source:FAQ release time:2021-04-26 Article author:Victoria Popular:pcb
In the process of SMT patch processing, because there are auxiliary agents such as flux, some pollutants or spots will be generated after oxidation or high temperature, so in the end, many pcbA need to be cleaned to be a perfect product. In terms of cleaning, whether solvent cleaning or water cleaning is used, it must undergo surface wetting, dissolution, emulsification, saponification, etc., by applying different methods of mechanical force to remove contaminants from the surface of the assembly board, and then rinse or rinse. Finally dry. Today, the editor of Wei Enchen will analyze it with you:
1. The surface is wet
The decontamination medium forms a uniform thin layer on the surface of the object to be washed, which wets the surface of the object to be washed and swells the contaminants on the surface of the object to be washed. The condition of surface wetting is that the surface tension of the cleaning medium is required to be less than the surface tension of the washing object. Add to the cleaning medium
These surfactants can significantly improve the wetting ability.
Second, dissolve
The main decontamination mechanism of organic solvent cleaning is dissolution. When choosing solvents, the principle of similar compatibility should be followed, and polar pollutants should be selected.
Polar solvents and non-polar pollutants should be selected non-polar solvents. However, polar solvents and non-polar solvents are often mixed and used in actual production. Adding some surfactants to the organic solvent cleaning can improve the detergent's ability to dissolve the thread residue.
(1) Ionic dissolution
Ionic dissolution refers to the dissociation of pollutants into ions in water.
The dissolution of this ionic substance will increase the conductivity of water. The negative ionic contaminants on the surface assembly board include the active material in the flux, the reactant of the active material in the flux and the metal oxide, the salt in the sweat of the hand, the polymer in the manufacture of printed circuit board, and the post-soldering Salt in the residue, etc. Such contaminants may cause poor electrical performance of electronic products or cause corrosion of solder joints.
(2) Non-ionic dissolution
Non-ionic dissolution means that pollutants dissolve in water without changing the conductivity of the water.
Typical non-ionic contaminants are flux bodies, such as polyvinylidene, dirt on hands, phases in water and similar compounds
These substances do not conduct electricity, but they can absorb moisture, which can also cause a decrease in insulation resistance and corrosion of solder joints in SMT processing.
3. Emulsification
In the water cleaning and semi-aqueous cleaning process, a certain amount of emulsifier can be added to the water. When cleaning synthetic trees, curing and contaminants, these contaminants and emulsifiers emulsify and dissolve in water. Adding surfactants can improve emulsification.
Four, saponification
Saponification is a pure chemical process and also a neutralization reaction
The pen chemical reaction uses fatty acid salt, which makes the rosin and acid saponification reaction, so that the residue on the surface of the washing is dissolved in water
And was cleared. The saponification agent will corrode the surface of aluminum and other metals, so when using the saponification agent, you should add the corresponding corrosion inhibitor
And observe the compatibility of the saponification agent with the components and other materials. The addition of surfactants can promote the saponification reaction.
5. Chelation
Chelation refers to the addition of complexes to dissolve insoluble substances (such as heavy metal salts).
Six, apply mechanical force
The application of mechanical force in different ways can speed up the cleaning speed and improve the cleaning efficiency.
① Scrubbing. There are two methods of manual scrubbing and mechanical scrubbing. Manual cleaning refers to the manual cleaning of the surface assembly board after welding by the operator holding a scrubbing tool. Mechanical scrubbing refers to the vigorous scrubbing performed by scrubbing tools installed on the cleaning equipment.
②Dip washing. Dipping refers to immersing the object to be washed under the surface of the cleaning agent. Different mechanical methods such as stirring, spraying or ultrasonic can be used to improve the efficiency of cleaning.
③Spray in the air. In a closed container, spray washing is performed by increasing the water pressure and flow rate. Spray cleaning has batch cleaning and online
Two methods of cleaning. The energy (pressure and flow) of the water flow directly affects the cleaning effect. Under the same water flow, the high pressure is more helpful for the cleaning of residues. However, if the pressure is too high, the cleaning effect will be affected due to the large splash back when the water hits the surface of the assembly board. The low-pressure water flow can have a soaking effect and is conducive to the dissolution of residues. Therefore, a spray washing method combining high and low pressure water flow is generally used.
④Immersed spray cleaning (jet cleaning). Refers to the flushing of the liquid stream immersed in the liquid surface. The nozzles are installed below the liquid surface and discharged at opposite positions on both sides of the washing machine. In order to ensure that the liquid flow does not look for each other. The formation of a flow hot bath effect. This method is suitable for washing products that are sensitive to sound waves, and for cleaning agents that are flammable, explosive, volatile, and easy to foam.
