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10.10.99 Electronic Pack….. Chapter 7 Production of PCBs. Slide 1 Chapter 7: Production of Printed Circuit Boards Focus on automated production of printed circuits by Surface Mounting Technology (SMT) and Hole Mounting Technology (HMT) The course material was developed in INSIGTH II, a project sponsored by the Leonardo da Vinci program of the European Union

Chapter 7: Production of Printed Circuit Boards

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Chapter 7: Production of Printed Circuit Boards. Focus on automated production of printed circuits by Surface Mounting Technology (SMT) and Hole Mounting Technology (HMT). The course material was developed in INSIGTH II, a project sponsored by the Leonardo da Vinci program of the European Union. - PowerPoint PPT Presentation

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Page 1: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 1

Chapter 7:Production of Printed Circuit Boards

• Focus on automated production of printed circuits by Surface Mounting Technology (SMT) and Hole Mounting Technology (HMT)

The course material was developed in INSIGTH II, a project sponsored by the Leonardo da Vinci program of the European Union

Page 2: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 2

Hole Mounting• Axial components:

Sequencing and mounting• Radial components:

Mounting• DIP components:

Mounting• Odd components:

Robot or hand mounting

Axial Components

Sequencing

Lead forming

Insertion

Cut-and-clinch

Wave soldering

DIP

Insertion

Lead forming

Cut-and-clinch

Radial Components

Insertion

Hand mounting ofspecial components

Electrical test

To customer

Faulty boards

Visual inspection

Cleaning

Robot mounting/hand mountingof odd compomnents

Repair

Fig. 7.1:The process for production of hole mounted PCBs

Page 3: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 3

Hole Mounting, continued

Fig. 7.2 a): Schematic example of the most efficient sequence of mounting the components of a particular PCB.

Page 4: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 4

Hole Mounting, continued

Fig. 7.2 b): The principle of sequencing.

Page 5: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 5

Hole Mounting, continued

Fig. 7.3: Sequencing machine.

Page 6: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 6

Hole Mounting, continued

Fig. 7.4: Axial inserter with two mounting heads.

Page 7: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 7

Hole Mounting, continued

Fig. 7.5: Simplified process in the axial inserter:

1): Cutting the components from the tape

2): Lead bending

3) - 4): Insertion

5): Cut and clinch

6): Return to starting position.

Page 8: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 8

Hole Mounting, continued

Fig. 7.6: DIP inserter.

Page 9: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 9

Hole Mounting, continued

Fig. 7.7: Manual mounting board with light guide.

Page 10: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 10

Hole Mounting, continued

Fig. 7.8:Wave soldering machine.

Page 11: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 11

Wave Soldering, principle

•Fluxing

•Pre-heating

•Soldering

•(Cleaning)

Fig. 7.9:

a): Principle of foam fluxer.

b): Control system for density and level of the flux bath.

Page 12: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 12

Wave Soldering principle, continued

Fig. 7.10: a): Principle of wave soldering.

b): The real shape of the wave.

Page 13: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 13

Wave Soldering, continued

Fig. 7.11:

a): Industrial in line cleaning machine.

b): The principle of ultrasound and vapour cleaning.

Page 14: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 14

ElectroStatic Discharge (ESD) Precautions

Fig. 7.12: An ESD protected working space. The resistors R normally are 100 Kohm - 1 Mohm.

Page 15: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 15

Surface Mounting• Soldering by wave solder process or by reflow process Fig. 7.13: Application of adhesive for SMD mounting by:

a): Screen printing

b): Dispensing

c): Pin transfer

Page 16: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 16

Surface Mounting: Wave Solder Process

• Apply adhesive by dispenser, screen printing or pin transfer• Cure by heat or UV• Turn board•Wave solder–Double-wave soldering machine common for SMT–Not all SMD components suitable for wave soldering

Page 17: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 17

Surface Mounting, continued

Fig. 7.14: a): Shadowing in SMD wave soldering.

b): Solder bridging on fine pitch package.

Page 18: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 18

Surface Mounting, continued

Fig. 7.15: Double wave for SMD soldering. The first is a turbulent wave that wets, followed by a gentle “lambda wave” that removes superfluous solder.

