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Sockets Succeed in a
Continually Evolving Marketplace
By John
MacWilliams and Lynda Nolen, Bishop & Associates Inc.
Socketing technology,
which accounts for approximately five percent of total world connector
sales, falls into two distinct categories:
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Sockets used in Equipment Production
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Sockets used in Semiconductor Test & Burn-In (T&B) and System
Test/Emulation
Each of these categories support specific applications and have
distinctly different characteristics.
Although production
sockets are occasionally used in test applications, rarely are test
sockets used in production applications, due to their high cost and
extended manufacturing time. This same general rule usually applies to
IC socket manufacturers. Some manufacturers of production sockets make
test sockets, but because most test sockets are machined sockets, it is
uncommon for a manufacturer of test sockets to be in the production
socket market.
Bishop & Associates estimates the worldwide IC socket market to be
approximately $1.9 million.
World IC Socket Market vs.
Total Connector Market
2005 - 2011
Why Use a Socket?
There are many trade-offs to consider when making the decision to use a
socket or to rely on direct attachment. Direct attachment, using
through-hole or surface mount, costs less than one-quarter cent per pin,
while socketing ranges from one-half cent to 10 cents or more per pin
(or pad). There are many reasons ICs are socketed, but the bottom line
is flexibility, and in the end, applied system cost.
Benefits of Using an IC Socket
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Avoidance of tariffs
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Protection of expensive components from damage or theft in a global
supply chain
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Ability
to repair a failed IC package
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Insurance against faulty designs in new systems
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Flexibility in the supply chain, motherboard design and final assembly
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Ability
to upgrade, expand or reconfigure after the sale
Typically the
processor (or CPU) is the most expensive and critical component of a
system, so it makes sense to socket it, even considering the increased
cost. In addition to the benefits cited above, the ability to foster a
multi-supplier global supply chain, while protecting the most critical
component, is the most important parameter.
As pin counts go up, cost and reliability challenges also increase. By
far the most elegant design today—outside of no package at all, the flip
chip—is the organic land grid array (OLGA). This design incorporates a
low-cost, high-performance substrate, and eliminates leads from the IC
package, replacing them with pads that are solder-balled (BGA) or
socketed (LGA). Although a solder-ball BGA package is not
socket-friendly because of solder plasticity (its tendency to ‘flow’
under mechanical stress), this can be accommodated with “cup” socket
designs or via an interposer. Even more cost-effective than the BGA is
the BLGA socket design. This design offers a solder ball bottom for
surface mount attachment and a stamped contact top, providing an elegant
combination of low, self-aligning mated height with high performance,
1,000+ contact points, and low cost.
Production IC Sockets
Production sockets have
evolved over the years from primarily DIP, SIP, PGA, and custom LGA, to
the current high-volume BLGA and DIMM sockets. Many legacy sockets, such
as the DIP, are still around, as are smaller volume machined sockets,
but the market for these is gradually declining. The predominate sockets
today are DDR2, SO-DIMM notebook, desktop, and server DRAM memory
sockets, as well as the various iterations of Intel/AMD microprocessor
sockets: PGA, mPGA,
and BLGA.
There continues to be proprietary LGA sockets for RISC/MIPS processors
in servers and workstations, such as those produced by IBM, SGI, Sun,
and others, but this category is fast merging with X86 systems that use
mPGA
and LGA socket designs.
One of the latest new
products is Socket F for AMD Opteron processors at 1207 pins. Shown
above, this is an LGA which fits at the base of a heat sink stacked on
Opteron motherboards with a steel backing plate. This arrangement allows
the IC package to be built with pads rather than leads, which reduces
cost and improves electrical performance.
Test and Burn-In Sockets
The test and burn-in socket market is characterized by several
challenging design and application parameters.
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Very
high cycle life: > 10,000 touchdowns, requiring a precision,
robust mechanical design.
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Multi-Gbps
Speed.
