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Questions and Answers
Questions and Answers
What best describes the primary function of a printed circuit board (PCB)?
What best describes the primary function of a printed circuit board (PCB)?
- To protect electronic components from external electromagnetic interference.
- To act as a heat sink for high-power components.
- To house components and establish electrical connections between them through a predetermined design. (correct)
- To provide structural support for electronic components only.
Which material(s) are commonly used as the conducting material in a PCB?
Which material(s) are commonly used as the conducting material in a PCB?
- Plastic and rubber
- Aluminum and tin
- Only copper
- Copper, silver, and gold (correct)
What advantage do printed circuit boards offer over older wiring methods?
What advantage do printed circuit boards offer over older wiring methods?
- PCBs are more difficult to adapt as plug-in units.
- PCBs require more manual wiring.
- PCBs reduce interconnecting wiring to lines of conductive material. (correct)
- PCBs increase the need for terminal boards and tie points.
What is the purpose of 'tie-in points' in electrical systems?
What is the purpose of 'tie-in points' in electrical systems?
How are the components typically attached to a basic single-sided PCB?
How are the components typically attached to a basic single-sided PCB?
What is the purpose of etching away part of the copper foil in the manufacturing process of a PCB?
What is the purpose of etching away part of the copper foil in the manufacturing process of a PCB?
What are the 'wires' or conductive paths on the surface of a PCB commonly referred to as?
What are the 'wires' or conductive paths on the surface of a PCB commonly referred to as?
What is located on the opposite side of the basic PCBs (single-sided boards)?
What is located on the opposite side of the basic PCBs (single-sided boards)?
What is the primary purpose of component sockets on a PCB?
What is the primary purpose of component sockets on a PCB?
What is the purpose of an edge connector on a PCB?
What is the purpose of an edge connector on a PCB?
What is a solder mask?
What is a solder mask?
What is the purpose of silk screen?
What is the purpose of silk screen?
What is a 'silk screen' on a PCB and what is its primary purpose?
What is a 'silk screen' on a PCB and what is its primary purpose?
What is the primary advantage of using double-sided PCBs compared to single-sided PCBs?
What is the primary advantage of using double-sided PCBs compared to single-sided PCBs?
How do multi-layer PCBs increase the wiring area compared to single-layer or double-layer boards?
How do multi-layer PCBs increase the wiring area compared to single-layer or double-layer boards?
What is the purpose of 'assembly methods' in the context of PCB manufacturing?
What is the purpose of 'assembly methods' in the context of PCB manufacturing?
What are the two main approaches to PCB assembly process?
What are the two main approaches to PCB assembly process?
What is a characteristic of Through Hole Technology (THT)?
What is a characteristic of Through Hole Technology (THT)?
What distinguishes Surface Mount Technology (SMT) from Through Hole Technology (THT)?
What distinguishes Surface Mount Technology (SMT) from Through Hole Technology (THT)?
Which statement accurately describes the characteristics of SMT components?
Which statement accurately describes the characteristics of SMT components?
What purpose do voltage and ground lines or planes serve on a printed circuit board?
What purpose do voltage and ground lines or planes serve on a printed circuit board?
What are 'terminals' or 'pads' on a PCB primarily designed for?
What are 'terminals' or 'pads' on a PCB primarily designed for?
What is the primary function of the substrate or laminate in a PCB?
What is the primary function of the substrate or laminate in a PCB?
What materials are a substrate or laminate typically made of?
What materials are a substrate or laminate typically made of?
Why is the metal foil referred to as cladding usually made of copper?
Why is the metal foil referred to as cladding usually made of copper?
What is the function of 'photoresist' in PCB manufacturing?
What is the function of 'photoresist' in PCB manufacturing?
What is the main difference between a 'negative-acting resist' and a 'positive-acting resist'?
What is the main difference between a 'negative-acting resist' and a 'positive-acting resist'?
What does the etchant solution typically do in the PCB manufacturing process?
What does the etchant solution typically do in the PCB manufacturing process?
What is the common etchant solution used in PCB's?