Lambda wave

Page 19: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 19

Surface Mounting, continued

Fig. 7.16: Temperature profile during wave soldering in a double wave machine.

Page 20: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 20

Reflow Solder Process

• Print solder paste

•Mount components

• Dry solder paste

• Solder by heating to melting of paste

Page 21: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 21

Solder Paste

• Consists of: –Solder particles (~ 80 % by weight)–Flux–Solvents and additives to give good printing properties (rheology)

• Typical mesh count in screen: 80 per inch

• Area ratio: Ao = a2 /(a+b)2

• Paste volume deposited: V = Vo • Ao • t

• "Solder ball test" for quality of solder paste and solder process

Page 22: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 22

Solder Paste, continued

Fig. 7.17: Microphotograph of Multicore solder paste type Sn 62 RMA B 3. The designation means 62 % by weight of Sn, 35.7% Pb, 2%, Ag, 0.3% Sb, RMA flux, 75 µm average particle size, 85% metal content, viscosity 400 000 - 600 000 centipoise.

Page 23: Chapter 7: Production of Printed Circuit Boards

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Production of PCBs. Slide 23

Solder Paste, continued

Fig. 7.18: Test of solder paste: The paste is printed through a circular opening with a diameter of 5 mm, in a 200 µm thick stencil. After reflow, the paste should melt into one body, without any particles spreading out.

Page 24: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 24

Screen Printing

• Woven screen (stainless steel or polyester) with organic photosensitive layer, which is patterned with holes (mask).• Metal stencil with etched or drilled openings.• Polyester stencil with punched or drilled

openings.• Definition and accuracy depends on type, mesh

count, thickness, tension, squeegee, speed, etc. Screen Printing is a complex craft!

Page 25: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 25

Screen Printing, continued

• Off-contact for screen printing, contact for stencil. Two-step stencil for best definition.

• The most advanced printers are fully automatic with vision system for alignment.

Page 26: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 26

Surface Mounting, continued

Fig. 7.19: Detail of printing stencil (left) and printing screen with fine line printing pattern.

Page 27: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 27

Surface Mounting, continued

Fig. 7.20: Detail of printing stencil with fine pitch printing pattern: Cross section of a stencil etched from both sides, with an acceptable, small amount of offset (40 x magnification).

Page 28: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 28

Surface Mounting, continued

Fig. 7.21: Two steps printing stencil.

Page 29: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 29

Surface Mounting, continued

Fig. 7.22: Printing through 0.3 mm diameter holes with Mylar stencil. To obtain the correct amount of solder paste two or three small holes may be used for each solder land.

Page 30: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 30

Surface Mounting, continued

Fig 7.23 a): Screen printer.

Page 31: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 31

Surface Mounting, continued

Fig. 7.23 b): The squeegee (DEK).

Page 32: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 32

IR Soldering

Fig. 7.24 a): IR furnace. Schematically with low temperature "area emitter".

Page 33: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 33

IR Soldering, continued

Fig. 7.24 b): Industrial IR furnace.

Page 34: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 34

Infrared Soldering

• Planck´s law:

W/A = k1/5 {exp(k2/T)-1}Shown on graph, where:W/A = emitted energy pr. second per m2

area per micrometer of radiation spectrum

k1 = 2 hc2 h = Planck´s constant

k2 = hc/k k = Boltzmann’s constantWavelength of max. radiation:

max = k3/T• Total radiated energy (Stefan

Boltzmann´s law): W/A = T4

= Stefan Boltzmann’s constant = emissivity (between 0 and 1)

Page 35: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 35

IR Soldering, continued

Fig. 7.25: Typical temperature profile for an IR furnace.

Page 36: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 36

Vapor Phase Soldering

• Newton´s law :

Q/t = h•A (Tf -Ts)

Where:• Q/t = energy transferred pr. sec. (W)

• A = total area

• h = heat transfer coefficient

• Tf = vapour temperature (boiling point)

• Ts = PCB temperature

• PCB temperature approaches Tf asymptotically:

(Ts -To) = [Tf -To]•[1 -exp (-t/to)]

Page 37: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 37

Vapour Phase Soldering

Fig. 7.26 a): Principle of in-line vapour phase soldering machine.

