ROBOTICS An Introduction

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Electronics ManufacturingBy Ed
Red Electronics manufacturing comprises 1/3 of
all manufacturing in the world!
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Objectives

• Review basic processes used to make ICs.
• Review basic processes used to make circuit
  boards.
• Review methods and equipment used to assemble
  circuit boards.

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IC production overview
An ingot is sliced into wafers of thickness about
0.02 inches, followed by polishing and edge
rounding.
Procedures are repeated until you build the
desired integrated circuit features that you
want..these are called dies.
A crystal growing process is used to grow single
crystal ingots of silicon of diameters
approaching 12 inches and lengths to 10 ft.
IC production process is a planar process
consisting of region-specific layering or
de-layering processes to constitute the many
microscopic electronic devices spread across the
wafer surface.
The process begins by producing from quartzite
(SiO2) an electronic-grade silicon (EGS) with
little impurity. The process involves mixing of
elements into a furnace, grinding of the
resulting alloy, and further chemical reaction
with the powder to produce the pure silicon.
Transfer of the IC to an electronics component is
called packaging.
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IC packaging
Through hole
An IC is comprised of millions of electronic
devices such as diodes, resistors, and
transistors, and is packaged in a plastic
enclosed body as a through hole or surface mount
device with leads (legs) for electrical
interfacing to circuit boards.
Surface mount
Two materials are typically used to encapsulate
the IC 1) plastics with no hermetic sealing
and 2) ceramics with hermetic sealing (e.g.,
alumina, Al2O3).
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IC packaging
The number of I/O terminals is a function of the
number of devices on the IC. The dependency
between the two is established by Rents Rule
(around 1960) nio C ncm where nio is the
number of I/O leads and nc is the number of
circuits on the IC, usually taken as the number
of logic gates. Some common values for C and m
are Microprocessor C 4.5 m 0.5
Static memory C 6.0 m 0.12
Lead spacing is about 20 mils
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IC etch
Photolithographic process applied to a silicon
wafer(1) prepare surface (2) apply
photoresist (3) soft bake (4) align mask and
expose (5) develop resist (6) hard bake (7)
etch (8) strip resist.
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IC MOSFET
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IC fab
IC fabrication sequence (1) Si3N4 mask is
deposited by CVD on Si substrate (2) SiO2 is
grown by thermal oxidation in unmasked regions
(3) the Si3N4 mask is stripped (4) a thin layer
of SiO2 is grown by thermal oxidation (5)
polysilicon is deposited by CVD and doped n
using ion implantation (6) the polysilicon is
selectively etched using photolithography to
define the gate electrode (7) source and drain
regions are formed by doping n in the substrate
and (8) P-glass is deposited onto the surface for
protection.
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IC wafer
This 8-inch "wafer" of silicon contains 212
MediaGX processors produced on the 0.35 micron
production line. (For comparison, a human hair is
50 to 70 microns wide.) (Photo courtesy of
National Semiconductor)
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IC manufacturing
Photo micrography captures intricate circuit
lines hundreds of times smaller than a human
hair. (Photo courtesy of National Semiconductor)
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IC manufacturing
Another micrograph photo. (Photo courtesy of
National Semiconductor)
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IC manufacturing
A manufacturing associate wears a "bunnysuit"
while handling wafers at this 1200-degree
Centigrade furnace. (Photo courtesy of National
Semiconductor)
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IC manufacturing
At National Semiconductor's wafer fabrication
plant in Arlington, Texas, many manufacturing
processes are computerized. (Photo courtesy of
National Semiconductor)
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IC manufacturing
A common clean room requirement of 100 implies
that no more than 100 particles of size 0.5 mm or
greater can exist in 1 ft3.
National's wafer fabrication facility in South
Portland, Maine, houses the latest sub-micron
manufacturing equipment. Containers in
foreground, called pods, protect wafers from dust
particles. (Photo courtesy of National
Semiconductor)
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IC manufacturing
National Semiconductor's new micro SMD packaging
enable dramatically smaller printed-circuit
boards. Because micro SMD packages are smaller
than chip capacitors, they look like mere dots on
the smaller board. (Photo courtesy of National
Semiconductor)
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IC manufacturing
Until the release of the micro SMD package, a
semiconductor device's die has always been much
smaller than its package. With micro SMD,
packaging can get no smaller because "The die IS
the package!(Photo courtesy of National
Semiconductor)
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IC manufacturing
Last year, National Semiconductor introduced the
worlds smallest dual op amp, the LMC6035. Now a
portfolio of products are available in this
package -- a package so small that several
devices fit on the head of a pushpin with room to
spare. (Photo courtesy of National Semiconductor)
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IC manufacturing
National Semiconductor's new four-, five-, and
eight-bump micro SMD packages comply with a JEDEC
standard. The chip-scale packages' solder-bump
pitch is 5 mm. (Photo courtesy of National
Semiconductor)
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IC yields
The IC manufacturing process consists of many
steps. The probability of good yield can be
computed from Y Yc Ys Yw Ym Yt where Yi is the
yield at each step. Typical yield values
are Crystal (Yc ) 50 Wafer slicing (Ys )
50 Wafer yield/processing (Yw ) 70 Wafer
multi-probe testing (Ym ) 10 - 90 Wafer full
testing (Yt ) 90
Y (0.5)(0.5)(0.7)(0.5)(0.9) 0.08 (lt 10)
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Circuit boards
copper foil
The printed circuit board (PCB) is a laminated
medium for mounting and interfacing electronic
components, thus providing for their electrical
connection. The layers are made of copper foil
conducting layers interspersed with insulating
layers made of polymer composites reinforced with
glass or paper fabrics. Copper foil thickness is
around 0.0015 in, while the insulation layer
ranges from 0.031 in. to 0.125 in. Single and
double-sided boards are produced in quantity and
then laminated to make multi-layer boards in a
fairly complex process, since via holes are
needed to electrically connect the different
layers.
insulator
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Circuit boards prep steps
1. Board preparation shearing to create the
proper board profile, hole making to create
tooling holes, and shaping operations to create
tabs, slots and other features. These phases are
followed with bar-coding and board cleaning. 2.
Hole drilling Circuit holes are drilled or
punched to create insertion holes or via holes.
Since the drill bit is usually small (lt 0.05)
and required to pass through different layers
having different properties, the drill speed is
usually very high (100,000 rpm) and thus requires
special drill motors/spindles.
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Circuit boards prep steps
3. Circuit pattern imaging and etching uses
either of two methods screen printing (tracks gt
0.01 in.) or photolithography (tracks lt 0.01 in.)
to create the tracks and land of the circuit.
The photolithography method is similar to that
used in IC production. The only difference is
that the photoresist covers portions of the
copper layer and chemical etching is used to
remove the exposed copper. 4. Plating used to
plate the holes to provide a conductive path.
Uses either electroplating or electroless plating
methods. 5. Cleaning/inspection - finished
boards are usually cleaned, inspected and tested
to complete the process. Visual inspection is
used to find obvious flaws, while continuity
testing is used to find more subtle problems,
particularly in multi-layer boards. Finally, the
board tracks and land surfaces are coated with
solder to protect the copper.
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Electronics assembly
Modern assembly plants use automatic insertion
machines, and sometimes robots for non-standard
parts. The Fuji CP-643E combines high-speed
placing with an innovative new PCB loading system
to increase throughput. The machine achieves a
placing speed of 0.09 sec/shot and can be loaded
with up to 140 part types.
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Electronics assembly control technologies

