People often confuse lead-free solder balls with lead-free solder balls, but they are not. The difference between lead-free solder balls and lead-free solder balls from solder ball manufacturers is the main difference in the mechanism of production. In addition, in terms of appearance and volume, the outer shape of lead-free solder balls is larger than that of lead-free solder balls, usually greater than 5mil in diameter. From the position of appearance, the lead-free solder balls are mainly concentrated in the middle of the chip component and the lower sides of the component body, while the lead-free solder balls are anywhere in the flux residue. In terms of quantity, lead-free solder balls are generally 1 to 4, while lead-free solder balls are not fixed, and the number is often many.

The mechanism of lead-free solder balls and lead-free solder balls

2.1 Formation mechanism of lead-free solder balls

The main reason for lead-free solder balls is that in the process of solder joint formation, the molten metal alloy "splashes" out of the solder joints for various reasons, and many scattered small solder balls are formed around the solder joints. They are often found in groups, discretely in the form of small particles trapped in flux residues, around component terminations or pads.

2.2 The formation mechanism of lead-free tin beads

Lead-free solder balls refer to some large solder balls before the solder paste is soldered, and the solder paste may exceed the printed pad due to various reasons such as collapse and extrusion. During soldering, these exceed the pad. The solder paste cannot be melted with the solder paste on the pad during the soldering process and is independent, and is formed near the component body or the pad, but most lead-free solder balls occur on both sides of the chip component.

Common causes of lead-free solder balls are:

⑴The material is heated or cooled too fast, especially the lead-free high temperature process, which will lead to the formation of lead-free solder balls.

(2) During reflow soldering, the evaporation rate of molten flux is too fast, the proportion of relatively high solvent in the flux composition is relatively high, or the excess of high-boiling point solvent, improper heating, etc. will increase the possibility of lead-free solder balls.

(3) The oxidation degree of tin in the soldered surface or in the solder is too high, which makes the heating and heating processes of each part of the solder as a whole inconsistent during soldering, which affects the thermal conductivity and heat transfer of the flux. The possibility of solder ball generation increases.

⑷ There are unfavorable factors in the use of solder paste that affect the use environment of the solder paste. Lead-free solder balls are formed due to splashing of solder paste.