The welding effect of solder wire is good or bad, and the choice of electric soldering iron is very important.
Because tin plating in solder wire mainly depends on the temperature in the welding head to melt it, so as to achieve the final welding purpose. The following are the key factors that should be paid attention to in the selection and use of electric soldering irons for engineers to discuss with us: 1. Solder wire must choose the most suitable welding head to obtain good welding effect.
According to the different designs of circuit boards and the temperature sensitivity differences of different products, it is particularly important to choose the appropriate soldering joints. Appropriate welding head can make the welding wire achieve twice the result with half the effort.
2. Welding wire welding must use electric soldering iron with good thermal performance. The welding head with good thermal performance can reduce the welding temperature in welding wire, which is particularly important for the consideration of heat resistance of electronic components and the requirements of safe operation.
3. Use the welding head provided by the manufacturer. The welding head will be oxidized after a period of use, and the welding head must be replaced at this time.
It should be emphasized that the replacement welding head must be the same as the original soldering iron. This can reduce all kinds of faults in the process of welding wire and improve safety.
4. solder wire must adjust the temperature of soldering iron before welding. We choose the welding temperature according to the characteristics of welding products, and then adjust the temperature in the welding head. We can't judge the temperature in welding head according to welding head's instruments, because the instruments may be damaged and produce errors.
Therefore, before welding wire, we should use thermometer to test the temperature of soldering iron tip before welding. 5. The welding effect of solder wire is also related to the regular maintenance of electric soldering iron.
The electric soldering iron will be oxidized, grayed or blackened after being used for a period of time, which will affect the tin-plating performance of solder wire. Therefore, it is necessary to regularly clean the soldering iron with a sponge dipped in flux to remove the oxide on the soldering iron and replace the welding head if necessary.
If there is no solder wire welding for more than 10 minutes, the power supply should be cut off. ① Temperature management in the welding head is very important. There is an electric soldering iron with temperature regulation. According to the solder used, it is very important to choose the most suitable welding head temperature setting.
Before working, it is very important to measure the temperature in the welding head with the welding head thermometer. (2) Using the genuine welding head matched by the manufacturer as a counterfeit welding head (such as white light tool), the aperture (into which the heating core is put) is large or small, and the thickness of the sleeve is different, all of which lead to the failure of the electric soldering iron, and sometimes lead to the failure of the electric soldering iron.
③ When soldering with lead-free solder, use an electric soldering iron with good thermal performance such as heat recovery. For the sake of heat resistance and safe operation of parts, the set temperature of the welding head is generally expected to be below 350 -370 degrees. Solder wire is mainly the welding material for welding circuit boards.
So what are the precautions when using solder wire to solder circuit boards? This article will be introduced by Double Chile Science and Technology Co., Ltd.: After welding, electrical components with too long pins (such as capacitors and resistors) should be cut short. After welding, look at the solder joint with a magnifying glass to see if there is any virtual welding and short circuit.
When connecting wires, be careful not to deepen the wires for too long, so that they are twisted on the rubber skin of the wires and are in a broken state. When the circuit is connected, it is best to clean the surface of the circuit with detergent to prevent the iron filings attached to the surface of the circuit board from shorting the circuit.
When multiple instruments are aging, pay attention to the connection of wires, zero line to zero line, face to face. When the last group turns, the connection should be tied up to prevent the line from being disordered.
The assembly and welding sequence of components is: resistor, capacitor, diode, triode, integrated circuit, high-power tube, and other components are small first and then large. Both the chip and the base are oriented. When soldering, the notches of the chip, the base and the PCB should strictly conform to the directions indicated by the notches on the PCB.
After installing the same standard, install another standard, and try to make the concave and convex of the resistance consistent. After soldering, the remaining pins exposed on the surface of the printed circuit board are cut off.
When soldering integrated circuits, first check whether the type and pin direction used meet the requirements. When welding, first weld two pins with opposite edges to locate them, and then weld them one by one from left to right and from top to bottom.
Many problems can be found in aging process, such as whether the connection is tight, whether the screws are tightened, and whether the connecting joints are damaged after repeated plugging and unplugging. When soldering, don't use too much tin, and it is best when the solder joint is tapered.
Brittleness (hardening ability) of heat affected zone (HAZ) in the welding process of welding wire. Under the condition of high cooling rate, the coarse-grained zone near the fusion line is easy to form hardened martensite structure. The main alloying elements Cr and Mo can significantly improve the hardening ability of steel.
Although the joint performance of multi-layer welding is much better than that of single-layer welding, the heat affected zone near the fusion line is still the weakest link. Preventive measures: increase the welding heating speed as much as possible by preheating; Medium welding line energy.
The softening of weld and heat affected zone in welding wire and slow cooling rate increase the residence time of joint near AC 1, and a "softening zone" appears, which reduces the impact toughness and leads to fracture. Precautions: Minimize welding line energy; The preheating temperature should not be too high.
