The PCB circuit board electrical measurement technology analysis

 One, the electrical test
 PCB board in the production process, inevitable due to external factors caused by short circuit, circuit and leakage electric on the flaws, plus PCB continuously in high density, fine pitch and multilevel evolution, if not timely bad plate screening out, and let it flow into the process, is bound to cause more cost of waste, so in addition to process control and improvement, improve testing technology can also provide PCB manufacturing to reduce the scrap rate and improve the product solution.
 Electronic products in the production process, due to defects caused by loss of cost, in each stage has different degree, the earliest discovered the lower the cost of recovery.
 " The Rule of 10 ' s" is an often used to assess the PCB in different process stages were found to be defective, remedial cost. For example, the empty plate production is completed, if the board of the circuit can detect out, usually only need fill line can improve defects, or to lose a empty plate; but if not detected circuit board, for shipment to the downstream assembly industry parts installation, also had a tin furnace and IR remelting, however, at this time was the detection of line circuit breaker condition, the general assembly to downstream industry make empty board manufacturing company for compensation parts costs, heavy fees, inspection fees. If more unfortunate, defective board in the assembly industry testing has not been found, and into the whole system of finished products, such as computer, mobile phone, automobile parts, and then again for testing found that loss, will be empty board timely detection of the times, a thousand times, even higher. Therefore, the electrical performance test for the PCB industry, as is the early detection of line defects.
  Downstream industry will usually require one hundred percent PCB manufacturer of electric test, so with PCB manufacturers on the test conditions and test methods agreed specifications, so the two sides will be on the following matters clearly defined:
 1, test data sources and formats
 2, test conditions, such as voltage, current, insulation and connectivity
 3, equipment manufacturing and sourcing
 In 4, beta chapter
 5, repair specification
 In the PCB manufacturing process, there are three stages must test:After 1, inner etchingIn 2, the outer line after etching3, finished productEach stage will usually have 2 ~ 3 of 100% tests, screening out bad plate for heavy processing. Therefore, the test station is also an analysis process of the best collection of data sources, by the statistical results, can obtain a circuit, short circuit and other insulation problem percentage, heavy line after the detection, data collection, using quality control method to find out the root of the problem, try to solve.
 Two, electrical measuring method and device
  Electrical test methods are: special type ( Dedicated ), UTV ( Universal Grid ), flying probe ( Flying Probe ), non-contact electron beam ( E-Beam ), conductive fabric ( rubber ), capacitance ( Capacity ) and brush ( ATG-SCAN MAN ), which measured the most frequently used equipment three kind of, respectively, is the special testing machine, universal testing machine and flying probe tester. In order to better understand the functions of various devices, the following will compare three main equipment characteristics.
 1, special type ( Dedicated ) testSpecial type of test is a special type, mainly because of its use of the jig ( Fixture, such as a circuit board for electrically testing needle tray ) applies only to a material number, different material on the board can be tested, and cannot be recovered using. Test points, single panel in 10240, double the less than 8192 points can be tested, the test density, due to the probe head thickness relationship, more suitable for pitch above board.
 2, UTV ( Universal Grid ) testUniversal test is the basic principle of PCB circuit layout is based on the lattice ( Grid ) to design, generally called line density refers to the distance of grid, is also by the spacing ( Pitch) to represent ( part can also be used to indicate the hole density ), and the test is based on this principle, on the basis of hole position in a G10 substrate for Mask, only in the hole of the location of the probe through the Mask for electrical measurement, so the governance of the production is simple and fast, and the probe can be used repeatedly. Universal test has many measurement standard Grid fixed large needle plate, can be respectively according to different materials and production activity type probe needle plate, needle plate as long as the change of production activities, can be of different material on the production test. In addition, in order to ensure the completion of PCB board system patency, in the use of high voltage ( such as 250V ) multiple measurement points of UTV electrical measurement tools, using a specific contact pin pads on the board of Open / Short electric test, the universal testing machine called "automatic testing machine." ( ATE, Automatic Testing Equipment ).
 Universal test points are usually in more than 10000 points, test density in or test called on-grid test, if applied in high density board, because the distance is too close, have been isolated from on-grid design, thus belonging to the off-grid test, the fixture must be special design, usually the UTV test density of up to QFP.
3, flying probe ( Flying Probe ) test
 Flying probe test principle is very simple, only needs two probes of X, y, Z mobile one by one to test lines of the two endpoints, therefore does not need to be additionally making expensive fixtures. But due to the endpoint test, so the speed is very slow, about 10 ~ 40 points / sec, so more suitable samples and small volume; in testing the density, flying probe test can be applied to high density board ( ), such as MCM.