PCBA Tech - What are the characteristics of PCBA assembly Welding process

The reliability of dip plug-in assembly for patch processing in PCB board factories is also the reliability of production technology for patch processing of PCB boards. Usually it refers to the ability of PCB boards and PCBA board not to be destroyed by normal operation when they are assembled and welded. If improperly designed, it is easy to damage or damage the welded joints or components. Stress-sensitive devices such as BGA, chip capacitance, crystal vibration, etc., are easy to be destroyed by mechanical or thermal stress. Therefore, PCB circuit boards should be designed in places where they are not easily deformed, or be reinforced or avoided by appropriate measures.

(1) Stress-sensitive components should be placed as far as possible away from bending during PCB assembly. In order to eliminate bending distortion during subboard assembly, as far as possible, the connector cloth connected with the parent PCB Factory should be placed at the edge of the subboard, and the distance from the screw should not exceed 10 mm.

For example, to avoid stress fracture of BGA solder joints, the BGA layout should be avoided in PCB assembly where bending occurs. The poor design of BGA can easily cause cracking of BGA solder joints when holding the board with one hand.

(2) Reinforcing the four corners of large BGA.

When PCB is bent, the solder joints at the four corners of BGA are subjected to force and crack or fracture. Therefore, strengthening the four corners of BGA is very effective to prevent the cracking of corner solder joints. Special glue should be used for strengthening, or PCBA patch can be used for strengthening. This requires that space be left in the layout of components and the requirements and methods for strengthening should be noted in the process documents.

The above two suggestions are mainly from the design aspect. On the other hand, the assembly process should be improved to reduce stress generation, such as avoiding one-handed pallets and installing screws with supporting tools. Therefore, the design of assembly reliability should not be limited to the layout improvement of components, but should start with the reduction of assembly stress - using appropriate methods and tools. Strengthening the training of personnel and standardizing the operation can only solve the problem of solder joint failure during assembly stage.

Welding industry is the main process of PCB circuit board in PCBA. This process is very important to PCBA. Everyone must pay special attention to it. In addition, the welding process of PCBA has its own characteristics and process, which is the most basic according to the process in order to ensure the effect. So, what are the basic processes and features of PCBA's welding process?

(1) The size and fillability of the solder joint mainly depend on the design of the pad, and the gap between the hole and the lead. In other words, the size of the peak solder joint mainly depends on the design.

(2) Heat application of patch-processed PCB circuit boards from PCB board manufacturers is mainly carried out by melted solder, and the amount of heat applied to PCB circuit boards mainly depends on the temperature of melted solder and the contact time (welding time) and area between melted solder and PCB circuit boards. Generally speaking, the heating temperature can be obtained by adjusting the transfer speed of PCB board, but, For mask selection, the welding contact area depends not on the width of the peak nozzle, but on the size of the tray window opening, which requires that the layout of the components on the mask selection welding surface should meet the requirements of the minimum size of the tray window opening.

(3) The shielding effect exists in the patch type, which is prone to leakage. The so-called shielding effect refers to the phenomenon that the encapsulation of the patch element prevents the solder wave from contacting the pad/end.