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High
density, approaching the limits of discrete connector technology.
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Challenging electrical parameters:
Low voltages and
noise margins
Higher power and
current loads
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Feature
sizes as low as 0.13 and 0.09mm, testing of 300mm wafers, on-chip Cu,
die shrink, etc.
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Minimal
footprint on IC or test pads.
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Reliable connection to various pad metallurgies and soft surfaces, such
as solder balls.
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High
operating temps: 70-1250C.
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New
designs to test multiple ICs in a magazine or other fixture, (e.g.
mBGA).
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Dimensional challenges created with the use of chip scale and flip chip.
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Wafer
scale test may change the market in some applications.
In addition to these
challenges, as test and burn-in costs keep rising, particularly in high
volume DRAM and flash applications, the development of new, more
cost-effective test and burn-in strategies will have to be developed.
Gryphics QFN Test Socket
Plastronics 0.5mm BGA Burn-in Socket
It is inevitable that
IC testing will be around for years to come, particularly as Moore’s Law
slows. IC testing will constantly go through periods of change. These
changes will include:
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Packages change from DIP and SIP to TSOP, BGA,
mBGA,
QFN, and C4/Flip Chip
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Continued reduction in pad or lead spacing—from 2.54mm and above, to
< 0.5mm
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Improvements in contact design, particularly in the immensely popular
BGA
Johnstech DIMM Test
Socket
Emulation
Technology Twist Lock Socket
Types of Contacts
IC
sockets use various contact designs based on the application. High
volume applications typically use stamped beryllium-copper (BeCu) or
phosphor bronze (PhBr) contact arrays, because they offer excellent
dimensional stability, fatigue, and corrosion resistance at a reasonable
price. They can be designed to capture PCB card edges (DIMM), PGA pins (mPGA),
or IC package contact pads (LGA).
Machined contacts are used in low volume and custom designs, and in some
IC test applications. Conductive elastomeric contacts, coiled springs,
and other unique contact designs have been developed and are used in
some applications. Contact robustness is an issue in all applications,
in addition to mating force, mated height, and numerous electrical
parameters. The socket should be both electrically “invisible” and able
to withstand prolonged (years) in situ contact without mechanical,
metallurgical, or electrical performance issues.
Dynamics of the Socket Market
The
major IC socket market is the computer industry, including PCs, servers,
mainframes, and supercomputers. The primary applications in this market
are the CPU (Intel Pentium/Xeon/Itanium, AMD Athlon/Sempron/Opteron,
various high-end RISC/MIPS processors) and memory sockets (DDR/dual
in-line memory modules). Many applications also use plastic-leaded chip
carriers (PLCC) and plastic quad flat-packs (PQFP). Sockets are used in
the open systems architecture of PCs, its global supply chain for
motherboards, daughtercards and other component parts, and for subsystem
and final assembly. They are also used in high performance computer
systems, which have historically used special CPUs with LGA socketing.
However, this segment of the market is subject to significant changes
(see Dynamics in the Computer Market, below).
The other broad area of IC socket use encompasses all other markets. A
wide variety of applications, ranging from industrial equipment to
vending machines to RFID security systems to central office telecom
gear, all use some sockets. Even legacy-type DIP and SIP sockets can be
found. This area of use is also where a variety of specialized machined
sockets in mid to small volumes are used. Equipment in the industrial
market can often be programmed for a variety of uses. The program
changes are accomplished by using various IC components, accepted via a
socket. This part of the market is extremely diverse and is slowly
evolving. With the digital convergence of embedded computer functions in
all types of equipment, more systems are using CPU, DIMM, SODIMM, and
PLCC-type sockets, and huge quantities of memory cards. This includes
the consumer product market.
Dynamics in the Computer Market
In
the computer market, years of evolution in proprietary customized
computer hardware has given way to standardization. Broadly speaking,
RISC/MIPS and other OEM workstations, servers, and even supercomputer
designs are shifting over to the X86 microprocessor architecture.
