PCB circuit design and terminology
1, Annular Ring hole ring
Refers to the copper ring that is flat on the surface of the board outside the wall of the through hole. This hole ring is often connected to the outside ground by a cross bridge on the inner deck and is more often used as the end point or over station of the line. In addition to the over-station of the line on the outer layer, it can also be used as a pad for soldering the parts. There are also Pad (with circle), Land (independent point), etc., which are synonymous with this word.
2, Artwork negatives
In the circuit board industry, this word often refers to black and white negatives. As for the brown “Diazo Film”, it is also named after Phototool. The negatives used in PCBs can be divided into “original negatives” Master Artwork and retreaded “working negatives” Working Artwork.
3, Basic Grid basic square
Refers to the vertical and horizontal grid of the layout of the conductor layout when the board is designed. The early grid spacing was 100 mils, and the basic grid spacing has now shrunk to 50 mils due to the prevalence of fine lines.
4, Blind Via Hole blind guide hole
In a complex multi-layer board, some of the vias are deliberately incompletely drilled because only a certain number of layers are interconnected. If one of the holes is connected to the hole ring of the outer layer, such as a cup The special hole in the dead end is called the Blind Hole.
5, Block Diagram circuit system block diagram
The assembled board and various required components are framed by square or rectangular empty frames on the design drawing, and various electrical symbols are used to contact each frame one by one to form a systematic structure. Figure.
6, Bomb Sight bullet
Originally referred to as the bombardment of the bomber. PCB In the production of the film, the target for the upper and lower alignment is also set in each corner for the purpose of alignment. The more precise official name should be called Photographers’ Target.
7, Break-away panel can be broken
Refers to many small-area boards. For the convenience of plug-in, placement, soldering, etc. on the downstream assembly line, in the PCB process, it is combined on a large board for various processing. When finished, the knife is used to perform a partial cut between the individual small plates, but a few pieces of “strength” (Tie Bar or Break-away Tab) with sufficient strength are retained. A few holes are drilled between the sheet and the edge of the board; or the V-shaped notches are cut up and down to facilitate the assembly process, and the boards can be broken apart. This small board joint assembly method will become more and more in the future, and the IC card is an example.
8, Buried Via Hole buried hole
Refers to a partial via hole of a multi-layer board. When it is buried in the inner layer of the multi-layer board, it becomes an “internal through hole”, and is not “connected” with the outer layer board, and is called a buried guide hole or a buried hole.
9, Bus Bar
Multi-finger the cathode or anode rod itself on the plating bath, or the cable to which it is attached. In the circuit board of the “process”, the outer edge of the gold finger is close to the edge of the board, the original one is used for communication (the gold plating operation must be covered), and another small piece (both for saving) It is necessary to reduce the area as much as possible. It is connected to each finger. This conductive connection is also called Bus Bar. The small piece that connects the individual fingers to the Bus Bar is called the Shooting Bar. When the board finishes cutting, both will be cut off.
10, CAD computer aided design
Computer Aided Design uses a special software and hardware to digitally layout the board and convert the digital data into an original film by an optical plotter. This kind of CAD is more accurate and convenient than the manual method for the pre-production engineering of the circuit board.
11, Center-to-Center Spacing center spacing
Refers to the center-to-center Nominal Distance of any two conductors on the board. If the conductors are arranged in series, and the width and spacing are the same (such as the arrangement of the gold fingers), the “center-to-center spacing” is also called the pitch.
12, Clearance room, clearance, empty ring
It means that on the inner layers of the multi-layer board, if the conductor surface is not required to communicate with the hole wall of the through hole, the copper foil around the through hole can be etched away to form an empty ring, which is especially called “empty ring”. The distance between the green paint printed on the outer panel and the rings is also called Clearance. However, due to the increasing density of the board surface, the original space of this green paint has been pushed to almost nowhere.
13, Component Hole part hole
Refers to the through hole that is inserted into the foot of the board. The hole has an aperture of about 40 mil on average. Nowadays, after the SMT is popular, the large-caliber jack has been gradually reduced. Only a few of the gold pinholes of the connector need to be soldered, and most of the other SMD parts have been modified.
