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
Electronic Pack….. Chapter 7 Production of PCBs.

2. Hole Mounting Axial components: Sequencing and mounting
Radial components: Mounting
DIP components: Mounting
Odd components: Robot or hand mounting
Fig. 7.1:The process for production of hole mounted PCBs
Electronic Pack….. Chapter 7 Production of PCBs.

3. Hole Mounting, continued
Fig. 7.2 a): Schematic example of the most efficient sequence of mounting the components of a particular PCB.
Electronic Pack….. Chapter 7 Production of PCBs.

4. Hole Mounting, continued
Fig. 7.2 b): The principle of sequencing.
Electronic Pack….. Chapter 7 Production of PCBs.

5. Hole Mounting, continued
Fig. 7.3: Sequencing machine.
Electronic Pack….. Chapter 7 Production of PCBs.

6. Hole Mounting, continued
Fig. 7.4: Axial inserter with two mounting heads.
Electronic Pack….. Chapter 7 Production of PCBs.

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.
Electronic Pack….. Chapter 7 Production of PCBs.

8. Hole Mounting, continued
Fig. 7.6: DIP inserter.
Electronic Pack….. Chapter 7 Production of PCBs.

9. Hole Mounting, continued
Fig. 7.7: Manual mounting board with light guide.
Electronic Pack….. Chapter 7 Production of PCBs.

10. Hole Mounting, continued
Fig. 7.8: Wave soldering machine.
Electronic Pack….. Chapter 7 Production of PCBs.

11. Electronic Pack….. Chapter 7 Production of PCBs.
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
Electronic Pack….. Chapter 7 Production of PCBs.

12. Wave Soldering, continued
Fluxing
Pre-heating
Soldering
(Cleaning)
Fig. 7.9:
a): Principle of foam fluxer.
b): Control system for density and level of the flux bath.
Electronic Pack….. Chapter 7 Production of PCBs.

13. Wave Soldering, continued
Fig. 7.10: a): Principle of wave soldering.
b): The real shape of the wave.
Electronic Pack….. Chapter 7 Production of PCBs.

14. Wave Soldering, continued
Fig. 7.11:
a): Industrial in line cleaning machine.
b): The principle of ultrasound and vapour cleaning.
Electronic Pack….. Chapter 7 Production of PCBs.

15. ElectroStatic Discharge (ESD) Precautions
Fig. 7.12: An ESD protected working space. The resistors R normally are 100 Kohm - 1 Mohm.
Electronic Pack….. Chapter 7 Production of PCBs.

16. Electronic Pack….. Chapter 7 Production of PCBs.
Surface Mounting
Soldering by wave solder process or by reflow process
Fig. 7.13: Application of adhesive for SMD mounting by:
a): Stencil or screen printing
b): Dispensing
c): Pin transfer
Electronic Pack….. Chapter 7 Production of PCBs.

17. Surface Mounting, continued
Fig. 7.14: a): Shadowing in SMD wave soldering.
b): Solder bridging on fine pitch package.
Electronic Pack….. Chapter 7 Production of PCBs.

18. Surface Mounting, continued
Lambda wave
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.
Electronic Pack….. Chapter 7 Production of PCBs.

19. Surface Mounting, continued
Fig. 7.16: Temperature profile during wave soldering in a double wave machine.
Electronic Pack….. Chapter 7 Production of PCBs.

20. Electronic Pack….. Chapter 7 Production of PCBs.
Reflow Solder Process
Print solder paste
Mount components
Dry solder paste
Solder by heating to melting of paste
Electronic Pack….. Chapter 7 Production of PCBs.

21. Electronic Pack….. Chapter 7 Production of PCBs.
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
Electronic Pack….. Chapter 7 Production of PCBs.

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  centipoise.
Electronic Pack….. Chapter 7 Production of PCBs.

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.
Electronic Pack….. Chapter 7 Production of PCBs.

24. Electronic Pack….. Chapter 7 Production of PCBs.
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!
Electronic Pack….. Chapter 7 Production of PCBs.

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.
Electronic Pack….. Chapter 7 Production of PCBs.

26. Surface Mounting, continued
Fig. 7.19: Detail of printing stencil (left) and printing screen with fine line printing pattern.
Electronic Pack….. Chapter 7 Production of PCBs.

