PWB vs PCB: Differences and Similarities

PWB and PCB are printing wiring boards and printed circuit boards. These terms are used for boards that offer physical support and electrical connections for components. Both are commonly used in electrical and electronic devices, but some differences will be covered here. So let’s get started with PWB vs PCB: Differences and Similarities.

What is a PWB Printed Wiring Board?

• The PWB stands for printed wiring board. PWB comes with an epoxy glass substrate that makes interconnections for making circuits. With that, PWB also involves creating an electrical network on the substrate.
• The PWB uses conductive paste for configuration circuits. The electrical connection is made on a conductive plate. PWB is the board where components are mounted and then connected.
• On this board, engineers connect wires from point to point on a dielectric substrate.
• PWB does not have a printed circuit. PWB board is made for the creation of substrate without components.
• The manufacturing comes with etching materials for conduction insulating between traces.
• On this board, conductive layers are connected on PWB with plated through holes. Hole used for connection of electronic components.

What is the PCB Board?

PCB full form is a printed circuit board, and it is a method that helps conductors to move from one side of the board to another side.

PCB boards are component configured. These boards come with electronic components on the surface.

The PCB board has conductive layers where components are connected and current flows them to complete the circuit work.

Different types of PCB boards are used based on layers and structures such as single-sided, double-sided, and multiple-layer.

Difference between PWB and PCB

• PCB stands for printed circuit board and PWB is printed wiring board.
• PCB and PWB are considered as same but PCB is mostly used.
• Both PCB and PWB define electrical boad created as one or more layers of copper laminated on the conductive plastic panel that supports and connects components with conductive layers.
• In some countries such as Japan, most PWB is used as compared to PCB.
• PWB is used earlier in industries for early phases when the circuit comes with a point-to-point connection. After that conductors are connected from one side of the board to another or from one layer to another and the board is made to come with a certain effect than point to a point-to-point connection
• PCB is then replaced with point-to-point wired boards. IN 1999 IPC referred to the use of PCB

Terms Related to PWB and PCB

PCBA is referred to as printed circuit board assembly. When PCB is assembled called PCBA.

Since 1999 PCBA has been used term for all assembled circuit boards.

PWA is printed wire assembly and archaic for PCBA.

CCA is a circuit card assembly and is like PCBA but CCA is less used.

PCA is a printed circuit assembly and is also like PCBA.

PWB, PCB, and circuit cards are the same terms and are defined as bare PCB boards and PCA, CCA, PWA,, and PCBA are the same and used for assembled circuit boards.

Materials Used for PWBs and PCBs

Conductive layer

• Copper gold and silver are commonly used materials in PCB boards for signal transmission on the conductive layer. Gold comes with good conductivity and less resistance, its high prices limit its use. Copper is best for PWB and PCB uses since it is less costly and provides good conduction. Copper layers can used on board through a process called etching, or pre-made copper foil strips on board.

Non-conductive Layer

• Low-conductivity materials make non-conductive layers. This layer uses FR4, a composite epoxy material, and ceramic. Mostly FR4 is used to enhance dielectric operation. Ceramic design substrates are best for high-power uses since have a high heat conductivity rate.

Prepreg Substance

• These materials are used in PWB and PCB. It keeps layers configured with each other such as board core. Manufacturers use resin-impregnated fiberglass when heated. It binds the layers before hardening and reinforcing bonds when cooled, it helps to minimize vibration and shock affect

Solder

• Solder paste is used on circuit boards, solder comes with tin and lead, that used for component connection to avoid copper from oxidation.

Coating

• Conductive traces can coated to avoid corrosion with the use of gold, silver, nickel,  and tin, offering protection from dust and moisture.

PWB Assembly Process

Solder paste

• It is the first phase of PWB assembly, solder paste is used for all parts where soldering is used. It is done before components mount on PWB. Component pads are points that need solder paste. Solder paste is a mixture of flux and grains of solder. The assembler puts the solder screen on PWB, and the screen moves and deposits solder paste on the screen through holes in the board. Assembler control solder paste amount for accurate joint creation.

Component placement

• It is the main step in PWB assembly and comes with a component connection on PWB. Components are connected to PWB. The solder component on the surface of the board is done. In earlier times manual process used pick and place components on PWB with the use of tweezers. But now the machine is used to pick and place components.

Reflow soldering

• In this process solder paste is solifiy. Solder paste and mounted components should be put in place PWB assembler is done through reflow. After component placement, the assembler shifts the board to the conveyor belt. The belt passes through the reflow oven. The oven is like the commercial pizza oven. The reflow oven comes with different heaters. Heater heated wiring board on set temperature. Solder paste melts and melted solder passes through cool heaters that cool and become solid

Inspection and test

• Inspection is time time-consuming process, but it is important. After board assembly completion inspection is done. Detailed inspection helps to detect faults or errors in PWB assembly. AOI inspection is used on printed wiring board assembly.

PWB Types and Manufacturing Process

Types

• PWBs are defined in different ways, for complicity is classified based on several layers. According to layers, PWB boards are of three types.
• Single-side, double-sided, and multilayer board
• There are two layers of circuits in multilayer PWB. That means it has one layer in the substrate below the board surface.
• The multilayer PWB comes with different interconnected layers. Common layer configurations are 4, 6, and 8 layers.
• Double-sided PWBs come with two interconnected layers. This PWB is easy to make as compared to multilayer. Single-sided PWB comes with a layer of circuitry.
• PWBs also are classified on the base of material. There are 3 types of boards based on materials flexible, rigid, and rigid-flex.
• Flexible PWB comes with polyester and polyimide substrate. These boards are flexible and best to use for different uses.
• Flexible PWBs easily bend and can handle many flexing cycles.
• Rigid PWB uses glass-reinforced epoxy resing for board creation. The thickness of rigid PWB is less thatn 0.1 inches. The rigid-flex PWB comes with rigid and flexible boards.

Manufacturing Methods

• There are two types of PWB based on the manufacturing process. The first one is subtractive and 2nd one is additive processing.
• Subtractive processing comes with removing copper selectivity from PWB to make a circuit. Manufacturers added other metals at the time of the plating process.
• Subtractive processing uses image transfer from an image file to the copper circuit on a board.
• Additive processing is the process where an image is made with the use of copper. This process does not come with etching or copper removal. The additive method used for the production of PWB

Read also:

• What is Ball Grid Array (BGA) on a PCB Board
• Industrial Control PCB Board
• Introduction to PCB Boards Inks, Types, Uses, & Applications
• How to Reduce the PCB Board Size for Projects
• Special Processes for Flexible PCB
• Difference between Double sided and Multilayer PCB Board

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