Failure analysis of discrete components

1,7252019-02-04

In the process of electronic product development and production, with the sample testing of electronic components, small batches, large batches, and increasing numbers, “zero defect” products do not exist, but defects are a necessity. Defects are not terrible. What people are most concerned about is how to correctly find out the cause after the failure of the product, determine the failure mechanism, and avoid the failure from happening again. Today I will share with you some basic steps and methods of failure analysis of discrete components. Due to the limited space, I mainly focus on electrical stress analysis. I hope it will be helpful to all engineers.

Concept

1.1: Failure analysis is part of product reliability.

1.2: There are three engineering methods for product reliability analysis: reliability data; reliability testing and failure analysis

1.3: Failure analysis refers to the analysis of the physical and chemical reactions of the failed product to find out the mechanism and analyze the underlying cause.

2. Process

3. Stress

The product is theoretically a “100%” good product when it leaves the factory. The reason for failure must be caused by external causes. These inducements are various stresses, mainly electrical stress, thermal stress, mechanical stress, chemical stress, etc. The most common type is electrical stress. How to determine whether it is electrical stress failure, current burnout or voltage breakdown?

4. Case study

Typical current burn out

When a large current passes through the chip, because the current is instantaneous and the impact of high energy, the contact point of the bond wire is often burned first, and the location will be close to the window, as shown above.

 

When a pulse voltage is generated in the component, because the voltage is also instantaneous, the charge can be quickly eliminated if the window is open with good conduction, and it is easier to breakdown away from the window. The breakdown often shows “melt holes” “shape.

 

 

In some ultra-thin structured diodes, since the chip and the frame are connected by soldering, no bonding method is used and no window is opened. So it is difficult to judge from the position alone. This is to observe the shape of the failure point, as shown in the figure above, it is the “popcorn” shape, which is the most common current burnout. Schottky diodes, because of their metal-semiconductor structure, have a thin metal film inside. Tip discharge is prone to occur during voltage breakdown. This is related to the surface roughness during the production of metal thin films. Therefore, the location of breakdown may also be close to the window. Several cases are common. Most of them are to test the failure analysis ability of the analyst. Personally, I suggest to improve from the following four points:

Rigorous thinking

Attention to detail

Calm analysis

Knowledge width