Now there are more and more patches for welding machine circuit boards because of its high efficiency and low cost. At present, the vast majority of welding machine maintenance personnel on the patch is still very strange. They have already become accustomed to plug-in components and are generally repulsive to patch welders. The headache of the patch is that the component is too small, there is no identification model on the component, the circuit board of the patch is too dense, and the patch component is unfamiliar. These factors have caused the patch welder to need to change the board to get it done, and there are very few people who can skillfully repair the patch circuit board. Welding machine circuit board patch is a major trend, maintenance personnel are faced with the urgent need to upgrade knowledge. Survival of the fittest, those who can't keep up with the pace of upgrading, the road will become narrower and narrower until they are eliminated. Here are some basics about patch components.
(1) Substitutions of some SMD diodes
M7 diode of patch can be replaced by IN4007 of plug-in; SS16 diode of patch can be replaced by SR160 of plug-in; SS14 diode of patch can be replaced by IN5819 of plug-in; US1M of patch can be replaced by UF4007 of plug-in; ES1J and RS1M can be replaced by FR107 of plug-in.
(2) Patch capacitor
Due to the limited volume of the patch capacitor, the capacitance value is not directly marked on the surface of the capacitor, and the surface of the patch capacitor has nothing (this is also a way to distinguish patch resistors and capacitors of the same size). The capacitance value of the patch capacitor is marked on the top of the commodity package. However, its reading method is the same as that of the chip resistor, but the unit is different. For example:
104=10 × 10 to the fourth power = 100000pF = 100nF = 0.1uF
Capacitance has three common units; pF, nF, uF, the conversion relationship of 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.
(3) Patch resistance
The resistance value of the chip resistor is usually directly marked on the surface of the resistor in digital form, so the resistance value of the read resistor can be directly read by the number on the surface of the resistor. There are generally three ways to express:
1. It consists of three numbers, indicating that the error of resistance is ± 5%. The first two digits are significant digits, and the third digit represents the multiplication by zero, and 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 second power of 10 (in short, the third digit is several, that is, the power of 10).
So the resistance value represented by 103 is 10 × 10 to the third power = 10 × 1000 = 10000Ω = 10KΩ
2. It is composed of four numbers, indicating that the error of the resistance is ± 1%. The first three digits are valid numbers, and the fourth digit represents a multiple of zero (that is, the number is a few, which represents the power of 10). For example, 1,502,150 is a valid number, write it down directly, and 2 means 10 to the second power.
So the resistance of 1502 is 150 × 10 to the second power = 150 × 100 = 15000Ω = 15KΩ
3, composed of numbers and letters, such as 5R6, R16, etc. All you need to do here is replace R with a decimal point.
5R6 = 5.6R = 5.6Ω R16 = 0.16R = 0.16Ω
(4) Benefits of using patch components
The first aspect: small size, light weight, easy to save and mail. The second aspect: patch components are easier to solder and disassemble than in-line components. patch components do not need through holes and use less tin. in-line components, disassembly is the most difficult and hurtful thing. all friends who have done this have this experience. even if there are only two pins on two or more layers of PCB boards, it is not easy to disassemble and damage the circuit board, not to mention multi-pin PCB boards. However, it is much easier to disassemble the patch components. Not only are the two pins easy to disassemble, but even if the components 1. 200 pins are disassembled several times, the circuit board will not be damaged. The third aspect: patch components also have a very important advantage, that is, to improve the stability and reliability of the circuit, for the production is to improve the success rate of production. This is because the SMD device is small and does not require vias, thereby reducing stray electric fields and stray magnetic fields, which is particularly important in high-frequency analog circuits and high-speed digital circuits. Once you have adapted and accepted the patch component, you may never want to use the in-line component again unless you have.
(4) Necessary tool for welding of patch components: tweezers
The main function of tweezers is to facilitate the clamping and placement of patch components. For example, when welding patch resistors, tweezers can be used to clamp the resistors and place them on the circuit board for welding. Tweezers require a pointed and flat tip to facilitate clamping of components