• Critical to advanced electronics manufacturing
  are
• Vision processes for part inspection, and
  rigid-body offsets for precision assembly
• Motion and I/O control, using asynchronous
  architectures
• Mechanism and tooling design and calibration

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Machine vision
Vision is used for testing/inspection, feature
finding, and rigid-body correction. Mechanisms
and their end-effectors (vacuum grippers, finger
grippers, etc.) must move to parts that will be
deposited on the IC boards, then pick them up,
move to the circuit board pad location, then
deposit the part. The accuracy requirements can
be in the thousandths of inches or less. The
accuracy will depend on the lead pitch
requirements(moving to 0.15 mm).
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Machine vision
Vision is used for testing/inspection, feature
finding, and rigid-body correction. Because of
errors in part presentation and the part picking,
it is required that vision systems view these
parts relative to the tool before placement to
correct for part picking rigid-body errors
(offsets) in both position and orientation.
Similar errors exist for the placement of the
circuit board on the board holder.
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Example - asynchronous control method
Server
Control process 1
Control process 2
Process 1 (Tool process) Process 2 (Vision
process) Pick up part while(1) Move
part under camera Wait until signal5
Part_there Set signal5 to Part_there
Take picture and load offsets Wait until
signal93 Vsn_Done Set signal93
Vsn_Done Read offsets and adjust target
Set signal5 Part_not_there
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Electronics assembly

• Assembly considerations
• Use control programs.
• Move components from reel feeders to the board.
• Insert components through holes or surface
  mount them.
• Through hole assembly - pre-form the
  leads. - insert leads into holes. - crop
  or clinch leads on the other side of the board.
  - wave solder the board undersides.

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Electronics assembly

• Assembly considerations
• Surface mounted component - rely on
  calibration procedures and sensor measurement.
  - place and orient the leads on mounting pads
  (land). - screening used to place solder
  paste onto the pads - boards passed through
  oven to reflow solder

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Electronics board testing (after cleaning)

• Testing methods
• Inspection
• Vision systems
• Functional testing ( tested by energizing
  circuits)
• Burn-in test to verify full functionality for a
  given period of time
• If the board fails any of these tests, then
  rework is often used to try to recover the board.

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Electronics assembly videos
We will now see videos on circuit board assembly.
Be sure to take notes because you will be tested
on the video material!
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The state of electronics manufacturing in the U.
S.
Reference - Electronic Manufacturing and
Packaging in Japan, Michael J. Kelly, Chair
William R. Boulton, Editor, John A. Kukowski,
Eugene S. Meieran, Michael Pecht, John W.
Peeples, Rao R. Tummala, JTEC (Japanese
Technology Evaluation Center) Panel Report,
February, 1995 Note See report link on class
website
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The state

• Report conclusions
• Japan leads the United States in almost every
  electronics packaging technology.
• Japan clearly has achieved a strategic advantage
  in electronics production and process
  technologies.
• Japan has established this marked competitive
  advantage in electronics as a consequence of
  developing low-cost, high-volume consumer
  products.

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The state

• Report conclusions
• Japan's infrastructure, and the remarkable
  cohesiveness of vision and purpose in government
  and industry, are key factors in the Japans
  success.
• Although Japan will continue to dominate consumer
  electronics in the foreseeable future,
  opportunities exist for the United States and
  other industrial countries to capture an
  increasingly larger share of the market.
• The JTEC panel identified no insurmountable
  barriers that would prevent the United States
  from regaining a significant share of the
  consumer electronics market.

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Electronics manufacturing
Report conclusions The Japanese can do it
Americans can do it. The issue that separates the
United States from Japan in high-volume, low-cost
electronic assembly is neither technology nor
manufacturing it is primarily the will to take
the measures necessary to compete and succeed.
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Electronics manufacturing
What have we learned?