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).
Electronic Pack….. Chapter 7 Production of PCBs.

28. Surface Mounting, continued
Two steps printing stencil work in the way that less solder paste will be deposited
Fig. 7.21: Two steps printing stencil to give less solder paste deposited.
Electronic Pack….. Chapter 7 Production of PCBs.

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.
Electronic Pack….. Chapter 7 Production of PCBs.

30. Surface Mounting, continued
Fig 7.23 a): Screen printer.
Electronic Pack….. Chapter 7 Production of PCBs.

31. Surface Mounting, continued
Fig b): The squeegee (DEK).
Electronic Pack….. Chapter 7 Production of PCBs.

32. Convection Soldering Convection soldering oven. 10.10.99
Electronic Pack….. Chapter 7 Production of PCBs.

33. Convection Soldering
Convection soldering oven: Temperature profile on PC screen.
Electronic Pack….. Chapter 7 Production of PCBs.

34. Electronic Pack….. Chapter 7 Production of PCBs.
IR Soldering
Fig a): IR furnace. Schematically with low temperature "area emitter".
Electronic Pack….. Chapter 7 Production of PCBs.

35. IR Soldering, continued
Fig b): Industrial IR furnace.
Electronic Pack….. Chapter 7 Production of PCBs.

36. IR Soldering, continued
Infrared Soldering
Planck´s law:
W/A = k1/l5 {exp(k2/lT)-1}
where:
W/A = emitted energy pr. second per m2 area per micrometer of radiation spectrum
k1 = 2 hc h = Planck´s constant
k2 = hc/k k = Boltzmann’s constant
Wavelength of max. radiation:
lmax = k3/T
Total radiated energy (Stefan Boltzmann´s law):
W/A = esT4
s = Stefan Boltzmann’s constant
e = emissivity (between 0 and 1)
Electronic Pack….. Chapter 7 Production of PCBs.

37. IR Soldering, continued
Graph of Planck`s law:
Electronic Pack….. Chapter 7 Production of PCBs.

38. IR Soldering, continued
Fig. 7.25: Typical temperature profile for an IR furnace.
Electronic Pack….. Chapter 7 Production of PCBs.

39. Electronic Pack….. Chapter 7 Production of PCBs.
Vapor Phase Soldering
Newton´s law :
dQ/dt = h•A (Tf -Ts)
Where:
dQ/dt = 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)]
Electronic Pack….. Chapter 7 Production of PCBs.

40. Vapour Phase Soldering
Fig a): Principle of in-line vapour phase soldering machine.
Electronic Pack….. Chapter 7 Production of PCBs.

41. Vapour Phase Soldering, continued
Fig b): Industrial in-line vapour phase soldering machine.
Electronic Pack….. Chapter 7 Production of PCBs.

42. Vapour Phase Soldering, continued
Fig. 7.27: Heat transfer coefficient for air and fluorocarbons. Boiling fluorocarbons, at the bottom, give times more efficient heat transfer than air.
Electronic Pack….. Chapter 7 Production of PCBs.

43. Vapour Phase Soldering, continued
Fig. 7.28: Temperature profile through in-line vapour phase soldering machine.
Electronic Pack….. Chapter 7 Production of PCBs.

44. 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).
Electronic Pack….. Chapter 7 Production of PCBs.

45. Vapour Phase Soldering, continued
Table 7.1: Physical properties of some primary vapours for reflow soldering.
Electronic Pack….. Chapter 7 Production of PCBs.

46. Other Soldering Methods
Impulse (hot bar-, thermode-) soldering
Hot plate / hot band soldering (thick film hybrid)
Hot air soldering
Laser soldering
Electronic Pack….. Chapter 7 Production of PCBs.

47. Thermode Soldering
Fig. 7.31: Two types of thermodes for thermode soldering.
Electronic Pack….. Chapter 7 Production of PCBs.

48. Thermode Soldering, continued
Fig. 7.32: Temperature profile for thermode soldering.
Electronic Pack….. Chapter 7 Production of PCBs.

49. Electronic Pack….. Chapter 7 Production of PCBs.
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)
Electronic Pack….. Chapter 7 Production of PCBs.

