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Complete Medical-grade Printed Circuit Board Manufacturing Process


As the medical industry continues to innovate and advance technology, more and more medical equipment and medical technologies require highly reliable electronic components and systems to support their functions. Therefore, medical-grade PCB design, assembly, prototyping, and complete machine assembly emerged. Printed circuit board assembly plays a vital role in the medical field such as medical equipment, medical monitoring equipment, medical devices, or medical sterilization equipment. A precisely executed and high-quality medical electronics PCBA manufacturing process is crucial to the success of medical PCB assembly services, ensuring reliability and performance stability.

Complete Production Process Flow of Medical Electronic PCB Assembly Manufacturing

1. Inner Layer  

Inner layer production is a crucial step in the medical PCB assembly process. The production process is:

● Cutting: Cutting PCB substrates to production dimensions to medical device specifications

● Pre-treatment: Clean the surface of the PCB substrate and remove surface contaminants;

●  Lamination: stick the dry film on the surface of the PCB substrate to prepare for subsequent image transfer;

● Exposure: Use exposure equipment to expose the coated substrate through ultraviolet light, and transfer the image of the substrate to the dry film to form the inner circuit;

● DE: After the exposure, the substrate is developed, etched, and film removed to complete the production of the inner layer board.

2. PCB Hole Drilling  

According to the design requirements of medical electronic products, use a drilling machine to drill holes of different diameters and sizes on the board to make holes between the boards for subsequent processing of plug-ins. The production process is:

●  Inter-layer alignment: Ensure accurate alignment between layers of multi-layer PCB to ensure accuracy and stability of drilling.

●  Drilling positioning: According to the design requirements, mark the drilling positions of each layer on the PCB board.

●  Drilling: Use professional circuit board drilling equipment to drill holes at the marked positions according to the design requirements to ensure the accuracy of the hole diameter and position.

●  Cleaning: Clean the PCB board after drilling to remove residual chips and debris to ensure the surface of the PCB board is clean and tidy.

●  Inspection quality: Conduct quality inspection on the printed circuit board after drilling to ensure that the drilled holes' size, location, and quantity meet the design requirements.

●  Packaging and assembly: After drilling is completed, the PCB board enters the next stage of medical PCB assembly, including patching, welding, packaging, and other process steps, and finally forms a medical electronic product.

3. Solder Mask Process  

● Solder mask preparation: Coat solder mask material on the surface of medical electronic PCB boards to protect circuit components from the external environment and improve board pollution resistance.

● Solder mask pattern design: According to the design requirements, design the solder mask pattern, including the pad area and the non-pad area, to ensure that the solder resist covers the pad and does not cover the non-pad area.

● Solder mask processing: Through screen printing or spraying, the solder mask material is accurately coated on the surface of the PCB board to form the designed solder mask pattern.

● Solder mask curing: The solder mask material coated on the surface of the PCB board is cured through processes such as hot air oven or UV curing equipment to ensure that it is firmly bonded to the surface of the printed circuit board.

4. Component Installation

● Patch selection: According to the circuit design requirements and the functional requirements of the medical equipment, purchase components that meet medical grade standards, and plan the type, size, location and other parameters of the patch components.

● SMT equipment settings: Set the parameters of the SMT machine, including temperature, speed, pressure, etc., to ensure the accuracy and stability of the SMT process and meet the requirements of medical electronic PCB assembly.

● Arrangement of components: Precisely arrange the chip components on the circuit to ensure their accurate position and consistent spacing.

● Component installation: Electronic components are installed on the PCB board through processes such as welding or SMT to ensure that the components are positioned accurately and the spacing is consistent.

Purchase components that meet medical grade PCBA standards

5. Soldering  

● Soldering: Use equipment such as a hot air stove or reflow oven to solder the components and firmly fix them on the PCB board to connect the circuit.

● Welding inspection: Conduct welding quality inspection on the completed PCB board, including solder joint appearance, welding strength, etc., to ensure that the welding quality meets the standards and requirements of the medical electronics industry.

● Cleaning treatment: Clean the PCB board after welding to remove the residue generated during the welding process to ensure that the surface of the circuit is clean and tidy.

6. High Voltage Test

● Test point determination: Determine the location and test points that require high-voltage testing on the PCBA, usually key nodes and high-voltage areas in the circuit.

