What are the advantages and applications of flexible microcircuits?
FPC Reinforcement Types
Criteria for Classification of electronic Component Classes
Four softwares suitable for beginners to draw PCB circuit boards
What information is needed for SMT processing?
What are the advantages of small and medium batch SMT processing?
PCB related knowledge- The purpose of each layer of the PCB
How to do heat resistance testing for PCB board
Detailed explanation of rigid-flex board and IC carrier board
PCBA prototype procedure
Defects which can be detected by the SPI
What are the spacing requirements for designing PCB circuit boards?
What are the classification and advantages of PCB metal substrates?
Difference between the processing technology of 1Layer AL PCB and 2Layer AL PCB
Introduction of FPC Cable and its usage
advantages of Shenzhen SMT assembly factory
inspection items before PCB ordering
usages of ceramic substrates
main applications of PCB boards
Cost-effective PCB product services
How to check short circuit of a circuit board during manual soldering
Identify the polarity of electronic components during PCBA processing
Means Which Can Prevent Component Shifting in SMT Processing
Skills of PCB prototype manual soldering
Reasons for the shift of Components in the SMT Process
Seven Types of PCB Probes
What Should Be Paid Attention to in Layout of High-frequency PCB
Precautions for PCB CCL Selection
Advantages of LED Plant growth light
Advantages of using LED grow lights to grow industrial hemp
Detailed explanation of PCB manufacturing process and precautions
Detailed explanation of PCB manufacturing process and precautions
How to draw multilayer PCB on Altium Designer
Three basic elements of interference and how to suppression them.
Decrease interference between digital circuit and analog circuit
SMT Component Placement Process Of Parts : Manual Placement
SMT factory incoming PCB material inspection
Basic concepts commonly used in PCB design
Ideas and principles of High speed PCB layout
Component layout rules and safety distance considerations
SMT assembly process quality specification
5 points in PCB layout
Professional interpretation of SMT
Advantages and disadvantages of different PCB surface treatment
Special process in PCB prototype
Why the via hole become open after component assembly
Keep the cost of the PCB as low as possible
what are the causes of PCB board heating radiation problem
Pad size and via diameter dimensions consideration in PCB prototyping
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

Content of PCB incoming testing

One company once did a statistics to classify the causes of PCBA product quality problems and found that there are four major causes: design, incoming materials, manufacturing process (production), and storage and transportation, respectively accounting for 25%, 50%, 20%, 5%. Issue of incoming materials accounted for 50%, so it came to the conclusion that incoming materials inspection is quite important. Similarly, in order to ensure the PCB base board quality used in the production of SMT production lines, these incoming materials must be tested before they are put into production to determine whether they meet the production standards. Incoming material inspection is generally carried out by visual inspection in actual production.

The content of PCB incoming inspection includes PCB size and appearance inspection, PCB warpage and twist inspection, PCB solderability test, PCB solder mask integrality test, PCB internal defect inspection.

PCB size and appearance inspection
PCB size inspection mainly includes: diameter inspection of processing holes, spacing and tolerance inspection, and PCB profile size inspection.
The appearance inspection mainly includes: inspecting the alignment of the solder mask and the pad; whether the solder mask has abnormal conditions such as impurities, peeling, wrinkles, etc; whether the fiducial marks conforms to the standard; whether the circuit conductor width (line width) and spacing meet the requirements; whether the multilayer board has delaminate issue, etc. In practical applications, special equipment for PCB appearance testing is often used for inspection. 
Typical equipment is mainly composed of computers, automatic workbenches, and image processing systems. This system can inspect the inner and outer layers of multilayer boards, single-sided/double-sided boards, and base photoimaging films; it can detect problems such as scratches, pinholes, conductor widths, conductor spacing, rough edges, and large-area defects etc.

PCB warpage inspection
Unreasonable design and improper processing in the processing process may cause PCB warpage. The test method is stipulated in the IPC-TM-650 standard. The test principle is: Expose the PCB under testing to a representative thermal environment of the assembly process, and conduct a thermal stress test on it. Typical thermal stress testing methods solder dipping test and float test. In this test method, the PCB is immersed in molten solder for a certain period of time, and then taken out for warpage testing. The method of manual measuring PCB warpage is to put the 3 corners of the PCB close to the desktop, and then measure the distance from the fourth corner to the desktop. This method can only be used for rough estimation, and more effective methods include the application of ripple imaging technology.

PCB solderability test
The solderability test of PCB focuses on the test of pads and plated through holes. The IPC-S-804 standard specifies the solderability test method of PCB, which includes edge dipping test, spin dipping test, wave dipping test and solder bead test, etc. The edge dipping test is used to test the solderability of surface conductors; the spin dipping test and wave dipping test are used for the solderability test of surface conductors and plated through holes; the solder bead test is only used for the solderability test of plated through holes.

PCB solder mask integrality test
PCBs used in SMT, dry film solder mask and optical imaging solder mask are generally used. These two kinds of solder mask have high resolution and immobility. The dry film solder mask is laminated on the PCB under the effect of pressure and heat. It requires a clean PCB surface and an effective lamination process. 

This kind of solder mask has poor viscosity on the surface of tin-lead alloy. Under the impact of thermal stress generated by reflow soldering, the phenomenon of peeling and breaking from the PCB surface often occurs. This kind of solder mask is also relatively fragile, and microcracks may occur under the influence of heat and mechanical force during HASL process. In addition, physical and chemical damage may also occur under the effect of cleaning agents. In order to discovery these potential defects of the dry film solder mask, strict thermal stress tests are supposed to be performed on the PCB during incoming material inspection. This inspection mostly uses the solder float test, the time is about 10-15s, and the solder temperature is about 260-288℃. When the solder mask peeling phenomenon is not observed during the test, the PCB test piece can be immersed in water after the test, and the capillary effect of the water between the solder mask and the PCB surface can be used to observe the solder mask peeling phenomenon. The PCB test sample can also be immersed in the SMA cleaning solvent after the test to observe whether it has physical and chemical action with the solvent.

PCB internal defect inspection
The internal defects of PCBs are generally inspected by microsection technology. PCBs are inspected for microsection after solder floating thermal stress test. The main inspection items are the thickness of copper and tin-lead alloy coatings, the alignment of the internal conductors of the multilayer board, laminate voids and copper cracks, etc.

In summary, incoming material inspection occupies an overwhelming position in the PCB assembly company's product quality control, so the quality control of incoming materials must be raised to a strategic position to deal with.