Modes in HDI Circuit Boards

When a circuit board is damaged it may be due to a variety of factors. Some of these include electrostatic discharge, thermal stress, moisture and electrical faults. Each of these problems requires specialized PCB repair techniques and processes to correct them.

These issues are especially important to consider when using HDI technology in your design. hdi circuit board allow you to put more components on both sides of the bare PCB, and use blind via, buried via and microvia technology to shrink footprints and reduce the amount of space needed for interconnections.

While these features offer many advantages, they can lead to a number of different failure modes in the finished product. Understanding these failure modes can help you plan for them during the design process and prevent your boards from reaching the end of their life cycle before they are ready to be soldered into a final product.

Common Failure Modes in HDI Circuit Boards

One of the most common failure modes in a hdi circuit board is delamination, which occurs when the layers in the circuit board separate from each other. This can be caused by an electrostatic discharge, a burn-through on a single layer or by a short on the board that causes the copper to overheat. Depending on the severity of this problem, it can cause the whole board to fail.

Another common issue is conductive anodic filaments (CAFs), which are metallic thread-like structures in the surface of a printed circuit board. These threads form when metal plating of vias is contaminated with glass, resin or ion contamination. CAFs can also form when the PCB is exposed to high levels of temperature and humidity.

Other common failure modes in a hdi board are thermal cycling and the failure of components due to stressing of the solder bond. Depending on the industry, a circuit board may be rated for specific numbers of expected thermal cycles to failure. However, in some applications, the number of cycles may exceed this rating and result in premature failure.

The quality of a hdi circuit board is also affected by the manufacturing process, which includes a series of sequential laminations and laser drills. It is important to select a manufacturer that has the right equipment for constructing this type of PCB.

A hdi circuit board can have several layers, and each layer is separated by partially cured laminates called prepregs. The prepregs are pressed, heated and then liquified to stick the layers together. The number of laminations in a hdi board depends on the complexity of the design and the type of via structure used. The more laminations in a hdi circuit board, the higher its cost.

In addition to reducing size, hdi circuit boards are more reliable than traditional PCBs. The use of buried and blind vias allows designers to place smaller components in the same footprint and improve signal integrity. This technology is often found in mobile and cellular phones, touch-screen devices and digital cameras. It is also incorporated into military devices such as avionics and smart munitions.