Frequently Asked Questions
Organize common question answers to answer your questions and clarify your doubts
1. What are the PCBA storage conditions and requirements?
After completing the final processing of PCBA, if the finished product assembly is not carried out in time, PCBA needs to be stored to prevent PCBA from exposing the air for a long time and affecting the performance of PCBA.
PCBA storage conditions are mainly:
1. Apply three anti -paint
For a long -term non -instrumental PCBA board, three -proof paint should be applied, which has the functions of moisture -proof, dustproof, and oxidation. It can effectively extend the storage time. After applying the three -month -proof paint, it can be extended for 9 months.
2. Vacuum packaging method
PCBA storage cannot be in contact with air and water. First of all, the PCBA board is packaged with a vacuum bag, and it needs to be surrounded by a layer of air bubble film on the side of the box. The water absorption of the bubble film is better. Less. Then classify and emit the label. After the box is sealed, the box must be partitioned and placed in a dry and ventilated place, and the sun should be avoided.
3. Control the temperature and humidity of the warehouse
The temperature of the warehouse saved by PCBA is best controlled at 23 ± 3 ° C, 55 ± 10%RH, the temperature with good storage conditions is less than 25 degrees, the relative humidity is less than 65%, with temperature control, and the indoor environment has no corrosive gas.
For the OSP process PCB, due to its thin protective membrane, PCBA needs to be stricter during storage.
2. Which PCBA virtual soldering detection machines can detect virtual soldering?
PCBA virtual soldering refers to the situation where the tin layer is not fully plated, making it difficult to see on the surface, and it is in a state where communication is not possible. Virtual soldering is an important reason for the high early repair rate of PCBA, therefore, detection equipment must be used to promptly identify the PCBA board with virtual soldering.
PCBA virtual welding can be divided into two situations. The first one is an unstable state caused by improper production processes, which is constantly on and off; The second type is caused by long-term use of electrical appliances, and some parts with severe heat generation are prone to aging and peeling of the solder joints at their solder joints.
Detecting virtual soldering requires the use of specialized PCBA virtual soldering detection machines, such as ICT, aging testing racks, and X-rays. The most accurate way to detect virtual soldering is through X-ray equipment, but this equipment is too expensive for most small and medium-sized enterprises to afford. However, ICT and aging testing racks can be used instead.
3. What is the PCBA probe used for?
The probe is a contact medium for PCBA testing, and is a high-end precision electronic hardware component. It is an object of the PCBA testing fixture. In the PCBA testing phase, specialized testing fixtures are usually made, which are equipped with probes to make contact with the PCBA testing points and ultimately test the performance parameters of the PCBA. The surface of the PCBA probe is coated with gold, which is beneficial for enhancing conductivity. Generally, manufacturers choose SK4 material, which has a high-performance spring with an average lifespan of 30000 to 1 million times inside. After multiple tests, the probe needs to be cleaned to ensure that it functions correctly.
4. What are the steps of PCBA cleaning method?
After the completion of the PCBA processing, it is common to see many residues on the surface of the PCBA. These residues not only affect the appearance, but also have an impact on the quality of the PCBA. Therefore, the cleaning of the PCBA is very important. Next, we will introduce the methods of manual cleaning and automatic cleaning.
1、 Manual cleaning
Generally, small and medium-sized PCBA processing plants use manual cleaning methods, which have low cleaning costs and are relatively cost-effective.
The tools for manual cleaning mainly include: cleaning tank, spray tank, brush, IPA or VIGON EFM, gloves, deionized water, wiping paper, air gun and sealing bag.
Steps for manual cleaning:
1. Clean the circuit board in IPA or VIGON EFM, or spray IPA and EFM onto the surface of the circuit board, using approximately 10 milliliters per 4 square inches.
2. Use a damp, soft short haired brush to continuously wipe the circuit board for about 10 seconds.
3. Rinse with deionized water, approximately 10 milliliters per 4 square inches. Effectively remove potential pollutant residues.
