Download Electronic Manufacturing

Design for Mass Production
Manufacturing Processes
• Printed Circuit Board Assembly (PCB): Must specify or
account for all components mounted into, onto or attached in
some way to a printed circuit board as well as test for same
– Electrical Components: Passives, IC’s, Optical, ElecMech, ElecMag,
Connectors, Switches, Sensors, Protection Devices, etc
– Mechanical Components: Heat Sinks, Thermal Grease, Pullers,
Stiffeners, Mounting Hardware, Sensors, Protection Devices, etc
• High Level Assembly (HLA): Must specify or account for
all elements or parts of an assembly level including testing
– Electrical Elements: PCB’s, Cables, Harnesses, Fans, Power
Supplies, Sensors, Protection Devices, User Displays, Switches, etc
– Mechanical Elements: Enclosures, Feet, Standoffs, Card Guides,
Gaskets, Sealants, Fasteners, Hardware, etc
Design for Mass Production
Printed Circuit Board Assemblies
• Printed Circuit Boards (PCBs):
– Convenient form of interconnecting electrical components using
industry standard attachment processes
– 3 Basic Types of PCB-Component Assembly Technology
• Thru Hole (TH)
• Surface Mount (SMT)
• Micro-electronic Multi-Chip-Module (MCM)
– 3 Basic Types of PCB substrate systems (fabs)
• Rigid epoxy including FR4, BT and others
• Ceramic, Alumina (Al203), AlNi or other exotics
• Flexible Substrate (flex circuit)
– Single, Double and Multi-Layered
Design for Mass Production
PCB Manufacturing Guide Links
•fullnet.com/u/tomg/gooteepc.htm
•ee.washington.edu/circuit_archive/text/design.html
•precisioncircuits.com.au/cid/hm_cid.html
•amscourseware.com/guidelines.htm
•filtranmicro.com/design.html
•goldengategraphics.com/pcgloss.htm
•elchempub.com/files/electroc2.htm
•pcbprotech.com/Dh3/DH3right.htm
•pcbprototyping.com/html/html_edu.htm
Design for Mass Production
Plated VIAs
Design for Mass Production
Basic Photo-Etch
PCB Mfg Process
Plated Through Hole
PCB Cross Section
Design for Mass Production
VIA Aspect Ratio – Very Important
Aspect Ratio =
Bd Thickness
VIA Diameter
Aspect Ratios > 5 May
Challenge Drilling,
Plating & other PCB
Mfg Processes
Cross Section Example of Failed VIA due to poor drilling, plating
Design for Mass Production
Cu PCB Trace Width & Depth
IPC Current Capacity Limitations
Design for Mass Production
Cu PCB Trace Conductor
IPC* Spacing vs Voltage Summary
(*Simplified)
Design for Mass Production
Signal Routing is Important!
The PCB is part of the circuit
Good Signal Routing
Equal Lengths, Uniform
Good Power
Bus Routing
Poor Power
Routing
Bypass Caps
Closest to IC
Power Pins
Bypass Caps and 1
Conductor too
Lengthy
Poor Signal Routing
Un-Equal Lengths, Non-uniform
Design for Mass Production
PCB Ionic Cleanliness is Important
• Acetate & Formate - These organic acids can be extracted from some solder masks. High levels can be indicative of an
incompletely cured solder mask. Incomplete cure can allow exposure of the copper traces to the environment resulting in
corrosion and board failure.
• Bromide: Brominated compounds are added to laminates as a flame retardant. Some laminates are employing alternate,
non-bromine, flame retardants. These are usually called specified as containing non-halogen flame retardants. The surface
bromide concentration is a function of the laminate heat history. Bromide has also been identified as a component in some
marking ink formulations and some solder masks.
• Chloride - Chloride ions are the single most damaging material that can be on the board. High levels are usually due
to insufficient washing prior to applying the solder mask. Chloride can also be transferred to the board by handling.
• Nitrate and Ammonium - Both of these can be introduced in various plating processes.
• Sulfate - Sulfate is rarely a problem. High levels are usually caused by poor housekeeping: dirty equipment, unpainted
walls or unsealed floors.
• Sodium & Potassium - Sodium can be induced by handling but is also a component of tap water and may be indicative of
poor water treatment. In this case, chloride, calcium and magnesium should also be present.
