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PCB Board Circuit Board Why The Need For A Test Point?
Jul 01, 2017

  PCB board circuit board why the need for a test point?

  On the school of electronic people, in the PCB board circuit board factory set up a test point is a natural thing, but the school of mechanical people, the test point is what?

  Basically set the test point of the intention is to test the circuit board factory components are not in line with standards and welding, for example, want to see a circuit board factory resistance there is no doubt, the most simple way is to take universal Meter measurement on both ends will be able to know.

  But there is no way in the mass production of the factory so that you use the meter to measure each piece of the board every resistance, capacitance, inductance, and even the IC circuit is not accurate, so there is the so-called ICT ( In-Circuit-Test, which utilizes multiple probes (commonly referred to as "Bed-Of-Nails" fixtures) to touch all parts of the board that are required to be measured , And then through the program to the main sequence, side by side as a supplement to measure the characteristics of these electronic parts, the general test so that all parts of the general board only need 1 to 2 minutes or so to end, depending on the circuit board factory parts The longer the parts, the longer the time.

  But if these probes directly touch the board to the top of the electronic parts or their feet, it is likely to destroy some electronic parts, but Destructive Enthusiasm, so the smart engineers to clear the "test point" in the two parts The extra leads to a pair of circular dots, there is no shield (mask), so that the test probe to touch these small points, without having to touch the touch of those electronic parts.

  Early in the circuit board factory are also the traditional plug-in (DIP) of the times, it will take parts of the welding feet as a test point to use, because the traditional parts of the welding feet enough robust, not afraid of needle, but often there will be exploration Needle touch bad image of the attack, because the general electronic parts through the wave soldering (wave soldering) or SMT to eat tin, the appearance of its solder will generally constitute a layer of solder paste flux residual film, this layer of film Impedance is very high, often the formation of poor touch of the probe, so it is often visible production line test operators, often with air spray guns desperately blowing, or take alcohol scrub the needs of the local test.

  Originally through the wave soldering test points will also have the probe touch bad questions. Later, after the prevalence of SMT, the test misjudgment of the scene has been greatly improved, the use of test points have also been greatly given the burden, because the SMT parts are generally very fragile, can not accept the test probe direct touch pressure, the use of test It is not necessary to allow the probe to touch the parts and their feet, not only to protect the parts from damage, but also greatly greatly improve the reliability of the test, because the scene of the miscarriage of the less.

  But with the evolution of science and technology, circuit board factory scale is getting smaller and smaller, a small circuit board factory to light up so many electronic parts have been some strenuous, so the test point occupied circuit board room space doubt, Often between the design side and the manufacturing side of the tug of war, but this issue in the future and then have time to talk about. The appearance of the test point is generally round, because the probe is also round, better production, but also relatively simple to close the probe closer, so that can add needle bed needle density.