QFN packaging structure strain measurement method based on microscopic DIC

Abstract

The invention relates to a QFN packaging structure strain measurement method based on microscopic DIC. The method comprises the following steps: manufacturing a QFN packaging circuit board; performing spot making treatment; heating the QFN pin and carrying out temperature monitoring; measuring a speckle image at a specific temperature; and calculating strain values before and after deformation of the QFN packaging pin. According to the method, the real deformation condition of the welding spot under the thermal load at the specific temperature can be directly obtained, a basis can be provided for simulation calculation and correction of an engineering algorithm, and a technical support is provided for positioning the defect position of the welding spot, optimizing the technological process and revealing a failure mechanism.

Description

Technical Field

[0001] The invention relates to a QFN packaging structure strain measurement method based on microscopic DIC, belonging to the technical field of electronic packaging. Background Art

[0002] In modern electronic equipment, especially those used in new energy vehicles, aviation, aerospace and other fields, people have higher and higher requirements for their reliability. During service, it is often difficult to bear the consequences of the failure of the entire electronic equipment caused by the failure of the packaging structure. For electronic packaging structures, solder joints not only serve as channels for electrical connections, but also provide mechanical connections between chips and substrates. Investigations into many electronic equipment failures have shown that most failures are mechanical in nature, about 70% occur at various electrical connectors and wiring harnesses, and most failures are caused by deformation of interconnected structures caused by heat or vibration. However, since the size of solder joints is in the millimeter range or even smaller, conventional measurement methods are difficult to directly measure the true deformation size and its distribution. Generally, the stress-strain results obtained through finite element simulation are used to evaluate the package life based on the fatigue life model. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the deficiencies of the above-mentioned prior art, the present invention proposes a QFN packaging structure strain measurement method based on micro-DIC, which can directly obtain the actual deformation of the solder joint under thermal load at a specific temperature. It can not only provide a basis for simulation calculations and correction of engineering algorithms, but also provide technical support for locating the position of solder joint defects, optimizing the process flow and revealing the failure mechanism, and has certain engineering application value.

[0005] (II) Technical solution

[0006] A method for measuring strain of a QFN package structure based on microscopic DIC comprises the following steps:

[0007] S1. Make QFN package circuit board;

[0008] S2. Use fluorescent microsphere solution to make spots on the QFN pins to be tested;

[0009] S3. Use a hot air gun to heat the QFN pin for a long time to stabilize the temperature of the area to be tested, and use a thermocouple to monitor the temperature of the QFN pin;

[0010] S4. Use a stereomicroscope DIC measurement system to measure the speckle image at a specific temperature;

[0011] S5. Calculate the strain value of the QFN package pin before and after deformation.

[0012] In step S4, the stereomicroscope DIC measurement system includes a left camera, a left eyepiece, a right camera, a right eyepiece, a focusing system, and an objective lens; the objective lens is arranged above the QFN pin to be measured, and the focusing system is arranged above the objective lens; two paths are arranged above the focusing system, the left path has a left eyepiece and a left camera, and the right path has a right eyepiece and a right camera.

[0013] In the step S3, the specific temperature is 100°C.

[0014] The step S5 is to obtain a strain cloud map by comparing the changes in image intensity resolution information before and after deformation.

[0015] (III) Beneficial effects

[0016] Compared with the prior art, the QFN package structure strain measurement method based on micro DIC of the present invention has the following beneficial effects:

[0017] (1) The present invention uses a specific solution to make speckles on the QFN pins, so that the speckle quality meets the observation requirements and the speckle pattern of the QFN pins to be tested has a large average grayscale;

[0018] (2) The present invention uses a hot air gun to heat the QFN pins and uses a thermocouple to monitor the temperature of the QFN pins, thereby realizing loading control of the QFN thermal environment.

[0019] (3) Compared with other measurement methods, the present invention is a non-contact, non-destructive measurement method that does not destroy the structure of the packaging structure itself and maintains the integrity of the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the optical path of a stereo microscope

[0021] Figure 2 Thermal loading test diagram of QFN pin under test

[0022] Figure 3 Measured displacement field of the pin in the horizontal direction DETAILED DESCRIPTION

[0023] A method for measuring strain of a QFN packaging structure based on microscopic DIC of the present invention comprises the following steps:

[0024] S1. Make QFN package circuit board;

[0025] S2. Use fluorescent microsphere solution to make spots on the QFN pins to be tested;

[0026] S3. Use a hot air gun to heat the QFN pin for a long time to stabilize the temperature of the area to be tested, and use a thermocouple to monitor the temperature of the QFN pin;

[0027] S4. Use a stereomicroscope DIC measurement system to measure the speckle image at a specific temperature;

[0028] S5. Calculate the strain value of the QFN package pin before and after deformation.

[0029] See also Figure 1 In step S4, the stereomicroscope DIC measurement system includes a left camera, a left eyepiece, a right camera, a right eyepiece, a focusing system, and an objective lens; an objective lens is arranged above the QFN pin to be measured, and a focusing system is arranged above the objective lens; two paths are arranged above the focusing system, the left path has a left eyepiece and a left camera, and the right path has a right eyepiece and a right camera.

[0030] See also Figure 2 In step S3, the specific temperature is 100°C.

[0031] See also Figure 3 In step S5, a strain cloud map is obtained by comparing the changes in image intensity resolution information before and after deformation.

[0032] The present invention proposes a QFN package structure strain measurement method based on microscopic DIC, which can directly obtain the actual deformation of the solder joint under thermal load at a specific temperature. It can not only provide a basis for simulation calculations and correction of engineering algorithms, but also provide technical support for locating solder joint defect positions, optimizing process flows, and revealing failure mechanisms. It has certain engineering application value.

Claims

1. A method for measuring strain of a QFN package structure based on microscopic DIC, characterized in that: The following steps are involved: S1. Make QFN package circuit board; S2. Use fluorescent microsphere solution to make spots on the QFN pins to be tested; S3. Use a hot air gun to heat the QFN pin for a long time to stabilize the temperature of the area to be tested, and use a thermocouple to monitor the temperature of the QFN pin; S4. Use a stereomicroscope DIC measurement system to measure the speckle image at a specific temperature; S5. Calculate the strain value of the QFN package pin before and after deformation.

2. The QFN package structure strain measurement method based on microscopic DIC according to claim 1, characterized in that: In step S4, the stereomicroscope DIC measurement system includes a left camera, a left eyepiece, a right camera, a right eyepiece, a focusing system, and an objective lens; the objective lens is arranged above the QFN pin to be measured, and the focusing system is arranged above the objective lens; There are two paths on the left and right above the focusing system, the left path has a left eyepiece and a left camera, and the right path has a right eyepiece and a right camera.

3. The QFN package structure strain measurement method based on microscopic DIC as claimed in claim 2, characterized in that: In the step S3, the specific temperature is 100°C.

4. The QFN package structure strain measurement method based on microscopic DIC as claimed in claim 3, characterized in that: The step S5 is to obtain a strain cloud map by comparing the changes in image intensity resolution information before and after deformation.

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