• Calcium and Magnesium - Calcium and magnesium come from rinse water and are indicative of poor water quality.
• Citrate - Citrate salts and acids are components of some gold plating solutions. They also are in many environmentally
friendly cleaners.
IPC-6012 mandates the total ionic cleanliness prior to solder mask be <10ug/in2 in NaCl equivelants (IPC-TM-650)
Most Low Signal Or High Bias, High Reliability Designs Require Much Lower Levels on Individual Ions
Design for Mass Production
TH: Thru-Hole Technology
Design for Mass Production
Thru-Hole Device Packages
• Passives and Discretes
 Axial Leaded (2 terminal, lying down)
o Resistors, Capacitors, Inductors, Diodes
 Radial Leaded (2 terminal, standing up)
o Capacitors, Inductors, LEDs, MOVs, Power Resistors, …
 T0 – Series (2-N terminals, Most Accommodate Std Heat Sink hardware)
o T0-92 Small Signal Transistors, Regulators, References
o T0-220 Moderate Power (~1W) Transistors, Regulators, Amplifiers
o T0-3 Higher Power (~3W) Transistors, Regulators, Amplifiers
Design for Mass Production
Transistor Package Examples
Design for Mass Production
Thru-Hole Device Packages
•
Integrated Circuits, Resistors, Relays

DIP (Dual In-Line Package)

PDIP, CDIP

SIP (Single In-Line Package)

Rectangular
Design for Mass Production
P-DIP (plastic) and C-DIP (ceramic) Examples
Design for Mass Production
SMT: Surface Mount Technology
Design for Mass Production
SMT – Surface Mount Technology Generations
20mm
DIP
Small Outline Package
Shrink SO Package
Thin Shrink SOP
3 mm
Depopulated, Very Thin, Quad Flat Pack, No
Leads
Design for Mass Production
Discretes: Rectangular
(Example 0402)
Design for Mass Production
SOT – Small Outline Transistors (SOT-3, SOT-223)
Design for Mass Production
QFP – Quad Flat Packs
Design for Mass Production
Quad Flat Pack – QFP, PQFP
Design for Mass Production
PLCC – Plastic Leaded Chip Carriers
Design for Mass Production
BGA – Ball Grid Arrays
Design for Mass Production
Typical BGA Pin Layout
Design for Mass Production
Electronic Assembly Quality
Design for Mass Production
Electronic Assembly Quality and Standards
Design for Mass Production
Component
Procure
Setup
Substrate
(Fab)
Fabrication
Fab, Comp
Prep
Bake, Clean
Thru Hole
Mechanical
Hand
Operations
Simplified Comparison
of Thru Hole and SMT
PCB Assembly Process
SMT
Screen
Solder Paste
Auto
Component
Insertion
Vision
System
Inspection
Auto
Component
Placement
Wave Solder
Vision
System
Inspection
Reflow
Solder
(Oven)
Lead
Trim
Stresses and
Test
Processes
Vision/Xray
System
Inspection
Design for Mass Production
Setup
Screen Print
SMT Placement
Hand Assembly
Wave Solder
Final Assembly
In Circuit Test
Stress Screen
Functional Test
Reflow
Wash
Pack / Ship
Typical SMT Complex Circuit Board Assembly
Design for Mass Production
Solder Geometry Variability in SMT and THT
Design for Mass Production
IPC = Institute of Printed Circuits, WWW.IPC.ORG
Association Connecting Electronics Industries
•
•
•
•
•
•
IPC-A-610 Acceptability of Electronic Assemblies
IPC-6011 Series of Board PCB Performance Standards
IPC/EIA J-STD-001 Requirements for Soldered Electrical and Electronic Assemblies
IPC-7095 Design and Assembly Process Implementation for BGAs
IPC-2221 Generic Std for Printed Board Design
IPC-D-279 Design Guidelines for Reliable Surface Mount Technology
Printed Board Assemblies
Quality!
Design for Mass Production
IPC Electronic Assembly Classifications
3.
High Reliability Electronic Products:
Ref: IPC-A-610, IPC-JSTD-001, IPC-7095
PROCESS CONTROL – PROCESS QUALITY
•
2.
1.
Aerospace, Military
Continued performance, performance on demand, and extended life is
critical and equipment downtime cannot be tolerated. Equipment must
function when required with a high level of reliability assurance.