4. Hold the edge of the circuit board and use a clean, lint free cloth to wipe off excess deionized water.
5. Visually inspect the cleanliness of the circuit board.
6. If necessary, use an air gun to dry the circuit board.
7. If it is necessary to store the circuit board or components for a period of time before coating, please place the circuit board or components in a sealed bag containing desiccant.
2、 Automated cleaning
The automated cleaning process is divided into three methods: water cleaning, semi water cleaning, and solvent cleaning.
The tools and materials for automated cleaning mainly include water cleaning machines, deionized water systems, conductivity testers, beakers, and deionized water.
Automated cleaning operation steps:
1. Preparation of deionized water: Using an electrodialysis device and an ion exchange resin tank to produce deionized water.
2. Conductivity testing: Use a conductivity tester to test the conductivity of water after electrodialysis and ion exchange resin tanks. If both meet the requirements, they can be used for water cleaning.
3. Introduction of water cleaning machine: Introduce deionized water from the water storage tank into the water cleaning machine.
4. Set the parameters of the cleaning machine: the washing room and rinsing room are set to 60 ± 10 ℃; Drying room setting
It ranges from 60 ℃ to 90 ℃.
5. Set chain speed: Generally control the chain speed between 50-150cm/min.
6. After the PCBA cleaning is completed, it is taken out of the cleaning machine and stored in an anti-static turnover container. The anti-static turnover container is required to be clean and dust-free to avoid secondary pollution of the PCBA after cleaning.
The above are two methods for cleaning PCBA, hoping to be helpful to you.
5. What are the methods of PCBA process control?
There are many production processes in PCBA, and to ensure the quality of PCBA processing, professional process control methods and tools are needed for control. Especially when producing high-end products, PCBA process control is even more necessary to produce products that meet customer requirements.
1、 IPQC process control
During the PCBA production process, a PCBA process control position, commonly known as an IPQC position, can be set up. The main responsibilities of IPQC include:
Check if all assembly processes and surface mount components comply with the IPC-A-610D standard;
Operation manual and automatic inspection of the entire PCBA process;
Ensure consistency in the electronic assembly process;
Significant deviations in management statistical methods and techniques;
Arrange a specialist to audit standard procedures and identify process improvement needs.
2、 PDCA and SPC
PCBA process control can also be controlled through tools such as PDCA mode and SPC statistical process control.
Process is a fundamental element of the quality management system, and studying the interrelationships and interactions between processes provides a clear idea for managing quality activities in the system, which is more conducive to effective and continuous control of many processes. The operation (control) of each process follows the PDCA cycle mode.
1. P (Plan) - Plan, determine policies and objectives, and determine activity plans;
2. D (Do) - Execute, do it on-site, and achieve the content of the plan;
3. C (Check) - Check, summarize the results of the execution plan, pay attention to the effectiveness, and identify problems;
4. A (Action) - Take action, process the results of summary checks, affirm successful experiences, and appropriately promote and standardize them; Summarize the lessons of failure to avoid recurrence, and place unresolved issues in the next PDCA cycle.
SPC: Statistical Process Control (SPC) is a tool for process control that applies statistical methods to evaluate and monitor various stages of the process in order to implement the principle of prevention. It establishes and maintains an acceptable and stable level of the process, thereby ensuring that products and services meet regulatory requirements.
With the increasing difficulty of electronic product processing, process control of PCBA has become increasingly important as a means to improve quality.
6. What does DFM mean? What is the significance of PCBA DFM?
DFM refers to Design for Manufacturability, which optimizes design to make product manufacturing or assembly easier, while reducing costs and improving quality and efficiency.
The significance of PCBA DFM
According to IPC statistics:
More than 60% of products are caused by early design concepts;
More than 75% of manufacturing costs are determined by design drawings and specifications;
More than 80% of product defects are caused by design stage issues.
The hazards of poor design in production:
Causing a large number of welding or assembly defects
Increase repair workload and process flow
Increasing manufacturing costs and repairing may damage components
Impact on product reliability after repair
Increase process difficulty and reduce production efficiency
Unable to produce and ship in a timely manner, losing market competition opportunities.
