Electronic products have been integrated into every corner of people's lives, whether it is our usual mobile phones, computers, or the TVs and games that we usually watch for entertainment; and some of the advanced equipment we need to learn and experiment are electronic products. . It can be said that electronic products bring great convenience to our lives and work. And how these electronic products are manufactured by tiny components, this article will introduce the manufacturing process of these electronic products.
Assembly and soldering of printed circuit boards Assembly and soldering of printed circuit boards Assembly and soldering of printed circuit boards Assembly and soldering The reliability of an electronic device depends mainly on the circuit design, the quality of the components and The quality of the circuit soldering during assembly. Most electronic devices use printed circuit boards. Components such as resistors, capacitors, transistors, and integrated circuits are soldered on a printed circuit board according to a pre-designed circuit to become a core component of a product with certain electrical performance. 1.1.1.1. Printed circuit board printed circuit board printed circuit board printed circuit board printed circuit board, English referred to as PCB (printed circuit board) or PWB (printed wiring board), is an important electronic component, is an electronic element The support of the device is called a "printed" circuit board because it is made by electronic printing.
Printed circuit boards are divided into single-sided printed circuit boards, double-sided printed circuit boards, and multilayer printed circuit boards.
The single panel is composed of a substrate, a wire, a pad and a solder resist layer. The single panel has only one side of copper foil, one side is a soldering surface, and the other side is a component surface, and is mainly used for low-end electronic products. The double-sided panel has copper foil wires on both sides, and the application is also extensive. The development of electronic technology requires increasing circuit integration and assembly density, and the use of multilayer printed circuit boards is required to connect complicated circuits.
Anti-static clothing and anti-static shoes should be worn during the assembly of printed circuit boards to prevent static electricity.
(1) The various components shall be re-inspected and pre-assembled according to the technical standards of product assembly. Anti-static clothing and anti-static shoes shall also be worn during processing. Unqualified devices shall not be used.
(2) Shape the components to meet the position requirements on the board. Component shaping should meet the following requirements: all component leads must not be bent from the root, generally should be more than 1.5mm. Because of the manufacturing process, the roots are easy to break; the manually assembled components can be bent at right angles, but the components assembled by the machine should not be bent, and the radius of the arc should be larger than 1 to 2 times the diameter of the pins; The component faces with characters are placed in an easily viewable position.
(3) Insert the components into the printed circuit board. The requirements are as follows: manual insertion and soldering, components that need to be mechanically fixed, such as heat sinks, brackets, clips, etc. of the power device, and then components to be soldered and fixed. Wear anti-static clothing and anti-static shoes when inserting. Do not touch the component pins and the copper foil on the printed board directly by hand. If the automatic mechanical equipment is inserted and soldered, the components with lower height should be inserted first. After installing the higher-level components, the valuable key components should be placed in the final package, and the heat sink, bracket, clip, etc. should be inserted close to the welding process.
(4) Inspection: Ensure that the inserted components are in the correct position and meet the requirements.
Wear anti-static clothing and anti-static shoes to prevent static electricity when soldering printed circuit boards
In the mass production of electronic products, the soldering of printed circuit boards is mainly wave soldering and dip soldering.
(1) Wave soldering Wave soldering means that the molten solder (lead-tin alloy) is sprayed into a solder peak required by the design by an electric pump or an electromagnetic pump, or may be formed by injecting nitrogen into the solder pool to make the The printed board with components is soldered to the solder joints of the components and the mechanical and electrical connections between the leads and the printed board pads.
Wave soldering is mainly done by wave soldering machine. It mainly consists of control system, transmission system, flux spray device, preheating device, tin bath and exhaust air cooling system.
(2) Dip welding Dip welding is divided into manual dip soldering and automatic dip soldering. Manual dip soldering is a welding process in which a professional operator holds a fixture, clamps a printed circuit board with components inserted, and immerses it in a solder bath at a certain angle. It can complete many solder joints of a printed circuit board at one time. Welding. Automatic dip soldering is done by automatic dip soldering machine. When the printed circuit board to be soldered with components is sent from the conveyor to the station, the solder slot automatically rises, and the component leads and printed circuit on the soldering board The pad is completely immersed in the solder bath. After a sufficient amount of time, the solder bath is lowered, removed from the solder, and cooled to form a solder joint to complete the soldering. Due to the continuous transmission of the printed circuit board, while immersing in the solder bath, the relative movement of the lead pad and the solder facilitates the removal of air and flux volatilization gas and increases the wetting effect.
In addition, the manual soldering process is also an indispensable technology for the manufacture of electronic products. Manual welding is required in small batch production and testing of the quality of machine welding products. The main tool for hand soldering is the soldering iron, which is based on the principle that current is generated by the heating device. The electric soldering iron mainly has two kinds of ordinary electric soldering iron and constant temperature electric soldering iron. Ordinary electric soldering irons have internal heat and external heat type. Ordinary electric soldering irons are only suitable for occasions where welding requirements are not high. The power is generally 20-50W. The heat-generating component of the internal heat type soldering iron is mounted inside the soldering iron tip and transfers heat from the inside of the soldering iron tip, so it is called an internal heat type soldering iron. It has the characteristics of fast heat generation, thermal efficiency of 85-90% or more, small size, light weight and low power consumption. An important feature of the constant temperature electric soldering iron is that it has a constant temperature control device, which makes the welding temperature stable and the temperature change soldering iron can be used to solder finer printed circuit boards, such as mobile phone circuit boards.
The manual welding process is as follows:
1 Prepare for welding. Clean dust and oil on the welding parts, insert the components, and connect the wires to the terminals to prepare for the welding.
2 heat welding. Touch the soldering iron tip with a small amount of solder to the soldered component for a few seconds. If you want to remove the components on the printed board, after the tip is heated, gently pull the component with your hand or tweezers to see if it can be removed.
3 Clean the welding surface. If there is too much solder in the soldered part, you can remove the solder on the soldering iron tip (be careful not to burn the skin or on the printed circuit board!), then use the soldering iron to "dip" some solder out. If the solder joint is too small and not smooth, you can use the soldering iron to "snap" some solder to repair the solder joint.
4 Check the solder joints. See if the solder joints are round, shiny, firm, and have solder joints with surrounding components.