# of Bds, # of solder joints
# of Mechanical Cycles
•
End-use environment is harsh
•
Includes equipment for commercial, military products, and for such
applications as life support or missile systems.
Dedicated Service Electronic Products:
10 Yr Stresses
4# of Power Cycles
# of Therm Cycles, Excursion
Telecom & Certain Medical
•
Continued performance, extended life and uninterrupted service is desired
but not critical.
•
Typically the end-use environment would not cause failures
•
Includes communications equipment, sophisticated business machines,
instruments and military equipment
General Electronic Products:
•
Function of the completed assembly is the major requirement
•
Cosmetic imperfections are not important
•
Includes consumer, some computer, peripherals, general military HW
Design for Mass Production
IPC Workmanship Classes: Solder Volume, Shape, Placement Control
3.
High Reliability Electronic Products: Includes the equipment for commercial and military products where
continued performance or performance on demand is critical. Equipment downtime cannot be tolerated, and
functionality is required for such applications as life support or missile systems. Printed board assemblies in
this class are suitable for applications where high levels of assurance are required and service is essential.
•
2.
Dedicated Service Electronic Products: Includes communications equipment, sophisticated business
machines, instruments and military equipment where high performance and extended life is required, and for
which uninterrupted service is desired but is not critical. Typically the end-use environment would NOT cause
failures.
•
1.
Requirement for Aero-Space, Certain Military, Certain Medical
Requirement for High Eng Telecom, COTS Military, Medical
General Electronic Products: Includes consumer products, some computer and peripherals, as well as
general military hardware suitable for applications where cosmetic imperfections are not important and the
major requirement is function of the completed printed board assembly.
100 %
100 %
75 %
75 %
50 %
50 %
25 %
25 %
0%
0%
Min PTH Vertical Fill: Class 2 = 75%
Ref: IPC-A-610, IPC-JSTD-001
IPC-7095
BGA Std
Class 1
Class 2
Class 3
Max Void Size
60% Dia
36% Area
45% Dia
20.3% Area
30% Dia
9% Area
Max Void
Size at
Interfaces
50% Dia
25% Area
35% Dia
12.3% Area
20% Dia
4% Area
Class 3 = 100%
Design for Mass Production
BGA Void Size and Locations, Uniform Void Position Distributions
Sampling_Grid
Position
Model
Solder_Joint_Radius
Void_Distance
Void_Radius
Void_Solder
Interface Distance
S = Shell
Potential for Early Life Failure (ELFO) if S < D/10 =
(solder_joint_radius)/10
S =Shell = solder_joint_radius – (void_distance + void_radius)
S
Design for Mass Production
CLASS 1
Solder Joint_Radius: 0.225 mm
Void_Radius: 0.135 mm
Void_Area: 36% of Joint Area
Failure criteria: D/10
P(D<10) = 81.11 %
CLASS 2
Solder Joint_Radius: 0.225 mm
Void_Radius: 0.1013 mm
Void_Area: 20% of Joint Area
Failure criteria: D/10
P(D<10) = 52.21 %
CLASS 3
Solder Joint_Radius: 0.225 mm
Void_Radius: 0.0675 mm
Void_Area: 9% of Joint Area
Failure criteria: D/10
P(D<10) = 27.00 %
Design for Mass Production
Class vs Shell Size Relative Probabilities
~ 2x more likely to exceed D/10 threshold with Class 2 vs Class 3
S = Shell
Depth
Design for Mass Production
Physics of Failure: Accumulated Fatigue Damage (AFD) is related to the number of stress
cycles N, and mechanical stress, S, using Miner’s rule
Exponent B comes from the S-N diagram. It is typically ~3 for 63/37 SnPb Solders
Example: Solder Joint
Shear
voids
Effective cross-sectional
Effective
crossForce
Area: D/2
F
sectional
Area: D
Applied stress:
Let  = 10, then
Applied stress:
AFD with voids will “age” about
1000x faster than AFD with no voids
Voids in solder joints
Design for Mass Production
IPC-A-610 Conditions
•
IPC-A-610 Workmanship Conditions
– Target Condition- This is the most desired condition and previously was referred
to as preferred. It is not always essential to achieve this condition for reliability
considerations.
– Acceptable Condition- is a condition that, while not at a Target Condition, will
result in a reliable product for the application. Corrective actions shall be
directed to move toward the Target Condition.