Tempering brittleness of welding wire: Cr-Mo steel and its welded joints gradually become brittle when running for a long time in the temperature range of 370-565℃. Take 2.25Cr- 1Mo steel as a typical example.
Preventive measures: reduce the content of O, Si and P in weld metal; ◇ Control line energy (below 43kJ/cm). Cold crack of welding wire: generally occurs in the coarse grain area of heat affected zone.
When the weld strength and hydrogen content are high, it will also occur in the weld. Preventive measures: same as low alloy structural steel.
Reheat crack: a crack caused by re-exposure to high temperature after welding (such as post-weld heat treatment). It is easy to occur on the welded joints of pearlite heat-resistant steels such as molybdenum steel, chromium-molybdenum steel and chromium-molybdenum-vanadium steel (mostly in the coarse grain area and a few in the weld metal).
2. What are the basic knowledge of electronic circuit board welding?
We know that the function of electronic products depends on the correct interconnection of electronic components, and the interconnection of these components is mostly based on circuit board welding.
Circuit board welding has always played an important role in electronic product assembly. Circuit board welding is an important part of electronic technology.
Correct solder joint design and good processing technology (namely circuit board welding technology) are the key factors to obtain reliable welding. The so-called "reliability" means that the solder joint should not only have all the properties required when the product is just produced, but also ensure that it works correctly during the whole service life of the electronic product.
The welding of electronic circuits has its own characteristics, that is, high reliability and miniaturization, which is consistent with the characteristics of electronic products. The welding quality of circuit board is affected by many factors.
Welding mode, welding temperature and time, gap size of metal to be welded, type and performance of flux, welding tools, etc. Not only the oxide on the surface of the lead of the soldered component and the intermetallic compound in the internal structure of the lead are the important reasons that affect the solderability of the lead, but also the oxide on the surface of the printed board is the main reason that affects the solderability of the pad.
3. What are the soldering skills of the circuit board?
The main skills of circuit board welding are as follows:
A. After soldering all pins, soak all pins with flux to clean the solder. Absorb excess solder when necessary to eliminate any short circuit and lap joint. Finally, use tweezers to check whether there is virtual welding. After the inspection, remove the flux from the circuit board, soak the hard brush in alcohol, and carefully wipe it along the pin direction until the flux disappears.
B, the circuit board welding engineer reminds you that patch resistance-capacitance components are relatively easy to weld. You can solder a solder joint first, then put one end of the component, clamp the component with tweezers, and see if it is put right after welding one end; If it is already in place, weld the other end. It takes a lot of practice to really master welding skills.
C, the circuit board welding engineer reminds readers that before welding, the solder pad should be coated with flux and treated with soldering iron to avoid poor soldering due to poor tin plating or oxidation of the solder pad, and the chip generally does not need to be treated.
D carefully place the PQFP chip on the PCB with tweezers, and be careful not to damage the pins. Align it with the pad and make sure that the chip is placed in the correct direction. Adjust the temperature of the soldering iron to above 300 degrees Celsius, dip a small amount of solder in the tip of the soldering iron, press the chip at the aligned position with a tool, add a small amount of flux to the pins at two diagonal positions, still press the chip, and weld the pins at two diagonal positions to make the chip fixed and immovable. After the diagonal is soldered, check the alignment of the chip again. If necessary, it can be adjusted or removed and realigned on the PCB.
E. When soldering all pins, solder should be added to the tip of soldering iron, and all pins should be coated with flux to keep wet. Touch the tip of the soldering iron to the end of each pin of the chip until the solder flows into the pin. When welding, the welding head should be parallel to the capillary to avoid overlapping due to excessive solder.
The above are the main welding skills for reference only. If you want to know about the circuit board, you can go to Guangzhou Yuede Company. They are well-known PCB manufacturers, specializing in the production of high-precision single-layer, double-layer and multi-layer blind buried printed circuit boards. The minimum line spacing is 0.07 mm (3 mils), and it has obtained UL certification in the United States. Their products are exported to Europe, America and Southeast Asia.
4. What points should be paid attention to in circuit board welding?
If you are welding general electronic components (there are no large-scale integrated circuits or other easily broken devices on the circuit board), the soldering iron may not be grounded; If there is, it must be grounding or wristband.
Generally, 30-60W external heating electric soldering iron is selected, and the solder below 1mm contains rosin. The welding head must be cleaned and wiped on a sponge containing water, and it is not allowed to be scratched by hard objects. When welding, the welding head should contact the device pin and the circuit board at the same time, and then feed the solder. If the temperature is right, you can see that the solder melts like mercury, spreads from the pin to the copper solder joint of the circuit board and fills it up, and the soldering iron and solder are recycled to complete the welding.
Pay attention to the shortest welding time, so it is very important to ensure the appropriate temperature. You can melt the solder with a soldering iron in advance and test it. You can practice more by yourself in other aspects.