With the LED market growing rapidly, both PCB producers and end users can expect consistent evolution in thermal management technologies. Recent developments include improved calculation methods to determine needs based on material properties. Product designs are moving toward 3D configurations. Material improvements include thinner, higher conductivity dielectrics and conductive inks for printed electronics. Alternative materials under development include carbon fiber and graphite-embedded PCBs offering higher conductivity. Consistent innovation is needed to address emerging challenges as the industry matures.

1. EnginEEring solutions for pcb manufacturing Electronics Forecast: Hot and
www.smtonline.com
Getting Hotter p.16
ju ly 2 0 1 1
Stategies for Beating the Heat:
Recent Developments — LED
Thermal Management 2.0 p.22
TECs and Micro TECs for Spot
Cooling on Electronics p.28
Thermal Stress in Electronic
Packaging p.32
July 2011 • SMT Magazine 1

2. Thermal Management
Strategies for
Beating the Heat:
Recent Developments — LED Thermal Management 2.0
by Yash Sutariya on an online registration form. With the rise of
SATuRn ELECTROnICS CORPORATIOn/ LEDs, however, thermal management’s role is
SATuRn FLEx SySTEMS now prominent and designers are proactively
addressing this discipline from the beginning.
The process has been analyzed, taken
apart and put back together while examining
In SuMMARy the inter-relationships between each element
in the finished product stack-up. We’ve
With the LED market exploding while still
come a long way, but there are still looming
in its infancy, both PCB producers and end
challenges.
users can expect to see consistent evolution
We believe that there is always a solution.
in not just standard MCPCB materials, but
You joined us in checking that long-dormant
also potentially disruptive and game-changing
thermal management requirement box…now
technologies and applications.
we’re ready to start looking outside of it. For
that, we turn our attention to Technology
Evolution: LED Thermal Management 2.0.
For the past two and half years, the PCB Where We’ve Been
industry has been beating the heat as if we For the past two years, we’ve invested a
were Dirk Nowitzki and the Dallas Mavericks. significant amount of resources into educating
Speaking from the PCB fabrication link in the the industry to properly calculate their needs
supply chain, the approach taken has been one based on commonly accepted methodologies
of refining loose methods of operation into a and materials. Instead of calling out thermally-
finely-tuned best practice methodology. conductive MCPCB materials by brand name
Prior to the recent rise of the LED, PCB (or no name at all), we have had industry
thermal management was an afterthought and experts define material properties and show
an obstacle—like one too many required fields us how to calculate our needs. (We’ve made a
22 SMT Magazine • July 2011

3. Thermal Management
year of promises, but the online version of the flex and rigid-flex PCB industry) proposed a
LED Thermal Resistance Calculator is finally reasonable alternative.
up-and-running.) Keep in mind that thermal conductivity
The central purpose asserted in each of values are almost meaningless without taking
these various presentations was constant: thickness into account. Most thermally
Calculate your needs in terms of maximum conductive materials have a minimum
thermal resistance, minimum electrical thickness of 0.003” to 0.004”. However, on
insulation and any other properties you felt a daily basis flex shops are using materials as
were critical to product performance. Then, thin as 0.001”. Therefore, even with a lower
let your supplier search the globe for the most thermal conductivity value, a material this
competitive solution both in terms of pricing thin would pose very little thermal resistance.
and lead time that meets your needs. Moreover, the flex PCB wraps around the
Now that we’ve firmed up the ground four sides of this light post while the FR4
we’ve been walking for years, it’s time to shake stiffener ensures thermal transfer by allowing
things up and rely on the innovation that has the PCB to be directly screwed to the metal
helped our industry survive for decades. As lamp housing.
with any other successful industry, we foresee Initial tests showed that the time to
materials and product evolution to change the equilibrium was approximately half that of the
current landscape in the coming years. prior design.
Here are a few product innovations that, Click here for Flex LED PCB Kit.
I believe, will emerge to address technology
refinements: 1) product design; 2) material Material Improvements
improvements; and 3) alternative materials/
methodologies. Thermally Conductive Dielectrics
As end users become emboldened with
Product Design their newfound calculators and materials
One gripe about MCPCBs is that they are testing methods, thermally conductive material
entirely two-dimensional and the product manufacturers have been coming out of
must be designed to conform around the the woodwork with either new or improved
PCB. We came across one such limitation alternatives to those offered by the current
in regards to a three-dimensional lamp post establishment. We are approached almost on a
application with a customer who was using weekly basis with new products offering lower
four separate MCPCBs and connecting them cost or increased performance, or both. We try
around the corners of the post using to keep our materials comparison chart updated
soldered wires. but, with the frequency of new materials being
Now, thermally conductive substrates, offered, it’s certainly a difficult task.
regardless of brand, are all polymers. Thus, For the most part, continued innovation
these thin materials (commonly used in the has enabled materials manufacturers to
improve the filler’s performance in increasing
thermal conductivity, while simultaneously
reducing thermal resistance by laminating
dielectrics in thinner layers.
While these are not game-changing
technologies, if you will, at the end of the day
they represent incremental improvements
to the currently accepted technology base.
Remember when you thought your two-
pound Walkman was the cat’s pajamas? Don’t
be surprised to see mainstream laminate
manufacturers enter this market within the
July 2011 • SMT Magazine 23

