Download presentation
Presentation is loading. Please wait.
1
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
2
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
3
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
4
Plated VIAs
5
Basic Photo-Etch PCB Mfg Process Plated Through Hole PCB Cross Section
6
VIA Aspect Ratio – Very Important
Bd Thickness VIA Diameter Aspect Ratio = Aspect Ratios > 5 May Challenge Drilling, Plating & other PCB Mfg Processes Cross Section Example of Failed VIA due to poor drilling, plating
7
Cu PCB Trace Width & Depth
IPC Current Capacity Limitations
8
Cu PCB Trace Conductor IPC* Spacing vs Voltage Summary (*Simplified)
9
IPC Capacitance Std Cross Sections
Reactance between two conductors, Opposes Any Change in Signal Voltage. Microstrip Stripline
10
The PCB is part of the circuit
Signal Routing is Important! The PCB is part of the circuit Good Signal Routing Equal Lengths, Uniform Good Power Bus Routing Bypass Caps Closest to IC Power Pins Poor Power Routing Bypass Caps and 1 Conductor too Lengthy Poor Signal Routing Un-Equal Lengths, Non-uniform
11
Flex Circuit Substrates
Caution: Must Protect via’s from bending forces.
12
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
13
TH: Thru-Hole Technology
14
Thru-Hole Device Packages
Passives and Discretes Axial Leaded (2 terminal, lying down) Resistors, Capacitors, Inductors, Diodes Radial Leaded (2 terminal, standing up) Capacitors, Inductors, LEDs, MOVs, Power Resistors, … T0 – Series (2-N terminals, Most Accommodate Std Heat Sink hardware) T0-92 Small Signal Transistors, Regulators, References T0-220 Moderate Power (~1W) Transistors, Regulators, Amplifiers T0-3 Higher Power (~3W) Transistors, Regulators, Amplifiers
15
Transistor Package Examples
16
Thru-Hole Device Packages
Integrated Circuits, Resistors, Relays DIP (Dual In-Line Package) PDIP, CDIP SIP (Single In-Line Package) Rectangular
17
P-DIP (plastic) and C-DIP (ceramic) Examples
18
SMT: Surface Mount Technology
19
SMT – Surface Mount Technology Generations
20mm DIP Small Outline Package Shrink SO Package Thin Shrink SOP Depopulated, Very Thin, Quad Flat Pack, No Leads 3 mm
20
Discretes: Rectangular (Example 0402)
21
SOT – Small Outline Transistors (SOT-3, SOT-223)
22
QFP – Quad Flat Packs
23
Quad Flat Pack – QFP, PQFP
24
PLCC – Plastic Leaded Chip Carriers
25
BGA – Ball Grid Arrays
26
Typical BGA Pin Layout
27
Electronic Assembly Quality
28
Electronic Assembly Quality and Standards
29
Simplified Comparison of Thru Hole and SMT PCB Assembly Process
Component Procure Setup Substrate (Fab) Fabrication Fab, Comp Prep Bake, Clean Simplified Comparison of Thru Hole and SMT PCB Assembly Process Thru Hole Mechanical Hand Operations SMT Auto Component Insertion Screen Solder Paste Vision System Inspection Wave Solder Auto Component Placement Vision System Inspection Lead Trim Reflow Solder (Oven) Stresses and Test Processes Vision/Xray System Inspection
30
Typical SMT Complex Circuit Board Assembly Processes
Setup Screen Print SMT Placement Reflow Hand Assembly Wave Solder Final Assembly Wash In Circuit Test Stress Screen Functional Test Pack / Ship Typical SMT Complex Circuit Board Assembly Processes
31
Solder Geometry Variability in SMT and THT
32
IPC = Institute of Printed Circuits, WWW. IPC
IPC = Institute of Printed Circuits, 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!
33
IPC Electronic Assembly Classifications
High Reliability Electronic Products: 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. 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: 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 Aerospace, Military 10 Yr Stresses # of Bds, # of solder joints # of Mechanical Cycles 4# of Power Cycles # of Therm Cycles, Excursion PROCESS CONTROL – PROCESS QUALITY Ref: IPC-A-610, IPC-JSTD-001, IPC-7095 Telecom & Certain Medical
34
IPC Workmanship Classes: Solder Volume, Shape, Placement Control
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. Requirement for Aero-Space, Certain Military, Certain Medical 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. 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 % 75 % 50 % 25 % 0 % 100 % 75 % 50 % 25 % 0 % 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 Min PTH Vertical Fill: Class 2 = 75% Class 3 = 100% Ref: IPC-A-610, IPC-JSTD-001
35
BGA Void Size and Locations, Uniform Void Position Distributions
Sampling_Grid Position Model Solder_Joint_Radius Void_Distance Void_Radius S 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)
36
P(D<10) = 81.11 % P(D<10) = 52.21 % P(D<10) = 27.00 % CLASS 1
Solder Joint_Radius: mm Void_Radius: mm Void_Area: 36% of Joint Area Failure criteria: D/10 P(D<10) = % CLASS 2 Solder Joint_Radius: mm Void_Radius: mm Void_Area: 20% of Joint Area Failure criteria: D/10 P(D<10) = % CLASS 3 Solder Joint_Radius: mm Void_Radius: mm Void_Area: 9% of Joint Area Failure criteria: D/10 P(D<10) = %
37
Class vs Shell Size Relative Probabilities ~ 2x more likely to exceed D/10 threshold with Class 2 vs Class 3 S = Shell Depth
38
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 Force voids Effective cross-sectional Area: D/2 Effective cross-sectional Area: D F Applied stress: Applied stress: Let = 10, then AFD with voids will “age” about 1000x faster than AFD with no voids Voids in solder joints
39
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. All the IPC-A-610 Measurements utilize Temp (Deg F/C) Mass (Oz/Kg) Distance (mils/mm) There are three key words used in the workmanship standards: Must, Shall and Should. 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!
40
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)
41
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.
42
J-Lead Component Geometries
NOTES 1. The maximum solder fillet shall not touch package body. 2. Properly wetted fillet evident.
43
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.
44
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.
45
Advanced Packaging
46
IC Packaging Progression:
Through Hole Surface Mount CSP / WLP (CSP = Chip Scale Package, WLP = Wafer Level Package) TSOP 25 mil pitch Limited by perimeter leads CSP/WLP Area array 0.8 mm to 0.5 mm Limited by substrate wiring 100 mil pitch Limited by through hole spacing IC Packaging Progression:
47
Fujitsu SuperCSP Solder balls on copper posts
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
48
Wafer Level Packaging Will Become Std
Density VOLUME Chip Scale CSP Wafer Level Stacked Die SiP Surface Mount QFP TSOP SOJ BGA Thru Hole DIP Pin Grid 1960 1980 2000 YEAR
49
µProcessor ASICs DRAM SRAM Flash Passives Analog ICs Power ICs
10000 Flip-Chip Underfill+ µProcessor 0.25 mm grid HDI PWB 1000 0.5 mm grid ASICs Pins (#) DRAM 100 SRAM Flash Passives 10 Analog ICs Power ICs Discretes 1 1 10 100 1000 Die Area (mm2)
50
Process Flow: Wafer Level Packaging vs. Conventional Packaging
* From Motorola
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.