micro vias
While micro vias offer a range of benefits, they also pose a number of reliability concerns. They are susceptible to manufacturing defects and other failures during the plating, filling, and assembly process that can cause issues when the device is operated. These failures can lead to a variety of issues, including electrical and thermal stresses that can compromise the functionality of the device and possibly result in system crashes or even total device failure.
The reliability of micro vias depends heavily on the materials used in their construction. The conductivity and adhesion of the copper that forms the conductive portion of the microvia are essential factors in ensuring that the vias function as intended. Additionally, the plating and finishing processes must produce void-free microvias that are resilient to environmental conditions such as vibration, moisture, and thermal cycles.
In order to minimize the effects of these environmental factors, the PCB industry has evolved with new materials and advanced fabrication techniques that are designed to provide improved performance and reliability for microvias. These innovations are driving a trend towards ever-smaller vias, sometimes called nano vias, which can be used to achieve even higher densities and enable flexible or rollable PCBs.
Can micro vias be used in autonomous vehicles?
Blind and buried microvias save space on the board as compared to traditional through-hole vias by allowing designers to place components closer together on the surface of the circuit board. This allows for increased component density and more complex PCB designs. In addition, they allow for a reduction in the amount of manual routing required to connect components on the board.
Depending on the design, microvias may be stacked or staggered. Staggered designs are often found in boards carrying fine-pitch BGA components, which require a small distance between the solder balls to prevent dog-bone fanout. While there are no definitive guidelines regarding the preferred design choice, it is generally recommended to stack no more than two microvias vertically and stagger them in the vertical interconnect. This helps to reduce the impact of voiding in the head of the microvia and can reduce the likelihood of failure at the interface between stacked microvias or the interface between the microvia and its capture pad.
The occurrence of voiding in microvias is one of the leading causes of failure in a printed circuit board (PCB). This can happen at various locations, but is most likely to occur at plated interfaces, such as the interface between two stacked or staggered microvias or at the interface between a microvia and its capture pad. In these cases, the high stress applied to the thin copper plate of the microvia can result in fracture at these points.
To avoid these problems, PCB manufacturers must employ a series of inspection and testing methods. These include electrical testing to verify the continuity and resistance of the via connections and thermal cycling tests that simulate the temperature variations that occur during operation. These tests can help to identify any potential weaknesses in the structure of the microvias that could lead to premature failure.
