How to detect electronic products? Basic knowledge of component product quality inspection

Date：2021-11-18 13:28:49 Views：1803

Product inspection is an essential means of quality control in the production of modern electronic enterprises. It mainly plays the role of process control, quality control and judging the qualification of products. The product inspection shall implement the "three inspection" system combining self inspection, mutual inspection and full-time inspection.

Concept of detection

Inspection is the conformity evaluation of electronic products through observation and judgment, combined with measurement and trial test when appropriate. The whole machine inspection is to observe, measure and test according to the contents specified in the technical requirements of the whole machine, and compare the results with the specified requirements to determine the qualification of various indexes of the whole machine.

Classification of inspection

The inspection process of the whole machine is divided into full inspection and random inspection.

(1) Full inspection。 It refers to 100% inspection of all products one by one. Judge whether the inspected single product is qualified or not according to the test results.

The main advantage of full inspection is that it can minimize the unqualified rate of products.

(2) Spot check。 It is to take some samples from the inspection batch for inspection, and judge the quality level of the whole batch of products according to the inspection results, so as to draw the conclusion whether the product is qualified or not.

Detection process

Testing can generally be divided into three stages:

(1) Inspection of assembly equipment. It mainly refers to the inspection of components, parts, outsourced parts and materials before warehousing. Sampling inspection is generally adopted.

(2) Process inspection. It refers to the inspection of one or more processes in the production process, or semi-finished products and finished products, mainly including welding inspection, unit circuit board commissioning inspection, system joint commissioning inspection after whole machine assembly, etc. Process inspection generally adopts the inspection method of full inspection.

(3) Complete machine testing of electronic products. The whole machine shall be inspected by multi-level and multiple re inspection. Generally, full inspection is adopted for warehousing, and sampling inspection is mostly adopted for outbound.

Electronic product test items

(1) Performance. Performance refers to the technical characteristics of the product to meet the use purpose, including the use performance, mechanical performance, physical and chemical performance, appearance requirements, etc.

(2) Reliability. Reliability refers to the performance of the product to complete the work task within the specified time and under the specified conditions, including the average service life, failure efficiency, average maintenance interval, etc.

(3) Security. Safety refers to the degree of ensuring the safety of products during operation and use.

(4) Adaptability. Adaptability refers to the adaptability of products to natural environmental conditions, such as the response to temperature, humidity, pH, etc.

(5) Economy. Economy refers to the cost of products and the consumption expenses for maintaining normal work.

(6) Timeliness. Timeliness refers to the timeliness of products entering the market and the timely provision of technical support and maintenance services after sales.

Appearance inspection

Appearance inspection refers to the process of inspecting the appearance, packaging and accessories of the whole machine by visual inspection.

1. Visual inspection: the appearance shall be free of damage and pollution, and the signs shall be clear; The mechanical assembly meets the technical requirements.

2. Packing: it is required to be well packed without damage and pollution; All signs are clear and intact.

3. Accessories: accessories and connectors are complete, intact and meet the requirements.

Performance test

It refers to the test and inspection of the electrical performance, safety performance and mechanical performance of the whole machine.

1．Electrical performance test

Test the electrical performance parameters of the whole machine, and compare the test results with the specified parameters to determine whether the inspected whole machine is qualified.

2．Safety performance test

It mainly includes: surge test, damp heat treatment, insulation resistance and electrical strength, etc. Security inspection should adopt the method of full inspection.

3．Mechanical properties are tested

It mainly includes the flexibility and reliability of panel operating mechanism and knob keys, as well as the installation tightness of the mechanical structure and parts of the whole machine.

Task description

According to the specific requirements of inspection process documents and electronic products, various inspections shall be carried out for the electronic products, and necessary aging tests shall be carried out.

Inspection before warehousing

Inspection before warehousing is an important prerequisite to ensure product quality and reliability. Raw materials, components, etc. required for product production may deteriorate and be damaged during new purchase, packaging, storage and transportation, or they are unqualified products. Therefore, these articles shall be visually inspected according to product technical conditions and agreements before warehousing, and can be warehoused only after they are qualified. Articles judged as unqualified shall not be used and shall be isolated to avoid mixing.

In addition, some components, such as transistors, integrated circuits and some resistance capacitance components, need to be aged and screened before assembly.

Inspection during production

Inspection in the production process refers to the inspection of each process in the production process, which is carried out by the combination of operator self inspection, production team mutual inspection and full-time personnel inspection.

Self inspection means that the operator checks the assembly quality of the assembled components and parts according to the requirements of the process guidance card of this process, and timely adjusts and replaces the unqualified components to avoid flowing into the next process.

