PCBA Tech - Reasons for SMT solder joint peeling and non-absorption

SMT patch processing to solve the method of solder joint peeling

There are two ways to solve this PCBA problem.

One is to choose a suitable solder alloy;

The other is to choose a suitable solder alloy.

The second is to control the cooling rate to make the solder joints solidify as soon as possible to form a strong bonding force.

In addition to these methods, PCB design can also be used to reduce the magnitude of stress, that is, to reduce the area of the copper ring that passes through the hole. A popular approach is to use SMD pads, which limit the area of the copper ring by using a green oil-repellent layer. But this method has two disadvantages. One is that the peeling of the lighter is not easy to see. Secondly, SMD pads are formed at the interface between the oil generation and the pads, which is not ideal from the point of view of service life. Some tears appear in the solder joints and are called tears or tears. Some suppliers in the industry believe that if this problem appears on the top through solder joints, it is acceptable. Mainly because the key part of the through-hole quality does not exist. However, if it occurs in a reflow solder joint, it should be regarded as a quality problem, unless its degree is small (similar to wrinkles)

The reason why SMT patch does not absorb material

The suction nozzle is an indispensable part of the placement machine, and it is a key part of the sucked component to paste and put the action. However, during the use of the placement machine, sometimes it is inevitable that the suction nozzle of the placement machine cannot absorb components. So what is the reason why the suction nozzle of the placement machine cannot absorb the components?

Common reasons why the nozzle of the placement machine cannot absorb components:

1. The influence of the feeder: poor feeding of the feeder causes deformation, rust damage, etc. of the press belt cover, spring and other operating mechanisms, resulting in components attracting deviation, standing sheets or unable to absorb components.

2. Suction nozzle wear: due to the wear and tear of the suction nozzle of the placement machine, the suction nozzle is deformed, blocked, or damaged, resulting in insufficient air pressure, resulting in the inability to absorb components.

3. Insufficient vacuum negative pressure: When the pick-up nozzle of the placement machine picks up the component, a certain negative pressure is generated at the suction nozzle, and the component is adsorbed on the suction nozzle. The negative pressure detection method is generally used to determine whether the suction nozzle picks up the component. Insufficient vacuum pressure will not provide enough suction to absorb the components.

Solution:

1. When in use, it should be checked regularly, and if any problems are found, they should be dealt with in time to avoid a lot of waste of devices.

2. Pay attention to regularly check the wear level of the suction nozzle, and replace the severe ones.

3. In the process of using the SMT placement machine, the vacuum negative pressure should be checked frequently, and the suction nozzle should be cleaned regularly, and also pay attention to the pollution of the vacuum filter element on each placement head. If it is found to be polluted and black If it is, it must be replaced.

The method to solve the problem that the nozzle of the SMT placement machine cannot absorb the components requires careful inspection, so that the root of the problem can be found.