Technical
How to Judge the Acceptance of PCB Quality
Which Color Circuit Board Sells the Most Expensive
Method to Solve the Noise Interference of Power Supply on High-frequency PCB Board
Disassembly Skills of Chip Components on PCB
What Factors Should Be Considered in the Selection of High-frequency PCB CCL
How to Place Special Components during PCB Layout
What Are the Functions of Capacitors in Circuits?
Testing Techniques for Common Electronics Components
What to do if There is a Short Circuit on the PCB
Desoldering Principles and knowhow during PCBA Processing
Black Oxidation of the Inner Layer of the Multilayer PCB
How to Ensure the High-performance Design of PCB
What Is the Printing Process of SMT Solder Paste?
PCB without fiducial mark, Is There Any Way to do SMT for It
What Are the Benefits of Reserving Break-up Tab for PCB Production
How Does SMT Affect PCB Production Time and Speed It Up
Classification of PCBs from three aspects
Common Problems and Solutions for Dry Film pasting during PCB Manufacturing process
Several Elements to Inspect after PCB Design
What is a halogen-free circuit board?
What Do Capacitive Coupling and Decoupling Mean?
What Are the Differences Between PCB Paste Mask and Solder Mask?
How PCBA Is Packaged and Shipped
How long can PCBA finished products be stored?
What Are the Differences and Relations Between PCB, PCBA, and SMT?
PCB Baking Specifications
PCB "Solder Mask Tenting" and "Solder Mask Opening"
Five reasons for PCB deformation and six solutions
Importance of first article inspection of PCBA board
Temperature zone standard for SMT reflow soldering
Small and medium volume PCB manufacturers in China
The main reason for PCBA cleaning
For power filter, the more capacitors, the better?
What does PCBA programming mean?
Content of PCB incoming testing
What conditions must be met for PCB circuit board soldering?
What is Blind via and Buried via
PCBA Manufacturers Temperature and Humidity Sensitive Components Management
Why choose Shenzhen SMT processing factory?
How long does it take to calculate the quotation for PCBA manufacturing?
Introduction of PCB design clearance requirements
Explanation of BOM, DIP, SMT, SMD
Introduction of the process of PCBA prototype
How to prevent pseudo soldering or cold soldering defects in PCBA manufacturing?
Factors that affect the Price of FPCB
What information is required for SMT processing at PCBA factory?
Skills of using 0ohm resistor in PCB design
How to select a PCBA manufacturer
SMT processing solder joint quality inspection
Characteristics difference between immersion gold PCB and gold plating PCB
Common malfunctions of Circuit Board Caused by Moisture
A Few Rules about PCB Panelization
Compare of multi-layer PCB with single/double layer PCB
Why do we need to introduce so many subdivided GND
Difference between immersion gold boards and gold plating boards
Aluminum PCB structure
Classification of different GND in circuit
Why PCB baking is necessary during manufacturing process
The handle and precautions of OSP board in SMT process
How to choose capacitors for filter decoupling
How to choose filter capacitor for switching power supply
5 database need for SMT process
Function of three-terminal capacitor
Introduction of PCB OSP surface treatment
Method of inspecting the quality of SMT by step
How to find the short point between VCC and GND
Difference between 850nm and 940nm infrared LED
Component layout of PCB SMT DFM
Pad shape influence on the strength and reliability of the soldering joints
The difference between high temperature solder paste and low temperature solder paste
Introduction to manual welding processing
Manual visual inspection in PCBA processing
Characteristics of the conformal coating process
Difference between hardware engineers and software engineers
PCBA processing operation rules
China PCB upstream materials has continued to soar
Difference between serial buses and parallel buses
The key points of quality control in PCBA processing
Common causes of solder beading during SMT process
Analysis of the advantages and disadvantages of HASL PCB surface
Requirements for layout of components during SMT assembly
Selection of electronic components and CCL for PCBA
Performance and appearance quality inspection of components.
Quality and Reliability of SMT Chip Processing and Production
Coupling and decoupling function of capacitor
Two methods to connect digital ground and analog ground
Common sense in SMT process

SMT processing solder joint quality inspection

With the advancement of technology, some electronic products such as mobile phones and tablet computers are trending towards being light, small and portable. The electronic components used in SMT processing are also becoming smaller. How to ensure the quality of solder joints has become an important issue for high-precision PCBA products. The solder joint is used as a bridge for components and PCB, and its quality and reliability determine the quality of electronic products. In other words, in the production process, the quality of SMT ultimately manifests as the quality of solder joints.

At present, in the electronics industry, the research of lead-free solder has made great progress, it has begun to be promoted and applied worldwide, and environmental protection issues have also received widespread attention. The soldering technology using Sn-Pb solder alloy is also soldering technology of electronic circuits.

A good solder joint should not fail in its mechanical and electrical properties during the life cycle of the equipment. Its appearance is as follows:
(1) Complete, smooth and shiny surface;
(2) Appropriate amount of solder, solder completely cover the soldering part of the pad and lead, and the height of the soldering is moderate;
(3) Good solderability, the edge of the solder joint should be thin, and the wetting angle between the solder and the surface of the pad should be less than 30degree, and the maximum should not exceed 60degree.

SMT processing appearance inspection content:
(1) Whether the components are missing;
(2) Whether the components are mounted correctly;
(3) Whether there is a short circuit;
(4) Whether there is a pseudo welding; the reason for the pseudo welding is relatively complicated.

I. How to judge the quality of welding
1. Use special equipment (e.g. online tester) for inspection.
2. Visual or AOI inspection. When it is found that there is too little solder in the solder joint, the solder infiltration is poor, or there is a crack in the middle of the solder joint, or the surface of the solder is convex angle, or the solder is not compatible with the SMD. It should be immediately judged whether there is a lot of pseudo welding problem.

The method of judgment is to see if there are many problems with the solder joints at the same position on the PCB. If it is only a problem on a single PCB, it may be caused by the solder paste being scratched, pin deformation, etc., If there are problems at the same position on many PCBs, it is likely to be caused by a bad component or a problem with the pad.

II. Causes and solutions of pseudo welding
1. The pad design is defective. The existence of through-holes on the pads is a major defect in PCB design. Do not use them if they are less than absolutely necessary. The through-holes will cause solder loss and insufficient solder; the spacing and area of the pads also need to be standardized, otherwise the design should be corrected as soon as possible.

2. The PCB board is oxidized, that is, the pad is black and does not shine. If there is oxidation, an eraser can be used to remove the oxide layer to reproduce the bright light. If the PCB board is suspected damp, it can be dried in a drying box. If the PCB board is polluted by oil stains, sweat stains, etc., it should be cleaned with absolute ethanol.

3. For PCBs that have been printed with solder paste, if the solder paste is scratched or rubbed, which reduces the amount of solder paste on the relevant pads and makes the solder insufficient. It should be made up in time. The method of making up can be done with a dispenser or pick a little with small sticks.

4. SMD (Surface Mount Components) is of poor quality, expired, oxidized, deformed, resulting in pseudo soldering. This is a more common reason.
The oxidized components are dark and not shiny. The melting point of the oxide rises. it can be soldered with more than 300 degree electric solder iron and rosin-type flux, because it is difficult to solder with 240 degree SMT reflow soldering and the use of less corrosive non-clean solder paste. Therefore, the oxidized SMD is not suitable for welding with reflow soldering furnace. When buying components, you must see if there is oxidation, and use them in time after you buy them. In the same way, oxidized solder paste cannot be used.