Wave soldering is to make the soldering surface of the board directly contact with high-temperature liquid tin for welding purposes. The high-temperature liquid tin maintains a slope, and the liquid tin forms a wave-like phenomenon by special means, so it is called "wave soldering". The main material is solder bars.
The principle of wave soldering:Wave soldering is a molten liquid solder that forms a specific shape of solder wave on the surface of the solder bath by the action of the pump, and inserts the PCB and the transmission chain of the component through a certain angle and a certain immersion depth. The process of solder joint soldering is achieved by solder peaks.
The surface of the crest surface is covered by the layer oxide scale, which remains almost static throughout the length of the solder wave. During the wave soldering process, the PCB contacts the front surface of the tin wave, the oxide scale ruptures, and the tin wave in front of the PCB The pleats are pushed forward, which means that the entire scale and the PCB move at the same speed as the wave soldering station. When the PCB enters the front end of the wavefront, the substrate and the pins are heated, and before leaving the peak, the whole The PCB is immersed in the solder, that is, bridged by the solder, but at the moment of leaving the end of the wave, a small amount of solder adheres to the pad due to the wetting force, and due to the surface tension, the lead wire appears. The center shrinks to a small state where the wetting force between the solder and the pad is greater than the cohesion of the solder between the two pads. As a result, a full, rounded solder joint is formed, and excess solder leaving the tail of the wave falls back into the solder pot due to gravity.
Supporting tools :
Electrostatic material box, tweezers, electrostatic wrist strap, label paper, wave soldering machine.
Wave soldering process steps1. Preparation before welding
a. Check the PCB to be soldered (the PCB has been coated with SMD adhesive, SMC/SMD patch, adhesive curing and complete THC insertion process), and the soldering surface of the component socket and the gold finger are coated. Solder or tape with a high temperature resistant tape to prevent the post socket from being blocked by solder. If there are large-sized grooves and holes, the high-temperature adhesive tape is also applied to prevent the solder from flowing to the upper surface of the PCB during wave soldering.
b. Connect the flux to the hose of the sprayer.
2. Open the furnace
a. Turn on the wave soldering machine and exhaust fan power.
b. Adjust the width of the wave soldering machine belt (or fixture) according to the width of the PCB.
3. Set parameters
Flux flow rate: Determined based on the contact of the flux with the underside of the PCB. The flux is evenly applied to the bottom surface of the PCB. It is also possible to observe from the through holes in the PCB that a small amount of flux should penetrate upward from the through holes to the pads on the through hole faces, but do not penetrate the assembly body.
1. Wave soldering preheating temperature:
A. "Preheating temperature" is set at 90-110 degrees. The term "temperature" as used herein refers to the actual heating temperature of the soldered surface of the PCB after preheating, rather than the "appearance" temperature; if the preheating temperature is not up to When it is required, it is prone to residual after welding, and it is easy to produce tin beads and pull tin.
B. There are several factors that affect the preheating temperature, namely: the thickness of the PCB board, the board speed, and the length of the preheating zone.
B1, the thickness of the PCB, is related to the series of problems of heat absorption and heat conduction when the PCB is heated. If the PCB is thin, it is easy to be heated and the PCB "part surface" is heated faster. If there are parts with heat-resistant impact, The preheating temperature should be appropriately lowered; if the PCB is thick, the "welding surface" will not be quickly transferred to the "part surface" after absorption, and such a plate can pass a higher preheating temperature.
B2, board speed: Under normal circumstances, it is recommended to set the speed of the board at 1.1-1.2 m / min, but this is not the value; if you want to change the board speed, you should usually change the preheating temperature to match For example, to speed up the board, in order to ensure that the preheating temperature of the PCB soldering surface can reach a predetermined value, the preheating temperature should be appropriately increased.
B3. Preheating zone length: The length of the preheating zone affects the preheating temperature. When debugging different wave soldering machines, the influence of this point on preheating should be taken into consideration. When the preheating zone is long, the temperature can be adjusted closer. The actual temperature of the board to be obtained; if the preheating zone is short, the predetermined temperature should be increased accordingly.
2. Wave soldering furnace temperature:
Take the 63/37 tin bar as an example. Generally speaking, the tin liquid temperature should be adjusted to 245255 degrees. It should not be more than 260 degrees, because the new tin liquid will accelerate at temperatures above 260 degrees. The amount of oxide produced is shown as follows: The relationship between the temperature of the tin liquid and the amount of dross generated: c. Conveyor speed: set according to different wave soldering machines and the PCB to be soldered (generally 0.8-1.92 m/min) )
1. Wave soldering and inspection (after all welding parameters reach the set value) sz-gsd.com
a. Gently place the PCB on the conveyor belt (or fixture) and the machine automatically sprays the flux, drying, preheating, wave soldering, and cooling.
b. Hold the PCB at the wave soldering exit.
c. According to the factory inspection standard
2. Continuous wave soldering production
a. The method is welded to the same piece.
b. At the wave soldering exit, catch the PCB. After inspection, put the PCB into the anti-static turnover box and send it to the repair board.
c. Each printed board shall be inspected for quality during continuous welding. For printed boards with severe soldering defects, the soldering shall be repeated immediately. If there is still a problem after repeated welding, the cause should be checked and the process parameters adjusted accordingly before welding can be continued.
Wave soldering process quality control requirements.1. Strict system: fill in the operation record and record the welding parameters such as temperature every 2 hours. Regularly or post-weld quality inspection of each printed board, find welding quality problems, adjust parameters in time, and take measures.
2. Regular inspection: According to the start-up working time of the wave soldering machine, periodically check the lead-tin ratio and impurity content of the solder in the solder pot. If the tin content is below the limit, some tin may be added. If the impurity content exceeds the standard, the tin should be replaced. .
3. Maintenance system: Always clean the residue of the wave nozzle and the oxide surface of the solder pot.
Comprehensive adjustment of wave soldering process parametersThe comprehensive adjustment of process parameters is very important to improve the quality of wave soldering.
Soldering temperature and time are necessary conditions for forming a good solder joint. The soldering temperature and time are related to the preheating temperature, the temperature of the solder wave, the tilt angle, and the transfer speed. When adjusting the process parameters comprehensively, the welding temperature and time must be ensured first. The first peak of the double wave soldering is about 235~240°C/1s, and the second peak is about 240-260°C/3s.
Welding time = contact length of the solder joint with the peak / transmission speed
The contact length of the solder joint with the peak can be measured by taking the peak of the high temperature glass test plate with the scale.
Transmission speed is a factor that affects production. Under the premise of ensuring the quality of welding, through reasonable and comprehensive adjustment of various process parameters, the purpose of increasing the output as much as possible can be achieved.
27 inch all in one computer,desktop computer 27 inch,desktop all in one 27 inch,all in one pc 27 inch i5, i5 all in one computer, intel i5 all in one pc, computer all in one core i5
Guangdong Elieken Electronic Technology Co.,Ltd. , https://www.elieken.com