What is the common etchant solution used in PCB's?
What is the final step in the PCB manufacturing process?
What is the final step in the PCB manufacturing process?
Why are copper pattern surfaces usually covered with a thin coating of solder?
Why are copper pattern surfaces usually covered with a thin coating of solder?
What are CAD programs used for in PCB manufacturing?
What are CAD programs used for in PCB manufacturing?
What benefits are CAD software for PCB design?
What benefits are CAD software for PCB design?
In PCB design, what is the objective of component layout?
In PCB design, what is the objective of component layout?
In context of printed circuit board (PCB), what does PWB stand for?
In context of printed circuit board (PCB), what does PWB stand for?
In conductor pattern of PCB, the board is made from?
In conductor pattern of PCB, the board is made from?
What is the purpose of 'heat sinks' on PCBs?
What is the purpose of 'heat sinks' on PCBs?
Wires can cross in which type of PCBs?
Wires can cross in which type of PCBs?
What is the relationship between component mounting and soldering in basic single-sided PCBs?
What is the relationship between component mounting and soldering in basic single-sided PCBs?
How do double-sided PCBs differ from single-sided PCBs in terms of component and wiring capability?
How do double-sided PCBs differ from single-sided PCBs in terms of component and wiring capability?
In PCB manufacturing, what is the purpose of the etchant solution, and what is a common type of this solution?
In PCB manufacturing, what is the purpose of the etchant solution, and what is a common type of this solution?
What characteristics differentiate component mounting using Through Hole Technology (THT) from Surface Mount Technology (SMT)?
What characteristics differentiate component mounting using Through Hole Technology (THT) from Surface Mount Technology (SMT)?
How does the application of solder mask during PCB manufacturing contribute to the board's reliability and functionality?
How does the application of solder mask during PCB manufacturing contribute to the board's reliability and functionality?
Questions and Answers
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Flashcards
Flashcards
What is a PCB?
What is a PCB?
A flat insulating surface where wiring and miniaturized components connect in a pre-determined design.
What is a Terminal Board?
What is a Terminal Board?
An electrical component used in constructing electrical systems, consisting of a board or panel with multiple connection points.
What are tie-in points?
What are tie-in points?
Existing electrical connection points where new components are connected.
What are electrical fittings?
What are electrical fittings?
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What does a PCB do?
What does a PCB do?
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What is copper circuit pattern?
What is copper circuit pattern?
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What is a PCB board made of?
What is a PCB board made of?
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What is a conductor pattern?
What is a conductor pattern?
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What are component and solder sides?
What are component and solder sides?
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What are component sockets?
What are component sockets?
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What is an edge connector?
What is an edge connector?
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What do metallic tracks on a PCB do?
What do metallic tracks on a PCB do?
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What is a Solder mask?
What is a Solder mask?
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What is the Silk Screen?
What is the Silk Screen?
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What is solder-mask?
What is solder-mask?
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What are Single-Sided PCBs?
What are Single-Sided PCBs?
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What are Single Sided printed Circuit boards?
What are Single Sided printed Circuit boards?
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What are Double-Sided PCBs?
What are Double-Sided PCBs?
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What benefits do Double-Sided PCBs provide?
What benefits do Double-Sided PCBs provide?
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What are Multi-Layer Boards?
What are Multi-Layer Boards?
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What is PCB assembly?
What is PCB assembly?
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What is Through-Hole Technology (THT)?
What is Through-Hole Technology (THT)?
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What are some characteristics of Through Hole Technology (THT)?
What are some characteristics of Through Hole Technology (THT)?
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What is Surface Mount Technology (SMT)?
What is Surface Mount Technology (SMT)?
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What is a PCB substrate?
What is a PCB substrate?
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What is photoresist?
What is photoresist?
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What is the etching process?
What is the etching process?
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What is Solder Coating?
What is Solder Coating?
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What is the PCB design process?
What is the PCB design process?
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What is the last step of PCB design?
What is the last step of PCB design?
