Printed Circuit Boards (PCBs) contain tracks, pads, and other features, etched from copper sheets and laminated onto a non-conductive substrate. These etched features electrically connect electronic components, and the PCB offers mechanical support as well.
The Evolution of Circuit Boards to the Modern PCB
Before PCBs, creating a circuit board was a “laborious process of point-to-point wiring,” as explained by SparkFun. Not only were these circuit boards time-consuming to configure, but they were far inferior in reliability. There are frequent failures at wire junctions in this type of circuit board, and as wire insulation wears down over time, it may crack, leading to short circuits.
The development of wire wrapping was a significant advancement in the circuit board world. Wire wrapping is a small gauge wire wrapped around a post at every connection point, which creates a gas-tight connection. This process was particularly beneficial to the longevity of circuit boards, as wire wrapping is both durable and easily changeable.
As the field of electronics evolved, gadgets became increasingly common for household and general consumer use. Naturally, manufacturers wanted smaller, more compact, and more reliable circuit boards to power the smaller electronics devices now appearing on retail shelves and in households everywhere. It’s from this demand that the PCB emerged as a preferred circuit board solution for many electronics applications.
PCB Layers, Components, and Processes
A PCB allows both signals and power to be routed between physical devices. Solder is used to connect the surface of the PCB and electronic components, which also serves as a mechanical adhesive. PCBs are generally comprised of four layers:
- Solder mask
- Substrate (usually fiberglass, FR4)
A variety of other components, materials, and processes are used to create the end-result PCB, including annular rings, pads, planes or pours, solder paste, and many other elements and techniques for creating the precise connections necessary for proper functionality. In advanced PCB configurations, additional components such as resistors, capacitors, and active devices may also be included.
Reliability Considerations in PCB Design
Each of the components that comprise a PCB has an impact on the reliability and durability of the unit as a whole, as they respond individually to exposure to a variety of circumstances, such as moisture, temperature, electrostatic discharge, other environmental and usage impacts. For this reason, design of PCBs and the electronics devices that rely on them is a complex process. Engineers must consider not only the materials and vendors, but the manner by which the various components are connected.
Designing PCBs with reliability in mind allows for a margin of error, mitigates risks resulting from product defects or malfunctions, and, ultimately, satisfies the end consumer. Demands of the modern marketplace make this an ever-more challenging task, thanks to the increasing complexity of electronic circuits, additional power requirements, new component and material technologies, and components that are less robust and durable than previous options.
An experienced team of mechanical and electrical engineers well-versed in the various materials and components, as well as an in-depth understanding of usability requirements, can easily meet these challenges with a robust, reliable, and durable design. In membrane switch design, PCB membrane switches offer the same feature options as those available in a silver flex membrane switch design, including:
- Both tactile and non-tactile options
- Rigid printed circuit boards
- Embedded LEDs
- Fiber-optic backlighting
- Electroluminescent Backlighting
The Role of the PCB in Modern Electronics
A PCB is just one component of a membrane switch assembly, making up the layer typically referred to as the circuit layer. In some assemblies, a secondary PCB or circuit layer is also incorporated in order to provide additional circuitry if required. But it’s the PCB that serves as the central hub of connectivity, enabling the various components of an electronic device to be interconnected and function as a single, cohesive unit.
PCBs, thanks to the reliability and durability possible through careful planning and design, are widely used in most electronic devices today. Products ranging from home electronics, appliances, to medical, industrial, and aerospace equipment rely on PCBs for reliable functionality. PCBs may connect LCD monitors to data processors, enable the input and output of a computing device (such as a PC or laptop) to communicate, and serve many other similar functions in modern electronics. In a computing device, the PCB is often referred to as a “motherboard.”
PCBs are also important components for electromagnetic shielding, impedance matching, and heat transfer. But the two most fundamental functions of the PCB are those required by even the most basic electronic designs:
- Providing mechanical support to the electronic components.
- Interconnecting the various components together, thus providing the input/output connections required for users to interact with a device.
Even the automotive industry relies on PCBs for a variety of functions now found in cars and trucks. In fact, electronics components alone make up a good portion of the total value of the materials used in the manufacture of automobiles.
PCB Market Continues to Grow to Accommodate the Increasing Prevalence of Digital Electronics
Typically, an electronic component that’s been around as long as the PCB has would ultimately become outdated and less popular as more advanced methods and components emerge. But PCBs are an exception, with the PCB market poised for continued growth in the coming years as the proliferation of digital devices for business, industrial, medical, and consumer use continues.
“Market research firm Lucintel (Irving, Texas) reports a global market for glass fiber in PCBs of 844 million lb in 2013 and forecasts a compound annual growth rate (CAGR) of 4.5 percent. At that rate, the use of glass fiber in the PCB market will reach 1.1 billion lb by 2019,” according to a report by CompositesWorld. (Glass fiber and epoxy laminates have served as the foundational structural substrate in PCB manufacture for decades. This is the thin, green, card-like component most people associate visually with a PCB.) “The growth will be fueled by the proliferation of mobile devices and digital control in appliances and cars, and new robotic applications in medical, defense and other manufacturing industries.”
PCBs aren’t going anywhere anytime soon, but they may get better. As market trends shift toward miniaturization (smaller devices for greater portability), improved speed and performance, better thermal management, and even 3-D printing options, PCB manufacturers may look toward better-performing substrate options.
“According to TTM Technologies, multilayer PCBs (including 4 to 6 layers, 8 to 16 layers and 18+ layers, see below) make up 47 percent of the market, with the highest growth projected for 8- to 16-layer boards. Rigid-flexible PCBs, now only 5 percent of the market, are forecast to grow fastest, reflecting the move toward smaller, higher-performance electronic devices,” according to CompositesWorld.
Globally, the PCB market has grown substantially in the past several years, from $35 billion in 2006 to $62 billion in 2013. With the pace of technology innovation showing no signs of slowing down, PCBs will continue to be a popular option in membrane switch design, serving a critical role in the functionality and reliability of modern electronics.