PCB Encapsulation defines the physical interface between electronic components and the PCB, providing the necessary information for PCB assembly and maintenance, such as the shape and symbol of the component, the number and location of pads, reference pins, polarity, and more.
Each component placed on the PCB must have its own package, which includes the copper area on the PCB where the component will be soldered. For example, a 16-pin SSOP package contains 2 rows of 8 rectangular pads each.
The image below depicts the footprint of a general purpose electronic component in a 16-pin SSOP package. The red part corresponds to the copper area on the layer, while the other colors represent the mechanical type layer.
There are several types of PCB packages, with the most common being:
1、 SOP (Small Outline Package)
This is the smallest footprint used for integrated circuits (ICs), typically measuring around 0.4″ x 0.4″.
2、QFP (Quad Flat Package)
This package typically has a larger PCB footprint compared to other ICs and integrated circuits, usually around 0.8″ x 0.8″, but can also be as large as 1″ x 1″.
3、BGA (Ball Grid Array)
This is a larger PCB package designed for ICs with numerous connections. Typically rectangular in shape with pins on all sides, allowing for flexibility in orientation. The size of the BGA package varies significantly based on the number of connections per IC, ranging from 0.5″ x 0.5″ to over 2″ x 2″.
1、Pads / Holes
Used to indicate the assembly of SMD component pads or holes used to fix the location of through-hole components, which is critical to the soldering, must be precisely defined.
2、Outline of the component
Can be defined as the protected area of the PCB package in which other components can be placed, the boundary defines the entire body of the component and is responsible for defining the main layers of the component shape.
3、Reference Indicator
That is, a letter or number code used to uniquely identify the schematic and PCB layout components. The following figure shows some reference indicators, for example, R3 for resistors and C5 for capacitors.
4、Pin 1 Indication
When placing components with a large number of pins (such as integrated circuits), it is important to clearly indicate the location of pin 1 on the package to prevent any confusion during the assembly stage. This is particularly crucial for components with QFP or DIP packages. The indication can be a white circle, a triangle, or a square, as illustrated below.
5. Mechanical Information
Some components may have mechanical parts or protrusions that extend over other components, potentially causing collisions or overlaps between components, such as a heat sink.
6. 3D Models and Symbols
Each PCB package includes a symbol in the schematic and, in most cases, a corresponding 3D model. This enables designers to generate a 3D model of the entire board, ensuring correct positioning and distances between components.
The figure below shows the complete PCB associated with an open source project containing highly integrated SMD components, including FPGAs. Upon examining the packages of all these components, as well as the arrangement and relative spacing of the pads, a dot (or circle) is included to identify pin 1. It is also worth noting that the component symbol for the X1 oscillator is displayed.
For PCB packaging, there are specific internationally applicable standards for defining packages, schematic symbols and 3D models.
1、IPC 7351 (PCB package)
The IPC 7351 standard (specifically, IPC-SM-7351-B) defines a set of equations that control the size of the pads around a component. Components complying with IPC 7351 will be designed in accordance with these standards.
2、ANSI Y32.2-1975 (schematic symbols)
This standard defines a list of graphical symbols used in electrical and electronic drawings and a series of category name letters. Some CAD tools engineers can set up themselves, but most CAD tools are default.
3、ISO 10303-21 (3D Models)
The ISO 10303-21 standard defines the file format used for STEP models that can be imported into 3D CAD software. The standard is more of a file format specification than a requirement for drawing component packages.
1、Pad Size
The size of the pad must be appropriate for the component leads or pins to allow for safe soldering and electrical connections. PCB pad size is typically specified in the component data sheet, or you can refer to standards such as IPC-7351B for guidance.
2、Pad Spacing
The spacing between pads should be suitable for the component leads or pins to facilitate proper soldering and electrical connections. Pad spacing information can be found in the component data sheet or determined using PCB design standards.
3、Pad Shape
Pads should be shaped to match the component leads or pins for safe soldering and electrical connections. The shape of the pad is typically specified in the component data sheet or determined using PCB design standards.
4、Through-Hole Placement
Accurate placement of through-holes is essential for ensuring proper alignment and secure connections of through-hole components. The location of the through-hole is usually specified in the component data sheet or determined using PCB design standards.
5、Reference Marks
Correct placement of reference markers is crucial for clear and accurate component identification. Reference markers are typically specified in the component data sheet or determined using PCB design standards.
6、Clearance and Creepage Distance
Adequate clearance and creepage distances between components and the rest of the PCB are necessary to prevent electrical shorts and ensure safety. Minimum clearance and creepage distances are typically specified in industry standards like IPC-7351B or IPC-SM-782.
7、Alignment Width
The width of alignments should be suitable for the current flowing through them to ensure a stable and reliable electrical connection. Width is determined by design rules considering voltage, current levels, length, and temperature of the alignment.