Page 38: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 38

Vapour Phase Soldering, continued

Fig. 7.26 b): Industrial in-line vapour phase soldering machine.

Page 39: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 39

Vapour Phase Soldering, continued

Fig. 7.27: Heat transfer coefficient for air and fluorocarbons. Boiling fluorocarbons, at the bottom, give 200 - 400 times more efficient heat transfer than

air.

Page 40: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 40

Vapour Phase Soldering, continued

Fig. 7.28: Temperature profile through in-line vapour phase soldering machine.

Page 41: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 41

Vapour Phase Soldering, continued

Fig. 7.29: Chemical composition of fluoro carbons for vapour phase soldering. Top: The liquid FC-5311 (3M): C14 F24 is derived from C14 H10. Bottom: The liquid LS 230 (Galden).

Page 42: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 42

Vapour Phase Soldering, continued

Table 7.1: Physical properties of some primary vapours for reflow soldering.

Property Units R113 FC-70 FC-5311 LS230Boiling point or range °C 47,6 215 215 230±5Molecular weight - 187 821 624 ~650Pour point °C -25 -20 -80Density of liquid at 25°C g cm3 1,57 1,93 2,03 1,82

Density of saturated vapour at BP mg cm3 7,38 20,3 15,6 19,5

Viscosity of liquid at 25°C cP 0,7 27 16 8Surface tension of liquid at 25°C mN/m 19 18 19 18Specific heat of liquid at 25°C J/gK 0,95 1,05 1,07 1,00Thermal conductivity at 25°C mW/mK 74 70 53 70Electrical resistivity Ohm cm 2 1015 >1015 1015

Heat of vaporisation, at BP J/g 67 68 63

Page 43: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 43

Other Soldering Methods

• Hot air soldering (Most used today)

• Impulse (hot bar-, thermode-) soldering

• Hot plate / hot band soldering (thick film hybrid)

• Laser soldering (too time-consuming single point soldering)

Page 44: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 44

Thermode Soldering

Fig. 7.31: Two types of thermodes for thermode soldering.

Page 45: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 45

Thermode Soldering, continued

Fig. 7.32: Temperature profile for thermode soldering.

Page 46: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 46

Component Placement

–Automatic, dedicated pick-and-place machines–Manual placement (prototypes, repair)–Semi-manual (light guided table, etc.)• Programmable robot• Elements of Pick-and-Place Machine

– Board magazine/feeder system– Mounting head(s) (with interchangable grip tools)– Programming/control unit– Component "storage" and feeder– Vision system (correct placement and control afterwards)

Page 47: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 47

Component Mounting

Fig. 7.33: SMD pick-and-place machine (Siemens).

The mounting head may also include an electronic vision system for very accurate placement of fine pitch components.

Page 48: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 48

Component Mounting, continued

Fig. 7.34: a): Mechanical gripper in a pick-and place machine. b): Detail of the component tape when a component is in position for picking.

c): Vibration feeder.

Page 49: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 49

Component Mounting, continued

Fig. 7.35: Fuji CP-II pick-and-place machine. The machine has magazine for over 100 types of small components, nominal speed up to 15 000 components per hour, placement accuracy 0.10 mm. It has a rotating head with 12 positions, bottom figure, and two alternative tools at each position. There are components at all 12 positions at any time, with a separate operation being performed. A CCD camera shows the accurate position and orientation on a CRT screen (Fuji).

Page 50: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 50

Component Mounting, continued

Fig. 7.36: Philips large hardware controlled pick-and-place machine.

Page 51: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 51

Solder faults

Fig. 7.38: Small SMDs standing on edge due to the "Manhattan-" or ”tombstone-" effect.

Page 52: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 52

Robot System for Placement

• Advantages:–Flexibility: Can handle most odd component types and boards, in low and high volumes–Uniform quality–High placement accuracy (~ 0.02 mm)–Non-manned operation (over night)–Can work in hostile environments–Tests and controls can be included in placement operation by special sensors on robot

Page 53: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 53

Robot Mounting

Fig. 7.39: Example of a programmable placement robot for electronics: The SCARA robot.

Page 54: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 54

Robot System for Placement

•Must be carefully considered:

• Cost, including the external equipment, fixtures, transport system

• Lower capacity than Pick-and-Place

• Requires careful planning, and often much dedicated surrounding equipment

Page 55: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 55

Robot Mounting, continued

Fig. 7.40: The main components of a robot system.

