Joining and Electronics Manufacturing Flashcards
What is Welding
What are the Limitations and Benefits
Joining of two or more metal parts, by coalescing them at the contact surfaces with applied heat or pressure
Limitations:
Dangerous (High Energy)
Inconvenient disassembly
Welded joints can have Quality Defects
Advantages:
Mobile (joining can be done in the field)
High Rate of Joining
Small Material Usesage & Fabrication Costs
Economical
Wide Range of Materials
Describe Fusion Welding
What is an Autogenous Weld
What are the benefits to Filler Material
Joining Processes that melt base Materials to coalesce parts
A Fusion Weld without Filler Material
Provides, Bulk & Added Strength to the joint
Explain this Process
Arc Welding (Fusion)
Electrode Melts surface of the parts to be joined
Melted Metal from both parts join a molten pool
Filler Material is added to Molten Pool
Molten pool cools and Forms a Welded joint
Explain the Defects
Describe Solid Sate Welding
Explain the 3 types of Solid State Welding
Joining Proceeds that utilises applied pressure to coalesce parts
Can be Just Pressure, or a Combo of Heat (Below Melting point) and Pressure
Diffusion Welding (DFW)-Surfaces held together under pressure at a elevated temperature
Friction Welding (FRW)- Heat of Friction used to join Surfaces
Ultrasonic Welding (USW) - Ultrasonic Oscillating motion in a parallel direction to contact surface , while parts are held under pressure
What are the Hazards of Arc Welding
High Temperature of Molten Metals
Flammable fuels (Gas Welding)
High Voltages
UV Radiation Exposure to Eyes (Must Wear Helmet)
Sparks & Molten Splatters
Smoke and Fumes
What are the Processes
Spot Welding (Top Left)
Seam Welding (Top RIght)
Flange Weld ( Bottom Left)
Surfacing Weld Bead (Bottom Right)
Explain What has Occured in the HAZ & Recystalisation Zones of the joint
Metal has experienced temperatures below melting point
Yet high enough to alter the microstructure of the metal
Religion is Considered Heat Treated
Negative Mechanical Properties
Welding Failures Occur Here
Explain what a Weld Visual Inspection Entails
What are the Limitations
Inspector Examines :
Warpage (Conformance to Dimensions )
Cracks
Cavities
Surface Defects
Incomplete Fusion
Limitations:
Only Surface Defects are Examinable
Additional Tests are usually required
Explain 4 Different Methods of Non-Destructive Weld Inspections
Explain Mechanical and Metallurgical Weld Inspections (Destructive)
Metallurgical - Preparation of specimens to examine microstructure defects and HAZ
Mechanical - Tensile and Shear Tests to test mechanical Properties
What are the Following Mechanical Weld Inspections
What are the six major steps to PCB creation
Core
Patterning
Vias
Pattern Plating
Solder Mask
Surface Finish
Explain the First Step to PCB Creation
Core
Two sheets of copper are laminated to an insulating material
Explain the Second Step to PCB Creation
Explain an alternate Step
Patterning
Photomask is Created in a Specific Design
Core is covered in photosensitive material
Core Is exposed to a light Source through the Photomask
Solution applied that develops the photosensitive material
Photosensitive material exposed to light is then rendered soluble and washed off to reveal pattern
Use of a milling machine to mechanically remove copper from core
Explain the Third Step to PCB creation
What is the Aspect Ratio?
Vias
Laser or drill bit used to create hole through core
Plate Inner Diameter of hole with deposited Copper (electroplate)
Layers of PCB are now Electrically Connected
Ratio of Depth/Diameter of the Hole
If too large it can cause difficulties in electroplating (4-6 typically)
