What causes Kirkendall voids?

The voiding phenomenon is often referred to as Kirkendall voiding or diffusion porosity. It is commonly believed that voids arise from the agglomeration of excess vacancies, as a result of the intrinsic diffusivity difference between the two diffusion species, Cu and Sn.

What causes solder voids?

When less than require solder is applied to a joint, it can result in empty spaces or holes inside the solder joint – these are known as Solder Voids. A Solder void is generated due to the insufficient availability of solder while creating the joint.

How do you avoid void in soldering?

How to Prevent Voids in Solder Joints

1. Extend the Preheat Time. Extending your preheat time will allow solvent in the flux to reach the optimum temperature and vaporize completely.
2. Extend the Soak Zone Time.
3. Reduce the Solder Paste Volatile Content Quantity.
4. Modify Your Circuit Board Stencil.

What is the Kirkendall effect Why does it happen?

The Kirkendall effect arises when two distinct materials are placed next to each other and diffusion is allowed to take place between them. In general, the diffusion coefficients of the two materials in each other are not the same.

What is Kirkendall voids wire bond?

Diffusion and void creation during the formation of intermetallic materials was studied by Kirkendall and so these voids have often been called Kirkendall voids. Excessive Kirkendall voiding can result in out-of-tolerance wire bond resistance and weakened wire bonds.

What is the interdiffusion coefficient?

The interdiffusion coefficient is usually a composition-dependent quantity. On the other hand, interdiffusion is due to the diffusive motion of A and B atoms, which in general have different intrinsic diffusion coef- ficients.

What is the cause of voiding in SMT?

Voiding mechanisms are investigated for applications involving solder paste in SMT. Generally, the voids are caused by the outgassing of entrapped flux in the sandwiched solder during reflow.

What is voiding in SMT?

Solder voiding is a common phenomenon within the surface mount process and affects all smt components with some more affected than others. A solder void is defined as a hole or enclosed volume of space within a solder joint that lacks solder material.

What is the difference between self-diffusion and interdiffusion?

Self-diffusion is the diffusion of an atom to a new site in a crystal when all atoms are of the same type. Whereas, inter-diffusion is the diffusion of atoms of one metal into another metal. With vacancy diffusion, atomic motion is from one lattice site to an adjacent vacancy.

How do you reduce BGA Void?

This problem can be alleviated by raising the reflow temperature above the melting point of lead-free balls. It is critical that the process be qualified for void acceptance before being released for production regardless of the type of paste or balls used.

What is electronic void?

formed by entrapment and do not contain air. Whatever their etiology, voids are signifi. cant because they can cause electronic failures . They occur in polymers such as molding com. pounds and flip chip underfills, in metals such.

What is BGA Void?

Voids can be found in a BGA solder ball, in the solder joint to BGA interface or in the solder joint to printed circuit board (PCB) interface. Various factors are responsible for these voids. Voids can be carried over from original voids in solder balls, which could be the result of the ball manufacturing process.

What is interdiffusion?

Interdiffusion is a process of diffusional exchange of atoms across two materials that are in contact. This is driven by the chemical potential gradient across the boundaries.

What are intermetallic compounds?

intermetallic compound, any of a class of substances composed of definite proportions of two or more elemental metals, rather than continuously variable proportions (as in solid solutions). The crystal structures and the properties of intermetallic compounds often differ markedly from those of their constituents.