How To Solve The Problem Of Tin Beads During Production Caused By Pad Mismatch

With the continuous improvement of the integration of electronic products, the requirements for the PCBA process are becoming higher and higher. For example, the universal application of 01005 size devices in smart capacitance products and mobile phone communication products, the application of closely spaced QFN and CSP packages have increased the complexity of the SMT process. In order to meet the reliability requirements of products, the formation of good solder joints depends on a reasonable pad design, a suitable amount of solder paste, a suitable furnace temperature zone line, etc., where the design process of steel mesh is the core part of improving the yield of SMT process This is also a huge challenge for engineers who have been in front-line production for many years. Only when you have accumulated rich production experience and solid technical skills can you quickly deduce the cause and mechanism of defects when handling abnormalities on the production line, and solve problems quickly and effectively.

 

In this issue, I will share with you the common problems of several types of bad solder balls in the SMT process. How to solve the problem by optimizing the opening of the steel mesh. At the same time, when optimizing the opening of the steel mesh, it is necessary to avoid the hole. The reduction in area leads to the problem of poor solder joints.

 

Generally, the bad phenomenon of tin bead is described as follows:

 

Tin bead refers to the irregular tin balls formed on the PCB surface at non-solder points due to solder paste splash or residue, overflow pads, etc. during the soldering process. The probability of tin beads appearing around the following components in the SMT process is relatively common, and the general branch locations are as follows:

Around resistance and capacitance element pads

Module components, around the shield

inductance, magnetic beads, crystal oscillators, LED lights, MOS tubes, fuses

The bottom flat package devices such as: filters, LGA package body side tin beads phenomenon