4. STRATEGIES FOR BEATING THE HEAT continues
thermal management
next six to 12 months with product offerings
that reduce cost and increase performance.
Inks for Printed Electronics
Over the past decade, the disruptive tech-
nology of printed electronics has been making
significant gains in flexible display/touch
screen, smart label and flex PCB market share.
Regardless of medium, the potential for
direct materials savings and streamlined
production accounts for a motivating one-two
knockout punch.
Alternative Materials/Methodologies
One of the most interesting ideas we’ve
played around with was the use of Pyrolytic
Graphite embedded into FR4 material to
achieve thermal conduction to the heatsink.
With a thermal conductivity value four times
Printed electronics involves screening
electrically conductive inks (as opposed to
etching copper circuits) and is used primarily
on low-voltage applications since the inks to
date have had too high an electrical resistance.
As evolution dictates, there has been
significant progress in reducing the electrical
resistance of inks. We were approached by one
of these manufacturers to help evaluate their
ink for LED applications. While this is still
in progress, the benefits of printing directly
to a coated metal substrate are clear: The
elimination of the often expensive and hard-
to-procure thermally-conductive dielectric that
is common to MCPCBs.
At the moment, thermal and electrical
material properties (responsible for
electrically insulating the barrier between the
conductive ink and the metal base) prevent
this realization; for this purpose, prepreg,
anodizing and even a simple coating of
soldermask are being considered. “Tucker, the Man and His Dream” Paramount Pictures.
24 SMT Magazine • July 2011

5. STRATEGIES FOR BEATING THE HEAT continues
thermal management
that of pure copper, Graphite PCB seemed It may no longer be the Wild West, but
like a home run; however, cost and process let’s not get comfortable with the status quo!
limitations represented challenges. Let’s make a commitment to keep the burr in
I was about to submit this concept to our saddles. SMT
the Tucker Motor Cars Hall of Fame when
I received a phone call from a materials *Standard PCB materials are comprised of a
manufacturer with a novel idea: Replace weave of fiberglass coated with epoxy (typically
the fiberglass yarn* with carbon fiber that FR4 or Polyimide).
has a thermal conductivity in excess of 200
W/mK. Hold that Tiger! Not only can you
drill and plate through nicely, but the carbon yash Sutariya received his BBA from
fiber acts as a heat spreader in the X, Y and the university of Michigan’s School
Z axes. of Business Administration. After
While the material for this particular is graduation, he worked in Valuation
still under development, with some creative and Bankruptcy/Turnaround
process applications it could surely be a Consulting. He is currently Vice
game changer offering the potential for both President of Corporate Strategy
significant performance increases as well as at Saturn Electronics Corporation (SEC) and
modest cost reductions. Owner/President of Saturn Flex Systems, Inc.
Conclusion Since joining the team, SEC has successfully
With the LED market exploding while still navigated from a low-mix, high-volume
in its infancy, both PCB producers and end automotive supplier to a high-mix, medium-
users can expect to see consistent evolution to high-volume diversified supplier. As a
in not just standard MCPCB materials, but result of the company’s transformation,
also potentially disruptive and game-changing manufacturing capabilities now range from
technologies and applications. quick-turn prototypes to scheduled volume
The main concern is whether or not we are production while attending a broad cross-section
keeping an open enough mind to see the value of industries to include industrial controls,
proposition in these, and what are we going telecommunications, aerospace and power
to do to foster and encourage out-of-the-box supply industries.
thinking?
26 SMT Magazine • July 2011

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Ad Index
Advances in Thermal Mgt. Conf... 69
Next Month in SMT Magazine
We all greatly depend on our electronics
Aegis............................................ 39
devices—perhaps a bit too much. We expect
Blackfox....................................... 49
Calumet Electronics...................... 45
them to work under a wide range of conditions
CA Picard..................................... 27 and failures can not only be irritating, but also
China Fastprint............................. 43 life-changing. The August issue of SMT Magazine
Digi-Key Corp............................. 1, 2 will highlight high-reliability electronics with
EasyBraid Co................................. 47 articles to help you make sense of process
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Hunter Technology Corp............... 31
strategies (Occam and others), and help solve
Imagineering Inc......................... 7, 9
IPC.......................................... 71, 73
issues such as tin whiskers.
Lenthor Engineering..................... 33 We’ll feature articles from these industry
Manncorp...................................... 5 experts: Photo Stencil’s Dr. Bill Coleman will
Meptec......................................... 67 discuss step stencils; Dr. Mike Pecht of CALCE
Nordson Asymtek......................... 25 and Dr. Sanjay Tiku of Microsoft will focus on
P. Kay Metal................................. 53 counterfeit products in military systems; Craig
Prototron Circuits......................... 41
Hillman, Gregg Kittlesen and Randy Schueller of
SMTA........................................... 61
DfR Solutions will tackle a better approach to tin
Sunstone Circuits......................... 59
Technica USA............................... 13 whisker mitigation; and many, many more.
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Totech.......................................... 11 Click here to receive SMT Magazine in your
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U.S. Circuit................................... 63 See you in August!
Zestron......................................... 21
July 2011 • SMT Magazine 77