Zulki’s PCB Nuggets: Soft Electronics Pose PCB Microelectronics Assembly Challenges

Medical electronics has made significant technological strides in the last few years. Mostly, electronic devices used in medical equipment have become smaller, yet more complex and powerful. Meanwhile, PCBs have moved from traditional large rigid boards to considerably smaller rigid and combinations of rigid and flex circuit boards, even to the point that bare chips and wire bonding are used during the PCB microelectronics assembly of these tiny boards.

Accordingly, EMS providers and contract manufacturers have had to make PCB assembly adjustments, adopt new ways of thinking, retraining its personnel, and investing in newer, more advanced assembly and manufacturing equipment to set up PCB microelectronics assembly to deal with those smaller devices and boards.

Even with these PCB assembly advances, the demands being placed on medical electronics continue without ceasing because the medical profession requires newer, more innovative products to perform better and more advanced patient care. Against that backdrop, today’s medical research findings promise to take medical electronics to an unprecedented level, in a completely different direction, and in a different dimension not before seen. You can call it a definite paradigm shift because it involves soft and not hard components, which PCB assembly has traditionally dealt with.

Evidence of that has already emerged. Take, for example, the research work performed at MIT. Reports coming out of MIT research engineering labs detail the design of a so-called light-sensitive hydrogel, and it is extolled as a new avenue to revolutionize medical procedures. There is no doubt that there is something very special about this new development from the medical perspective, and it’s giving us pause in our industry.

That light-sensitive hydrogel can be integrated with medical devices that doctors insert into the human body to treat, diagnose, or monitor disorders. Once those devices are no longer needed, they can then be dissolved inside the body by exposing them to light from an ingestible LED. Therefore, this automatic elimination process saves doctors from performing endoscopic surgery to remove such devices.

This light-sensitive hydrogel for ingestible medical devices was the most recent development involving this particular hydrogel material. Five years earlier, however, another group of MIT engineers [1] developed “a rubbery material, mostly composed of water, designed to bond strongly to surfaces, such as gold titanium, aluminum, silicon, glass, and ceramic.” They called this material hydrogel, but this research centered on external human body applications.

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It was described as a “water-based Band-Aid that senses temperature, lights up, and delivers medicine to the skin,” according to published reports [1]. Researchers said that it could also be used externally because they claim it has certain characteristics that are similar to human skin.

They called it a Band-Aid, in this instance, because this stretchable and flexible material could be applied to various parts of the body, like an elbow or a knee. A key advantage is the hydrogel keeps embedded electronics functional, robust, and intact. This is largely due to the fact it has good bonding strength like gold, titanium, aluminum, or silica gel, which are normally used in conventional PCB assembly.

Is It Too Far Out?

To many in PCB assembly and manufacturing, this business about new developments like light-sensitive hydrogel, ingestible, and insertable medical devices may be too far out in the future. Traditional large and small PCB assembly houses may be solely focused on day-to-day customer PCB production, and they’re not thinking about how to perform this new assembly and how to collaborate with the medical OEMs driving these newer technologies.

But to those with a keen interest in the future of medical electronics, it’s a good time to conduct preliminary meetings with those visionary medical OEMs. Certain aspects have to be considered when entering this new paradigm shift. For starters, data exchanges about chemical compounds should be on the discussion agenda.

Then, more specifically, discussions must be centered around how to create the microelectronics circuitry needed to embed it in the hydrogel. Further, exploratory talks should concentrate on ensuring that connectivity remains the same and that the hydrogel’s thickness is enough to implant micro-devices like flip-chips, die-attach, or micro-electromechanical systems (MEMS) into those hydrogels. That’s important to let us know that body functions can continue to properly perform and still allow the inserted medical device to be able to monitor in real-time the required diagnosis, analysis, or conditions of the body.

