Transcript ROBOTICS An Introduction

Electronics
Manufacturing
By Ed Red
Electronics manufacturing comprises 1/3 of all
manufacturing in the world!
ME 482 - Manufacturing Systems
Objectives
• Review basic processes used to make IC’s.
• Review basic processes used to make circuit boards.
• Review methods and equipment used to assemble circuit
boards.
ME 482 - Manufacturing Systems
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
IC production process is
process
is
used
to
The process begins by producing from a planar process
grow
single
crystal
quartzite
(SiO2)
an electronic-grade silicon
consisting of regioningots
of
silicon
of
(EGS) with little impurity. The process specific layering or dediameters
involves mixing of elements into a furnace,
layering processes to
approaching
12
grinding of the resulting alloy, and further
constitute the many
inches
and
lengths
to
chemical reaction with the powder to produce
microscopic electronic
10
ft.
the pure silicon.
devices spread across
the wafer surface.
ME 482 - Manufacturing Systems
Transfer of the IC to an
electronics component is
called packaging.
IC packaging
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.
Through
hole
Surface mount
ME 482 - Manufacturing Systems
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).
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 Rent’s
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
ME 482 - Manufacturing Systems
Lead
spacing is
about 20
mils
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.
ME 482 - Manufacturing Systems
IC MOSFET
ME 482 - Manufacturing Systems
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.
ME 482 - Manufacturing Systems
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)
ME 482 - Manufacturing Systems
IC manufacturing
Photo
micrography
captures intricate
circuit lines
hundreds of times
smaller than a
human hair.
(Photo courtesy of
National
Semiconductor)
ME 482 - Manufacturing Systems
IC manufacturing
Another micrograph
photo. (Photo courtesy
of National
Semiconductor)
ME 482 - Manufacturing Systems
IC manufacturing
A manufacturing
associate wears a
"bunnysuit"
while handling
wafers at this
1200-degree
Centigrade
furnace. (Photo
courtesy of
National
Semiconductor)
ME 482 - Manufacturing Systems
IC manufacturing
At National
Semiconductor's
wafer fabrication
plant in Arlington,
Texas, many
manufacturing
processes are
computerized.
(Photo courtesy of
National
Semiconductor)
ME 482 - Manufacturing Systems
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)
ME 482 - Manufacturing Systems
IC manufacturing
National
Semiconductor's
new micro SMD
packaging enable
dramatically
smaller printedcircuit boards.
Because micro
SMD packages
are smaller than
chip capacitors,
they look like
mere dots on the
smaller board.
(Photo courtesy of National
ME 482 - Manufacturing Systems
Semiconductor)
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)
ME 482 - Manufacturing Systems
IC manufacturing
Last year, National
Semiconductor
introduced the world’s
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)
ME 482 - Manufacturing Systems
IC manufacturing
National
Semiconductor's
new four-, five-, and
eight-bump micro
SMD packages
comply with a
JEDEC standard.
The chip-scale
packages' solderbump pitch is 5
mm. (Photo courtesy of
National Semiconductor)
ME 482 - Manufacturing Systems
IC yields
The IC manufacturing process consists of many steps. The
probability of good yield can be computed from
Y = Y c Ys Yw Ym Yt
where Yi is the yield at each step.
Typical yield values are
Crystal (Yc ) – 50%
Y = (0.5)(0.5)(0.7)(0.5)(0.9) = 0.08 (< 10%)
Wafer slicing (Ys ) – 50%
Wafer yield/processing (Yw ) – 70%
Wafer multi-probe testing (Ym ) – 10% - 90%
Wafer full testing (Yt ) – 90%
ME 482 - Manufacturing Systems
Circuit boards
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.
ME 482 - Manufacturing Systems
copper foil
insulator
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 (< 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.
ME 482 - Manufacturing Systems
Circuit boards – prep steps
3. Circuit pattern imaging and etching – uses either of two methods –
screen printing (tracks > 0.01 in.) or photolithography (tracks < 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.
ME 482 - Manufacturing Systems
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.
ME 482 - Manufacturing Systems
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
ME 482 - Manufacturing Systems
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).
ME 482 - Manufacturing Systems
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 rigidbody errors (offsets) in both position and orientation.
Similar errors exist for the placement of the circuit board on
the board holder.
ME 482 - Manufacturing Systems
Example - asynchronous control method
Control
process 1
Server
Process 1 (Tool process)
Pick up part
Control
process 2
Process 2 (Vision process)
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
ME 482 - Manufacturing Systems
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.
ME 482 - Manufacturing Systems
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
ME 482 - Manufacturing Systems
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.
ME 482 - Manufacturing Systems
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!
ME 482 - Manufacturing Systems
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
ME 482 - Manufacturing Systems
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.
ME 482 - Manufacturing Systems
The state
Report conclusions:
• Japan's infrastructure, and the remarkable cohesiveness of
vision and purpose in government and industry, are key
factors in the Japan’s 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.
ME 482 - Manufacturing Systems
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.”
ME 482 - Manufacturing Systems
Electronics manufacturing
What have we learned?
ME 482 - Manufacturing Systems