Medical Design Briefs - June 2024 - 23

Implantable cardiac devices such as pacemakers often
demand compact battery designs, biocompatible materials,
and long-lasting power supplies, since battery replacement
is difficult or impossible. (Credit: Emerson)
Fig. 2 - Cutaway of a button cell battery. (Credit: Emerson)
ing critical space limitations within a
particular device.
Whatever their shape or ultimate capacity,
all medical device batteries rely
on precision assembly processes. Ultrasonic
metal welding technology is typically
used. To bond the often thin and
fragile foil electrodes, tabs and cases
used in each battery, ultrasonic welding
generates high-frequency (40-60 kHz),
low-amplitude vibratory energy, then
drives it through specialized acoustic
tooling (a sonotrode or horn above,
with a part-holding anvil below) that
welds the fragile materials under controlled
compression until bonding takes
place (see Figure 1).
Unlike other welding processes that
use high energy inputs, ultrasonic welding
is clean; it generates no sparks and
does not melt the fragile metals involved.
Instead, the process creates solid-state,
molecular-level bonds by generFig.
3 - Specialized long-reach tooling can reach down
into the narrow cavity of a battery or product case, either
to weld the " tabs " of a battery electrode to the
base of the battery case or to join elements within the
device to battery power. (Credit: Emerson)
ating frictional heat and compression
between the metal parts. The acoustic
tooling that accomplishes the ultrasonic
welds is specified based on the battery
application. Tooling for button
cell batteries is relatively straightforward,
since these typically employ a
two-piece case, with the anode bonded
to one side and the cathode to the other,
with the center filled with an electrolyte
(see Figure 2). But the production
of devices that use cylindrical
batteries often requires more specialized
" long reach " tooling, a needle- like
sonotrode that can reach down into
the narrow cavity of a battery or product
case, either to weld the " tabs " of a
battery electrode to the base of the battery
case or to join elements (bulbs,
displays, circuits) circuitry within the
device to battery power (see Figure 3).
In the coming years, companies such
as Emerson will continue to evolve ultrasonic
metal welding technologies to answer
the needs of an ever-changing field
of medical devices and the batteries that
power them. Developing new assembly
technologies will maximize the performance
and precision of ultrasonic metal
welding to satisfy the new design, size,
and power requirements of advancedperformance
medical devices.
This article was written by Alex Yeung,
Global Product Manager, Branson Welding
and Assembly, Emerson, St. Louis,
MO. For more information, visit www.
emerson.com.
The Role of Photochemical Etching in Thermal
Management
The process enables components to work more effectively.
By Jochen Kern, micrometal
he photochemical etching (PCE)
process is distinguished by its capacity
to fabricate metal parts with
unparalleled accuracy. This process
sidesteps the typical stresses and deformations
linked to conventional metalworking,
like stamping or laser cutting,
which can compromise material integMedical
Design Briefs, June 2024
T
rity. Such fidelity is crucial in the manufacture
of components for thermal
management systems, where material
integrity and component precision are
non-negotiable for ensuring effective
heat creation or dissipation. PCE's ability
to craft parts with smooth, burr-free
edges and exact dimensions means heat
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management components work more
effectively, bolstering the reliability and
extending the service life of micro electronic
devices.
One of the most significant advantages
of the PCE process is its extraordinary
flexibility in handling a wide array of
metals and alloys. This adaptability is
23
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Medical Design Briefs - June 2024

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