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Flashcards
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Study Notes
Study Notes
Printed Circuit Boards (PCBs)
- Printed Circuit Boards are commonly called PCBs.
- PCBs are also referred to as Printed Wiring Boards (PWBs).
- PCBs consist of a flat insulating surface upon which printed wiring and miniaturized components are connected following a predetermined design.
- Components connect to the board through printed wiring located on the reverse side.
- Interconnecting wiring is reduced to lines of conducting material such as copper, silver, or gold, deposited directly on the surface of the insulating circuit board.
- PCBs are easily used as plug-in units, eliminating terminal boards, fittings, and tie points.
- PCBs are found in almost every electronic device.
- PCBs keep components in place and provide connections between them.
- As electronic devices become more complex, PCBs have become more populated and dense with wiring and components.
- Basic PCBs have a copper circuit pattern or foil on one side of the board.
- Holes are drilled, component leads are inserted through the holes, and then soldered to the copper foil to complete circuit connections.
Conductor Pattern
- The board is made from an insulating and non-flexible material.
- Thin wires (tracks) on the surface are part of a copper foil that initially covered the whole board.
- The manufacturing process involves partially etching away copper foil.
- The remaining copper forms a network of thin wires referred to as the conductor pattern or tracks.
- The conductor pattern provides electrical connections between components mounted on the PCB.
Component Mounting
- To fasten components to a PCB, their legs are soldered to the conductor pattern.
- On basic PCBs (single-sided), components are on one side of the board, with the conductor pattern on the opposite side.
- Holes in the PCB allow the component legs to penetrate the board.
- Legs are soldered on the opposite side of where the components are mounted.
- The component side and solder side are the respective terms for each side of the board.
- Component sockets are used if a component needs to be removable.
- Sockets are soldered to the board, allowing component replacement without solder.
- Sockets are used to plug and unplug components on PCBs.
Edge Connectors
- Edge connectors are often used to connect one PCB to another.
- They consist of small uncovered copper pads (holes) located along one side of the PCB.
- These copper pads are part of the conductor pattern.
- An edge connector can be inserted into a matching connector (slot) on another PCB.
- The metallic tracks on the edge of the PCB engage with the contacts in the socket to provide an external electrical connection.
- In a PC, graphic cards connect to the main board using edge connectors.
Solder Mask and Silk Screen
- The solder mask gives the PCB its green, clear, or colored appearance.
- This mask is an insulating and protective coat.
- It protects the thin copper wires and prevents solder from attaching outside the connection points for components.
- On top of the colored mask a silk screen is printed.
- Silkscreen is text and symbols (often white) printed on the board to label locations and is also referred to as the legend,.
Silk Screen
- Part outlines and text cannot be drawn on the copper layer as they are electrically conductive and would interfere with the circuit.
- The silkscreen layer consists of ink that is non-conductive and can be placed on top of traces without interference.
Solder Mask
- Solder mask is a coating that protects the circuit from corrosion and electrical shorts.
- It keeps solder on the pads rather than flowing onto traces.
- The solder mask coats the entire board, except for the pads, allowing solder parts to them.
Types of PCBs
- Single-sided PCBs have components mounted on one side and a conductor pattern on the other.
- They are also known as Single-Sided PCBs.
- They have severe limitations when routing wires in a conductor pattern because no wires can cross.
- Single-sided PCBs are typically used in very basic circuits.
- Single-sided circuit boards have a single layer of conducting material on one side.
- Double-sided PCBs have a conductor pattern on both sides.
- The surface area for the conductor pattern is twice as large as with single-sided boards.
- Wires can cross by routing them on opposite sides.
- Double-sided PCBs are more suited for complex circuits than single-sided PCBs.
- They can mount conductive copper and components on both sides.
- Double-sided boards allow closer routing traces by alternating between top and bottom layers using vias.
- Usual layers used in single-sided PCBs, like substrate, copper, silkscreen, and solder mask, are applied to both sides.
- Multi-layer boards have one or more conductor patterns inside the board to increase the area available for wiring.
- Achieved by laminating boards together with insulating layers in between.
