Shrinking Medical Electronics
Bring Assembly Challenges
By Sean Fenske, Editor-in-Chief
As more electronic medical devices are made portable, wearable, or even implantable, medical device designers will struggle with the challenge of getting more functionality and longer lasting power into their creations. With this in
mind, this month’s Roundtable approached the topic of electronics assembly and got key insights into new innovations, trends,
and tips for aiding in what can present as a significant obstacle to
Beginning with the factors driving the electronics assembly
landscape, Michael Allen, president of Z-Axis offered his view for
the medical device realm. “The biggest trend continues to be making systems smaller and portable. Two main factors helping us do
that are smaller, more integrated ICs and new battery technology.
For the ICs, component suppliers keep further integrating parts.
We can get more features in a single IC that replaces multiple ICs.
At the same time, packages for transistors, ICs, and microcontrollers have continued to shrink. Twenty years ago, the SOT- 23 was
common; five years ago, it was the SC70 at half the size; and now,
many parts are available in the SOT-523, a third of the size of the
SOT- 23. We also use a lot of micro BGAs.
Speaking about the second factor, he continued, “Battery
technology is the second main factor enabling portable medical
systems. Today’s lithium ion batteries pack enough energy and
last long enough so that we’re now able to use battery power for
devices where just five years ago, we’d need to use line power.”
Also speaking to power related issues was Andy Kelly, IC/sys-
tems architect with Cactus Semiconductor, “Energy storage density
presents the biggest miniaturization challenge for most of our devices.
Even though we have access to the latest energy storage technologies
and employ ultra-low-power design techniques, the battery is still
typically the largest single component in most of our devices.”
Undoubtedly, when it comes to electronic medical devices that
are shrinking in size, that battery can seem like an even bigger
component and, as such, challenge to optimizing the assembly.
While not addressing the issue involving the power source,
Lars Uffhausen, senior director of technology trends, innovation,
and investments with Jabil did share some insights on a relatively
newer technology solution that can certainly alleviate the issue of
getting all the necessary electronics into a shrinking footprint. He
spoke to the innovation of metallizing circuits, which is the ability
to “print” the electronic circuitry onto the device “shell.”
“By metalizing circuits, designers are able to reduce or elimi-
nate the use of flexible circuits and adhesives to integrate electron-
ics on medical devices,” explained Uffhausen. “Thus, they are able
to integrate functionality without adding interfaces (flex PCB)
and reduce the size and weight of the product. It has also been
recognized that it allows for some unique shapes and geometries
that maybe are not possible with the use of traditional flex or
FR4 PCB. While this has been successful in niche medical device
applications, the technology needs to be adopted on a larger scale
and for applicable designs.
Still enthused by the benefits of flexible circuit technology,
Heather Andrus, Sr. VP & GM of product innovation at Radius
Product Development shared her comments on that option to
ease the challenges of medical electronics assembly. “We see size,
weight, and cost impacts. Printed electronics allow most of a
circuit to be printed onto low cost, light weight PU. In addition,
the circuits are flexible, allowing for smaller, more ergonomic
form factors. We also see the ability to integrate components such
as sensors and heaters directly into the printed electronics, with
dramatic increases in reliability and decreases in weight and cost.”
Another “tip” for medical device designers when it comes to
using technologies that shrink the space requirements in assembly
came from Kelly. “Die-stacking is a powerful technology used to
reduce the footprint required for multiple ICs in a device. What
is often overlooked by device developers is that a successful die-
stack requires the die sizes, aspect ratios, and pin configurations of
all the ICs in the stack to work in concert. If the planned die-stack
includes all standard-product ICs, it is very unlikely for all of these
to align effectively. If at least one IC in the stack is a full-custom
design, then that IC can be designed to accommodate the unique
characteristics of the other ICs in the stack, and may result in a
significantly improved die-stack system.”
Before some final words from Allen, readers should be aware
that with every Roundtable feature in print, the participants’ full
comments are provided on the MDT website as individual blogs.
Just search for this (or another) Roundtable article and find the
links to all the comments made by participants.
In closing, Allen offered the following consideration for medical
device designers, “If you don’t have first-hand experience in PCB
assembly — and even if you do — you should involve your manufacturing partner early in your layout process. Many contract
manufacturers have a layout designer on staff; some have electrical and mechanical engineers as well who can provide higher-lev-el assistance. They will have a thorough understanding of their
own specific manufacturing processes since they live it every day.
They can give you a shortcut to ‘learning from the mistakes of
others’ since they’ve pretty much seen it all.” MDT