14, Component Side component surface
In the early days when the board was fully loaded with through-holes, the parts must be mounted on the front of the board, so it is also called the “component surface”. The opposite side of the board is also called the “Soldering Side” because it only passes through the solder wave. At present, SMT’s board has to be attached to both sides of the board, so there is no such thing as “component surface” or “solder surface”. It can only be called front or back. The name of the manufacturer of the electronic machine is usually printed on the front side, and the UL code and date of manufacture of the board manufacturer can be added to the reverse side of the board.
15, Conductor Spacing conductor spacing
Refers to the conductor of a board surface, from its edge to the edge of the nearest conductor, the span of the insulating substrate surface covered, that is, the conductor spacing, or commonly known as the spacing. Also, the Conductor is a generic term for various forms of metal conductors on a board.
16, Contact Area contact resistance
On the board is the contact point of the gold finger and the connector, the resistance that appears when the current passes. In order to reduce the formation of oxides on the metal surface, the positive gold finger portion and the negative clip of the connector are all plated with metal to prevent the occurrence of “loading resistance”. Plugs of other electrical products are squeezed into the socket, or there is contact resistance between the guide pin and its socket.
17, Corner Mark corner mark
On the board’s backsheet, special marks are often left at the four corners as the actual boundaries of the board. If the inner edges of these marks are wired, it is the boundary of the contour of the finished board contour (Contour).
18, Counterboring deep hole expansion, countersink
The circuit board can be screwed and fixed in the machine. The matching non-conducting hole (NPTH) must have a “reaming” that can accommodate the nut so that the entire screw can sink into the surface of the board. To reduce the obstacles caused by the appearance.
19. Crosshatching Crossing Area
Some large-area conductor areas on the board surface, in order to get better adhesion between the board surface and the green paint, often turn off some of the copper surface, leaving a number of crisscross cross lines. Such as the structure of the tennis racket, this will be able to solve the large area of copper foil, the floating crisis due to thermal expansion. The cross pattern obtained by etching is called Crosshatch, and this improvement is called Crosshatching.
20, Countersinking cone reaming, horn hole
It is another kind of screw hole for locking. It is mostly used in wood furniture and is rarely used in the precision electronics industry.
21, Crossection Area cross-sectional area
The size of the line cross-sectional area on the circuit board will directly affect its current-carrying capacity. Therefore, it should be listed first when designing. It often turns off some of the copper surface, leaving a number of criss-cross cross lines, such as tennis balls. The structure is the same, so that the large area of copper foil can be solved, and the floating crisis exists due to thermal expansion. The cross pattern obtained by etching is called Crosshatch, and this improvement is called Crosshatching.
22. Current-Carrying Capability
Refers to the wire on the board, which can continuously pass the maximum current intensity (amperes) under specified conditions without causing deterioration of the electrical and mechanical properties of the board. The maximum current amperage is The “current carrying capacity” of the line.
23. Datum Reference Baseline Reference
In the process of PCB manufacturing and inspection, in order to be able to correctly position the film pattern on the board surface, a certain point, line, or hole surface is selected as the reference for its figure, called Datum Point, Datum Line, Or Datum Level (Plane), also known as Datum Hole.
24, Dummy Land dummy pad
In order to grasp the height of the existing parts during assembly, the surface of the parts under the belly of some parts needs to be raised, so that the dispensing can have better adhesion. Generally, the etching technology of the board can be used to deliberately leave there. Dummy Land is used as a “fake copper pad” for padding without powering up. However, due to poor design on the board surface, a large area of copper-free substrate surface will appear, with a few through holes or lines. In order to avoid excessive current concentration of the independent conductors during copper plating, various non-functional dummy pads or false wires can be added, and some current is distributed during plating to make the current density of a few independent conductors. Not too high, these copper faces are also known as Dummy Conductors.
25, Edge Spacing board edge
Refers to the open space between the edge of the board and its “nearest conductor line”. The purpose of this open space is to avoid the problem that the conductor is too close to the edge of the board and may be short-circuited with other parts of the machine. Special attention to this project. Generally, the shortcomings such as white edge layering of the board cannot penetrate into the half of the width of the “edge”.
