As long as electronic products were large, conventional printed circuit boards (PCBs), even complex PCBs, sufficed. However, with the advent of modern smartphones, wearables, and the Internet of Things (IoT), the tendency to go for thinner and smaller products is prevailing. Component manufacturers have responded positively to this trend by making their products ever smaller.
Now, increasingly, everyone wants smaller electronic products with more advanced features. PCBs have also undergone a drastic change in technology, going from thick, rigid structures to thin and flexible types. However, with no relaxation in the trend for reduction in size of products, even thin and flexible PCBs are not enough. Manufacturers now use advanced PCB manufacturing techniques to make multilayered boards. These are the High-Density Interconnect (HDI) boards, forming the backbone of the electronic industry.
For instance, mobile phones today are much thinner and lighter than most of their counterparts from just a few years ago. Even so, their functionality is far superior to that of their predecessors. This is because they now use an HDI PCB inside that accommodates far more components and offers substantially improved functionality.
Specifications Leading to Advanced PCB Design
The specifications of modern electronic devices such as wearable electronic devices, requires multi-layer HDI PCB solutions with large number of components on the surface and even within the PCB. This requires fine conductor widths with spaces between them narrower than conventional designs allow. As normal through-hole vias will never fit into the available space, fabricators had to resort to laser-drilled blind and buried microvias.
Manufacturers are making more boards with buried microvias as these help to increase the number of interconnections in the board, while freeing up valuable space on the outer layers for placing more number of components.
Another aspect of such advanced PCB design, apart from microvia technology and increasing number of layers is that complex PCBs are becoming thinner. Fabricators are now using thinner prepregs and cores than they did for conventional designs.
Manufacturing Techniques for Complex PCBs
With use of miniature devices increasing at tremendous speeds, production equipment at PCB factories are under great strain to produce complex PCBs. Producing HDI PCBs requires many of the equipment that conventional board manufacturers also use, as several stages in the fabrication process are similar, however, there are differences. HDI PCB requires working with tiny geometries that only sophisticated equipment can handle.
For instance, complex PCBs made with HDI technology incorporate blind and or buried micro vias in the several layers that make up the stack. Making these micro vias not only requires several additional steps, but the fabricator has to repeat these steps several times. The repetition increases the complexity and the risk of error.