How Micro Vias Can Be Used in Next-Generation
In electronics, micro vias provide a highly efficient path for electrical signals. They can also help to reduce noise and signal timing delays. But these benefits come with a cost, and careful planning is required to ensure PCB reliability.
As technology trends toward miniaturization, the demands placed on printed circuit boards (PCBs) are increasingly challenging. This push towards smaller components and higher density has prompted the use of various advanced PCB fabrication techniques, including micro vias. Compared to traditional through-hole vias, these tiny structures can significantly increase PCB routing densities.
To create these holes, laser drilling is employed. A precise manipulation of the laser settings is necessary to guarantee that the resulting hole has the right size and shape. Additionally, particular plating processes must be used to connect the drilled micro vias with the surrounding copper on PCB layers.
How Micro Vias Can Be Used in Next-Generation Computing Systems
Staggered or stacked micro vias can be used to connect different layers of the board. This can be beneficial for reducing manual routing time and improving signal integrity, but careful consideration must be given to the aspect ratio of these structures to prevent structural failures. A recent IPC reliability warning indicated that stacked blind and buried vias with high aspect ratios are more likely to experience reliability problems than those with lower aspect ratios.
The problem is believed to be related to a mismatch between the coefficient of thermal expansion (CTE) of the metallization in the microvia and the CTE of the surrounding copper layer. This mismatch causes thermal stress to build up in the via neck and cause microvia failures. These microvia failures have been described as interfacial separation between the base of a microvia and its target pad, barrel cracks, corner/knee cracks, and microvia pull out.
Fortunately, these types of microvia failures can be prevented by selecting a reputable PCB manufacturer that utilizes high-quality materials. The choice of copper for the conductive filling is crucial, as it must be able to handle the current loads required by the microvias and dissipate heat effectively. In addition, the laser drilling and plating processes must be conducted with extreme precision to ensure that the microvias are of a high quality.
In order to avoid these issues, it is important for designers to work closely with their PCB fabricators to establish the correct microvia design and size. In addition, proper PCB layout is essential to ensure that the microvias do not interfere with other components or traces.
In the past, plated through-hole vias were the preferred PCB interconnect solution for many electronic devices. However, today, with advances in high-density interconnect (HDI) technology, micro vias are the standard for most modern electronic devices. These tiny structures can save space and improve routing density, enabling manufacturers to pack more power into handheld electronic devices. They are particularly useful in high-speed digital and RF applications, where maintaining signal integrity is critical.