Content of PCB incoming testing_
Technical
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 is 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
Soldering solution to large heat absorption solder joints and easily oxidized pads
Reflow soldering stage in the BGA assembly process
Introduction of Capacitors
Practical method to use the AOI system at present
How to choose a LED placement machine
Explains and prospects of application LED in greenhouse plant
methods to improve the efficiency of FPC testing
The key points that affect the service life of soldering iron tip
PCBA product storage period
Design skills of RF PCB and microwave PCB
Replace IC skills to make PCB circuit design more perfect
PCB failure analysis
How to get an irregular shape PCB design

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.