Magnetics Business & Technology - January/February 2021 - 16

TECH TIPS

Embedding Magnetics Achieves Reliability & Consistency, Part 3 of 3
By Jim Quilici, SCC America

Figure 1, GbE Media Filter
Parts 1 and 2, provided an overview of embedded magnetics
construction and presented a design example for a GbE media
filter. Performance data showed that the embedded magnetic
devices are highly consistent. Part 3 looks at the material used
in the PCB construction and summarized reliability data. Figure
1 shows an example of a surface mount GbE media filter fabricated with embedded magnetic technology.
During reliability testing, parts are stressed under heat and
humidity conditions to try and accelerate failures and identify
weak spots in the design. Parts will undergo thermal cycling
and be cooked in an autoclave under high pressure and humidity to heighten internal stresses. These tests can accelerate
deterioration and provide an indication of how the part will hold
up under normal operating conditions. Vibration and mechanical shock test the mechanical integrity of the package. With an
embedded magnetic design, the conductors are laminated and
plated onto the FR-4 substrate and it is essentially a solid-state
construction. There are not free-floating wires or internal solder
joints that can be become brittle and fail under thermal stress,
vibration and mechanical shock. So in this case, the parts are
surface mounted onto a test coupon and we are really testing
the integrity of the solder balls on the I/O pads.
The GbE media filters are generally deployed on personal
computers and LAN networking equipment. The working environment in an office or data center will usually be temperature
controlled and have an operating range between 0C to 70C.
If utilized in a security camera or wireless access node, then
there is the potential for outdoor deployment. Outside deploy-

16

Magnetics Business & Technology * January/February 2021

ments can experience temperatures ranging from -40C to
+85C.
Table 1 summarizes the reliability testing that was used to
stress the embedded magnetic media filters. For this case, the
parts were stressed tested for use in an indoor environment.
Samples size was 20 units and the pass criteria was determined by testing for opens, shorts and the Open Circuit Inductance (OCL ≥ 350 uH) of the transformers on all 4 channels.
Parts were also tested for Hipot (voltage breakdown) before
and after undergoing the stress testing.
Hipot is a safety issue and warrants special consideration. It is
a voltage stress test and provides a metric of the transformer's
ability to isolate the end node/user from a voltage surge or
lighting strike that may hit the transmission cable. Wire wound
GbE transformers are wound with 32AWG magnet wires that
is coated with about 0.04 mm of polyimide insulation. This is
sufficient to provide 1500Vrms of isolation, as long as the wire
is not kicked or scratched during fabrication. PCB materials are
also good dielectric insulators. FR-4 laminates are commonly
rated at 29kV/mm (750V/mil), and will generally hold against
breakdown as long as there is ≥ 0.08 mm (3 mils) separation
between conductors. Similarly, liquid image solder mask has
breakdown voltages rating of 19.5kV/mm (500V/mm). The issue with solder mask is that it is applied with a screen printing
process and there can be small pin-holes in the covering, due
to micro bubbles or micro-cracks. During hipot testing, the air
around the exposed I/O pads will become ionized and an ion
cloud can form above the device surface. In that case, break-

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Magnetics Business & Technology - January/February 2021

Table of Contents for the Digital Edition of Magnetics Business & Technology - January/February 2021

Magnetics Business & Technology - January/February 2021
Editor’s Choice/ Features
eTrucks and eBuses with Permanent Magnet Powertrains Charge into Commercial Vehicle Market
Linear Labs Rolls Toward Production of Its Magnetic Flux Tunnel Motors
Protean Electric’s In-Wheel Motor Reaches for Traction in Global EV and Industrial Markets
Embedding Magnetics Achieves Reliability & Consistency, Part 3 of 3
Tech Tips
Research & Development
Product News
Industry News
Events Calendar/ Advertising Index
Visions
Magnetics Business & Technology - January/February 2021 - Magnetics Business & Technology - January/February 2021
Magnetics Business & Technology - January/February 2021 - Cover2
Magnetics Business & Technology - January/February 2021 - 3
Magnetics Business & Technology - January/February 2021 - Editor’s Choice/ Features
Magnetics Business & Technology - January/February 2021 - 5
Magnetics Business & Technology - January/February 2021 - eTrucks and eBuses with Permanent Magnet Powertrains Charge into Commercial Vehicle Market
Magnetics Business & Technology - January/February 2021 - 7
Magnetics Business & Technology - January/February 2021 - 8
Magnetics Business & Technology - January/February 2021 - 9
Magnetics Business & Technology - January/February 2021 - Linear Labs Rolls Toward Production of Its Magnetic Flux Tunnel Motors
Magnetics Business & Technology - January/February 2021 - 11
Magnetics Business & Technology - January/February 2021 - Protean Electric’s In-Wheel Motor Reaches for Traction in Global EV and Industrial Markets
Magnetics Business & Technology - January/February 2021 - 13
Magnetics Business & Technology - January/February 2021 - 14
Magnetics Business & Technology - January/February 2021 - 15
Magnetics Business & Technology - January/February 2021 - Tech Tips
Magnetics Business & Technology - January/February 2021 - 17
Magnetics Business & Technology - January/February 2021 - Research & Development
Magnetics Business & Technology - January/February 2021 - 19
Magnetics Business & Technology - January/February 2021 - Product News
Magnetics Business & Technology - January/February 2021 - 21
Magnetics Business & Technology - January/February 2021 - 22
Magnetics Business & Technology - January/February 2021 - 23
Magnetics Business & Technology - January/February 2021 - 24
Magnetics Business & Technology - January/February 2021 - 25
Magnetics Business & Technology - January/February 2021 - Industry News
Magnetics Business & Technology - January/February 2021 - 27
Magnetics Business & Technology - January/February 2021 - 28
Magnetics Business & Technology - January/February 2021 - 29
Magnetics Business & Technology - January/February 2021 - 30
Magnetics Business & Technology - January/February 2021 - 31
Magnetics Business & Technology - January/February 2021 - Events Calendar/ Advertising Index
Magnetics Business & Technology - January/February 2021 - 33
Magnetics Business & Technology - January/February 2021 - Visions
Magnetics Business & Technology - January/February 2021 - Cover3
Magnetics Business & Technology - January/February 2021 - Cover4
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