Trends in Flex Printed Circuit Boards

Posted on June 8, 2017

The last 25 years or so have been a sea change in the electronic industry. The speed of technology is changing at a geometric rate. Where earlier mobile phones were the size of shoes, now there are slim smart phones that easily slip into a shirt pocket. The changes expected in the next two decades will make the previous decades pale in comparison. One of the key ingredients in this heady mixture is the flexible printed circuit board, also known as the Flex PCB.

Market Trends in Flex PCB

According to the Global Industry Analysts Inc., the projection for Flex PCBs in the global market is pointing towards US$15.2 billion by 2020. Several factors are contributing to this trend. Chief among these are the emergence of wearable electronics, polymer plastic solar cells and foldable and rollable smartphones. This has led to an unrelenting focus on the manufacture, performance, and design of special printed circuit boards, mainly of the flexible type. The growth in the market is coming from technological advances in conductive and substrate materials, along with developments in fabrication such as in special copper etching techniques.

Market Areas Driving the Demand

The burgeoning opportunities for flexible electronics are mainly coming from the healthcare sector and are driving the main benefit for growth. With electronic packaging shrinking in size, the need for superior packaging flexibility is driving the interest in flexible PCBs. The growth of disposable electronics is also causing a spurt in the opportunities. Technological advances in flexible ceramics are helping manufacturers shrink the size of substrate materials. The auto end-use sector is helping to drive the demand for flex PCBs as more promising applications are discovered in the areas of haptics and structural electronics.

Technological Trends in Flex PCB Design and Manufacturing

Although from the technological point of view, a conventional multilayer PCB still corners a large share of the market, the global trend of shrinking of electronic products is pushing up the requirements for HDI, Rigid-Flex, and Flex technology. The challenge to the manufacturers comes from designing ultra-thin PCBs that must also meet the requirements of signal integrity and EMC specifications while still being low cost.

The PCB industry often needs to increase the layer count within reducing thicknesses of circuit boards—all without compromising the electrical performance and structural rigidity of the PCB. For instance, they expect to reduce the current PCB thicknesses of 0.5-0.7 mm to lower than 0.4 mm in the future. Similarly, the 0.7 mm pitch of a BGA package has already come down to 0.4 mm, and expected to reach 0.3 mm—offering higher pin counts within reduced PCB real estate.

Following the same pattern, pad/hole sizes of microvia are fast coming down to 150/75 µm. For drilling microvia, the PCB industry currently uses CO2 laser, but they are moving on to new lasers working at picosecond pulses. These will offer still finer holes, and lower the thermal damage drastically. HDI technology is coming up with Any Layer Via (ALV), although this is still expensive, requiring state-of-the-art technology. The next generation of wearable and handheld devices is already demanding a buildup of 10 to 12 layers of microvia.

Manufacturers are moving toward embedded passives within the substrate material of the PCBs. They are embedding passive components such as resistors, capacitors, and others into the substrate material, following the standard IPC-2316. This leads to improved system performance and signal integrity, while reducing EMI and parasitic. It achieves higher board yield and active circuit density, while reducing the circuit board size and weight, leading to a reduction in assembly cost.

Manufacturers are also experimenting with new substrate material such as Resin Coated Copper (RCC), Liquid Crystal Polymer (LCP), Resin Coated Film (RCF), and vacuum-laminated films for flexible PCBs. These offer cost-effective solutions with high performance of low and ultra-low dielectric loss.

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