PCB Assembly; Challenges, Solutions, and Future

By Mulugeta Abtew, VP, Manufacturing Technology Development, Sanmina

Driven by the influx of smart devices and electronic products, the pervasiveness of PCBs has continued to expand. Besides technology advancements and innovations, a wide spectrum of industry requirements has further amplified the manufacturing methods of PCB. The designs are becoming more complex but smaller as well as efficient owing to advancements in the electronics industry. Additionally, the demands in the industry have been met by the development of materials, components and also new manufacturing technology yielding bespoke products. Some of the technology transformations that revolutionized the PCB industry includes high density interconnects, high power boards, Flex PCBs, internet of things (IoT), commercial off-the-shelf-components, and also the component supply chain control. Industry experts predict that like other verticals of the manufacturing industry, the PCB sector will also embrace 3D printing technology as it offers better miniaturization and denser boards.

"The PCB assembly technology is largely shaped by the proliferation of innovative technologies in the field of automotive, telecom, medical, and aerospace sectors"

Mulugeta Abtew, VP, Manufacturing Technology Development at Sanmina sheds his valuable insights on the PCB design sector. Abtew is an experienced professional in the field of electrical and electronic manufacturing industry. He is skilled in DFX, Reliability Engineering, Six Sigma, Manufacturing, as well as failure analysis.

What are some of the industry trends that shape the PCB industry?

The PCB assembly technology is largely shaped by the proliferation of innovative technologies in the field of automotive, telecom, medical, and aerospace sectors. The arrival of IoT products has also contributed to this massive sea change happening in this niche market. In response to the demand of smaller and thinner PCBs High Density Interconnect was developed. The technology not only helped in the development of smaller and thinner PCBs but also products with greater capabilities in terms of routing traces. The requirement of higher power boards also increased drastically in the last few years. This includes boards with up to 48V supply. These boards were developed for solar energy based systems and electric vehicles where voltages are in the range of hundreds. Advent of IoT products demanded multi-tiered design strategy that required fast communication between different layers and components such as sensors. Remote monitoring and control systems became the benefactor here leveraging this technology. Flex and rigid-flex PCBs are also gaining enough traction these days. In my opinion, in the field of component supply chain, our primary focus should be elimination of counterfeit products and components that risks the quality of the products that we develop. This is particularly important in the field of mission-critical systems development.

What are the challenges that you see in the automotive sector when it comes to PCB assembly technology?

Peak dissipation is one of the significant challenges in assembling PCBs for the automotive industry. This is because of the high power requirements of components used in this field. In order to reduce the heat generated due to high power flow, a cooling system has to be kept. For instance, consider an interconnect having a void. The presence of the void narrows down the heat dissipation. PCBs often bend when they are subjected to high-temperature changes. This affects the heat passage and also the structure of the PCB. Some of the components when subjected to varying temperatures, they tend to change structural as well as chemical composition. Components made of alloys when subjected to temperatures other than its operating point may alter the structure and breaks down. In some cases, it chemically reacts with chemicals present in other components. There are automotive products used for control applications and navigation that are to be manufactured in high volumes. Producing those in high volumes is a challenge.

Shed us some light on applications in the medical sector and also technical challenges while assembling?

The biggest challenge in medical applications is the usage of disposable components which are environmentally friendly. Factors such as chemical cleanliness, contamination-free surfaces, etc. have to be taken care of while assembling devices for medical applications. A number of chemicals are used while soldering a PCB. Keeping a level of cleanliness mandated by different safety and quality control departments is not trivial. Ionic contamination is another severe concern in this area. While working with disposable medical devices such as patches that are used on the human body, the chemicals used should not cause any reactions. Additionally, using environmentally friendly chemicals and substances while working on various medical devices is another issue in this field.

Tell us more about the telecom field, aerospace and also oil and gas?

PCBs used in the telecom applications are more massive and requires high thermal mass. The larger size is due to vast amounts of components. Because these are top density boards, the soldering temperature is usually high. Here the challenge is there are chances of the PCB getting damaged while they are exposed to higher soldering temperatures. IPC has come up with the standard of thermal stress in order to mitigate the problems to this end.

A combination of different packages such as ceramic as well as plastic and metal are used in the aerospace assembly. Errors and also defects are common and hard to fix here. For instance, if an assembly is dip coated; chances for the coating to flow underneath packages like BGAs (Ball Grid Array) and QFNs (Quad Flat No-lead) are high. During thermal cycling, the coating will expand and lift the component off the board. Failing of solder connections is a very common problem. The problem gets worse with high temperatures. Although X-Ray based systems help in detecting the defects, the industry lacks tools to detect these defects readily and fix it permanently. Partial connections are also another problem. To this end, IPC has come up with lead coplanarity as a measurement to solve this, but still, the issue persists. Components used in the oil and gas industry work in extreme temperature and also pressure conditions. And so the PCBs should have the capability to withstand high temperature.

What are some of the industry best practices that should be followed for mitigating some of the technical challenges?

Working closely with component suppliers is essential as they should know the soldering conditions. A generic data sheet is not enough to this end. The PCB assembly house and the component manufacturer should work closely to understand the characteristics of each component. Making sure that the assembly process does not induce any strain or stress in the package is also another practice the industry should follow to reduce defects. Industry consortiums like IPC are working towards this end to ensure quality and reliability in the PCB industry.