PCB Tech - PCB printed circuit board special processing technology

Additive Process

refers to the non-conductor substrate surface, with the assistance of an additional resist, the direct growth process of local conductor lines with an electroless copper layer (see Circuit Board Information Issue 47 P.62 for details). The addition method used in PCB copy board can be divided into different methods such as full addition, half addition and partial addition.

Backpanels, Backplanes support plate

is a thicker (such as 0.093", 0.125") circuit board, which is specially used to connect other boards. The method is to first insert the multi-pin connector (Connector) into the tight through hole without soldering, and then wire the wires one by one on the guide pins of the connector passing through the board. A general PCB copy board can be inserted into the connector. Because of this special board, the through hole cannot be soldered, but the hole wall and the guide pin are directly clamped for use, so its quality and aperture requirements are particularly strict, and its order quantity is not very large, and general circuit board manufacturers are not willing It is not easy to accept such orders, and it has almost become a high-grade specialized industry in the United States.

Co-Firing

is a process in which ceramic hybrid PCB circuit boards (Hybrid) are made. The circuits on which various types of precious metal thick film paste have been printed on the small board are fired at high temperature. The various organic carriers in the thick film paste are burned away, leaving the lines of precious metal conductors as interconnecting wires.

Crossover is the three-dimensional cross of two wires that cross the board, and the gap between the intersections is filled with insulating medium. Generally, the addition of carbon film jumpers on the green paint surface of the single-sided board, or the wiring of the upper and lower layers of the build-up method are all such "crossovers".

Discreate Wiring Board scattered wire PCB circuit board, double wire board

is another term for Multi-Wiring Board, which is formed by attaching a round enameled wire to the board surface and adding through holes. The performance of this kind of multi-line board in terms of high-frequency transmission line is better than the flat square circuit formed by etching of general PCB.

In addition to precious metal chemicals, Frit glass frit is used in Poly Thick Film (PTF) printing pastes, so that glass frit must be added in order to achieve agglomeration and adhesion effects in high-temperature incineration, so that the blank ceramic substrate Printing paste can form a firm precious metal circuit system.

Fully-Additive Process

is the method of electroless deposition of metal (mostly chemical copper) on a completely insulated sheet surface to grow selective circuits, which is called the "full additive method". Another not-so-correct term is the "Fully Electroless" method.

Hybrid Integrated Circuit

It is a circuit in which precious metal conductive ink is applied by printing on a small ceramic thin substrate, and then the organic matter in the ink is burned away at high temperature, leaving a conductor circuit on the board surface, and can be used for welding of surface-mounted parts . It is a circuit carrier of thick film technology between the printed circuit board and the semiconductor integrated circuit device. In the early days, it was used for military or high-frequency applications. In recent years, the price of the hybrid is very expensive and the military is declining, and it is not easy to automate production, coupled with the increasing miniaturization and precision of circuit boards, the growth of this type of Hybrid has been greatly lower than in the early years. .

Interposer interconnect conductive objects

refers to any two layers of conductors carried by an insulating object, and the place where it is to be connected is filled with some conductive fillers, which is called Interposer. For example, in the bare holes of the multilayer board, if the silver paste or copper paste is filled to replace the orthodox copper hole wall, or the material such as the vertical unidirectional conductive adhesive layer, it belongs to this type of Interposer.

Micro Wire Board

The round cross-section enameled wire (glue-sealed wire) attached to the board surface is made into a special circuit board with PTH to complete the inter-layer interconnection. It is commonly called Multiwire Board "multi-wire board" in the industry. ), and those with a very small wire diameter (below 25mil) are also called micro-sealed circuit boards.

Moulded Circuit molded three-dimensional circuit board

Using three-dimensional molds, injection molding (Injection Moulding) or transformation method to complete the three-dimensional circuit board manufacturing process, called Moulded circuit or Moulded Interconnection Circuit.

Multiwiring Board (or Discrete Wiring Board)

It refers to the use of very fine enameled wires, three-dimensional cross wiring directly on the board surface without copper foil, and then fixed with glue, drilling and plating holes, the obtained multilayer interconnection circuit board, called "multi-wire plate". This is developed by American PCK, and is still in production by Hitachi. This kind of MWB can save design time and is suitable for a small number of models with complex circuits (the 60th issue of the Circuit Board Information Magazine has a special article).

Noble Metal Paste

is a conductive paste for thick film circuit printing. When it is printed on a porcelain substrate by a screen method, and then the organic carrier is burned away at a high temperature, a fixed precious metal circuit appears. The conductive metal particles added in this printing paste must be precious metals to avoid the formation of oxides at high temperatures. The users of the commodities are gold, platinum, rhodium, palladium or other precious metals.

Pads Only Board

In the early through-hole insertion era, some high-reliability multi-layer boards, in order to ensure solderability and circuit safety, only left the through-holes and solder rings outside the board, and the interconnection lines are hidden on the next inner layer. . This kind of two-layer board will not be printed with solder resist green paint, it is very particular in appearance, and the quality inspection is extremely strict. At present, due to the increase in wiring density, many portable electronic products (such as mobile phones) have only SMT pads or a few lines left on the circuit board surface, and many dense interconnections are buried in the inner layer, and the layers are also changed. Difficult blind holes or "Pads On Hole" (Pads On Hole) are used as interconnections to reduce the damage of all-through holes to the ground and high-voltage copper surfaces. This type of SMT tightly mounted board is also only a backing board.

Polymer Thick Film (PTF) thick film paste

refers to the ceramic substrate thick film circuit board, the precious metal printing paste used to make the circuit, or the printing paste used to form the printed resistive film, the process includes screen printing and subsequent high-temperature incineration. After the organic carrier is burned away, a firmly attached circuit system will appear. This type of board is generally called hybrid circuit board (Hybrid Circuits).