- Up to 100 layers can be made, though more than 6 or 8 is uncommon.
- All layers are almost always dedicated to Ground and Power.
- Layers are classified as Signal, Power, or Ground planes.
Assembly Methods
- Components are physically mounted to the board itself through a process known as the assembly process.
- The two main approaches to this process are:
- Surface Mount Technology (SMT) assembly.
- Through-Hole Technology (THT) assembly.
Through Hole Technology (THT)
- Through-hole components, soldered from the bottom side, are used with single-sided boards.
- Each component leg requires a hole to be drilled in the PCB.
- Their legs occupy space on both sides of the board.
- Components have better mechanical connections compared to surface mounts.
Surface Mounted Technology (SMT)
- Component legs are soldered to the conductor pattern on the same side as the components.
- No holes in the PCB are required for every component leg.
- Surface-mounted components can be mounted on both sides of the PCB.
- SMT components are much smaller than THT components, allowing more dense PCBs by forgoing ‘through hole’ component mounting.
- Component legs are often too small and difficult to solder by hand, so are typically machine soldered.
Printed Circuit Labels
- Foil patterns take various shapes that depend on the function of the circuit.
- Heat sinks dissipate heat from components and require large areas.
- Voltage and ground lines are long and slender and provide power to components on board.
- Terminals or pads are points drilled with holes to accommodate component leads.
- Conductors or runs are thin foil strips between components.
- Edge connectors are part of the foil that connects circuit boards to other boards to form a system.
Base or Substrate
- The base material of a PCB is typically referred to as the substrate or laminate.
- The substrate or laminate is an insulator, often made of phenolic paper, epoxy paper, or epoxy-reinforced glass fiber.
- Metal foil, referred to as cladding, is usually made of copper.
- The substrate board is made first, then cladding is bonded to it.
Photoresist
- Photoresist (or resist) is a light-sensitive material used in several processes to form a patterned coating on a surface.
- Circuit patterns are placed on copper cladding through several methods.
- Patterns may be chemically drawn, applied with special circuit tape, then produced by silk-screening or photographic means.
- Photographic methods are normally used when producing many boards.
- Copper must be cleaned of the oxide layer with chemical cleaners and then rinsed.
- Photoresist provides photo exposure of the circuit layout.
- Resist must be applied in a dark area to prevent exposure to ambient light.
Printed Circuit Drying
- A preheat step normally follows in the process, to dry the resist material.
Printed Circuit Photo Expose
- The next step is to photo-expose the circuit pattern onto the board.
- Negative-acting resist-A negative photoresist is a type of photoresist in which the portion of the photoresist that is exposed to light becomes insoluble in the photoresist developer; the unexposed portion is dissolved by the developer.
- Positive-acting resist – A positive photoresist is a type of photoresist in which the exposed portion becomes soluble to the photoresist developer, and the unexposed portion remains insoluble.
Etchant Solution
- The exposed board is placed into a solution called an etchant.
- The etchant dissolves the copper and resist that has been exposed to light.
- Ferric chloride (FeCl3) is the most often used etchant solution.
- The process typically involves immersing the PCB in the solution, which selectively removes copper in areas where the circuit pattern is to be formed.
- Finally, the board is placed into a cleaning solution to remove any traces of resist.
PCB Manufacture
- Copper tracks on PCBs are formed by using photoresist film, copper film, and base substrate.
Printed Circuit Finished
- Copper pattern surfaces are usually covered with a thin coating of solder.
- This solder coating:
- Reduces the effects of oxidation.
- Improves soldering process of components.
- Once applied, the finished printed circuit board is then dried.
PCB and Schematic Comparison
- The transition from circuit design to PCB design is based on circuit complexity.
- It can be done manually or, for complex circuits, with CAD programs.
- CAD programs are specifically for printed circuit board track layout.
PCB Manufacture Example
- Components on a circuit need to be mounted to a printed circuit board.
- Components are laid out on the board for ease and economy of construction.
- From here, the component layout is copied and a circuit track is designed. Once finalized, it is then used to manufacture the printed circuit board.
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