– Nonconforming Process Indicator- Is when a condition exists which does not
affect the use of the product, but is not optimum. May result in repair, rework or
scrap depending upon the customer’s requirements. Corrective action is
necessary to bring the result back toward the Target.
– Nonconforming Defect Condition- is when a condition exists that does not meet
the reliability or performance in the application. Correction action is mandatory.
There are three key words used in the
workmanship standards: Must, Shall and
Should.
All the IPC-A-610 Measurements utilize
•
•
•
Temp (Deg F/C)
Mass (Oz/Kg)
Distance (mils/mm)
Must means mandatory for Class 1, 2, & 3
Shall means mandatory for Class 3 only.
Should means recommended only for Class
1,2 & 3.
Quality!
Design for Mass Production
Solder Joints
•
Solder Joints: A solder joint is formed when two metal surfaces are soldered together.
The solder fills the void between the surfaces and is the area most important. It provides
the majority of “strength of attachment.” A solder fillet is formed after the solder joint is
filled, and, is the visible solder verifying the presence of the solder joint.
–
–
–
–
Blow Hole Defects: Blowholes are solder voids visible from the surface going into the solder joint
alongside a through-hole lead. A blowhole is a nonconforming process indicator provided the
solder connection meets the minimum circumference and depth requirements.
Dewetting Defects: Solder joints are visually inspected for wetting characteristics. Dewetting
occurs because the flux has been burned off and moisture attacks the surfaces. A good indicator of
dewetting is solder pooling and pulling back off leads or lands.
Oxidation Defects: When moisture in the air attacks a solder joint, it forms a protective rust-like
layer. This is referred to as oxidation, which attacks metal surfaces. Oxidation dramatically reduces
the transfer efficiency of thermal energy.
Dimensional Defects: For any of the above in addition to poor placement, screening, reflow and
other processes, solder joint geometric defect limits are clearly specified in these Stds (see above)
Design for Mass Production
Discrete Component Geometries
NOTES
1. The maximum fillet may overhang the land or extend onto the top of the chip cap metallization; however the
solder shall not extend further onto the component body.
2. Properly wetted fillet evident.
Design for Mass Production
J-Lead Component Geometries
NOTES
1. The maximum solder fillet shall not touch package body. 2. Properly wetted fillet evident.
Design for Mass Production
Gull Wing Component Geometries
NOTES
1. Solder fillet may extend through the top bend. Solder must not touch the package body or end seal, except for low profile
SMD devices, e.g., SOICs, SOTs. Solder should not extend under the body of low profile surface mount components whose
leads are made of Alloy 42 or similar metals.
2. Must not violate minimum design conductor spacing.
3. Properly wetted fillet evident.
Design for Mass Production
Thru-Hole Component Geometries
NOTES
1. Wetted solder refers to solder applied by the solder process.
2. The 25% unfilled volume includes both source and destination side depressions.
Design for Mass Production
Advanced Packaging
Design for Mass Production
Through Hole
Surface Mount
CSP / WLP
(CSP = Chip Scale Package,
WLP = Wafer Level Package)
TSOP
CSP/WLP
 25 mil pitch
 Area array 0.8 mm to 0.5 mm
 Limited by perimeter leads
 Limited by substrate wiring
100 mil pitch
 Limited by through hole spacing
IC Packaging Progression:
Design for Mass Production
Fujitsu SuperCSP
Redistribution
Trace (Cu)
SiN
Al Pad
Polyimide Layer
Die
Encapsulant
Barrier Metal
Solder Ball
Metal Post (Cu)
• Solder balls on copper posts
• Redistribution wiring to posts
• Encapsulant is molded onto wafer
Design for Mass Production
Wafer Level Packaging Will Become Std
VOLUME
Thru Hole
•DIP
•Pin Grid
1960
Surface Mount
•QFP
•TSOP
•SOJ
•BGA
1980
2000
YEAR
Chip Scale
•CSP
•Wafer Level
•Stacked Die
•SiP
Design for Mass Production
10000
Flip-Chip
Underfill+
µProcessor
1000
ASICs
Pins (#)
DRAM
SRAM
Flash
100
Passives
Analog ICs
10
Power ICs
Discretes
1
1
10
100
Die Area (mm2)
1000
Design for Mass Production
Process Flow:
Wafer Level Packaging
vs.
Conventional Packaging
* From Motorola