50. Electronic Pack….. Chapter 7 Production of PCBs.
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.
Electronic Pack….. Chapter 7 Production of PCBs.

51. 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.
Electronic Pack….. Chapter 7 Production of PCBs.

52. 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 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).
Electronic Pack….. Chapter 7 Production of PCBs.

53. Component Mounting, continued
Fig. 7.36: Philips large hardware controlled pick-and-place machine.
Electronic Pack….. Chapter 7 Production of PCBs.

54. Electronic Pack….. Chapter 7 Production of PCBs.
Solder faults
Fig. 7.38: Small SMDs standing on edge due to the "Manhattan-" or ”tombstone-" effect.
Electronic Pack….. Chapter 7 Production of PCBs.

55. 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
Electronic Pack….. Chapter 7 Production of PCBs.

56. Electronic Pack….. Chapter 7 Production of PCBs.
Robot Mounting
Fig. 7.39: Example of a programmable placement robot for electronics: The SCARA robot.
Electronic Pack….. Chapter 7 Production of PCBs.

57. 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
Electronic Pack….. Chapter 7 Production of PCBs.

58. Robot Mounting, continued
Fig. 7.40: The main components of a robot system.
Electronic Pack….. Chapter 7 Production of PCBs.

59. Robot System Components
Manipulator
Learning unit
Control unit
Types of Manipulator Coordinate Systems
Cartesian
Cylindrical (including "Scara")
Spherical
"Human-like"
Electronic Pack….. Chapter 7 Production of PCBs.

60. 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.
Electronic Pack….. Chapter 7 Production of PCBs.

61. Robot System Components, continued
Programming
"Lead-and-learn”
"Jog-and-learn”
"Synthetic programming"
Electronic Pack….. Chapter 7 Production of PCBs.

62. Robot Mounting, continued
Fig. 7.42: Multi gripper head.
Electronic Pack….. Chapter 7 Production of PCBs.

63. 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.
Electronic Pack….. Chapter 7 Production of PCBs.

64. Robot Mounting, continued
Fig. 7.43: Robot cell for electronic component placement (Adept)
Electronic Pack….. Chapter 7 Production of PCBs.

65. 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
Electronic Pack….. Chapter 7 Production of PCBs.

66. Electronic Pack….. Chapter 7 Production of PCBs.
Process Sequences
Fig 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.
Electronic Pack….. Chapter 7 Production of PCBs.

67. Electronic Pack….. Chapter 7 Production of PCBs.
Process Sequences
Fig 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.
Electronic Pack….. Chapter 7 Production of PCBs.

68. Electronic Pack….. Chapter 7 Production of PCBs.
Process Sequences
Fig 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.
Electronic Pack….. Chapter 7 Production of PCBs.

69. Electronic Pack….. Chapter 7 Production of PCBs.
Process Sequences
Fig 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.
Electronic Pack….. Chapter 7 Production of PCBs.

70. Electronic Pack….. Chapter 7 Production of PCBs.
Board Testing
Functional test
"In-circuit" test
NB: Good designs use one-sided testing
Test jigs are expensive
Two-sided jigs very compicated
Electronic Pack….. Chapter 7 Production of PCBs.

71. Electronic Pack….. Chapter 7 Production of PCBs.
Testing of PCBs
Fig. 7.45: Two methods for single sided test of a board with components on both sides.
Electronic Pack….. Chapter 7 Production of PCBs.

72. Testing of PCBs Fig. 7.46: Bed-of-nails test fixture. 10.10.99
Electronic Pack….. Chapter 7 Production of PCBs.

73. Electronic Pack….. Chapter 7 Production of PCBs.
Testing of PCBs
Fig. 7.47:
a) Detail of single sided test fixture.
b) Double sided fixture.
Electronic Pack….. Chapter 7 Production of PCBs.

74. Testing of PCBs Fig. 7.48: Two types of test pins. 10.10.99
Electronic Pack….. Chapter 7 Production of PCBs.

75. Electronic Pack….. Chapter 7 Production of PCBs.
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.
Electronic Pack….. Chapter 7 Production of PCBs.

76. 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?
Electronic Pack….. Chapter 7 Production of PCBs.