Reliable forming method of novel vehicle gauge level BGA (Ball Grid Array)

Abstract

The invention relates to the technical field of semiconductor packaging, in particular to a reliable forming method of a novel vehicle-gauge-grade BGA (ball grid array), which comprises the following steps: adding a thermoplastic high polymer 1 and a solvent into a ball mill, stirring and dissolving at a set operation temperature, and coating around a product; adding the thermoplastic high polymer 2 and a solvent into a ball mill, and stirring and dissolving at a set operation temperature; and then, second-time coating is conducted on the surface of the product obtained after first-time coating is conducted. According to the reliable forming method of the novel vehicle gauge level BGA, after the product is formed, the reliability of temperature circulation is obviously improved, gradient design is adopted, the problem of glass edge breakage of the BGA product is solved, and thermal stress borne by the glass can be obviously relieved; when the forming method is adopted for production and processing, the production efficiency is also obviously improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor packaging technology, and in particular to a reliability molding method for a novel automotive-grade BGA. Background Art

[0002] Automotive-grade semiconductors, also known as "automotive chips", are mainly used in vehicle control devices, vehicle monitoring systems, and vehicle electronic control devices. These semiconductor devices are mainly distributed in the body control module, as well as in the vehicle infotainment system, including powertrain integrated control system, active safety system and advanced driver assistance system. Among them, the vehicle camera, as one of the most critical devices, mainly includes interior view camera, rear view camera, front camera, side view camera, surround view camera, etc. At present, the camera is mainly used in the functions of reversing image and 360-degree panoramic view, forward collision warning, lane departure alarm and pedestrian detection in the car, which is an important supplement to radar. With the continuous improvement of the penetration rate of high-level assisted driving functions, the average number of cameras per vehicle is also increasing. At present, the L2 level is equipped with 5-8 cameras, the L3 level is equipped with 8-11 cameras, and the L4 level is generally equipped with more than 13 cameras. Compared with consumer and security CIS products, automobiles have higher requirements for high reliability, and the reliability requirements are mainly reflected in the service life and the use environment. However, the automotive-grade BGA product has glass edge collapse after reliability temperature cycling. Therefore, research on the reliability of the proposed vehicle-mounted CIS sensor has also received widespread attention. Summary of the invention

[0003] The technical problem to be solved by the present invention is that automotive-grade BGA products experience glass edge collapse after reliability temperature cycling, and their reliability is limited.

[0004] The technical solution adopted by the present invention to solve its technical problem is: a reliability molding method for a new type of automotive-grade BGA, wherein the products are evenly placed in a coating station, the first batch of thermoplastic polymers and solvents are added to a ball mill, the inside of the ball mill is heated, and after reaching the desired operating temperature, the materials are stirred and dissolved by the ball mill, and then the dissolved materials are guided to the product position through a discharge port, coated on the side of the BGA with a thickness of 20 microns and cleaned with acetone, and then the slurry is cured at 60°C in a vacuum drying oven, and the coated product is cooled, cured and dried; then the second batch of thermoplastic polymers and solvents are added to the ball mill, the inside of the ball mill is heated, and after reaching the desired operating temperature, the materials are stirred and dissolved by the ball mill, and then the dissolved materials are guided to the product position through a discharge port, secondary coating is performed around the product, and the product is placed in a vacuum drying oven at 60°C for secondary curing.

[0005] The operating temperature inside the ball mill is 40-160°C.

[0006] The stirring and dissolving time of the ball mill is 0.5-1.5 hours.

[0007] The beneficial effects of the present invention are:

[0008] (1) After the product is formed, the reliability of the temperature cycle of the novel automotive-grade BGA of the present invention is significantly improved. The gradient design not only solves the problem of glass edge collapse of the BGA product, but also significantly alleviates the thermal stress borne by the glass.

[0009] (2) By adopting this molding method for production and processing, the production efficiency is also significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0011] Figure 1 It is a schematic diagram of the double-layer adhesive gradient design of the present invention.

[0012] Figure 2 Effect of adhesive gradient design on Von Mises stress at glass edge. DETAILED DESCRIPTION

[0013] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0014] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0015] Figure 1 and Figure 2The gradient design A shown is as follows: high modulus polymer slurry 1 and low modulus polymer slurry 2 are respectively coated on the side of the BGA cleaned with acetone with a thickness of 20 microns, and the slurry is cured in a vacuum drying oven at 60°C to form two groups of BGA samples. Gradient design B: low modulus polymer slurry 2 is coated on one side of the high modulus polymer slurry 1 experimental group, and high modulus polymer slurry 1 is coated on one side of the low modulus polymer slurry 2 experimental group, and the samples are placed in a vacuum drying oven at 60°C for secondary curing. After curing, six thickness tests are performed on each sample and an error analysis is performed to obtain the coating thickness under different gradient distributions. Based on the geometric model and elastic parameters of the actual test, a finite element model of temperature field-stress field coupling is established, and the simulation results of the Von Mises stress prediction of the glass edge point under temperature cycling conditions for reliability analysis of BGA products can be obtained (such as Figure 2 shown).

[0016] Figure 2 The results shown show that the calculation results of the change of Von Mises stress with the number of cycles reveal that both gradient designs can relieve the stress generated by temperature cycling. Among them, the double-layer gradient design B with a soft lower layer and a hard upper layer can effectively relieve stress. In other words, the preparation method based on gradient coating of the present invention can effectively improve the reliability of BGA products and provide a fast and accurate evaluation technology for the preparation, development and design of high-performance BGA products.

[0017] In the prior art, in order to improve the production efficiency of the product, a common solution is to use a polymer adhesive. However, after the BGA product is prepared, after the reliability test of the temperature cycle, the upper layer of glass will collapse and crack and fail. After the glass collapses, the product performance deteriorates rapidly. Based on the method of coating the polymer twice when the BGA product is formed, the present invention not only significantly improves the reliability of the temperature cycle after the product is formed. Therefore, not only the problem of glass collapse of the BGA product is solved, but also the thermal stress of the glass can be significantly alleviated. In addition, the production efficiency is also significantly improved.

[0018] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A new reliability molding method for automotive-grade BGA, characterized by: The products are evenly placed at the coating station, the first batch of thermoplastic polymers and solvents are added to the ball mill, the inside of the ball mill is heated, and after reaching the desired operating temperature, the materials are stirred and dissolved in the ball mill, and then the dissolved materials are guided to the product position through the discharge port, coated on the side of the BGA with a thickness of 20 microns and cleaned with acetone, and then the slurry is cured at 60°C in a vacuum drying oven, and the coated products are cooled, cured and dried; then the second batch of thermoplastic polymers and solvents are added to the ball mill, the inside of the ball mill is heated, and after reaching the desired operating temperature, the materials are stirred and dissolved in the ball mill, and then the dissolved materials are guided to the product position through the discharge port, secondary coating is performed around the product, and the product is placed in a vacuum drying oven at 60°C for secondary curing.

2. According to the reliability molding method of a novel automotive-grade BGA according to claim 1, it is characterized by: The operating temperature inside the ball mill is 40-160°C.

3. According to the reliability molding method of a novel automotive-grade BGA according to claim 1, it is characterized by: The stirring and dissolving time of the ball mill is 0.5-1.5 hours.

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