What does PCBA function test mainly include? What test equipment is required?

Date：2021-09-22 16:24:00Views：2333

The process flow of PCBA patch processing is very complex, including PCB manufacturing process, component procurement and inspection, SMT patch assembly, dip plug-in, PCBA testing and other important processes. PCBA function test refers to a test method that provides a simulated running environment for the test target board to make it work in various design states, so as to obtain the parameters of each state to verify the function of PCBA. Simply put, it is to load appropriate excitation on PCBA and measure whether the output response meets the requirements. It generally refers to the PCBA function test after the actual circuit board is powered on.

PCBA function test includes the measurement of voltage, current, power, power factor, frequency, duty cycle, position measurement and other functional parameters. The function test of PCBA includes the following contents: general part:

1: Power part test - whether the power supply works normally, test the voltage at each point - use a comparator or other

2: Port (Interface) test, whether there is short & open, resulting in an exception

3: IC I / O read / write function test of integrated circuit module - Flash & EEPROM & CPU & SDRAM & Logic IC etc

4: Special function test (different circuit boards have different requirements) - if there is infrared, an external receiver is required

PCBA function test involves analog, digital, memory, RF and power circuits, and usually uses different test strategies. The test includes a large number of actual important functional paths and structural verification (it is determined that there is no hardware error) to make up for the missing parts in the previous test process. This requires a large number of analog / digital stimuli to be continuously added to the PCBA, while monitoring the same number of analog / digital responses and fully controlling their execution process. There are many forms of PCBA function test system and equipment, which have their own advantages and disadvantages in cost, time, effect and maintainability.

PCBA function test equipment

Model test system

Theoretically, the simplest way to test the function of a device (circuit board or module) is to put it in the same model system or subsystem as the real environment, and then see whether it works normally. If it is normal, we can be sure that it is good. If it is not normal, the technicians will test it, hoping to find out the cause of the failure to guide the maintenance. But in fact, this plug-in power on method has many disadvantages and is rarely effective, although it can sometimes be used as a supplement to other test schemes.

Test bench

The test bench is a routine test environment, including excitation / response interface with the tested equipment, test sequence and control specified in special test procedures. Excitation and response are usually provided by standard power supply and experimental instruments, special switches, loads and terminal custom electronic devices (such as digital excitation). Here, the fixture is a very important part, which can provide the correct signal path and communication to the equipment under test. In many cases, fixtures are basically customized for each application and need to be set in combination with manual operation. The test process and control are usually carried out manually, sometimes with the assistance of PC and specified by written agreement or procedure. The test bench is connected to specific products, which has the advantages of relatively low cost and simple equipment, but it has poor flexibility in dealing with a variety of products.

Special test equipment

Theoretically, the special test equipment is the system that makes the operation of the test bench automatic. The heart of the system is usually a computer, which is controlled by special bus and some programmable instruments. Speed, performance, applicability, cost and other factors affect the selection of instrument bus and structure. Various instruments and general equipment are stacked in one or more vertical boxes and then connected to the equipment under test. With automatic processing, setting time, test time and overall operation are faster and easier than manual test bench. Ste can be extended to meet a variety of performance needs, usually used in production or maintenance centers. The most obvious cost of ste is the overall cost: equipment investment cost, operation cost and program development cost.

Automatic test equipment

General automatic test equipment (GPATE, or ate for short) is a very advanced and flexible scheme, which can meet the test requirements of a variety of products and programs. System integration, signal connectivity and flexibility, value-added software and hardware, test oriented language, graphical user interface, etc. are the main differences between ate and ste. In addition to the advantages of full instrument integration, ate can also provide a better scheme for signal routing and connection. In most cases, the ate dedicated backplane includes an analog bus, which allows the instrument to be directly connected to any pin without complicating the internal and external leads. This flexibility can usually be extended to combine analog and digital channels, allowing the user to connect digital or analog excitation at any time and measure any pin of the receiver. As a result, not only the cost is greatly simplified and reduced, but also the test program is easier to implement. According to different control modes, it can be divided into: manual control PCBA function test, semi-automatic control PCBA function test and full-automatic control PCBA function test. With the rapid development of science and technology, in order to save production cost and improve production efficiency, some PCBA function tests use fully automatic test schemes. At present, for the PCBA function test of some simple tested boards, manual or semi-automatic test schemes are still adopted based on the consideration of simplifying the design and reducing the production cost.

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