26, Edge-Board contact board gold finger
It is the exit of the whole board for external contact. Usually, there are two sides on the upper and lower sides of the board, which can be plugged into the matched board edge connectors.
27, Fan Out Wiring/Fan in Wiring fanout wiring / fan-in wiring
Refers to the wires and through-holes and other conductors drawn from the pads around the QFP, so that the soldered parts can be interconnected with the board. Since the rectangular pads are arranged very tightly, the external contact must be routed in a fan-shaped manner by means of an open space outside the rectangular pad square or the rectangular pad square ring, which is called “fan-out” or “fan-in”. Lighter, thinner and shorter dense PCBs, where more pads can be placed on the outer layer to take in more parts, and the wiring required for interconnection is hidden to the next layer. The connection between the pads and the leads between the different layers is directly connected by the blind holes in the pads, and there is no need to fan-out the fan-in wiring. At present, many high-function small-sized wireless telephones have adopted this new type of lamination. With the wiring method.
28, Fiducial Mark optical target, reference signal
For the downstream assembly of the board surface, it is convenient for the operation of the visual aid system. On the empty ground of the outer edge of each pad of the board assembly position, the large-scale IC adds a triangular “optical target” to the upper right and the lower left to assist. An example is the placement of the machine for optical positioning. The PCB process often adds more than two reference marks for the alignment of the film and the plate surface.
29, Fillet inner round fillet
Refers to two planes or two straight lines, in the case of an arc filled at its vertical intersection. In the circuit board, it is often referred to as the solder joint of the component lead, or the inner circle of the intersection of the T-shaped or L-shaped circuit of the board surface, etc., to enhance the mechanical strength and current circulation convenience.
30, Film negatives
Refers to the film of the existing line graphic. Usually available in thicknesses of 7 mils and 4 mils, the photosensitive film is black and white silver halide, and brown or other color azo compounds, also known as Artwork.
31. Fine Line Thin Line
According to the current technical standards, four lines between holes or an average line width of 5 to 6 mils or less are called thin lines.
32, Fine Pitch dense pitch, dense line distance, dense pad distance
Those with a Lead Pitch equal to or less than 0.635 mm (25 mil) are called a close distance.
33, Finger finger (continuous alignment of the board edge)
In order to enable the function of the whole assembly board to be externally contacted on the circuit board, a gold-plated continuous contact on the side of the board can be used to insert the clip on another system “female” continuous adapter to enable To achieve the purpose of interconnecting systems. The official name of Finger is “Edge-Board Contact”.
34, Finishing finishing, final repair
Refers to the final modification or finishing work of various finished products to make the product more beautiful, protective, and textured. Metal Finishing refers to metal parts or products, which are specially treated to enhance the corrosion protection function and view, such as various plating layers, anodized coatings, organic or inorganic coatings, etc. It.
35, Form-to-List wiring instructions list
A list of written instructions that indicate various cabling systems.
36, Gerber Date, Gerber File
It is a series of complete software files developed by Gerber Company for the circuit board circuit graphics and holes. The designer or the company that buys the board can convert all the graphic data of a certain item number into Gerber File (the official scientific name is “RS 274 format”), which is directly transmitted to the PCB manufacturer via Modem, and then from its own CAM. The medium output, combined with the operation of the laser plotter (Laser Plotter), results in drilling, testing, line film, green lacquer film, and even downstream assembly and other specific work materials, so that PCB manufacturers can immediately engage in proofing or production. Save a lot of communication and waiting time. This kind of circuit board “pre-production engineering” computer software of various materials, currently in the global industry are based on Gerber File. In addition, there is another software development of IPC-D-350D, but it is still not widely used.
37, Grid standard grid
Refers to the basic latitude and longitude squares when the board is wired. The early long and wide grids are each 100 mils, which is based on the pitch of the “integrated circuit” (IC) pin. This Grid is approached to 50 mils or even 25 mils. Located at the intersection of the grid