Furthermore, the usual concepts of conventional PCB assembly will require extremely close scrutiny and analysis. This study will help to determine if the usual ways of PCB assembly can apply to the new requirements that a soft hydrogel technology pose. This scenario presents questions as to how to incorporate electronics with signals floating from point A to point B. It also introduces the question of how to process different aspects of electronics into a jelly-like material. That step is critical to make sure those electronics work through sensors, MEMS, and biosensors and allow signal monitoring needed to observe human body conditions.

Other questions come into the mix. What about the circuit board itself? Will it be similar to a flex circuit, which features agility and nimbleness and isn’t a hard surface compared to FR-4 or other rigid material? Further, instead of soldering the components on a substrate, can an epoxy gel or something similar be effective? How long can signal wires operate effectively before starting to degrade? Controlling electromagnetic signals will be another point of careful evaluation while ensuring signal to noise ratio (SNR) in hydrogel embedded devices are within the tolerance listed in the spec sheet.

This is a whole new ballgame where you have different chemical and mechanical properties associated with new “soft electronics materials.” Plus, there’s also the issue of device selection and associated questions pertaining to LED brightness, its heat, and thermal expansion. And perhaps there may be new types of electronics devices that are more conducive for interacting with hydrogel material.

In short, we’re confronted with a brand-new thing. Navigating through this unknown phase and processes will be a true challenge for our industry. That’s why it’s never too early to begin collaborating with medical OEMs.

Reference

  1. J. Chu, “Stretchable hydrogel electronics,” MIT News Office, December 7, 2015.

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

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2020

Zulki’s PCB Nuggets: Soft Electronics Pose PCB Microelectronics Assembly Challenges

07-08-2020

Zulki Khan explains how PCBs have moved from traditional large rigid boards to considerably smaller rigid and combinations of rigid and flex circuit boards, even to the point that bare chips and wire bonding are used during the PCB microelectronics assembly of these tiny boards.

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Zulki’s PCB Nuggets: Medical Miniaturization and PCB Microelectronics Assembly

06-24-2020

Medical electronics continue to be a gamechanger, with miniaturization being foremost today in the minds of medical OEMs. Zulki Khan discusses how there is a growing demand for even greater device and component miniaturization that plays a major role in the PCB microelectronics assembly of these medical devices today.

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Zulki’s PCB Nuggets: Add Hi-rel to ISO 13485 for More Robust Ventilator PCBs

05-13-2020

It's important to meet FDA and ISO 13485 standard quality and reliability requirements for ventilators and other medical equipment. Zulki Khan explains how there’s still more that ventilator OEMs need to put into practice, specifically in the high-reliability or “high-rel” area to further add to ISO 13485.

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Zulki’s PCB Nuggets: Urgent Call for Ventilators—PCB Technology at the Ready

04-15-2020

An urgent call is out to medical equipment makers that thousands—even millions—of ventilators are in the greatest demand in our history due to the worldwide COVID-19 outbreak. Zulki Khan explains how new ventilator makers—as well as traditional ones—must weigh a number of key PCB design, assembly, and manufacturing factors.

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Zulki’s PCB Nuggets: Putting the Heat on for Thermal Profiling

03-11-2020

A unique thermal profile is designed for each PCB job undergoing conventional SMT assembly, as virtually every PCB assembly professional knows. But what about a PCB assembly project involving both conventional rigid board and an extraordinarily small rigid or rigid-flex circuit undergoing microelectronics assembly? Zulki Khan covers PCB hybrid assembly, which requires two separate, unique, and distinctly different thermal profiles.

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Zulki’s PCB Nuggets: 7 Steps to Successful Assembly for Medical Devices Using Microelectronics

02-12-2020

Seven major steps need to be taken to achieve successful SMT and microelectronics assembly for medical electronic devices. Zulki Khan explains how these key steps take on special significance for newly emerging implantable and ingestible medical devices and result in medical devices that are robust, smaller, highly reliable, more powerful, and lighter.

