PCB Technical - What should I do if pcb manufacturer, poor welding, welding error?

What should I do if PCB manufacturer, poor welding, welding error?

Usually when you get a BGA slice photo, the first thing to judge is which side belongs to the package surface of the BGA, and which side belongs to the circuit board assembly surface. For this problem, my method is to judge from the thickness of the copper foil. The thicker side of the copper foil is usually the circuit board assembly surface. Because the carrier board of the BGA package is usually thinner than the circuit board of the electronic assembly, it will Choose a thinner copper foil thickness.

Secondly, if the double ball phenomenon can be clearly seen, the larger side of the ball is usually the original solder ball on the carrier board, because the volume of the BGA solder ball has already undergone a Reflow, and the solder paste printed on the PCB has passed through it once. The remaining volume of Reflow flux after volatilization is only half of the original volume, so the sphere on the BGA surface is usually larger. As for the size of the solder pad (pad), it depends on whether you insist on designing [Cooper Define Pad Design (copper foil independent solder pad design)] when designing your own PCB layout.

Then judge the quality of the BGA welding. The following figure can clearly see the typical [HIP] welding problem. Those who don’t know can click the [HIP (Head-in-Pillow)] link for further discussion. 99% of HIP occurs on the outermost row of solder balls around the BGA. The reason is almost all that the BGA carrier board or PCB deforms and warps when the board passes through the Reflow. The deformation becomes smaller after the board returns to temperature, but it is molten. The tin has cooled, so it looks like two balls are close together. HIP is a serious BGA solder defect. It can easily flow to customers through the test procedures in the factory, but after a period of use, the product will be sent back for repair due to problems.

The second type of BGA solder defect is the solder ball between HIP and normal solder. Do you know how to judge which side is the PCB side? The BGA solder ball and the solder paste on the PCB have completely melted together, because the double balls are not visible, but the entire solder ball has been pulled up and down and almost broken. You can also find the solder balls by observing the solder on the PCBA board. The area in contact with the PCB solder pads has become smaller, and there is also an angle that is not long. This is because the solder balls are pulled up entirely. This kind of solder cracking should only be a matter of time, and the vibration of the client when it should be used or the thermal expansion and contraction of the switch machine will accelerate its cracking.

BGA solder ball soldering is acceptable. The sphere also has solder that is flattened to form a horizontal ellipse, but it can still be seen that the solder ball near the PCB end is still a little pulled apart.

The solder ball is similar to a "lantern type", and the solder ball covers the entire PCB pad. However, sometimes the solder pads are designed to be covered with green oil.