Aug. 22, 2019
What are the common types of PCBA substrates?
1. Fr-4 plate is an epoxy plate, with high mechanical properties and dielectric properties, better heat and moisture resistance, and good mechanical processing.
2. Aluminum substrate is a kind of metal substrate copper clad plate with good heat dissipation function. Generally, a single panel consists of three layers, namely, circuit layer (copper foil), insulation layer and metal base layer. Aluminum substrates are commonly used in LED lighting products. There are two sides, the white side is welded LED pin, and the other side shows the color of aluminum. Generally, the thermal conductivity part will be contacted after applying thermal conductivity coagulation.
3. FPC board is a polyimide or polyester film as the substrate made of a highly reliable, excellent flexible printed circuit board. It has the characteristics of high wiring density, light weight, thin thickness and good bendability. Used in mobile phones, hard drives and other high-end products.
According to different product USES, the choice of PCBA substrate will be different. In general, the more high-end products, the more advanced and expensive PCBA substrate will be used.
Introduction of ICT testing technology in High precision PCBA testing:
During ICT testing, the test probe is mainly used to contact the test points on the High precision PCBA board, which can detect the short circuit, open circuit, component welding and other fault problems. Can quantitatively on the resistor, capacitor, inductor, crystal and other device to measure, the diode, triode, light lotus root, transformers, relays, operational amplifier, power supply module function test, for small and medium scale integrated circuit function test, such as all 74 series, the Memory type, commonly used driver IC, exchange, etc.
Some approaches to ICT testing are;
1. Simulator test
Test with operational amplifier. The concept of "virtual land" from "A" point is as follows:
∵ Ix = Iref
∴ Rx = v/where V0 * Rref
Vs and Rref are respectively excitation signal source and instrument calculated resistance. If we measure V0, then Rx can be solved. If the Rx to be measured is capacitance and inductance, then Vs ac signal source and Rx is impedance form, C or L can also be solved.
2. Vector test
For digital IC, Vector test was adopted. PCBA Supplier shares that Vector testing is similar to the measurement of truth table, which can stimulate input vector and measure output vector, and judge the quality of devices through the actual logic function test. Such as: and not gate test
Analog IC test, according to the actual function of IC excitation voltage, current, measurement of the corresponding output, as a function block test.
3. Non-vector tests
With the development of modern manufacturing technology and the use of vlsi, it often takes a lot of time to write the vector test program of devices, such as the 80386 test program takes a skilled programmer nearly half a year. The large number of applications of SMT PCBA processing devices make the fault phenomenon of open pin become more prominent. To this end, the companies non - vector testing technology, Teradyne launched MultiScan; GenRad - driven Xpress non - vector testing technology.
ICT test is at the back end of the production process, the first step of PCBA test, which can timely find problems in the production process of PCBA board, and help to improve the process and improve the production efficiency.