PCB circuit design and technical terms

- Nov 27, 2019-

PCB circuit design and technical terms

1.Annular Ring

Refers to the copper ring that is affixed on the surface of the board around the wall of the hole. This hole ring on the inner layer board is often connected to the outer earth by a cross bridge, and is more often used as the end point or crossing of the line. In addition to being used as a station for wiring, the outer layer board can also be used as a pad for part pin welding. Synonymous with this word are Pad (distribution ring), Land (independent point) and so on. 2.Artwork negatives

In the circuit board industry, this word often refers to black and white negatives. The brown "Diazo Film" is named after Phototool. The negatives used by PCB can be divided into "original negatives" Master Artwork and "photographic negatives" Working Artworks. 3. Basic Grid

Refers to the vertical and horizontal grids where the conductor layout of the circuit board is positioned during design. The early grid spacing was 100 mil. At present, due to the popularity of fine lines and dense lines, the basic grid spacing has been reduced to 50 mil.

4.Blind Via Hole

Refers to a complex multilayer board, because some of the vias only need a few layers of interconnection, deliberately and incompletely drilled through. If one of the holes is connected to the ring of the outer board, this is like a cup The special hole in the dead end is called "Blind Hole".

5.Block Diagram

Assemble the assembly board and various required components in the design drawing with a square or rectangular empty frame, and use various electrical symbols to connect the relationships of each frame one by one to make a systematic architecture. Illustration.

6.Bomb Sight bullet

Originally referred to the bomber's aiming screen. During the production of the PCB, the target for the alignment of the upper and lower layers is also set in each corner for the purpose of alignment. The more accurate official name of the PCB should be called Photographers' Target.

7.Break-away panel

Refers to many small-area circuit boards. For the convenience of plug-in, placing, and soldering operations on downstream assembly lines, they are combined on a large board in the PCB manufacturing process for various processing. When the work is completed, the cutting mode is used to locally cut out (Routing) between the independent small plates, but a few "Tie Bars" or "Break-away Tabs" with sufficient strength are retained. Drill a few small holes between the plate and the edge of the board; or cut the V-shaped notches up and down to facilitate the breaking of the boards after the assembly process is completed. This kind of small board joint assembly method will be more and more in the future, IC card is an example.

8.Buried Via Hole

Refers to a local via hole of a multilayer board. When it is buried in the internal layers of the multilayer board and becomes an "internal via hole", and it is not "connected" with the outer layer board, it is called a buried via hole or simply a buried hole.

9.Bus Bar

Multi-finger refers to the cathode or anode rod itself on the plating tank, or the cable connected to it. In the "process" circuit board, the outer edge of the gold finger is close to the edge of the board, and there is an original connecting wire (which must be covered during the gold plating operation), and then a small narrow piece (both to save gold) Need to reduce its area as much as possible) and each finger is connected, this kind of conductive connection is also called Bus Bar. The small piece connected to the Bus Bar with each individual finger is called Shooting Bar. When the board finishes cutting the shape, both will be cut off together.

10.CAD computer-aided design

Computer Aided Design uses special software and hardware to digitize the layout of the circuit board, and uses an optical plotter to convert the digital data into original negatives. This kind of CAD is more accurate and convenient for circuit board pre-manufacturing than manual method.

11.Center-to-Center Spacing

Refers to the Nominal Distance of the center to center of any two conductors on the board. If successive conductors are arranged with the same width and pitch (such as the arrangement of gold fingers), then this "center-to-center spacing" is also called pitch.

12, Clearance room, clearance, empty ring

Refers to the inner layer of the multilayer board, if you do not want its conductor surface 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 called "empty ring". The distance between the green lacquer printed on the outer plate surface and each ring is also called Clearance. However, due to the increasing density of circuit boards, the original room for this kind of green paint has been squeezed to almost nowhere.

13.Component Hole

Refers to the through-holes through which the foot of the part is inserted. The hole diameter of this foot hole is about 40 mils on average. Now that SMT is prevailing, the large-aperture jacks have gradually decreased, leaving only a few gold pinholes for connectors that still need to be soldered. Most of the other SMD parts have been surface-bonded.