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Zulki’s PCB Nuggets: Successful PCB Microelectronics Assembly

01-15-2020

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2019

Zulki’s PCB Nuggets: Vital Details for Implantable Medical Devices

12-04-2019

In addition to smart pills and smart cameras, which Zulki Khan covered in a previous column, another segment of the medical electronics devices market is rapidly growing, as well: implantable medical devices, which medical personnel surgically or otherwise insert into various parts of the human body. Zulki explains the extra measures required for these devices.

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Zulki's PCB Nuggets: Multi-tier Wire Bonding—Diving Into PCB Microelectronics

11-07-2019

As the name implies, multi-tier wire bonding involves several levels of wire bonding beyond the single level of wire bonding, which is traditionally used in semiconductor and/or PCB microelectronics assembly. Here, you have two, three, and four levels of wire bonding, in some cases, called stacked wire bonding. Also, multi-tier wire bonding offers OEMs a solution when the number of inputs/outputs (I/Os) are far beyond the traditional ones that are used in the single wire-bonding application.

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Zulki’s PCB Nuggets: Smart Pills & Cameras—The Next Frontier for PCB Microelectronics

10-23-2019

"Take two aspirin and call me in the morning," is the proverbial, jovial, and often-cited elixir that doctors have prescribed over the years for whatever ails you. Today, medical electronics are adopting the same concept but with new technologies. Now, the phrase, "Take two aspirin," takes on new meaning, as medical electronics move into new frontiers of inspecting a human’s gastrointestinal tract with new, revolutionary ingestible smart pills and "pill cams."

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Zulki's PCB Nuggets: A Better Grasp of Glob Top Epoxy Factors

09-25-2019

In my last column, I cited important aspects of glob top epoxies, calling attention to the fact there are different epoxy manufacturers. In this column, I will continue to emphasize six other important factors of glob top epoxies.

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Zulki’s PCB Nuggets: Get a Handle on Glob Top Epoxies

09-12-2019

Most often, glob top is the prevalent method EMS providers use today. However, the most important point to be made about glob top is the fact that multiple manufacturers are producing different glob top epoxies. And within each manufacturer, there are numerous types of epoxies being produced. Another key point is that EMS providers and contract manufacturers generally are the ones deciding on the kind of epoxy to use. This column will further describe how you can get a handle on glob top epoxies.

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Zulki’s PCB Nuggets: Protect the Die and Wire Bonding for Effective PCB Microelectronics Assembly

07-31-2019

Protecting bare dies on a PCB or substrate is a major process of microelectronics assembly. As we’ve said before, microelectronics assembly and manufacturing work in tandem with traditional SMT manufacturing for complete PCB hybrid manufacturing of today’s smaller form factor products, including IoT, wearables, and portable devices.

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07-18-2019

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Zulki’s PCB Nuggets: Three Die Attach Methods for Microelectronics Manufacturing

06-27-2019

Die attach technology is increasingly being applied in PCB hybrid manufacturing (i.e., combining traditional SMT manufacturing with microelectronics) to comply with the requirements of small PCBs, especially rigid, flex, and combination rigid-flex circuit boards. These smaller boards are used in a variety of IoT, wearable, and portable applications.

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Zulki’s PCB Nuggets: Consider the Integrity of Wire Bonding

06-12-2019

While reliability and integrity can be regarded as synonymous as far as PCB manufacturing with microelectronics assemblies is concerned, the integrity of wire bonding—the methodology of interconnecting the wire to the bond pad—takes on other reliability-associated process qualities. Here are three factors that need to be implemented to create the integrity of wire bonding.

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Zulki’s PCB Nuggets: Avoid PCB Wire-bond Loop Failures

05-30-2019

Today, hybrid PCB manufacturing is making greater inroads into our industry, which is the marriage of traditional SMT manufacturing together with microelectronics and wire bonding. In many cases, the OEM working with EMS providers doesn’t fully understand the nuances of effective wire bonding and related failures.

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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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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

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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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09-11-2013

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