Analysis of the Differences between Online Testers and Automatic Visual Inspection Instruments

Analysis of the Differences between Online Testers and Automatic Visual Inspection Instruments

I. Preface Recently, many friends have had such a question: "Our company hopes to introduce a set of automatic circuit board testing equipment, but we don't know how to choose between the online tester and the automatic visual inspection instrument?" . When answering these friends' questions, the author deeply felt that these friends in the electronics field lack sufficient information when facing new testing technologies. At the same time, it is also believed that some key issues should be clarified. Therefore, this article attempts to explain these two methods of circuit board testing.

Second, cost differences: In terms of cost, it should include two items: equipment procurement cost and subsequent usage cost. Online testing instruments and automatic visual inspection instruments each have different advantages in these two aspects of cost. In terms of equipment procurement costs, generally speaking, online testers have a price advantage. The price of an automatic visual inspection instrument is several to dozens of times that of an online testing instrument. Relatively speaking, if there are people within the enterprise who can program and debug the automatic visual inspection instrument, the usage cost will be relatively low. The online tester also has inevitable costs such as needle discs and probes in use, and its usage cost is higher than that of the automatic visual inspection instrument. The total cost depends on the actual situation. Each enterprise has different circumstances and cannot be generalized.

Third, differences in testing speed: In terms of testing speed, online testers using needle discs have obvious advantages. To achieve the same number of tests, several automatic visual inspection instruments are needed to be equivalent to one online testing instrument. This situation varies as the size of the circuit board to be tested increases. Take the computer motherboard as an example. Using a relatively new online tester, the testing time is approximately 10 seconds. However, it usually takes several minutes to use an automatic visual inspection instrument.

Four. Differences in test Coverage In terms of test coverage, 稆 each has its own advantages. The automatic visual inspection instrument performs relatively well in the "visible" part, while the online test instrument performs better in terms of electrical characteristics. The relevant projects are as follows in Table 1. The project online tester and automatic visual inspection instrument can measure the open circuit and short circuit of the circuit base plate, but cannot measure the open circuit and short circuit of solder. Most of them can be measured. Some components, due to their special properties, cannot be tested. For integrated circuit boards such as PLCC or PGA, BGA, etc., the open/short circuit of pins cannot be tested, but most of the missing components can be tested. Some components cannot be tested due to the characteristics of the circuits. If a large capacitor is connected in parallel with a small capacitor, the values of the small capacitor cannot be measured, and the values of the measurable components have deviations or defects. If the measurable and non-measurable components are installed incorrectly, most of them can be measured. Some components cannot be tested due to the characteristics of the circuits. If a large capacitor is connected in parallel with a small capacitor, the small capacitor cannot be measured while the majority can. There is something measurable. Some components cannot be tested because they have no external markings. If a capacitor is attached, it cannot be measured. The defect of the integrated circuit bracket is measurable and unmeasurable. The post-production cracking of surface mount components during reflow soldering is measurable and unmeasurable. The tombstones produced by the 砀 of surface mount components during reflow soldering are measurable and measurable. The polarity of electrolytic capacitors is measurable, but due to the long required testing time, The common users do not test the false solder parts, the empty solder parts, the surface mount devices that are not fully loaded, and whether they are tested or not

V. Differences in Accuracy: In terms of accuracy, both devices depend on the debugging of the program. However, the online tester also requires the cooperation of a needle bed, which poses a certain degree of complexity. On the other hand, the difficulty of program debugging for automatic visual inspection equipment is relatively high. Therefore, in terms of accuracy and misjudgment rate, these two types of equipment must be judged automatically by the user through actual use.

Six. Differences in Application Scope Generally speaking, online testers are suitable for circuit boards with reliable measurement points. If the pin cannot be inserted due to the circuit board wiring, the online tester will be in a predicament where it has no place to be put to use. Secondly, online testers are suitable for products with large quantities. Due to the certain cost of the needle size, if the output of the product is too small, the average cost of the needle bed that each circuit board has to bear will be too high, which is not cost-effective from an economic perspective. The automatic visual measuring instrument is not restricted by the needle bed, but due to its relatively slow testing speed, it is not suitable for mass-produced products. Additionally, the relatively high purchase cost makes it unsuitable for products with lower profits. Therefore, the automatic visual inspection instrument is suitable for a small number of diverse products. On the one hand, it can save the cost of the needle bed; on the other hand, the slow speed does not pose a pressure on the testing of a small number of products.

Vii. Conclusion. Online testing instruments and automatic visual inspection instruments each have their own advantages and disadvantages, and their application scopes are also different. In some respects, it can even play a complementary role. If a choice must be made, then taking all the above aspects into consideration, a correct decision should be achievable.