Nowadays, more and more patches are used for circuit boards of welding machines, because of its high efficiency and low cost. At present, most welding machine maintenance personnel are still very unfamiliar with the patch. They have long been accustomed to plug-in components, and generally reject the soldering machine of the patch. The headache for the maintenance personnel is that the components are too small, there is no marked model on the components, and the circuit boards of the patch are too dense, making them unfamiliar with the patch components. These factors cause the patch welding machine to need to change the board to get it done. At present, there are very few people who can skillfully repair the patch circuit board. The patching of circuit boards for welding machines is a major trend, and maintenance personnel are faced with the urgent need to upgrade their knowledge. Those who survive the fittest and cannot keep up with the pace of upgrading will have a narrower path in the future until they are eliminated. Here are some basics about SMD components.

Substitution of some SMD diodes

The SMD M7 diode can be replaced by the plug-in IN4007; the SMD SS16 diode can be replaced by the plug-in SR160; the SMD SS14 diode can be replaced by the plug-in IN5819; the SMD US1M can be replaced by the plug-in UF4007; ES1J and RS1M It can be replaced by the FR107 of the plug-in.

Chip capacitors

Due to the limited size of chip capacitors, the capacitance value is not directly marked on the surface of the capacitor, and there is nothing on the surface of the chip capacitor (this is also a way to distinguish chip resistors and capacitors of the same size). The capacitance value of the chip capacitor is marked on the top of the product packaging. However, the reading method is the same as that of the chip resistor, but the unit is different. E.g:

104=10×10 to the fourth power=100000pF=100nF=0.1uF

There are three common units of capacitance; pF, nF, uF, the conversion relationship between the three is: 1uF=1000nF=100000pF, that is, the relationship between the two is a multiple of 1000.

Therefore, when reading the capacitance value of the capacitor, keep in mind the conversion relationship between the three units, because different manufacturers may use different units. If it is a single chip capacitor, use a capacitance tester to measure its capacity, and some multimeters can also measure it.

Chip resistors

The resistance value of the chip resistor is usually marked directly on the surface of the resistor in digital form, so the resistance value of the resistor can be read directly by looking at the number on the surface of the resistor. There are generally three representations:

1, consists of three numbers, indicating the error of the resistance ±5%. The first two digits are significant digits, and the third digit represents the multiplication by zero. The basic unit is Ω. For example, 103, 1 and 0 are valid numbers and can be written down directly, 2 means multiplying by zero, that is, the power of 10 (simply put, the third digit is a few, which is the power of 10).

So the resistance value represented by 103 is the cube of 10×10=10×1000=10000Ω=10KΩ

2, consists of four numbers, indicating the error of the resistance ± 1%. The first three digits are significant digits, and the fourth digit represents a multiple of zero (that is, the number is a few, it represents the power of 10). For example, 1502, 150 is a significant number, write it down directly, 2 represents the power of 10.

So the resistance of 1502 is the square of 150×10=150×100=15000Ω=15KΩ

3. It consists of numbers and letters, such as 5R6, R16, etc. Just replace R with a decimal point here.

5R6=5.6R=5.6ΩR16=0.16R=0.16Ω

The benefits of using SMD components

The first aspect: small size, light weight, easy to store and mail. The second aspect: SMD components are easier to solder and disassemble than in-line components. SMD components do not need through holes and use less tin. In-line components are the most troublesome and frustrating to disassemble. Friends who have done it have this experience. On a PCB with one or more layers, even if there are only two pins, it is not easy to remove and it is easy to damage the circuit board, not to mention the multi-pin. It is much easier to disassemble the SMD components, not only the two pins are easy to disassemble, even if the components with one or two hundred pins are disassembled several times, the circuit board will not be damaged. The third aspect: SMD components also have a very important benefit, which is to improve the stability and reliability of the circuit, which is to improve the success rate of production for production. This is because SMD components are small and do not require vias, thereby reducing stray electric and magnetic fields, which are especially important in high-frequency analog circuits and high-speed digital circuits. As long as you get used to and accept SMD components, you may never want to use in-line components again unless absolutely necessary.

A must-have tool for chip component soldering: tweezers

The main function of tweezers is to easily pick up and place SMD components. For example, when soldering SMD resistors, tweezers can be used to clamp the resistors and place them on the circuit board for welding. Tweezers need to be pointed and flat to facilitate gripping components