PCB Designing Overview

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Questions and Answers

What is the primary function of the reverse mask in the semi-additive process?

To expose parts of the substrate for copper plating (correct)

To insulate the areas not needing copper

To coat the entire board in copper

To etch away unwanted copper from the board

Which chemical is commonly used for chemical etching in PCB fabrication?

Hydrochloric acid

Sodium hydroxide

Acetic acid

Ammonium persulfate (correct)

What is one significant advantage of the additive method over the subtractive method in PCB manufacturing?

It requires more intricate drilling techniques.

It produces more waste material.

It creates a thicker copper layer.

It removes less copper. (correct)

In PCB milling, what is primarily milled away from the substrate?

Copper foil Signup and view all the answers

What is typically used for drilling holes through a PCB?

Solid coated tungsten carbide bits Signup and view all the answers

During the semi-additive process, what is applied to create conductive vias in multi-layer boards?

Electroplating Signup and view all the answers

Which process involves vaporizing paint to define areas where etching will occur?

Laser resist ablation Signup and view all the answers

What typically happens to the bare copper areas during the chemical etching process?

They are etched away Signup and view all the answers

Which material is most commonly used for the base of a printed circuit board?

Fiberglass Signup and view all the answers

What technology is characterized by components being soldered directly onto the surface of the PCB?

Surface Mount Technology Signup and view all the answers

Which of the following describes the main types of PCBs?

Single sided, double sided, multilayer Signup and view all the answers

What does FR in FR-4 denote regarding PCB materials?

Flame Resistant Signup and view all the answers

Who first developed the printed circuit board?

Paul Eisler Signup and view all the answers

Which of the following is NOT a characteristic of through-hole technology?

Utilizes a flat surface for soldering Signup and view all the answers

Which process was used for PCB design before computerized methods became common?

Manual tape on film Signup and view all the answers

What type of PCB uses high-temperature plastic as its substrate?

Flexible PCB Signup and view all the answers

What is the primary reason for recommending coated tungsten carbide drill bits for PCB manufacturing?

They remain sharp, minimizing damages while drilling. Signup and view all the answers

What file type is used to control the placement of drill bits during PCB drilling?

A numerically controlled drill file. Signup and view all the answers

What are micro vias, and how are they typically created?

Small holes created by mechanical bits or laser drilling. Signup and view all the answers

Which type of via connects an internal copper layer to an outer layer?

Blind via. Signup and view all the answers

What purpose does the solder mask serve after PCBs are etched?

To protect the exposed copper. Signup and view all the answers

What is the primary method of making conductive holes in PCBs?

Electroplating or inserting metal eyelets. Signup and view all the answers

What treatment is applied to bare copper to prevent surface oxidation?

Benzimidazolethiol treatment. Signup and view all the answers

How do buried vias differ from blind vias?

Buried vias do not connect to outer layers, while blind vias do. Signup and view all the answers

What is the primary function of panelization in PCB manufacturing?

To assemble multiple PCBs into a single manufacturing panel Signup and view all the answers

Which method is NOT typically used in the depaneling process of PCBs?

Using heat to melt the connections Signup and view all the answers

Which function is associated with the PCB CAM system?

Verifying fabrication data and compensating for manufacturing deviations Signup and view all the answers

What is the purpose of silk screen printing in the copper patterning process?

To apply a protective mask on the copper foil Signup and view all the answers

What does the term 'depaneling' refer to in PCB manufacturing?

The process of separating PCBs from a manufacturing panel Signup and view all the answers

Which of the following statements about bare board manufacturing panels is true?

They are utilized for plating process requirements Signup and view all the answers

What role does subsequent etching play in copper patterning?

It removes unwanted copper to form the desired pattern Signup and view all the answers

Which technique is utilized for high-resolution requirements in photoengraving?

Direct imaging techniques Signup and view all the answers

Study Notes

PCB Designing

Printed Circuit Board (PCB): A non-conductive substrate mechanically supporting and electrically connecting electronic components. Components are connected using etched tracks, pads, and other features on a laminated copper sheet.
Printed Circuit Board Assembly (PCBA): A PCB populated with electronic components.
History: First developed by Australian engineer Paul Eisler. Earlier point-to-point wiring and later wire wrapping preceded PCBs.
Types of PCBs:
- Single-sided
- Double-sided
- Multilayer
PCB Materials:
- Copper-clad fiberglass (or thin copper sheets)
- Copper foil
- Copper plating
- Solder flow
- Solder mask
- Traces
- Slots and cutouts
Through-Hole Technology: Early PCBs used this method to install components. Leads pass through holes in one side of the board and are soldered to traces on the other side. Boards can be single- or double-sided.
Surface Mount Technology (SMT): Emerged in the 1960s. Components with small metal tabs or end caps are directly soldered to the PCB surface.
PCB Base Material: Fiberglass, specifically FR-4. FR-4 is a flame-retardant composite material.
PCB Design Equipment (Early Days): Design and layout was done manually using tape placed on translucent film, then photographically reduced for manufacturing.
Modern PCB Design Equipment: Computerized design, PCB CAM (Computer-Aided Manufacturing) systems, and software packages for improved efficiency and more features (like simulations and complex routing).
PCB CAM Functions:
- Input of fabrication data.
- Data verification (and potentially Design for Manufacturing (DFM).
- Compensation for manufacturing process deviations (e.g., scaling).
- Panelization: Grouping multiple PCBs for manufacturing onto a larger panel. Can use single design or mix several designs on a single panel.
- Output of digital tools (copper patterns, solder mask, legend, drill files, and other data needed for production).
Depaneling: Breaking the panel into individual PCBs. The process is often assisted with lines or cuts in the panel, and now often done by lasers for better results.
Copper Patterning: Reproducing the copper pattern using either silk screen printing, photoengraving (using UV-sensitive resists), or other direct imaging techniques, to create the desired copper layout, removing unwanted copper.
PCB Milling: A mechanical method to remove copper.
Laser Resist Ablation: A process for removing unwanted copper using a laser and a coating for resistance in certain areas.
Subtractive, Additive, and Semi-Additive Processes:
- Subtractive method: Removing copper from an entire copper-coated board.
- Additive method: Adding the desired copper pattern on a plain substrate.
- Semi-additive: The board starts with a thin copper layer and a reverse mask to deposit more copper to the desired areas.
Chemical Etching: Using chemical solutions (like ammonium persulfate or ferric chloride) to remove copper from a PCB. Crucial for Plated-Through-Holes (PTH).
Drilling: Using small drill bits (often made of tungsten carbide) to create holes in the PCB.
Vias: Small holes for connecting board layers, or for passing components and signals between layers. Can also have micro vias.
Blind Vias: Connecting an internal layer to an outer layer without passing through the entire board.
Buried Vias: Connecting layers on a PCB but do not pass through the outer layers.
Plating and Coating: Applying solder, tin, gold, or nickel to the copper to act as a physical and/or chemical coating/resistance to allow copper etch/removal.
Legend Printing: Using screen printing, liquid photo imaging, or ink-jet printing to print labels and other information onto the board.
Final Steps: Testing, soldering, packaging, and protection after the PCB assembly is completed.
Advantages of PCBs: Fixed components, minimal short circuit/wiring concerns, inexpensive for mass production, perfect for reproduction.
Disadvantages of PCBs: Not easily repairable once damaged, potential environmental impact, difficult to update designs, and limited to specific circuits.

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Description

Explore the fundamentals of Printed Circuit Boards (PCBs) in this quiz. Learn about their types, materials, and technologies like Through-Hole and Surface Mount Technology (SMT). This is a great resource for anyone interested in electronics and circuit design.