Within this dynamic, which is most closely associated with Intel and
Microsoft, are two others:
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The
rise of AMD and open source Linux operation systems has an inexorable
drive for lower cost, which promotes the use of standard systems, its
component parts, and the market volumes already achieved by them in the
mainstream of the computer market. This includes motherboards, Pentium,
Xeon, and AMD processors, DDR memory, and IC sockets. In servers, rack
and blade server systems are beginning to resemble PCs, and are rapidly
gaining against big box systems. At the very high end, massively
parallel systems composed of hundreds of PCs are challenging proprietary
supercomputer designs in performance at greatly lower costs. Many of
these systems have 2, 4, 16, or more CPUs (and sockets). Many of these
systems have multiple CPUs (and sockets)—from 16 to several hundred per
system.
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Multi-core CPU technology is also on the rise. As Moore’s Law has
slowed, it has given rise to multi-core computing. This means 2 to 4
cores, instead of 1 CPU within the package. This number will increase to
8, 16, and 32 or more cores, within the next 10 years. The impact of
this on sockets is still unclear. It may reduce the number of sockets in
a multi-CPU system. It may also increase or decrease the number of I/Os
depending on the application and it will most likely ease thermal
issues, which have become a major concern. In any event, this multi-core
technology shift will be significant and bears further investigation.
Bishop &
Associates’ Summary
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IC
sockets are composed of two distinct categories: Sockets for test and
burn-in, and sockets for production.
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Bishop
& Associates estimates the 2006 worldwide IC socket market to be
approximately $1,888.1 million, growing to approximately $2,844.4
million by 2011.
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The
semiconductor and computer markets are key to IC socket trends.
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In ICs,
key technologies include microprocessors, ASICs, DRAM, and flash.
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In
electronic equipment, key markets include PCs, servers and HPC systems.
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CPU
socketing has shifted toward X86 and away from proprietary RISC, MIPS
systems.
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As
Moore’s Law slows, new applications for sockets will emerge, including
multi-core CPUs.
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The
impact of multi-core CPUs on the number of IC sockets used is yet to be
determined.
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As with
all other connectors, time-to-market and cost will remain crucial design
elements.
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WEEE
and RoHS requirements will continue to affect socket design and
packaging.
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The
massive trend toward global assembly of systems, coupled with an
increasing need for system flexibility, will continue to drive OEM usage
of IC sockets over direct attachment.
 Lynda
Nolen
Product Specialist, Bishop & Associates Inc.
Lynda Nolen has been in the interconnect industry for over 28
years. She has worked in sales, sales management, marketing, and
product management for such companies as TRW Electronics
Components Group, Sunbelt Components, Cinch Connectors, Arrow
Electronics, PEI Genesis, and Delphi Interconnect. Nolen has
extensive experience in competitive cross-referencing, drawing,
web and catalog review, new product introduction programs,
harness and connector assembly programs, account management, and
customer service programs. Lynda received her Bachelor of Arts
degree from Roger Williams University in Rhode Island in 1979,
and has completed various electrical engineering courses.
 John
MacWilliams
Senior Consultant and Analyst, Bishop & Associates Inc.
John
MacWiIliams has been in the electronics industry for over 40 years. His
main areas of experience have included: U.S. competitiveness programs,
market research studies, authored articles, field sales and management,
product marketing management, strategic marketing, new product planning,
venture development, advertising and media relations, direct sales,
manufacturers representative, distribution sales management, and
international marketing. MacWilliams has worked with AMP, Diceon
Electronics, TRW, and IRC in marketing management positions. Prior to
joining Bishop & Associates, MacWilliams served as the group director of
marketing and new product planning for AMP.
MacWilliams graduated from Lehigh University with a Bachelor of Science
degree in business management and minors in mechanical and industrial
engineering. |
