What causes solder whiskers to appear after solder paste soldering? A brief discussion.

withLead-free solder pasteAfter welding, sometimes it can be inSMTWhite whisk-like substances were found at the solder joints of the components' pins. This situation is very likely because tin whiskers grow on the pins. Now, the solder paste manufacturer will take you to understand how to understand solder paste.

How to understand tin whiskers?

Tin whiskers: It is a very common situation on the machines of electronic equipment products. If you want to understand tin whiskers, you first need to know exactly what crystal whiskers are. Whiskers are a kind of crystal similar to hair, which need to grow naturally from the surface of a solid, and thus are also called "intrinsic whiskers". Whiskers usually grow in many metals, among which the most common ones are usually tin, zinc, indium, cadmium, antimony and other metals. Under normal circumstances, whisker conditions are more likely to occur frequently in relatively soft and highly malleable materials, especially in low-melting-point metals. Whiskers are not commonly found in lead, silver, gold, iron and nickel. However, sometimes whiskers also grow on tin-lead alloys, but the probability of this occurrence is relatively small.

From top to bottom, it can be known that tin whiskers are the whiskers of tin, which is a single crystal structure and also has electrical conductivity. There are several shapes of tin whiskers, such as straight, twisted, grooved, crossed, etc. Sometimes, hollow ones may also appear, with grooves on the outer surface.

The diameter of the tin whiskers can reach10μmSometimes the length can be so long that it has already exceeded10㎜Its capacity to transmit current can reach10Milliamperes, when the transmission current is large, the tin whiskers are generally burned out. Even though tin whiskers do not seem long and fragile, they can still cause two practical problems in precision electronic components: both can lead to electronic short circuits, and the damage comes from the release at the bottom layer, resulting in mechanical damage. Such a phenomenon has an impact on manufacturers who prefer to use tin rather than lead for interconnection circuits. The lack of understanding and judgment of the growth factors of tin whiskers leads to the application of pure tin interconnection lines and hazardous electroplating materials in high-reliability systems such as satellite systems, and the lack of testing methods for the growth factors of tin whiskers. However, it is generally believed that the market demand for environmentally friendly components will outweigh the potential drawbacks of tin whiskers components.