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PCB board welding method and matters needing attention
At present, the use of visual soldering machine to solder PCB boards is a wide range. In order to better use the visual soldering machine, it is necessary to know the precautions of the PCB board and the soldering machine, so as to achieve a better soldering effect. So how does the visual soldering machine work when soldering the PCB board? Let me explain it briefly for you!
How does the visual soldering machine solder PCB circuit boards?
First of all, the surface of the weldment should be clean. In order to achieve a good bond between the solder and the weldment, the surface of the weldment must be kept clean. Even for weldments with good weldability, if there is an oxide layer, dust and oil on the surface of the weldment. Be sure to clean before soldering, otherwise it will affect the formation of the alloy layer around the weldment, so that the quality of the solder cannot be guaranteed.
Secondly, the weldment must be weldable. The quality of soldering mainly depends on the ability of the solder to wet the surface of the weldment, that is, the wettability of the two metal materials is the solderability. If the weldability of the weldment is poor, it is impossible to weld qualified solder joints. Solderability refers to the performance of weldment and solder to form a good bond under the action of appropriate temperature and flux.
Next, the soldering time should be set appropriately. Soldering time refers to the time required for physical and chemical changes in the soldering process. It includes the time for the weldment to reach the soldering temperature, the melting time of the solder, the time for the flux to function and the formation of metal alloys.
The soldering time of the circuit board should be appropriate. If it is too long, it will damage the soldering parts and components. If it is too short, it will not meet the requirements.
What are the common PCB electronic components that need to be soldered?
With the continuous improvement of technology, some of the above-mentioned PCB board electronic components have undergone wave soldering or patching, with high efficiency and more reliable stability. The remaining components cannot pass the furnace and cannot be pasted. It can only be solved by the welding process after the automatic soldering machine. There are many actual cases encountered in PCB circuit board soldering. Usually, the engineering department of the factory will make process improvements and require more stable and reliable welding methods. Their starting point is to require more stable quality. efficient .
Take the medical B-ultrasound motherboard as an example. On a PCB board, there are hundreds of electronic components, and the total number of solder joints is hundreds of thousands. It is indeed very cumbersome to require manual operations. Weak soldering often occurs, and poor control of the amount of tin leads to poor solder connection on the pads. In order to solve these processes, they found our automatic soldering machine. According to our understanding of PCB board pads and electronic components. What kind of tin wire is used for the specific pad position, how much tin should be produced by the automatic soldering machine, and how much temperature should be heated will be set according to strict parameters.
Can grasp the detailed position transition of each solder joint on the PCB, including the way of the soldering iron head of the automatic soldering machine, including whether the soldering pad requires tin penetration or not, the parameters will be strictly set and compared, and the actual effect will be used to verify this The quality and efficiency of solder joints. The position of the automatic soldering machine is also very important for PCB board welding. Okada Technology has independently developed automatic soldering machines for many years. It has rich practical experience in automatic PCB soldering, and can complete the process requirements of each solder joint item by item according to customer requirements.
We have common problems in PCBs that are not well soldered with automatic soldering machines. Based on more than 10 years of analysis, let’s take a look.
It is common that the soldering pad of the PCB board is covered by green oil. In this case, it can be soldered well with an ordinary constant temperature soldering iron. However, due to the short time of the automatic soldering machine contacting the soldering pad, the soldering of the soldering pad may be poor in many cases. This problem requires PCB board manufacturers to make improvements in order to solve the problem.
Regarding the oxidation of PCB pads:
The phenomenon of oxidation of gold-plated plates was not common before, but now it is very common. The main reason is that the price has gone up, but the price of PCB processing has not risen much. Therefore, the PCB production industry only has to be thinner and thinner, and the gold cylinder is not well maintained, and the impurity content is large, which appears when the weather is bad. The probability of oxidation is increasing. Oxidation is divided into the following two situations:
One is that the nickel surface has not been oxidized when gold is plated. If this happens, there is basically no way to deal with it. Only the gold layer and the nickel layer are returned. I know that there is a potion that can do it without hurting the copper surface, but the price Higher
The second is the oxidation after gold plating. The cause of the oxidation is that the nickel and copper ions in the gold cylinder exceed the standard, or the gold plating time is only 3-5 seconds, and the gold layer does not cover the nickel surface, causing the underlying nickel to oxidize.
So oxidation is very difficult for automatic soldering machine welding conditions and instability, using flux, and some are difficult to deal with. Under normal circumstances, after wave soldering or patching, the next post-soldering process will be performed immediately. After decades of soldering experience, this problem has been successfully solved.
About the electronic components on the PCB board are some cutting feet?
If the cutting feet of electronic components on the PCB board are too long, there is a high possibility that they will block the position under the soldering iron head and resist the soldering head of the automatic soldering machine, resulting in poor soldering, and the cutting is too short, and it is easy to cause defects, such as Some automatic soldering machine manufacturers do not need tin penetration, or require efficiency, and sometimes there are false soldering on site. These practical problems are actually common in the case of automatic soldering machine welding.
How to install PCB heat sink
What is the installation method of the PCB heat sink? Many devices in communication products consume large amounts of power and require heat sinks to dissipate heat. There are two ways to fix the radiator: mechanical fixation and glue fixation.
Common design failures mainly include the adhesive radiator falling off, the screw mounting the radiator causing the PCB to bend and even the device, especially the BGA solder joint, fails.
(1) The radiator shall be fixed mechanically. Flexible installation shall be adopted. It is strictly forbidden to use inelastic screws to fix.
(2) It is not recommended for multiple chips to share a heat sink, especially BGA chips. It will fall freely during soldering, and its height from the PCB surface is difficult to control. Therefore, generally when multiple chips share a heat sink, the heat sink should be installed and fixed. Only the design of thermally conductive rubber pad plus radiator and mechanically fixed can be used, but this design often causes the BGA solder joints to squash or break due to the installation sequence of the screws during installation.
(3) Adhesive technology should be used to consider the matching of the adhesive area and the expensive quality of the radiator and the wettability of the adhesive and the surface of the radiator (for example, some glue is not wetted with the Ni plating), otherwise it will easily fall off fall.
