How Should The Quality Acceptance Criteria Be Clarified in The PCB Procurement Contract?
In PCB procurement contracts, it is crucial to clarify the quality acceptance standards. The following are some specific methods and points:
Citing relevant international, national or industry standards
International standards: You can cite internationally accepted standards such as IPC standards (American Electronic Circuit and Electronic Interconnection Industry Association standards), and specify specific version numbers, such as IPC-A-600H, etc. This standard has detailed specifications for the appearance, size, electrical performance and other aspects of PCBs, providing an international general basis for acceptance.
National standards: You can also refer to relevant domestic standards, such as GB/T 4677 "Printed Board Test Methods", etc. These standards stipulate various indicators of PCBs from the perspective of domestic industries, which can ensure that products meet the basic requirements of the domestic market.
Industry standards: Some specific industries may have their own dedicated PCB standards, such as PCBs in the aerospace industry must follow aerospace-related standards, and the automotive industry may have standards formulated by the Automotive Electronics Committee (AEC). For PCBs used in these industries, it is necessary to clearly follow the corresponding industry standards.
Refine product specifications
Dimensions and tolerances
Dimensions: Accurately specify the length, width, and thickness of the PCB, such as 100mm±0.1mm for length, 80mm±0.1mm for width, and 1.6mm±0.05mm for thickness.
Aperture size: Specify the size and tolerance of various apertures, such as 1.0mm±0.05mm for plug-in holes, 0.5mm±0.03mm for vias, etc.
Line size: Detail the minimum line width, line spacing, and their tolerances, such as 0.15mm±0.02mm for minimum line width and 0.15mm±0.02mm for minimum line spacing.
Materials and processes
Board type: Determine the board to be used, such as FR-4, polyimide, etc., and put forward requirements for the performance indicators of the board, such as dielectric constant, loss factor, etc.
Surface treatment: Specify the surface treatment method, such as tin spraying, immersion gold, OSP, etc., and clarify the thickness, uniformity and other requirements of the surface treatment, such as the thickness of immersion gold must reach 3-5μm.
Solder mask and silk screen: Specify the color, thickness, adhesion of the solder mask layer, as well as the content, clarity, and friction resistance of the silk screen.
Clarify performance indicators
Electrical performance
Insulation resistance: Specify the minimum value of insulation resistance, such as it must be greater than 1000MΩ.
Withstand voltage: Specify the voltage range that the PCB can withstand, such as no breakdown, arcing, etc. at a test voltage of 500V.
Impedance: Determine the characteristic impedance value and its tolerance range based on product requirements, such as the characteristic impedance of the coaxial cable is 50Ω±1Ω.
Signal transmission delay: For PCBs with high-speed signal transmission, specify the maximum value of signal transmission delay, such as no more than 50ps/cm.
Mechanical properties
Bending strength: Specifies the bending strength of the PCB under certain conditions, such as the bending angle does not exceed 10° under a pressure of 10N.
Hardness: Specifies the hardness requirements of the PCB surface, such as reaching H grade or above.
Solderability: Requires that the wetting time and spreading area of the PCB pads meet certain standards under specified welding conditions.
Environmental performance
High and low temperature resistance: Specifies the performance requirements of the PCB under high and low temperature environments, such as after being stored at high temperature of 85℃ and low temperature of -40℃ for 24 hours, there is no significant change in electrical and mechanical properties.
Moisture resistance: Specifies that under certain humidity conditions, such as relative humidity of 95% and temperature of 40℃, the PCB has no obvious moisture, deformation, short circuit, etc. after being placed in an environment for a certain period of time.
Determine the inspection method and process
Inspection means
Appearance inspection: Use visual inspection or tools such as magnifying glasses and microscopes to check whether there are scratches, stains, exposed copper, short circuits, open circuits and other defects on the PCB surface, and specify the allowable range and type of defects.
Electrical performance test: Use professional testing equipment, such as impedance analyzer, insulation resistance tester, withstand voltage tester, etc., to test the electrical performance indicators of PCB, and clarify the parameter range and accuracy requirements of the test.
Mechanical performance test: Use bending tester, hardness tester and other equipment to test the mechanical properties of PCB, record the test data and compare with the standard.
Reliability test: Conduct reliability tests such as high and low temperature cycle test, humidity test, salt spray test, etc. to simulate the actual use environment and test the performance stability of PCB.
Inspection process
First piece inspection: Before mass production, conduct a comprehensive inspection of the first product, and mass production can only be carried out after confirming that all indicators meet the requirements.
Process inspection: During the production process, regularly or irregularly conduct random inspections on products to promptly discover quality problems in the production process and make adjustments.
Final inspection: After the product is produced, a comprehensive final inspection is carried out to ensure that all products meet the quality acceptance standards before they can be shipped.
Specify the acceptance time and place
Acceptance time: Specify the specific acceptance time limit after delivery, such as starting acceptance within 3 working days after delivery and completing acceptance within 5 working days. For some complex PCB products that require long-term testing, the acceptance time can be appropriately extended.
Acceptance location: Acceptance can usually be carried out at the delivery location or the inspection site designated by the purchaser, such as the purchaser's laboratory or production workshop, to ensure that the acceptance environment meets the test requirements.
Agreed quality problem handling method
Determination of unqualified products: According to the inspection results, clearly stipulate what kind of situation is considered unqualified, such as size exceeding the tolerance range, electrical performance not meeting the standards, serious appearance defects, etc.
Handling measures: If the inspection finds that the PCB has quality problems, the purchaser has the right to require the supplier to take measures such as replacement, return, repair, etc., and bear the corresponding expenses.
Compensation liability: The supplier shall bear the compensation liability for the losses caused to the purchaser due to quality problems, such as production delay losses, customer claims losses, etc., and the contract shall clearly specify the calculation method of losses and the scope of compensation.
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