PCBA Tech - About SMT processing flying probe detector

About SMT processing flying probe detector

The flying probe tester is an improvement of the online needle bed tester. The flying probe tester uses two or more sets of probes that can move in a certain test area to replace the non-movable needle bed. At the same time, a movable probe drive structure is added, which uses various types of motors to drive. The positioning in the horizontal direction is in contact with the test point in the vertical direction. The flying probe tester usually has 8 test probes in total with 4 heads, and the minimum test gap is 0.2 mm. When working, move the test probe to the test point and contact it according to the pre-arranged coordinate position program. Each test probe performs open circuit, short circuit or component test on the assembled components according to the test program. The flying probe test probe is selected according to the actual test needs and the shape of the test point. In addition, the height of the flying probe movement, the movement and angle of the probe access to the test point, the direction of movement, the impact force, the search method, and other flying probe movement need to be considered. The details of the process, especially the different heights of the components on the various assembled circuit modules, should be considered when programming, and these data are often not accurately given in the circuit design files.

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1. Basic composition of flying probe tester

1) Computer system

The computer system is usually equipped with a dedicated instrument card, image card and drive card for the test system on the basis of a personal computer. If there are higher functional requirements, a network hub or workstation system may also be used. The operating system and test software of the flying probe test system in Europe and the United States mostly use the currently popular Microsoft Windows. The Japanese series of online test systems basically use DOS, and the test software interface and operation are relatively simple and applicable.

2) Meter and measurement module

Most of the meters and measurement modules are placed at the bottom of the test system, and basically include test excitation signals and measurement devices. Types involve programmable DC voltage and current sources, multi-function waveform (sine, triangle, square wave) generators, clock generators, voltmeters, counters, pull-up/pull-down resistors, etc. Correspondingly, in the instrument interface card A switch system is integrated for testing with different excitation signals or measuring devices in conjunction with the test program.

3) Motion and drive system

For the basic flying probe movement, there are two types of horizontal and vertical relative to the working area. For the horizontal movement of the Cartesian coordinate system, it can be divided into two types. The main purpose of the xy drive is to find and locate the test point through the digital camera. The screw drive system drives the arm to move when moving; the vertical motion drive has a single purpose, which is to contact the probe in the vertical direction of the test point. . Generally, the contact between the probe of the flying probe test system and the test point will have a certain inclination angle, and the angle between it and the vertical direction is usually 5. about. The probe motion system requires fast and high-precision positioning capabilities. The probe holder arm and probe movement are driven by a motor. Usually *, the y-axis is driven by a brushless motor and a precision lead screw with an integrated encoder, which is also used by some manufacturers Mechanisms such as air suspension and linear motors; the z-axis of the probe is generally driven by linear motors or precision stepping motors.

SMT factory processing flying probe detector

4) Test area

The specific test area of the flying probe online test system is generally equipped with an operation panel near it. In addition to the mechanical positioning device of the tested circuit board in the area, the bottom side is generally used to expand the ability of flying probe online testing. Add auxiliary access device to connect to power supply, test excitation signal, non-vector test device, etc. The general test area also has a protective cover to protect the safety of testers.