Mutual inspection is the inspection of the next operation against the previous operation. Before the operation of this process, the operator shall check whether the assembly and adjustment quality of the previous process meets the requirements, feed back the parts with quality problems to the previous process in time, and shall not operate this process on unqualified parts.

The full-time inspection is generally carried out in the next process after the assembly and commissioning of components and complete machine. During the inspection, the quality of each assembly and adjustment process in the production process of parts and complete machine shall be comprehensively inspected according to the inspection standards. Inspection standards are generally expressed in the form of words and drawings. For some defects that are inconvenient to be expressed in words and drawings, standard samples shall be established in kind as the inspection basis.

Whole machine detection

The whole machine inspection is to check whether the product meets the predetermined functional requirements and technical indicators after the product passes the final assembly and commissioning. The whole machine inspection mainly includes visual inspection, function inspection and main performance index test.

The contents of visual inspection include: whether the product is clean; Whether the coating, decorative parts, marks and nameplates on the plate surface and casing surface are complete and damaged; Whether various connecting devices of the product are intact; Whether all metal parts have rust spots; Whether the structural parts are deformed or broken; Whether the silk screen printing and handwriting on the surface are complete and clear; Whether the measuring range meets the requirements; Whether the rotating mechanism is flexible; Whether the control switch is in place, etc.

Function test is to check all functions required by product design. Different products have different inspection contents and requirements. For example, TV sets should be inspected for program selection, image quality, brightness, color, sound and other functions.

Main performance index test refers to judging whether the product meets the national or industrial standards by using instruments and equipment with specified accuracy to check the technical indexes of the product. The current national standards stipulate the basic parameters and measurement methods of various electronic products. Generally, only the main performance indexes are tested in the inspection.

Sample test of electronic products

The test is a routine verification of finalized products or products produced for a long time in order to fully understand the special performance of products. In order to truly reflect the product quality, the sample machine for test shall be randomly selected from the qualified whole machine. The test includes environmental test and life test.

(1) Environmental test

Environmental test is a method to test the adaptability of products to the environment. It is a test to evaluate and analyze the impact of the environment on product performance. It is usually carried out under various natural conditions that may be encountered by simulated products. Environmental test includes mechanical test, climate test, transportation test and special test.

Mechanical test includes vibration test, impact test, centrifugal acceleration test, etc.

Climate test includes high temperature test, low temperature test, temperature cycle test, humidity test and low pressure test.

Transportation test is to test the adaptability of products to packaging, storage and transportation environmental conditions.

Special test is to check the product's ability to adapt to special working environment, including smoke test, dust test, mold resistance test and radiation resistance test.

(2) Life test

Life test is the test to investigate the regularity of product life, and it is the test in the final stage of product. It is a test conducted by simulating the actual working state and storage state of the product under specified conditions and putting a certain sample into operation. During the test, the failure time of the sample shall be recorded and statistically analyzed to evaluate the reliability quantitative characteristics of the product, such as reliability, failure efficiency, average life and so on.

In order to ensure the production quality of complete electronic products, the power on aging of the whole machine is usually carried out after assembly, commissioning and inspection. The so-called aging of the whole product is to let the whole product work continuously for several hours under certain environmental conditions, and then test whether the performance of the product still meets the requirements. Through aging, the potential defects existing in the manufacturing process of products can be found, and the faults (early failure) can be eliminated before leaving the factory.

Aging is a routine process of an enterprise. Usually, every product must undergo aging before leaving the factory.

1. Determination of aging conditions

The aging of complete electronic products shall be carried out when the power supply is connected. The main aging conditions are time and temperature. According to different conditions, the continuous aging time of 8h, 24h, 48h, 72h or 168h can be selected at room temperature. Sometimes, the method of increasing the indoor temperature (sealing the aging chamber so that the working heat of the product itself is not easy to dissipate, or adding an electric heater) and even putting the product into a constant temperature test chamber are adopted to shorten the aging time.

During aging, pay close attention to the working state of the product. If an individual product is found to be abnormal, it shall be immediately removed from power on aging and sent to the maintenance department.

2. Static aging and dynamic aging

When aging the whole electronic product, if only the power is connected and no signal is injected into the product, this state is called static aging. If the working signal is also input to the product at the same time, it is called dynamic aging. Take a TV as an example. During static aging, there is only a grating on the picture tube, while during dynamic aging, a signal is sent from the antenna input, an image is displayed on the screen, and a sound is emitted from the horn. For another example, the computer only turns on the power supply and does not run the program during static aging, while the test program should be continuously run during dynamic aging. It is obvious that dynamic aging is more effective than static aging.