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 ResistorSlug leads mold bake seal- cheap, poor tolerance, rugged

Wire-wound resistorwind wire leads mold seal- high power, low resistance, high frequency apps

Film resistorFilm 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

Quartzite (SiO2) + Carbon (C) + Heat + catalysts Si + CO2Raw Si:

Si + HCl SiCl4 + Hydrogen Fractional distillation

SiCl4 + H2 + catalysts Si + HCl

Pure Si:

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

MOSFETMetal-Oxide SiliconField 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 anodizationFilm thickness is ≤ 5 m

Thick Film Processes (silk-screening)

Print liquid or paste through a screen (mask) onto substrate firing (baking) Film thickness is ~ 10 m

Silk-screening

IC’s: Resistive elements depositionvacuum deposition

Subtractiveprocess

Additiveprocess

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 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 componentsStructure of a Surface mount component

SOIC packageSmall 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

Dual Inline Package and its lead-frame

Steps in Lead Frame Manufacture:

(1) Cut copper strips(2) Clean in a chemical bath(3) laminate a layer of photoresist(4) Expose photoresist through mask(5) Develop and etch(6) Remove lamination(7) Plate internal regions with gold/silver

Dual Inline Package and its lead-frame

Steps in Lead Frame Manufacture:

(1) Cut copper strips(2) Clean in a chemical bath(3) laminate a layer of photoresist(4) Expose photoresist through mask(5) Develop and etch(6) Remove lamination(7) Plate internal regions with gold/silver

- 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: deflash, trim the leadframe, form the leads, singulate (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

Types of PCB's single-side, double-side and multi-layer

Which type to use ?(a) Circuit complexity(b) Available space(c) Cost

Typical PCB

insulated substrate

copper connections

protective covering

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 onMulti-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 resistCover PCB with solder resist except Lands

Land

Step 2. Flux application

Foam fluxing Spray fluxing Ultrasonic Spray fluxing

Automatic soldering..

Step 3. Solder Application

Dip solderingDip soldering

Dual wave solder bath

Automatic soldering..

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

air-jet

Hot air jet knifeSOLDER

WAVE

air-jet

Hot air jet knifeSOLDER

WAVE

Types of circuit boards

Special considerationsfor SMT boards