetrate, and non-oxidized metals to ensure that they are grounded and extend the life of the probe;
(6) The diameter of the inspection point is not less than 0.4mm, and the distance between adjacent inspection points is most fortunately 2.54mm or more, but not less than 1.27mm;
(7) Components with a height exceeding 6.4mm cannot be placed on the inspection surface. Components that are too high will cause poor contact between the online inspection fixture probe and the inspection point;
⑻The distance C from the center of the inspection point to the edge of the chip component has the following connection with the SMD height H: SMD height H≤3mm, C≥2mm; SMD height H≥3mm, C≥4mm.
(9) The inspection point should be placed in the positioning hole (the collaborative inspection point is used for precise positioning, preferably non-metalized holes, and the fault of the positioning hole should be within ±0.05mm) outside of the ring's 3.2mm;
2. Electrical preset requirements
(1) The inspection points should be evenly distributed on the PCB circuit board to reduce the pressure stress of the probes;
(2) When setting inspection points on circuit traces, the width can be expanded to 1mm;
(3) Each electrical contact must have a check point, and each IC must have a power and ground check point, which is as close as possible to the component, most fortunately within 2.54mm;
(4) Try to lead the SMC/SMD inspection points on the component side to the soldering surface through via holes. The diameter of the via hole is greater than 1mm, which can be inspected by a single-sided needle bed to reduce inspection costs;
(5) The power supply line on the PCB circuit board should be divided into areas to set inspection breakpoints to facilitate the decoupling of the power supply or the inquiries of obstructive points. When setting the breakpoint, consider the power carrying ability after the rehabilitation check the breakpoint.

Question: How to leave inspection points for PCB circuit boards?
Answer: Today's electronic products are becoming thinner and thinner, and the default wiring of PCB circuit boards is becoming more and more messy and difficult. In addition to coordinating functionality and safety, it also needs to be produced and inspectable. For testability requirements, rules are provided for the reference of preset wiring engineers. If you can focus on this, it will save your company a considerable amount of manufacturing costs for fixtures and promote inspections that depend on the durability of the fixtures and the service life of the fixtures.
LAYOUT rules
1. Although there are double-sided fixtures, it is best to put the measured points together. The key consideration is to be able to make a one-sided inspection.
If there is hardship, the TOP SIZE needle point is less than the BOTTON SIZE.
2. Priority of measuring points:
1.. Check point (Test pad)
2. Component lead
3. Via hole -> but not Mask.
3. The distance between the two measured points or the measured point and the pre-drilled hole should not be less than 1.27mm (50mil). It is better to be larger than 2.54mm (100mil). The second is 1.905mm (75mil).
4. The measured point should be at least 2.54mm away from its neighboring parts (the one located on the same side). For parts higher than 3mm, the distance should be at least 3.05mm.
5. The measured points should be evenly distributed on the PCB surface, and the blocking part should be too dense.
6. The best diameter of the measured point should not be less than 0.7mm (28mil), if it is on the upper needle board, the best is not less than 1.00mm, and the shape is preferably square (round ones are also possible)
7. If the empty feet are within the allowable scale, the inspectability should be considered. If there are no inspection points, the points must be pulled.
8. Requirements for positioning holes:
1.. Each piece of PCB must have more than 2 positioning holes, and no tin is allowed in the holes. (Aperture at least 3mm)
2. Choose the 2 holes with the diagonal line and the farthest distance as the positioning holes. (Distributed on four sides)
9. Is CAD GERBER FIEL converted to CAM (FAB-MASTER) compatible program?
10. The distance between the screw holes of TEST-PAD is at least 6mm.
11. Does each NET have TEST-PAD?
12. Is the tin surface of TEST-PAD SIZE 3mil?
13. The distance between the center of TEST-PAD TO TEST-PAD is at least 54mil.
14. TEST-PAD is at least 5mm away from the edge of the board.
15. The distance between the edge of the PAD of SMD CHIP1206 and the center of the TEST-PAD is at least 100 mils.
16. The distance between the edge of PAD of SMD CHIP1206 and the center of TEST-PAD is at least 60mil.
17. The distance between SOIC and TEST-PAD, if the distance is at least 50 mil in the horizontal direction, and at least 35 mil in the vertical direction.
18. The thickness of the PCB circuit board must be at least 0.62″ (1.35mm). PCBs with a thickness less than this value are simply bent and require special treatment.
19. Stop placing the measuring point on the SMT part. Not only the measurable area is too small to live on, but also the parts are simply harmed.
20. To prevent the application of too long parts foot (greater than 0.17"; 4.3mm) or too large aperture (greater than 1.5mm) as the measured point.
21. Negligence 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. No through holes are allowed in the PAD.
24. All NET LIST must pull TEST POINT instead of VIA HOLE.
25. The NC of IC plate & CONNECTOR must pull out TEST POINT without applying PIN.
26. TEST POINT cannot be layed 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 reopened.
28. GUIDE PIN is 2.8∮ or 3.0∮
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Checkpoint manufacturing in DXP
. Directly double-click the via to pop up the via feature setting dialog box.
. Testpoint checkpoint: It is used to set whether the via is used as a check point. Pay attention to the vias on the top and bottom layers that can be used as check points.