14.Component Side

In the early days when the circuit board was fully inserted through-holes, the parts must be installed on the front side of the board, so it is also called the "assembly side". The back side of the board is also called "Soldering Side" because it only allows the solder wave to pass through. At present, SMT boards need to be bonded to both sides of the board, so there is no so-called "component side" or "solder side", it can only be called the front side or the reverse side. Usually the name of the electronic machine's manufacturer is printed on the front side, and the UL symbol and production date of the circuit board manufacturer can be added on the reverse side of the board.

15.Conductor Spacing

Refers to a conductor on the circuit board surface, from its edge to the edge of another nearest conductor, the span of the insulating substrate surface covered by it, which is called the conductor spacing, or commonly known as the spacing. Also, Conductor is a general term for various forms of metal conductors on a circuit board.

16.Contact Area

On the circuit board, it refers to the contact point between the gold finger and the connector, which is the resistance that appears when the current passes. In order to reduce the formation of oxides on the metal surface, usually the positive gold finger part and the female clip of the connector need to be plated with metal to prevent the occurrence of "load resistance". The plug of other electrical appliances is squeezed into the socket, or there is contact resistance between the guide pin and its socket.

17.Corner Mark

On the negatives of circuit boards, special marks are often left at the four corners as the actual boundary of the board. If the inner edges of these marks are connected, it is the boundary of the contour of the finished board.

18. Counterboring fixed depth reaming, countersinking

The circuit board can be fixed in the machine with screws. The matching non-conducting hole (NPTH) must have an "opening" for the nut to allow the entire screw to sink into the board. In order to reduce the obstacles caused by appearance.

19.Crosshatching

Some large-area conductor areas on the circuit board surface, in order to obtain better adhesion between the board surface and the green paint, often the copper surface of the sensing part is turned away, leaving a number of cross lines that cross vertically Like the structure of a tennis racket, this will eliminate a large area of copper foil, and the floating crisis due to thermal expansion. The etched cross pattern is called Crossshatch, and this improvement is called Crosshatching.

20. Countersinking cone reaming, horn hole

It is another type of screw hole for locking. It is mostly used in woodworking furniture and rarely appears in the precision electronics industry.

21.Crossection Area

The size of the cross-sectional area of the circuit board will directly affect its current carrying capacity. Therefore, it should be included first when designing. The copper surface of the sensing part is often turned away, leaving a number of cross lines, such as tennis. The structure of the film is the same. In this way, a large area of copper foil can be eliminated, and the floating crisis due to thermal expansion. The etched cross pattern is called Crossshatch, and this improvement is called Crosshatching.

22.Current-Carrying Capability

Refers to the wires on the board that can pass the maximum current strength (amps) continuously under specified conditions without causing degradation of the electrical and mechanical properties of the circuit board (Degradation). The amperage of this maximum current is The "current carrying capacity" of the line.

23.Datum Reference

In the PCB manufacturing and inspection process, in order to correctly position the negatives on the board surface, a certain point, line, or hole surface is specifically selected as the reference reference for the figure, which is called Datum Point, Datum Line Also known as Datum Level (Plane), also known as Datum Hole.

24.Dummy Land

In order to hold the height of the existing parts during assembly, the board surface of some parts needs to be raised so that the adhesive can have better adhesion. Generally, the etching technology of the circuit board can be used to intentionally leave it there. "Fake copper pads" that are not used for power-up but only for padding are called Dummy Land. However, sometimes due to poor design on the board surface, there will be a large area of the substrate surface without a copper layer, with a few through holes or lines distributed. In order to avoid excessive current concentration of these independent conductors during copper plating, and for various defects, it is also possible to add some non-functional dummy pads or wires, and share some current during plating, so that the current density of a few independent conductors Not too high, these copper faces are also called Dummy Conductors.

25.Edge Spacing

Refers to the open space from the edge of the board to its "closest conductor line". The purpose of this open space is to avoid the problem that the conductor may be short-circuited with other parts of the machine because the conductor is too close to the edge of the board. This project is particularly particular about it. Disadvantages such as the white edge delamination of general boards cannot penetrate half of the width of this "edge".

