1. The purpose of PCB process selectionWith the development of electronic technology, printed circuit boards have gradually developed from single-sided boards to double-sided boards, multi-layer boards, flexible boards and rigid-flex boards. The manufacturing and processing technology continues to move towards high precision, high density, fine aperture, and fine aperture. The development of wires, small pitch, high reliability, multi-layer, light weight, and thin profile. The technical content of printed circuit board processing is getting higher and higher, and the technical difficulty is getting more and more difficult. The performance and quality of printed circuit boards are beginning to become Important factors affecting the performance, quality and reliability of electronic products.Common PCB types are shown in the figure.In fact, the performance and quality of the printed circuit board are related to the structure type of the printed circuit board, the choice of base material...

When PCB boards undergo reflow soldering, most of them are prone to board bending and warping. In severe cases, it may even cause components such as empty soldering and tombstones. How to overcome it? To1. The harm of PCB board deformationIn the automated surface mount line, if the circuit board is not flat, it will cause inaccurate positioning, components cannot be inserted or mounted on the holes and surface mount pads of the board, and even the automatic insertion machine will be damaged. The circuit board with the components is bent after soldering, and the component feet are difficult to cut neatly. The board cannot be installed on the chassis or the socket inside the machine, so it is also very annoying for the assembly plant to encounter the board warping. The current surface mount technology is developing in the direction of high precision, high speed, and intelligence, which puts forward higher flatness requirements for PCB boards that are home to various components. ToIn the...

【Inner layer circuit】The copper foil substrate is first cut into a size suitable for processing and production. Before pressing the film on the substrate, the copper foil on the surface of the substrate should be roughened by brush grinding and micro etching, and then the dry film photoresist should be tightly attached to it at appropriate temperature and pressure. The substrate with dry film photoresist is sent to the UV exposure machine for exposure. The photoresist will polymerize in the transparent area of the negative film after being exposed to ultraviolet radiation, and the line image on the negative film will be transferred to the dry film photoresist on the plate surface. After tearing off the protective adhesive film on the film surface, the UN illuminated area on the film surface is removed with sodium carbonate solution, and then the exposed copper foil is corroded and removed with hydrogen peroxide mixed solution to form a circuit. Finally, light oxide aqueous solution wa...

For surface mount boards, especially for BGA and IC, the via hole plug hole must be smooth, convex and concave plus or minus 1mil, and there should be no red tin on the edge of the through hole. In order to meet the customer's requirements, the through hole plug hole process can be described as varied, with a long process flow and difficult process control. Oil often drops during hot air leveling and green oil solder resistance test; curing After explosion oil and other problems occurred. According to the actual conditions of production, this paper summarizes various plug hole processes of PCB, compares and expounds the process flow, advantages and disadvantages: Note: the working principle of hot air leveling is to remove the excess solder on the surface and hole of printed circuit board by using hot air, and the remaining solder is uniformly covered on the pad, the non blocking solder line and the surface packaging point, which is one of the surface treatment methods of printed circ...