One, electrical test

PCB in the process of production, hard to avoid the short circuit, open circuit and leakage caused by external factors, such as electrical flaws, coupled with the continuous toward high density PCB, fine spacing and the evolution of multi-level, and failure to timely to bad plate screening out, and let it flow into the process, is bound to cause waste more cost, so in addition to the improvement of the process control, Ang mga pinahusay na diskarte sa pagsubok ay maaari ring magbigay ng mga solusyon sa mga tagagawa ng PCB upang mabawasan ang mga rate ng scrap at mapabuti ang ani ng produkto.

Sa proseso ng produksyon ng mga elektronikong produkto, ang pagkawala ng gastos na sanhi ng mga depekto ay may iba’t ibang degree sa bawat yugto, at mas maaga ang pagtuklas, mas mababa ang gastos sa remediation. The Rule of 10 “s is commonly used to estimate The cost of remediation when a PCB is found to be defective at different stages of The process. Halimbawa, pagkatapos ng pagkumpleto ng walang laman na produksyon ng plato, kung ang board sa circuit ay maaaring napansin sa real time, karaniwang kailangan lamang ayusin ang depekto, o higit sa pagkawala ng isang walang laman na plato; Gayunpaman, kung ang circuit ay hindi napansin, ang board ay ipinadala sa downstream assembler upang makumpleto ang mga bahagi ng pag-install, at ang furnace lata at IR remelting, ngunit ang circuit ay napansin sa oras na ito, tatanungin ng pangkalahatang tagalabas ng agos ng taon ang walang laman na kumpanya ng pagmamanupaktura ng board upang mabayaran ang gastos ng mga bahagi, mabigat na bayarin sa industriya, bayad sa inspeksyon, atbp. If the more unfortunate, the defective board is still not found in the assembly industry’s test, but into the overall system of finished products, such as computers, mobile phones, automobile parts, and so on, then the test to find the loss, will be empty board timely detection of a hundred times, a thousand times, or even higher. Thus, electrical testing for PCB manufacturers is all about early detection of defective boards.

The downstream operator usually requires the PCB manufacturer to perform 100 percent electrical testing and therefore agrees with the PCB manufacturer on specifications for testing conditions and methods, so both parties will first clearly define the following:

1. Test data source and format

2, test conditions, such as voltage, current, insulation and connectivity

3. Production method and selection of equipment

4. Kabanata sa pagsubok

5, repair specifications

There are three stages in PCB manufacturing that must be tested:

1. After etching the inner layer

2. After etching the outer circuit

3, ang tapos na produkto

Ang bawat yugto ay karaniwang may 2 ~ 3 beses ng 100% na pagsubok, i-screen ang masamang plato para sa mabibigat na pagproseso. Therefore, the test station is also the best data collection source to analyze the process problem points. According to the statistical results, you can obtain the percentage of open circuit, short circuit and other insulation problems, and then test after reengineering. After sorting out the data, use the quality control method to find out the root of the problem and solve it.

Two, electrical measurement method and equipment

Kabilang sa mga pamamaraang elektrikal na pagsubok ang: Dedicated, Universal Grid, Flying Probe, e-beam, conductive cloth, Capacity and ATG-scan MAN are the three most commonly used devices. They are special test machine, general test machine and flying needle test machine. In order to better understand the functions of each device, the features of the three major devices are compared below.

1. Dedicated testing

Fixtures (such as the pins and dials used to test circuit boards) only work with one material number. Boards with different material numbers cannot be tested and recycled. Sa mga tuntunin ng mga puntos ng pagsubok, ang isang solong panel ay maaaring masubukan sa loob ng 10,240 puntos, at ang magkabilang panig sa loob ng 8,192 puntos. Sa mga tuntunin ng density ng pagsubok, dahil sa kapal ng probe head, mas angkop ito para sa mga board sa taas ng pitch.

2. Universal Grid testing

Ang pangunahing prinsipyo ng pangkalahatang-paggamit ng pagsubok ay ang layout ng PCB circuit ay dinisenyo ayon sa Grid. Sa pangkalahatan, ang tinaguriang density ng linya ay tumutukoy sa distansya ng Grid, na kung saan ay ipinahiwatig ng Pitch (kung minsan ay maaari ding ipahayag ng density ng butas), at ang pangkalahatang paggamit ng pagsubok ay batay sa prinsipyong ito. According to the hole position, a G10 substrate is used as a Mask. Only at the hole position, the probe can pass through the Mask for electrical measurement, so the manufacturing of the fixture is simple and fast, and the probe can be reused. The standard Grid fixed large needle tray with many measuring points can be used to produce movable probe needle tray according to different material numbers. As long as the movable needle tray is changed during mass production, it can be used for mass production test of different material numbers. In addition, in order to ensure the circuit system of completed PCB board is unobstructed, it is necessary to conduct Open/Short electrical test on the board with the needle plate of specific contact point on the general-purpose electric measuring machine with high voltage (such as 250V) multi-measuring points. This kind of universal TesTIng machine is called “AutomaTIc TesTIng Equipment” (ATE).

General-use test points are usually more than 10,000 points, and the test density is called on-grid test. If it is used in high-density boards, the spacing is too close, and it has been separated from on-grid design, so it belongs to off-grid test, and the fixture must be specially designed. The test density of the generic test can reach QFP.

3. Flying Probe test

The principle of the flying needle test is very simple. Only two probes are required to move x, y and Z to test the two ends of each line one by one, so there is no need to make another expensive fixture. Gayunpaman, dahil sa endpoint test, ang bilis ng pagsukat ay napakabagal, mga 10 ~ 40 puntos / SEC, kaya angkop ito para sa mga sample at maliit na dami ng produksyon; In terms of testing density, the flying needle test can be applied to very high density plates (), such as MCM.