An example of a correctly designed PCB package is provided.
As a PCB expert, I would like to provide some insights on PCB packaging.
Each component placed on the PCB must have its own package, which includes the copper area on the PCB where the component will be soldered. For example, a 16-pin SSOP package contains 2 rows of 8 rectangular pads each.
The image below depicts the footprint of a general purpose electronic component in a 16-pin SSOP package. The red part corresponds to the copper area on the layer, while the other colors represent the mechanical type layer.
There are several types of PCB packages, with the most common being:
1、 SOP (Small Outline Package)
This is the smallest footprint used for integrated circuits (ICs), typically measuring around 0.4″ x 0.4″.
2、QFP (Quad Flat Package)
This package typically has a larger PCB footprint compared to other ICs and integrated circuits, usually around 0.8″ x 0.8″, but can also be as large as 1″ x 1″.
3、BGA (Ball Grid Array)
This is a larger PCB package designed for ICs with numerous connections. Typically rectangular in shape with pins on all sides, allowing for flexibility in orientation. The size of the BGA package varies significantly based on the number of connections per IC, ranging from 0.5″ x 0.5″ to over 2″ x 2″.
1、Pads / Holes
Used to indicate the assembly of SMD component pads or holes used to fix the location of through-hole components, which is critical to the soldering, must be precisely defined.
2、Outline of the component
Can be defined as the protected area of the PCB package in which other components can be placed, the boundary defines the entire body of the component and is responsible for defining the main layers of the component shape.
3、Reference Indicator
That is, a letter or number code used to uniquely identify the schematic and PCB layout components. The following figure shows some reference indicators, for example, R3 for resistors and C5 for capacitors.
4、Pin 1 Indication
When placing components with a large number of pins (such as integrated circuits), it is important to clearly indicate the location of pin 1 on the package to prevent any confusion during the assembly stage. This is particularly crucial for components with QFP or DIP packages. The indication can be a white circle, a triangle, or a square, as illustrated below.
5. Mechanical Information
Some components may have mechanical parts or protrusions that extend over other components, potentially causing collisions or overlaps between components, such as a heat sink.
6. 3D Models and Symbols
Each PCB package includes a symbol in the schematic and, in most cases, a corresponding 3D model. This enables designers to generate a 3D model of the entire board, ensuring correct positioning and distances between components.
The figure below shows the complete PCB associated with an open source project containing highly integrated SMD components, including FPGAs. Upon examining the packages of all these components, as well as the arrangement and relative spacing of the pads, a dot (or circle) is included to identify pin 1. It is also worth noting that the component symbol for the X1 oscillator is displayed.
For PCB packaging, there are specific internationally applicable standards for defining packages, schematic symbols and 3D models.
1、IPC 7351 (PCB package)
The IPC 7351 standard (specifically, IPC-SM-7351-B) defines a set of equations that control the size of the pads around a component. Components complying with IPC 7351 will be designed in accordance with these standards.
2、ANSI Y32.2-1975 (schematic symbols)
This standard defines a list of graphical symbols used in electrical and electronic drawings and a series of category name letters. Some CAD tools engineers can set up themselves, but most CAD tools are default.
3、ISO 10303-21 (3D Models)
The ISO 10303-21 standard defines the file format used for STEP models that can be imported into 3D CAD software. The standard is more of a file format specification than a requirement for drawing component packages.
1、Pad Size
The size of the pad must be appropriate for the component leads or pins to allow for safe soldering and electrical connections. PCB pad size is typically specified in the component data sheet, or you can refer to standards such as IPC-7351B for guidance.
2、Pad Spacing
The spacing between pads should be suitable for the component leads or pins to facilitate proper soldering and electrical connections. Pad spacing information can be found in the component data sheet or determined using PCB design standards.
3、Pad Shape
Pads should be shaped to match the component leads or pins for safe soldering and electrical connections. The shape of the pad is typically specified in the component data sheet or determined using PCB design standards.
4、Through-Hole Placement
Accurate placement of through-holes is essential for ensuring proper alignment and secure connections of through-hole components. The location of the through-hole is usually specified in the component data sheet or determined using PCB design standards.
5、Reference Marks
Correct placement of reference markers is crucial for clear and accurate component identification. Reference markers are typically specified in the component data sheet or determined using PCB design standards.
6、Clearance and Creepage Distance
Adequate clearance and creepage distances between components and the rest of the PCB are necessary to prevent electrical shorts and ensure safety. Minimum clearance and creepage distances are typically specified in industry standards like IPC-7351B or IPC-SM-782.
7、Alignment Width
The width of alignments should be suitable for the current flowing through them to ensure a stable and reliable electrical connection. Width is determined by design rules considering voltage, current levels, length, and temperature of the alignment.
An example of a correctly designed PCB package is provided.
As a PCB expert, I would like to provide some insights on PCB packaging.