⑤ Please wash after centrifugation. The principle is to use the torque formed by the power of the motor to generate centrifugal force on the laundry. And made by centrifugal force
Use to keep dirt away from the surface of the assembly board. This cleaning method can make the cleaning liquid and lotion penetrate the parts that are difficult to clean, such as narrow spacing, tiny gaps, holes, and holes, to achieve the cleaning purpose. Centrifugal cleaning is suitable for post-welding cleaning of high-density surface mount boards.
⑥Ultrasonic cleaning. Ultrasonic cleaning relies on cavitation and acceleration to promote physical and chemical reactions. This kind of ultrasound
Cavitation can penetrate into small areas that are difficult to reach by other cleaning methods, and the cleaning efficiency is relatively high.
Read recommendations:
Single-sided double-layer AL base PCB
Six-layer Immersion Gold Board (BGA)
Popular recommended products
High frequency PCB
2021-04-27Six-layer Immersion Gold Board (BGA)
2021-05-27Six-layer Immersion Gold Board (BGA)
2021-05-27Silver oil perforated plate (double-sided)
2021-04-27Laminate copper-based PCB after 4L (sample)
2021-04-27Computer card board (four layers)
2021-04-25Six-layer Immersion Gold Board (BGA)
2021-05-24Single-sided double-layer AL base PCB
2021-04-27High frequency PCB
2021-04-27High frequency PCB
2021-04-27Six-layer Immersion Gold Board (BGA)
2021-05-24Six-layer Immersion Gold Board (BGA)
2021-05-27Single copper base PCB
2021-04-27Six-layer Immersion Gold Board (BGA)
2021-05-27Six-layer Immersion Gold Board (BGA)
2021-04-27Mobile phone template (six layers)
2021-04-27Aluminum substrate (double-sided)
2021-04-27Network communication board (sixth floor)
2021-04-29High frequency PCB
2021-04-27Display board (six layers)
2021-04-27Six-layer Immersion Gold Board (BGA)
2021-04-27Six-layer Immersion Gold Board (BGA)
2021-04-27Six-layer Immersion Gold Board (BGA)
2021-04-27DIP plugin
2021-05-27Six-layer Immersion Gold Board (BGA)
2021-04-26Six-layer Immersion Gold Board (BGA)
2021-04-26SMT stickers
2021-05-27Six-layer Immersion Gold Board (BGA)
2021-04-26DIP plugin
2021-05-27Mobile phone board
2021-04-27Six-layer Immersion Gold Board (BGA)
2021-04-26SMT stickers
2021-05-27Mobile phone board
2021-05-27Six-layer Immersion Gold Board (BGA)
2021-04-26Related Information
Composition of PCB
2024-09-29What is the difference between PCB and PCBA
2024-09-10PCB usage tips
2024-08-20Why do the circuit boards are green
2024-08-12How to clean the aluminum substrate?
2024-08-06Maintenance of Chemical Copper Plating Solution on PCB Board
2024-07-22single-sided PCB board and double-sided PCB board
2024-07-15PCB board production process flow
2024-07-09PCB CTI level
2024-07-01Via technology in circuit board factory.Automotive Electronics PCB
2024-06-25The role of FPC flexible circuit board solder mask
2024-06-18Detailed explanation of PCB board sampling production process
2024-06-11pcb v-cut depth standard
2024-05-27Multilayer Printed Circuit Board.What is the eq of PCB
2024-05-20The relationship between PCB safety distance and voltage
2024-04-22SMT surface mount processing.Hybrid circuit board PCB
2024-04-15PCB enterprises should pay attention to SMT matters.Electronic components PCB
2024-04-03PCB - the core building block of electronic products.Automotive Electronics PCB
2024-03-25PCB - the bridge and link of the electronic world
2024-03-18How to define high-frequency and high-precision circuit boards.Industrial Electronics PCB
2024-03-11USB PCB interface layout and wiring requirements
2024-01-22Electrolytic capacitor PCB.Steps for using PCB pins
2024-01-15Automotive ElectronicWhat aspects should be considered when processing and manufacturing PCB boards?
2024-01-08Electrolytic capaciWhat is the difference between a gold-plated circuit board and a gold-plated one?
2023-12-25When grinding PCB boards, attention should be paid to.Oscillator (belonging to crystal) PCB
2023-12-18Industrial Electronics PCB!What precautions should be taken when copying and grinding PCB boards
2023-12-11Do you know who is more suitable for LED direct display, regarding the difference between PCB board
2023-12-05Aluminum electrolytic capacitor PCB.What are the standards for selecting PCB boards
2023-11-27Surface Mount Technology (SMT) Phase PCB
2023-11-20Oscillator (belonging to crystal) PCB.The main functions of PCB board
2023-11-13