Chip test methods and precautions

Chip for testing is extremely important part, there are defects in the chip can be found the earlier the better. There is a tenfold law in the field of chip technology, from the design -> manufacturing -> packaging function test -> system level application, each night can find themselves a teaching link, the chip as the company needs to pay the cost will increase tenfold!

Therefore, testing is a special concern for design companies. If you sell a functionally defective chip to a customer, the loss is huge, not only in terms of financial compensation, but also in terms of credibility. Therefore, the cost of chip testing is getting higher and higher!

I. Common Test Methods, CP (Chip Probe) Test and FT (Final Test) Test:.

1, CP test

There are two stages to test a chip. The first is CP (Chip Probing) test, also known as wafer test. The other is FT (Final Test) test, failure analysiswhich is to test the chip before packaging.

CP (Chip Probing) refers to wafer testing. During the entire chip manufacturing process, CP test is between wafer manufacturing and packaging. After the wafer is made, thousands of bare chips (unpackaged chips) are regularly distributed throughout the wafer. Because they are not scribed and packaged, all of the chip's pins are exposed, and these tiny pins need to be connected to the tester via a finer probe bench.

In the whole Wafer without the traditional scribing package, through the electronic probe will be exposed to the chip and the test machine how to connect, so that the chip system test method can be carried out is CP test.

Wafer CP test is commonly used in functional testing and performance testing to detect whether the chip function is normal,wafer level testing screening out the faulty chip in the wafer method.

2、FT test

FT test of packaged products is commonly used in function test, performance test and reliability test to check whether the chip function is normal and whether there are defects in the packaging process, and to help detect the chip in the reliability test after the "fire, snow, lightning" whether it can still work. To apply the equipment is mainly automatic test equipment (ATE) + robot + instrumentation, to do the hardware is to test the carrier board) + test socket and so on.

Second, the chip test notes

1. Before testing to understand the integrated circuit and related circuitry works

Before checking and repairing integrated circuits, you must first familiarize yourself with its function, internal circuitry, the main electrical parameters, the role of each pin, as well as the pin's normal voltage and waveforms and peripheral components composed of the circuit's operating principle. If the above conditions are met, it is much easier to analyze and check.

2, test we do not develop to cause a short circuit between the pins

When using an oscilloscope probe to measure the voltage or test waveforms, the meter pen or probe should not slide, resulting in a short circuit between the pins of the integrated circuit. Any instantaneous short circuit can easily damage the integrated circuit, so be especially careful when testing flat-package CMOS integrated circuits.

3, it is strictly prohibited in the absence of an isolation transformer, wafer testthe use of grounded test equipment to contact the bottom of the charged TV, audio, video and other equipment.

Television, audio, video and other equipment without the use of power isolation transformer, it is prohibited to test directly with grounded equipment. Although most recorders have a power transformer, but when access to more specific types of TV or audio equipment, especially those with higher output power or less understanding of the nature of the power supply used in the TV or audio equipment, the first thing to figure out whether the chassis is charged, or else it is easy to be shorted by the power supply of the chassis of the TV, audio and other equipment in the chassis, resulting in short circuits in the chassis, spreading to the integrated circuits, which will lead to the failure of the further expansion of the fault.

4. Pay attention to the insulation properties of the soldering iron.

Not allowed to carry out electrified equipment using the attention of the soldering iron welding, to confirm that the soldering iron is not electrified, it is best to protect the iron's shell grounding, the MOS circuit design should need to be careful to be able to use the 6 ~ 8V low-voltage control circuits iron is safer.

5, to ensure the quality of welding

Welding firm indeed, the buildup of solder, air holes easily caused by false soldering. Soldering time is generally no more than 3 seconds, soldering iron power supply should be endothermic 25W or so. Has been soldered integrated circuits should be carefully inspected, it is best to use an ohmmeter to measure whether there is a short circuit between each pin, to confirm that there is no welding adhesion phenomenon before connecting the power supply.

6. Do not judge the damage of the IC easily.

Do not easily determine whether the integrated circuit is damaged. As the vast majority of integrated circuits are directly coupled, once a circuit is abnormal, it may lead to multiple voltage changes, and these changes are not necessarily caused by the integrated circuit damage, in addition, in some cases, the pin voltage measured with the normal value of the same or close to the same, may not be a good integrated circuit. Because some soft faults do not cause changes in DC voltage.

7, test meter internal resistance to be large

Measurement of IC pin DC voltage, should choose the internal resistance greater than 20KΩ / V multimeter, otherwise the voltage of some pins will have a large measurement error.

8, to pay attention to the power for integrated system circuit heat dissipation

Power integrated circuits should have good heat dissipation, do not allow high-power work in the absence of heat sinks.

9, the lead should be reasonable

If you need to increase the peripheral components to replace the internal damage to the integrated circuit, you should choose small components, wiring should be reasonable, to avoid unnecessary parasitic coupling, especially between the audio power amplifier integrated circuit and the preamplifier circuit ground terminal to be dealt with.