Limitations For Needle Bed In Circuit Testing

- Jun 24, 2018-

1. There are some inherent limitations in the use of a needle bed for circuit testing, such as: the probe minimum diamete has a certain limit, and the needle with too small diameter is easy to break and damage.

2. The distance between the needles is also limited, because each needle must come out of a hole, and a flat cable must be welded to the back end of each needle. If the adjacent holes are too small,contact short circuit will be appeared between the needles, the interference of the flat cable is also a big problem. 

3. Needles cannot be placed next to some high parts.If the probe is too close to the high part, there will be a risk of damage caused by collision with the high part. In addition, due to the high part, usually it is necessary to avoid opening holes on the needle bed seat of the test fixture, which indirectly leads to the failure of needle insertion.A test point on a circuit board that becomes increasingly difficult to hold all components on.

4. As PCB boards are getting smaller and smaller, the appearence and scrap of test points are often discussed. Now some methods to reduce test points have appeared, such as net test, test jet, Boundary Scan, JTAG, etc.There are other test methods that want to replace the original needle bed test, such as AOI and X-ray, but at present each test seems unable to replace ICT 100%.


Flocking needle ability should ask for ICT fixture manufacturers, the minimum diameter of test point and the minimum distance between adjacent test points, usually will have a hope of minimum value and ability you can achieve the minimum, but big-scaled producers will require minimum test points and minimum points distance can not exceed some quantity, otherwise fixture is easy to damage.