热拔球应用案例Hot Bump Pull/Hot Pin Pull

The shift from tin-lead to lead-free materials has had many affects on the surface mount technology and printed circuit board industries. These affects continue to be a major focus of many sectors from telecommunications, military, aerospace to consumer electronics.

A common failure mode in lead-free assemblies is pad cratering, where the contact pad on a PCB or package substrate lifts away. There are many factors that cause this failure mode to be more prevalent in lead-free assemblies compared to tin-lead assemblies, these include:

• Lead-free solders are mechanically stiffer than tin-lead solders, hence it transfers more strain to the assembly.

• Lead-free solder requires higher reflow temperatures as well as cooling rates compared to tin-lead. This can lead to increased strains on the assembly.

Mechanical testing such as bend and shock testing are common practices on surface mount assemblies and printed circuit boards in order to verify product design, ensure quality and ultimately to ensure product longevity. The mechanical stresses applied, evaluate the susceptibility of a product to failure.

Although these mechanical test methods test the entire assembly, it can however be difficult to differentiate the types of failure modes occurring during the test. Common factors which contribute to different failure modes include:

• Solder metallurgy

• PBA materials

• Reflow conditions

It is therefore important to isolate the failure modes in order to identify any weaknesses in the assembly. This is an important part of development and production, as it ensures correct design of product, anufacturing process control as well as quality of product produced.