Wear anti-static clothes and anti-static shoes when assembling the printed circuit board
Electronic products have been integrated into all corners of people's lives, whether it is our usual mobile phones, computers; TVs and game consoles for our usual entertainment; and some advanced equipment we need for learning and experiments are all electronic products. . It can be said that electronic products have brought great convenience to our lives and work. And how these electronic products are manufactured through tiny components, this article will introduce the manufacturing process of these electronic products.
Printed circuit board assembly and welding Printed circuit board assembly and welding Printed circuit board assembly and welding Printed circuit board assembly and welding The reliability of an electronic device mainly depends on the circuit design, the quality of components and The quality of circuit soldering during assembly. Most electronic equipment uses printed circuit boards, and the resistors, capacitors, transistors, integrated circuits and other components are welded on the printed circuit board according to the pre-designed circuits to become the core components of the product with certain electrical properties. 1.1.1.1. Printed circuit board printed circuit board printed circuit board printed circuit board printed circuit board, English abbreviation PCB (printed circuit board) or PWB (printed wiring board), is an important electronic component, an electronic element The support of the device, because it is made by electronic printing, is called a "printed" circuit board.
Printed circuit boards are divided into single-sided printed circuit boards, double-sided printed circuit boards and multilayer printed circuit boards.
The single-sided board consists of a substrate, wires, pads and a solder mask. The single-sided board has only one side of copper foil, one side is the soldering side, and the other side is the component side. It is mainly used in low-end electronic products. There are copper foil wires on both sides of the double-sided board, which is also widely used. The development of electronic technology requires continuous improvement of circuit integration and assembly density, and multi-layer printed circuit boards are required to connect complex circuits.
When assembling the printed circuit board, wear anti-static clothes and anti-static shoes to prevent static electricity
(1) Perform re-inspection and pre-assembly pre-assembly of various components in accordance with the technical standards of product assembly. Anti-static clothing and anti-static shoes are also required when handling. Unqualified components cannot be used.
(2) Reshape the components to meet the position requirements on the circuit board. Component shaping should meet the following requirements: all component pins must not be bent from the root, generally should be more than 1.5mm. Because of the manufacturing process, the root is easy to break; the components assembled by hand can be bent at right angles, but the bending of the components assembled by the machine should not be a dead angle. The radius of the arc should be greater than 1 to 2 times the diameter of the pin; Place the face of the components with characters in an easy-to-observe position.
(3) Insert the components on the printed circuit board. The requirements are as follows: manual insertion and welding. The components that need to be mechanically fixed should be inserted first, such as the heat sink, bracket, clip, etc. of the power device, and then the components that need to be welded and fixed. Wear anti-static clothing and anti-static shoes when inserting. Do not touch the pins of the components and the copper foil on the printed circuit board with your hands; when inserting and soldering automatic mechanical equipment, you should insert those lower-height components first , After installing those components with higher heights, valuable key components should be put in the final assembly, and the inserting of radiators, brackets, clips, etc., should be close to the welding process.
(4) Inspection: Ensure that the inserted components are in the correct position and meet the requirements.
Wear anti-static clothes and anti-static shoes to prevent static electricity when soldering printed circuit boards
In mass production enterprises of electronic products, the soldering of printed circuit boards mainly adopts wave soldering and dip soldering.
(1) Wave soldering Wave soldering refers to the molten solder (lead-tin alloy) sprayed by an electric pump or electromagnetic pump into the solder wave required by the design. It can also be formed by injecting nitrogen into the solder pool to make The printed circuit board equipped with the components realizes the soft soldering of the mechanical and electrical connection between the solder end or the pin of the component and the printed board pad through the solder wave.
Wave soldering is mainly completed by the wave soldering machine, which mainly includes: control system, transmission system, flux spray device, preheating device, tin bath and exhaust cooling system.
(2) Dip soldering Dip soldering is divided into manual dip soldering and automatic dip soldering. Manual dip soldering is a soldering process in which a professional operator holds a fixture, clamps the printed circuit board with inserted components, and dips it into the solder bath at a certain angle. It can complete many soldering points on the printed circuit board at one time Welding. Automatic dip soldering is done by using an automatic dip soldering machine. When the printed circuit board that has been inserted into the component is sent to the station by the conveyor belt, the solder tank automatically rises, and the component pins and the printed circuit on the board to be soldered The board pad is completely immersed in the solder tank. After holding it for a sufficient time, the solder tank is lowered, separated from the solder, and cooled to form a solder joint to complete the soldering. Due to the continuous transmission of the printed circuit board, it drags a period of time and distance while immersing in the solder tank. This relative movement between the pin pad and the solder is beneficial to eliminate air and flux volatilized gas and increase the wetting effect.
In addition, the manual soldering process is also an indispensable technology for electronic product manufacturing. In some small batch production and testing the quality of machine welding products, manual welding is required. The main tool for manual soldering is an electric soldering iron, which is made based on the principle that electric current passes through a heating device to generate heat. Electric soldering irons mainly include ordinary soldering irons and constant temperature soldering irons. Ordinary electric soldering iron has internal heating type and external heating type. Ordinary electric soldering iron is only suitable for occasions with low welding requirements. The power is generally 20-50W. The heating components of the internal heating electric soldering iron are installed inside the soldering iron tip, and heat is transferred from the inside of the soldering iron tip to the outside, so it is called an internal heating electric soldering iron. It has the characteristics of fast heat generation, over 85-90% thermal efficiency, small size, light weight and low power consumption. The 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 changes very little. The constant temperature electric soldering iron can be used to weld finer printed circuit boards, such as mobile phone circuit boards.
The manual welding process is as follows:
① Prepare for welding. Clean the dust and oil on the welding part, the insertion of components, and the hook connection of wires and terminals, so as to prepare for the welding.
② Heat welding. Touch the soldering iron tip with a little solder to the soldered component for about a few seconds. If you want to remove the components on the printed board, after the soldering iron tip is heated, gently pull the components with your hands or tweezers to see if they can be removed.
③Clean the welding surface. If there is too much solder on the soldering part, you can shake off the solder from the soldering iron tip (be careful not to burn your skin or throw it on the printed circuit board!), and then "dip" some solder out with the soldering iron tip. If the solder joint is too small and not smooth, you can use an electric soldering iron tip to "dip" some solder to repair the solder joint.
④Check the solder joints. Check whether the solder joints are round, bright and firm, and whether there is continuous soldering with surrounding components.