Electronics Manufacturing Processes
Manufacture of Electronics Components
Manufacture of Printed Circuit Boards (PCB’s)
Assembly of components on PCB’s

Electronics Manufacturing Processes
Manufacture of Electronics Components
Manufacture of Printed Circuit Boards (PCB’s)
Assembly of components on PCB’s

Electronics Component Manufacture
Electronics Components
Mechanical and Electro-mechanical:
PCB mounted DIP switches, mains switches, disc drives
Passive Solid State Devices:
Resistors, Capacitors
Active Solid State Devices:
Transistors, Diodes, Thermionic valves, FETs and MOSFETs

Passive devices: resistors
Carbon Composite Resistor
Slug
 leads
 mold
 bake
 seal
- cheap, poor tolerance, rugged
Wire-wound resistor wind wire
 leads
 mold
 seal
- high power, low resistance, high frequency apps
Film resistor
Film is cut by laser
 high precision
- low frequency applications

Passive devices: capacitors
Tabbed tubular paper capacitor
Disk-ceramic capacitor
Tubular ceramic capacitors

Active devices: Silicon wafer production
Raw Si:
Pure Si:
Quartzite (SiO
2
) + Carbon (C) + Heat + catalysts  Si + CO
2
Si + HCl

SiCl
4
SiCl
4
+ Hydrogen

+ H2 + catalysts  Si + HCl
Fractional distillation

Pure Monocrystalline Si:
Melt pure Si, Seed crystal drawn out slowly
Typical Single Crystal Ingot sizes:
1-2m long, 8cm / 15cm / 30 cm diameter

Ingot sliced (Diamond saw)

Active Devices: Doping pure silicon
Silicon Dopant: Phosphorus, N-type Dopant: Aluminum, P-type
Doping processes:
Diffusion (heat wafer in atmosphere with atoms of dopant)
Ion implantation (ions of dopant are accelerated, bombard surface)
Diode (showing doping)

Active components: Transistors
NPN transistor
MOSFET
Metal-Oxide Silicon
Field Effect Transistor

Active components: Integrated Circuits
Monolithic IC: Entire circuit made on a single crystal wafer
Hybrid IC: Monolithic IC + other components directly assembled into it
Hybrid micro-circuit film components

Active components: IC’s..
Depositing films of materials on substrate to make circuits
Thin Film Processes:
Form components on circuits by vacuum evaporation, sputtering, or anodization
Film thickness is ≤ 5 m m
Thick Film Processes (silk-screening)
Print liquid or paste through a screen (mask) onto substrate
 firing (baking)
Film thickness is ~ 10 m m
Silk-screening

IC’s: Resistive elements deposition vacuum deposition
Subtractive process
Additive process

Diffused Junction Process
- Photolithography is the most commonly used process
- Photoresists: positive: more soluble when exposed negative: less soluble when exposed
- Feature size = f(wavelength)
 small features need low l radiation
- Mask = = Artwork
- Projection:
- Direct: mask scale is 1:1
- Reducing: mask scale is 10:1

Packaging of components
- Packaging puts the chip (silicon) into a protective case
- Package provides external connections that are spaced conveniently
(at distance, arranged in array) for soldering
Exploded view of TO package

Packaging of components
Structure of a Surface mount component
SOIC package
Small Outline IC
Avoiding possible heat damage to IC during soldering:
- Solder a chip carrier to the PCB
- Insert chip into carrier
IC
Chip carrier

Integrated Circuit (IC) Manufacture
Slicing the Silicon ingot
Fabrication of IC’s (Lithography, Sputtering, diffused junction, …)
Testing each IC on the slice
[source: www.towajapan.co.jp]
Dicing (cutting each chip out with a diamond saw)
Packaging

Packaging
- Make leadframe
Die attachment (chip bonded to leadframe using epoxy)
Wire bonding (ultrasonic welding)
Encapsulation (moisture resistant coating)
Molding (plastic package)
Marking (chip number, co. name, marked on package [laser, silkscreen])
DTFS: d eflash, t rim the leadframe, f orm the leads, s ingulate (cut dambars)
Leadfinishing : electroplating the leads

Electronics Manufacturing Processes
Manufacture of Electronics Components
Manufacture of Printed Circuit Boards (PCB’s)
Assembly of components on PCB’s

PCB Manufacture
Typical PCB copper connections protective covering insulated substrate
Types of PCB's single-side, double-side and multi-layer
Which type to use ?
(a) Circuit complexity
(b) Available space
(c) Cost

Manufacturing glass reinforced epoxy resin copper-clad boards
Boards are produced in " clean-rooms "
Manufacturing process: hot-pressing
• Place copper sheet on the lower plate
• Place few layers of glass cloth impregnated with epoxy on top
• [IF two-sided PCB's]: Place copper sheet on above
• Press between steel plates in a steam-heated hydraulic press (~7,000,000 Pa)
• Water cooling to 25º C
• Trim to clean out extruded epoxy
• Punch/Drill holes for alignment
• Make circuit on PCB (lithography)
• Drill through holes (for component leads)

Multi-layer PCBs
• Similar process as single layer, but takes several steps
Schematics and features on
Multi-layer PCB’s

Electronics Manufacturing Processes
Manufacture of Electronics Components
Manufacture of Printed Circuit Boards (PCB’s)
Assembly of components on PCB’s

PCB Assembly
- Insert leaded component into holes on PCB
- Solder
- Protective coating
Manual electronics assembly
Automated electronics assembly

Automated PCB Assembly
Component inputs:
Leaded Component IC’s, components with no wire leads

PCB Manufacture
Surface mount chip assembly:
- Silk-screening to apply solder paste on the board
- Automated assembly of components (>30,000 components per hour)
- IR or Wave soldering

Automatic soldering
Step 1. Application of the solder resist
Cover PCB with solder resist except Lands
Land
Step 2. Flux application
Foam fluxing Spray fluxing
Ultrasonic Spray fluxing

Automatic soldering..
Step 3. Solder Application
Dual wave solder bath

Automatic soldering..
Step 4. Automatic removal of solder bridges: Hot air-jet knives

Types of circuit boards

Special considerations for SMT boards