● Test program preparation: Prepare high-voltage test procedures and processes, including test parameter settings, test time, test methods, etc.

● Test equipment settings: Set the parameters of high-voltage test equipment, such as voltage, current, test time, etc., to ensure that the test equipment is in correct working condition.

● High-voltage test: Use high-voltage testing equipment to conduct high-voltage testing on printed circuit board assembly, and apply high-voltage voltage to conduct insulation testing between test points to ensure the safety and reliability of the PCB board under high-voltage conditions.

● Test result analysis: Analyze the high-voltage test results, check whether there are insulation breakdowns, leakage, and other problems, and record the test data.

● Problem-solving: If problems are discovered during the testing process, troubleshoot and solve them promptly to ensure safety and reliability.

● Test report: Generate a high-voltage test report to record the test process, test results, and related data as an important reference for quality control of medical PCBA products.

7. Surface Treatment

Clean the PCB assembly surface to remove possible dirt, grease and other substances to ensure the effect of surface treatment.

● Surface treatment process: According to the requirements of medical circuit boards, you can choose a variety of treatment methods, such as lead-free HASL, electroplated gold (ENIG), electroplated tin (ENIG), and immersion gold (Immersion Gold) wait. For the selected surface treatment method, prepare corresponding treatment equipment and chemicals to ensure the controllability and stability of the treatment process. Then select a surface treatment process, such as chemical cleaning, surface activation, electroplating or deposition, to form the required metal protective layer or alloy layer on the PCB surface.

● Quality inspection: Conduct quality inspection on the processed PCB board, including the thickness, uniformity of the surface treatment layer and adhesion to the PCB substrate, etc.

8. Functional Testing  

● Test environment preparation: Set up a suitable test environment, including temperature, humidity, and other environmental parameters, to ensure that the test environment meets the requirements for medical electronic use.

● Functional testing: Functional testing is performed on the PCBA board to test whether the various functions of the circuit are working properly, including testing of input and output signals, measurement of voltage and current, etc.

● Communication interface test: Test the communication interface on the PCBA to ensure that its communication function with external devices is normal, including serial port, USB interface, Ethernet interface, etc.

● Data processing test: Test the data processing function on the circuit board, including testing of data collection, processing, storage and other functions.

● Medical-specific function test: Test the special functions of medical electronic products, such as electrocardiogram data collection, body temperature measurement function, vital signs monitoring, etc.

● Automated testing: Use automated testing equipment or software to conduct functional testing to improve testing efficiency and repeatability.

● Exception handling: When abnormal conditions are discovered during the testing process, they will be recorded and investigated promptly to ensure the quality and reliability of the final product.

● Test report generation: Generate test reports for functional tests, record the test process, test results, and abnormal situation handling, as an important reference for product quality control.

Medical electronic PCBA for functional testing

9. FQA ( Full Inspection )  

Due to the medical industry's particularity and the products' importance, stricter sampling standards are adopted for medical-grade PCBA FQA.

● Sampling test: After completing all PCBA production processes, randomly select PCBA products samples from the production batch, and conduct comprehensive tests on the selected samples in terms of functionality, reliability, etc.

● Functional testing: Functional testing is performed on the selected samples to ensure the normal operation of various circuit board functions, including special functions required by medical equipment.

● Reliability test: Conduct reliability tests on the selected samples, such as temperature cycle tests, vibration tests, humidity tests, etc., to verify the stability and durability of the circuit board in the medical environment.

● Inspection and evaluation: Evaluate the sample based on the test results to determine whether it meets the quality standards and requirements of the medical industry.

● Exception handling: Conduct detailed exception analysis and processing for abnormal situations discovered during testing to ensure that problems are solved promptly.

● Report generation: Generate FQA report to record the test process, test results and abnormal situation handling as the final confirmation and review before the product leaves the factory.

● Audit and confirmation: The quality management department or person in charge will audit and confirm the FQA report to ensure that all samples meet the quality requirements of medical PCB circuit boards.

● Product release: According to the results of the FQA report, qualified samples are released to ensure that the quality and reliability of medical printed circuit board assembly meet the requirements of the medical industry and can be delivered to customers for use.

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