Integrated circuit testing is a crucial step in ensuring chip quality, with the two main types of testing being CP testing (Chip Probing) and FT testing (Final Test). These two testing methods run through the pre - and post production stages of chip production, testing the wafer of the chip and the packaged finished product separately.

CP Testing (Chip Probing) - Preliminary Screening
CP testing refers to the electrical and functional testing of each chip unit (Die) directly on the wafer before cutting and packaging, in order to identify and eliminate non-conforming chips as early as possible and avoid unnecessary subsequent costs.
1. Purpose of CP testing
·Identify and eliminate bad die: Through electrical performance and basic functional testing, eliminate unqualified chip units in advance.
·Reduce the cost of subsequent processes: avoid wasting packaging costs, as defective chips after packaging cannot be recovered.
·Monitoring the yield of the previous process: By testing the results, the stability and quality of the wafer manufacturing process can be evaluated, providing data support for subsequent improvements.
2. Characteristics of CP testing
·Test object: Each Die (chip unit) on the wafer.
·Testing stage: The stage where the wafer has not been cut and packaged, which belongs to the testing of the previous process.
·Test project: Mainly focuses on basic electrical performance testing, with low testing power and limited high current testing by probe cards.
·Testing difficulties: accuracy of probe cards, probe interference, and challenges of parallel testing. Especially in large-scale integrated circuits, ensuring the contact accuracy and stability of probe cards is a major challenge.
Final Test - Finished Product Inspection
FT testing is the testing of packaged chip products, aimed at conducting comprehensive and rigorous functional and performance testing on the packaged chips to ensure that they meet design requirements and operate reliably in practical applications.
1. Purpose of FT testing
·Ensure packaging quality: Check whether the packaging process has affected the chip.
·Comprehensive functional verification: Ensure that all functions of the chip comply with design specifications and meet customer needs.
·Reliability testing: Testing the reliability of chips under different temperature and pressure conditions to ensure their performance in practical application environments.
2. Characteristics of FT testing
·Test object: Packaged finished chips.
·Testing phase: The subsequent process testing after the completion of chip packaging.
·Test items: There are more functional test items with strict testing conditions. Common tests include functional testing, electrical performance testing, power testing, thermal stability testing, etc.
·Testing difficulty: Ensure the performance of the chip in actual usage environments, especially the functional stability under extreme conditions such as high temperature and low temperature. In addition, FT testing also checks the power consumption and output performance of the chip, which cannot be fully tested during the CP phase.
3、 The difference between CP and FT testing
1. Different test objects: CP testing mainly targets chip units on wafers, that is, unpackaged bare chips; FT testing is aimed at finished chip products that have already been packaged.
2. Different testing stages: CP testing is conducted in the preceding process of wafer manufacturing, usually completed before wafer cutting; FT testing is the final step after the chip packaging is completed to ensure that the chip can be shipped normally.
3. Different testing purposes: The purpose of CP testing is to remove chips that are clearly unqualified and monitor the process yield of wafer manufacturing; The purpose of FT testing is to ensure the functional integrity and reliability of the chip in practical applications.
4. Different testing items: CP testing mainly conducts basic electrical performance tests, such as threshold voltage, on resistance, leakage current, etc. These testing items are relatively basic and have low testing power; The FT testing project is more comprehensive, including functional testing, performance testing, reliability testing, etc. The power of FT testing is relatively high, allowing for high current testing, while the testing environment requirements are more stringent.
5. Different testing conditions: CP testing is usually only conducted at room temperature, with relatively simple conditions; FT testing needs to be conducted in different temperature environments, especially in high or low temperature environments, to test the stability and reliability of the chip.
CP testing and FT testing are two indispensable steps in the integrated circuit testing process. CP testing eliminates defective chips during the wafer stage to reduce subsequent costs; FT testing ensures that the functionality and performance of the chip meet the design requirements after packaging. Although they differ in terms of testing objects, stages, and projects, they together constitute the core process of chip quality control.

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