During pcb manufacturing process components package type


During pcb manufacturing process ,most surface assembly discrete components are in plastic packages. The package outline of power components with power consumption below a few watts has been standardized. Currently, commonly used discrete components include diodes, triodes, small outline transistors, and chip oscillators.

During pcb manufacturing process components package type

During pcb manufacturing process ,the two ends of the SMD have a diode and a few triodes devices, the three-terminal SMD is generally a triode-type device, and the four- to six-terminal SMD mostly packages two triodes or FETs.


1, Diode

A diode is a unidirectional conductive component. The so-called unidirectional conductivity means that when a current flows from its forward direction during pcb manufacturing process , its resistance is extremely small; when a current flows from its negative electrode, its resistance is large, and thus the diode is a polar component. The package is available in a glass package, a plastic package etc.


Diodes for surface assembly are available in three package styles. The first type is a cylindrical leadless diode, which is packaged in a thin glass tube with internal electrodes during pcb manufacturing process , and a metal cap is attached to both ends of the thin glass tube as positive and negative electrodes. Dimensions are available in 1.5mm x 3.5mm and 2.7mm x 5.2mm.


The second type is a plastic package rectangular thin-film diode with a size of 3.8mmx1.5mmx1.1mm, which can be used in VHF (Very High Frequency) to Frequency-band, and is packaged in plastic tape.

The third type is a chip diode in the SOT23 package, which is used to package composite diodes and is also used to package high-speed switching diodes and high-voltage diodes.


2, Triode

Triode is one of the basic components of semiconductors during pcb manufacturing process , with current amplification, is the core component of electronic circuits. The triode is made up of two closely spaced PN junctions on a semiconductor substrate. The whole semiconductor is divided into three parts. The middle part is the basic area, and the two sides are the emitter area and the collector area. The arrangement ways are PNP and NPN. The corresponding electrodes are taken from the three regions, which are the base region b, the emitter region e, and the collector region c.


The reason why the triode has the function of current amplification is that the triode can control the large change of the collector current with a slight change of the base current, which is the most basic and important characteristic of the triode. The current amplification factor is a fixed value for a triode, but there will be some changes in the base current as the triode operates.

The surface mount three poles can be divided into bipolar triode and field effect tubes during pcb manufacturing process , which are generally called chip triode and sheet field effect tubes.

The chip triode is packaged in many forms. Generally, the chip triode has few power tubes. The chip triode has 3 pins and 4 to 6 pins. Among them, 3 pins are low-power ordinary triode, and 4 pins are double-gate FETs or high-frequency triode, and 5~ The 6-pin is a combined triode.



3, Small outline transistor

Small Outline Transistor (SOT), also known as microchip transistor, is one of the first surface-mounting active devices. It is usually a three-terminal or four-terminal component, mainly used for hybrid integration. The circuit, which is assembled on a ceramic substrate during pcb manufacturing process , has been widely used in the assembly of epoxy fiber substrates in recent years. Small outline transistors mainly include SOT23, SOT89 and SOT143.


(1) SOT23. SOT23 is a general purpose surface mount transistor. The SOT23 package has three wing-shaped pins and is made of alloy No. 42 with good strength but poor solderability. Such packages are commonly found in small power transistors, field effect transistors, diodes, and composite transistors with resistor networks. The package can accommodate a maximum chip size of 0.03inx0.030in and can dissipate up to 200mW of heat in air. It has low, medium and high end view to meet the different requirements of hybrid circuits and printed circuits. The high-lead package is more suitable for PCBs because it is easier to clean.

The surface of the SOT23 is printed with markings, and the corresponding polarity, model and performance parameters can be found through the relevant semiconductor component manual. The SOT23 is packaged in braided tape and is now commonly packaged in molded plastic cavity.


(2) SOT89. In order to more efficiently dissipate heat through the substrate, the package is mount flatly on the surface of the substrate. The collector, base and emitter of SOT89 are drawn from the same side of the tube during pcb manufacturing process . The bottom of the tube has a metal fin and a collector. The SOT89 has three thin, short pins that are distributed across one end of the transistor and are typically used for larger power components. The SOT89 has a maximum package tube core size of 0.6inx0.60in. It dissipates 500mW of heat in air at 25°C. This type of package is commonly found on silicon power surface mount transistors.


(3) SOT143. The SOT143 has four wing-shaped short pins, and the wider pins is the collector. Its heat dissipation performance is basically the same as that of SOT23. Such packages are commonly used in dual-gate FETs and high-frequency transistors, and are generally used as RF transistors. It is similar to the SOIC package except that the PCB gap is small. The packaged tube core outline size, heat dissipation performance, packaging method, and position on the tape are basically the same as those of the SOT23 during pcb manufacturing process .


The most common way to provide SOT23, SOT89 and SOT143 is in the form of tape or reel in the EIA standard RS-481. Among them, the most popular one is a conductive tape with a molded groove in which the device is placed. These packages are the only active devices that are soldered using both wave soldering and reflow soldering. The remaining active devices, such as SOIC and PLCC, are mostly soldered only by reflow soldering. These types of packages differ slightly in appearance factor, but for electronic machines using SMT during pcb manufacturing process , they can meet the mounting accuracy requirements. The polarity of the products and the pins are basically the same, and have certain interchangeability.

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