Explore the Mysteries of Multilayer Circuit Boards
The iPhone 7 is coming. Everyone is talking about how beautiful the curved screen of the iPhone 7 is, how cool the 3D touch technology is, and it is waterproof and wirelessly charging. Let ’s make it more important. As engineering students, we must defend our dignity in the topic. We may need to analyze its essence through these cool appearance functions, such as its entire “skeleton” —circuit board, scientific name PCB .
Figure 1 Traditional mobile phone deconstruction
PCB, PrintedCircuitBoard printed circuit board, is both a support for electronic components and a carrier for electrical connection of electronic components. Before the advent of PCBs, the connection between electronic components was accomplished by direct wire connections; today, the wire connection method is only used in laboratory tests, and PCBs have occupied absolute control in the electronics industry.
History, PCB past and present
The history of PCB development can be traced back to the early 20th century. In 1936, the Austrian Paul Eisler applied PCBs to radios, putting PCBs into practical use for the first time; in 1943, the United States widely applied the technology to military radios; in 1948, the United States officially recognized that the invention could be used business use. As a result, PCBs have been widely used since the mid-1950s, and have subsequently entered a period of rapid development.
Figure 2 PCB father Paul Eisler
As PCBs become more and more complex, when designers use development tools to design PCBs, it is easy to get confused about the definition and use of each board layer. When our hardware developers draw the PCB by themselves, it is easy to cause unnecessary misunderstandings in production because they are not familiar with the purpose of the PCB layers. In order to avoid this situation, we will use AltiumDesignerSummer09 as an example to introduce the classification of each PCB layer.
Differences between PCB layers
Signal Layer (SignalLayers)
AltiumDesigner can provide up to 32 signal layers, including top layer (TopLayer), bottom layer (BottomLayer) and middle layer (Mid-Layer). The layers can be connected to each other through vias, blind vias, and buried vias.
Figure 3 PCB hole
1, the top signal layer (TopLayer)
Also called component layer, it is mainly used to place components. For double-layer boards and multilayer boards, it can be used to arrange wires or copper.
2.Bottom signal layer (BottomLayer)
Also called solder layer, it is mainly used for wiring and soldering. It can be used to place components for double-layer boards and multilayer boards.
There can be up to 30 layers, which are used to arrange signal lines in multi-layer boards. Power lines and ground lines are not included here.
Internal power planes (InternalPlanes)
Generally referred to as the internal electrical layer, it only appears in multilayer boards. The number of PCB layers generally refers to the sum of the sum of the signal layer and the internal electrical layer. Similar to the signal layer, the internal electrical layer and the internal electrical layer and the internal electrical layer and the signal layer can be connected to each other through through holes, blind holes, and buried holes.
Figure 4 PCB layers
A PCB board can have a maximum of 2 silkscreen layers, which are the top silkscreen layer (TopOverlay) and the bottom silkscreen layer (bottomoverlay). They are generally white and are mainly used to place printed information, such as component outlines and annotations, and various comments Characters, etc., to facilitate PCB component welding and circuit inspection.
1.Top silk screen layer (TopOverlay)
Used to mark the projected outline of a component, the component's label, nominal value or model, and various comment characters.
As with the top silkscreen layer, if all labels marked on the top silkscreen layer are already included, the bottom silkscreen layer can be turned off.
The mechanical layer is generally used to place indicative information about the board making and assembly methods, such as the overall dimensions of the PCB, size marks, data materials, via information, assembly instructions, and other information. This information varies depending on the requirements of the design company or PCB manufacturer. The following examples illustrate our common methods.
Mechanical1: Generally used to draw the border of the PCB as its mechanical shape, so it is also called the shape layer;
Mechanical2: We used to place the PCB processing process requirements form, including size, plate, board layer and other information;
Mechanical13 & Mechanical15: the body size information of most components in the ETM library, including the three-dimensional models of the components; for the simplicity of the page, this layer is not displayed by default;
Mechanical16: The footprint area information of most components in the ETM library can be used to estimate the PCB size early in the project; for simplicity of the page, this layer is not displayed by default, and the color is black.
Masking Layers (MaskLayers)
AltiumDesigner provides two types of mask layers (SolderMask) and PasteMask (MaskLayers). There are two layers: top layer and bottom layer.