PCB Hybrid Manufacturing: Coming Your Way

There is no big secret. PCB manufacturing is changing now more than ever before in its long history. Initially, it involved through-hole assembly and manufacturing with the most notable Intel 8086 motherboard. Later, through-hole and surface mount technology (SMT) began merging and sustained a long product cycle.

But today, PCB manufacturing is rapidly evolving to include SMT as well as microelectronics, such as chip-on-board (CoB) installation, flip-chip assembly, wire bonding, and die attach. SMT merged with microelectronics is also known as hybrid manufacturing (Figure 1). This is occurring because PCBs have begun shrinking at a faster pace in recent years due to the introduction of wearables (i.e., medical, commercial, and aerospace industries), IoT devices, and portables demanding smaller circuit boards.

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Figure 1: Hybrid manufacturing.

PCB assembly and manufacturing continue at a high rate to use small rigid, flex, and a combination of rigid-flex circuit boards to comply with OEM product requirements. When you have such small boards, you then have to rely on newer methods and technologies on the SMT floor and in cleanrooms. At the same time, you have to adapt your thinking away from SMT and more into the intricacies of microelectronics, also known as wire bonding.

Wire bonding is not new since it has been used since the early transistor days. But now, there are newer techniques that must be mastered and applied for SMT/microelectronics manufacturing. There are different wire bonding methods and different types of wires, gold, aluminum, silver, and more. Each type and method must be carefully evaluated for the right application. If poorly chosen, the OEM customer could incur poor performance or failures in the lab or the field at a later stage.

Savvy OEMs with wearable, industrial IoT devices, and other portable products should start familiarizing themselves with PCB hybrid manufacturing. It’s a new world involving not only different wire bonding but also the integrity and reliability of each type of wire bonding. Also, understanding the best methods for die attach is crucial because you want to use the correct method, whether it’s epoxy, eutectic, or solder attach. Each has its merits for certain applications, and it is crucial to know and understand.

Also, some components used in microelectronics have different coefficients of thermal expansion (CTEs) compared to traditional SMT components. This aspect needs to be carefully evaluated and verified so that when SMT manufacturing is performed, it doesn’t adversely affect the microelectronics portion of the assembly.

One has to keep in mind that traditional SMT components undergo unleaded or lead-free assembly with fluxes and pastes conducive to SMT manufacturing. However, when it comes to microelectronics, there may be different epoxies with various chemical compositions. That’s when thermal profiles with different aspects come into the picture. Keeping the thermal profile intact and in the right place is highly critical. The reason for this is components expand and contract at various temperature cycles. Contraction and expansion are at different rates for traditional SMT components compared to microelectronics components.

Also, component placement and its design during layout are most important, depending on board size and packages populating the PCB. The reason for this is you want to keep analog and digital components separate because analog typically operates at a higher current and with more heat compared to their digital counterparts. Similarly, care must be taken when SMT and microelectronics are merged together on a PCB regardless of its size. This ensures that SMT/microelectronics component placement is easy for different manufacturing tools to physically reach certain areas to perform microelectronics manufacturing and assembly after SMT manufacturing is completed.

Again, hybrid manufacturing is a major industry endeavor. It’s critical for existing and new OEMs launching into the next round of small PCB designs to gain a clear understanding of all the upcoming manufacturing technologies supporting new products. It is especially important to place extra emphasis on microelectronics manufacturing and its requirements for absolutely clean surfaces so that these assemblies are properly performed without jeopardizing reliability.

Zulki Khan is the president and founder of NexLogic Technologies Inc.

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2019

PCB Hybrid Manufacturing: Coming Your Way

05-15-2019

Today, PCB manufacturing is rapidly evolving to include SMT as well as microelectronics, such as chip-on-board (CoB) installation, flip-chip assembly, wire bonding, and die attach. SMT merged with microelectronics is also known as hybrid manufacturing. This is occurring because PCBs have begun shrinking at a faster pace in recent years due to the introduction of wearables, IoT devices, and portables demanding smaller circuit boards.

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2014

Tighter Scrutiny Needed for PCB Cleaning Agents

05-13-2014

PCB cleanliness on the assembly floor is now getting more attention, due to tiny residues and contaminants being left on assemblies after new, advanced assembly processes. Cleaning methodologies, testing, analysis, and special chemistries are being taken to a new level to assure customers of ultraclean boards to avoid costly latent issues.

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Zulki's PCB Nuggets: Tighter Scrutiny Needed for PCB Cleaning Agents

05-13-2014

PCB cleanliness on the assembly floor is now getting more attention, due to tiny residues and contaminants being left on assemblies after new, advanced assembly processes. Cleaning methodologies, testing, analysis, and special chemistries are being taken to a new level to assure customers of ultraclean boards to avoid costly latent issues.

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Uncovering Assembly Problems of High-Speed PCBs

03-12-2014

The high-speed board may be perfect when it comes to BGA assembly. All the balls properly collapse; all the thermal profiles are accurately determined and performed. All soak temperatures, pre-heat, soak, and cool-off periods fall within manufacturer limits and ranges. Yet, this high-speed board fails at high speed at the time of system functional level testing in the system.

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Zulki's PCB Nuggets: Uncovering Assembly Problems of High-Speed PCBs

03-12-2014

The high-speed board may be perfect when it comes to BGA assembly. All the balls properly collapse; all the thermal profiles are accurately determined and performed. All soak temperatures, pre-heat, soak, and cool-off periods fall within manufacturer limits and ranges. Yet, this high-speed board fails at high speed at the time of system functional level testing in the system.

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EMS Discovers Mature IC Technologies

01-14-2014

Columnist Zulki Khan asks, "Did you know that really new, up-to-the-moment PCB technologies are nesting on the doorstep of PCB assemblers?" In fact, he says some of these technologies are very mature, but they're completely new to the assembly side of things.

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Zulki's PCB Nuggets: EMS Discovers Mature IC Technologies

01-14-2014

Columnist Zulki Khan asks, "Did you know that really new, up-to-the-moment PCB technologies are nesting on the doorstep of PCB assemblers?" In fact, he says some of these technologies are very mature, but they're completely new to the assembly side of things.

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2013

Another Look at AOI

11-13-2013

PCB inspection is taking on greater significance as boards and packaging become increasingly smaller, with greater functionality. Automated optical inspection (AOI) and its backup associate, X-ray, team up to catch a variety of board assembly problems. But it's AOI that's at the forefront of this process.

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Zulki's PCB Nuggets: Another Look at AOI

11-13-2013

PCB inspection is taking on greater significance as boards and packaging become increasingly smaller, with greater functionality. Automated optical inspection (AOI) and its backup associate, X-ray, team up to catch a variety of board assembly problems. But it's AOI that's at the forefront of this process.

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Zulki's PCB Nuggets: ECOs Reviewed - The Importance of Accuracy

09-11-2013

Designers can perfectly layout a design and, in theory, follow written specifications to the letter, but when one factors in the practicality of that design, virtually everything associated with it has its limitations--ranging from the material used to make the board to assembly, machine tolerances, and process limitations.

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