PCBA DFM can make the design more suitable for production requirements, while also requiring customers to fully consider the production situation during the design process, so that the designed products can be produced and have more choices in production, which can effectively reduce costs.
7. What should be noted in the PCBA gluing process?
PCBA gluing is commonly used on the motherboard of washing machines and has a very good waterproof effect. When carrying out the PCBA gluing process, the following precautions should be taken.
1. Choose a suitable adhesive: commonly used silicone and epoxy sealing adhesives, and at least understand the parameters of "operation window time" and "curing time".
2. The temperature of PCBA before the can glue needs to be roughly consistent with the temperature of the glue.
3. The PCB that needs to be sealed with glue needs to be heated through a drying oven and baked to 50 ℃.
4. Excessive residue of flux needs to be cleaned to keep the PCBA board surface clean.
5. It's best to pour glue into the glue box first, and then put the PCBA in.
6. The proportion of polyurethane sealing adhesive must be accurate. The two commonly used ratio methods are 100:50 and 100:74, which are formulated based on the properties of the adhesive.
When applying PCBA glue, it is easy to generate bubbles, which is a very important issue to pay attention to.
8. What are the contents of PCBA board reliability testing?
When completing welding processing on PCBA boards, corresponding PCBA reliability tests are required to ensure the quality of PCBA. There are many contents of reliability tests, and we will list them one by one.
PCBA board reliability testing
1. ICT testing
ICT testing is conducted on the soldering of components, as well as on the open and short circuits of circuits, to ensure the soldering quality of the board.
2. FCT testing
After burning the program, connect the PCB board to the load, simulate user input and output, perform functional testing on the PCB board, achieve software and hardware debugging, and ensure normal front-end manufacturing and welding.
3. Aging test
Conduct long-term power on testing on the PCBA board, simulate user usage, and detect issues with virtual or false soldering of the PCBA.
4. Vibration testing
For some PCB boards with vibration testing requirements, professional vibration testers are used for long-term testing to ensure that there is no detachment of welded components. The sampling test ratio is determined according to customer requirements.
5. High and low temperature testing
Customers with this testing requirement will be equipped with professional testing rooms for their products and provide targeted testing services for common temperature ranges such as -40 ℃ to 100 ℃, fully simulating the environmental temperature of the product and maximizing its reliability.
6. Drop test
Place the PCBA at a certain height for free drop to test its welding stability.
The reliability required for different PCBA board products will vary greatly, and specific problem specific analysis is required.
9. What are the job responsibilities of a PCBA technician?
In addition to basic maintenance skills, PCBA technicians also need to know a lot of content, generally requiring a high school education or above and relevant work experience.
Job responsibilities of PCBA technicians:
1. Analyze and repair various defective products produced by the company, provide customer service with defective product repair, and provide technical support for the products.
2. Analyze the causes of defective product failure and propose improvement suggestions
3. Fill out a detailed defect analysis report.
4. Production process yield improvement work
5. Responsible for product development, debugging, and preparation of product related R&D documents;
6. Responsible for product trial production, drawing surveying and mapping, and process planning;
7. Assist in completing pre production preparation, and prepare drawings, material lists, and component drawings;
8. Electronic BOM (Bill of Materials, abbreviated as BOM) is a technical document that describes the composition of a company's products. It is used for production and schematic verification.
Due to differences in PCBA factories, the job responsibilities of PCBA technicians may vary.
10. What are the methods for PCBA processing inspection?
The PCBA processing process is quite complex, and to ensure product quality during assembly and welding, it is necessary to use corresponding equipment for testing at the end of the processing and production stages.
The methods for PCBA processing inspection include: manual visual inspection, solder paste detector, ICT (online testing), FCT (functional testing), AOI (optical testing), AXI (X-ray testing), and aging testing.
When conducting PCBA processing inspection, it is necessary to comply with the international inspection standard IPC-A-610E to ensure that the product meets customer requirements.