Page 56: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 56

Robot System Components

•Manipulator–Learning unit–Control unit

• Types of Manipulator Coordinate Systems–Cartesian–Cylindrical (including "Scara")–Spherical–"Human-like"

Page 57: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 57

Robot Mounting, continued

Fig. 7.41: Types of robot arms: a): Cartesian motion. b): Cylindrical. c): Spherical. d): "Human like". The SCARA robot is a special version of the cylindrical type.

Page 58: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 58

Robot System Components, continued

• Programming–"Lead-and-learn”–"Jog-and-learn”–"Synthetic programming"

Page 59: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 59

Robot Mounting, continued

Fig. 7.42: Multi gripper head.

Page 60: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 60

Robot Uses in Electronics

• Production–Component placement–Production of parts (coils, cables,....–Board feeding–Handling of boards, components in testing–Automatic trimming in test–Parts assembly for board, rack, chassis, etc.–Screw and glue operation–Soldering, welding• etc.

Page 61: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 61

Robot Mounting, continued

Fig. 7.43: Robot cell for electronic component placement (Adept)

Page 62: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 62

Types of Boards: SMD and Mixed Assembly

• SMD side A

• SMD side A and hole components side B

• SMD side A and B

• SMD both sides, hole components side B

Page 63: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 63

Process Sequences

Fig. 7.44 a -d): Process sequences for boards with different types of components on the two sides.

The steps marked "For all processes" on figure a) are not repeated on the other figures.

Page 64: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 64

Process Sequences

Fig. 7.44 a -d): Process sequences for boards with different types of components on the two sides. The steps marked "For all processes" on figure a) are not repeated on this figure.

Page 65: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 65

Process Sequences

Fig. 7.44 a -d): Process sequences for boards with different types of components on the two sides. The steps marked "For all processes" on figure a) are not repeated on this figure.

Page 66: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 66

Process Sequences

Fig. 7.44 a -d): Process sequences for boards with different types of components on the two sides. The steps marked "For all processes" on figure a) are not repeated on this figure.

Page 67: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 67

Board Testing

• Functional test

• "In-circuit" test

• NB: Good designs use one-sided testing–Test jigs are expensive–Two-sided jigs very compicated

Page 68: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 68

Testing of PCBs

Fig. 7.45: Two methods for single sided test of a board with components on both sides.

Page 69: Chapter 7: Production of Printed Circuit Boards

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Production of PCBs. Slide 69

Testing of PCBs

Fig. 7.46: Bed-of-nails test fixture.

Page 70: Chapter 7: Production of Printed Circuit Boards

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Production of PCBs. Slide 70

Testing of PCBsFig. 7.47:

a) Detail of single sided test fixture.

b) Double sided fixture.

Page 71: Chapter 7: Production of Printed Circuit Boards

10.10.99 Electronic Pack….. Chapter 7

Production of PCBs. Slide 71

Testing of PCBs

Fig. 7.48: Two types of test pins.

Page 72: Chapter 7: Production of Printed Circuit Boards

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Production of PCBs. Slide 72

Testing of PCBs

Fig. 7.49: Unacceptable testing. The test point should be on the Cu foil on the board, not on the component lead.

Page 73: Chapter 7: Production of Printed Circuit Boards

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Production of PCBs. Slide 73

End of Chapter 7: Production of Printed Circuit Boards

•Important issues:– When manufacturing PCBs:

• Understand the basic manufacturing steps:– Sequencing and mounting of Hole Mounted Components– Wave soldering: Basics. Why we want to avoid (yield and reliability problems) When to

use it for Surface Mount Components (Mixed boards)– Reflow soldering process: Basics. Solder paste. Silk screen and stencil printing. Reflow

heating with hot air, IR, vapor phase, etc.• Component placement:

– Automatic, manual, semi-automatic, and using robots• Types of SMD boards manufactured: Understand and remember the basic flow

diagrams:– SMD side A– SMD side A and hole components side B– SMD side A and B– SMD both sides, hole components side B

• Board testing:– Functional test– In-circuit test

•Questions and discussions?