26.Edge-Board contact gold finger

It is the outlet for the external connection of the whole board. Usually, the upper and lower symmetrical sides of the board edge are usually set and can be inserted into the matched board edge connector.

27. Fan Out Wiring / Fan in Wiring

Refers to the conductors such as the lines and through holes led by the solder pads around the QFP, so that the soldered parts can complete the interconnection with the circuit board. Because the rectangular solder pads are arranged very closely, the external contact must use the open space inside the square pad of the rectangular pad or outside the square pad of the rectangular pad and route it in a fan-shaped manner, which is called "fan-out" or "fan-in". Lighter, thinner and shorter dense PCBs can be equipped with more pads on the outer layer to accept more parts, and hide the wiring required for interconnection to the next layer. The connection between the solder pads and the leads between different levels is directly connected by blind holes in the pads, and there is no need to do fan-out fan-in wiring. At present, many high-function small-sized wireless phone handset boards use this new type of stack. And wiring method.

28. Fiducial Mark optical target, reference signal

In order to facilitate downstream assembly on the board surface and facilitate the operation of its visual aid system, a large-scale IC is added to the open space on the outer edge of each pad on the board assembly position, and a triangular "optical target" is added to the upper right and lower left to assist An example is the placement of a machine for optical positioning. For the PCB process, in order to align the negative and the surface of the board, more than two reference marks are often added.

29. Fillet inner fillet

Refers to two planes or two straight lines, in terms of arcs filled at their vertical intersections. In the circuit board, it is often referred to as the padding of the pin of the part, or the inner circle of the T-shaped or L-shaped line on the board, to enhance the mechanical strength and the convenience of current flow.

30. Film

Refers to the film of the existing circuit pattern. Usually there are two thicknesses of 7mil and 4mil. The photosensitive film includes black and white silver halide, and brown or other color azo compounds. This term is also called Artwork.

31.Fine Line

According to the current technical level, the four lines between the holes or the average line width of 5-6mil or less is called a thin line.

32. Fine pitch pitch, dense line pitch, dense pad pitch

Where the lead pitch is equal to or less than 0.635mm (25mil), it is called dense pitch.

33. Fingers (continuously arranged contacts on the edge of the board)

On the circuit board, in order to enable the function of the entire assembly board to communicate with each other externally, a gold-plated continuous contact on the side of the board can be used, and it can be inserted and clamped on the female continuous connector of another system to enable. To achieve the purpose of interconnected systems. Finger's official name is "Edge-Board Contact".

34.Finishing

Refers to the final modification or trimming of various finished products in appearance to make the product more beautiful, protective, and textured. Metal Finishing refers specifically to metal parts or products. The externally treated layers are specially added to enhance the anti-corrosion function and appearance. Of it.

35. Form-to-List wiring instruction list

A written description list indicating various wiring systems.

36. Gerber Date, Gerber File

It is a series of complete software files developed by American company Gerber for circuit board surface pattern and holes. The designer or the company that buys the board can convert all the graphic data of a material number into a Gerber File (official scientific name is "RS 274 format"), transfer it directly to the PCB manufacturer through the Modem, and then from its own CAM The middle output, combined with the operation of the Laser Plotter, can obtain drilling, testing, circuit negatives, green paint negatives ... and even downstream assembly and other specific operating data, so that PCB manufacturers can immediately engage in proofing or production, Save a lot of communication and waiting time. This kind of computer software for "pre-manufacturing" of circuit boards uses Gerber File as the standard operation in the global industry. In addition, another set of software for IPC-D-350D has been developed, but it has not yet been widely used.

37.Grid Standard Grid

Refers to the basic longitude and latitude grids of the circuit board wiring pattern. In the early days, the long and wide grid spacing was 100 mil, which is based on the pitch of the "Integrated Circuit" (IC) pins. This kind of Grid is approached to 50 mil or even 25 mil. Located at the intersection of the grid is called On Grid.

38.Ground Plane

 


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