TWI664049B - Preparation method of Cu (copper)-cored solder balls for high-end electronic packaging - Google Patents

Abstract

A method for preparing copper core solder balls for high-level electronic packaging, which is prepared through successive steps of copper ball preparation, surface treatment, anti-oxidation treatment, screening treatment, plating treatment, secondary anti-oxidation treatment, and screening of finished products. In the process, copper pellets or copper wires are first processed into copper balls, and then the surface of the copper balls is ground and slightly acid-etched before being subjected to anti-oxidation treatment. After that, the copper balls with roundness and dimensions that meet the requirements are screened. Then electroplating treatment is performed to make copper-core solder balls, and then the copper-core solder balls are subjected to a second anti-oxidation treatment, and finally copper-core solder balls with true roundness and dimensions suitable for electronic packaging are selected.

Description

Preparation method of copper core solder ball for high-level electronic packaging

The invention relates to a method for preparing a copper core solder ball; more specifically, it relates to a method for preparing a copper core solder ball for high-end electronic packaging.

In recent years, with the development of lighter weight, thinner and more versatile mobile electronic products, traditional electronic packaging technology has been unable to meet the requirements of miniaturization, narrow pitch and multi-pin. In order to meet these market requirements, a The three-dimensional space (3D) packaging technology represented by stacked package (POP) came into being, and the three-dimensional space (3D) packaging technology originated from the stacked packaging of flash memory and synchronous dynamic random access memory (SDRAM). This is a packaging technology in which two or more layers of chips are stacked vertically in the same package without changing the size of the package. Its main features include: multifunction, high performance, large capacity, high density and low cost.

Generally, three-dimensional space (3D) packaging process requires multiple re-soldering. However, the traditional ball grid array package (BGA) solder balls will be melted when the solder bumps are subjected to multiple reflows at 250 ° C. When the ball grid array package (BGA) solder ball solder bumps are melted and the pressure of the multilayer electronic parts is pressed, the solder bumps will deform unpredictably, which will lead to a narrower packaging space and solder joints and soldering. Problems such as sticky shorts can occur between points or between solder joints and parts.

In order to solve the problem that traditional ball grid array package (BGA) solder balls can be melted after repeated re-soldering, copper balls are used in the industry to replace traditional ball grid array package (BGA) solder balls. This is because of the melting point of copper. (1083 ° C) is much higher than the reflow temperature (250 ° C) at the time of packaging, so even after multiple reflow processes, copper balls will not deform during reflow and can maintain the packaging space unchanged, and this is stable The space can accommodate and package other electronic parts, so the use of copper balls can ensure the stability of the packaging space after reflow, which is conducive to achieving high-density three-dimensional (3D) packaging.

In addition, with the development of multifunctionalization, miniaturization and high performance of electronic products, the development of high-density packaging has also been greatly promoted, and the input / output (I / O) on the packaged chip has been greatly promoted. Increasing the number of pins and reducing the solder joint area lead to higher current density. However, the increase of current density will accelerate the electromigration failure of solder joints. Compared with traditional ball grid array package (BGA) solder ball solder joints, copper balls have more Good resistance to electromigration and thermal migration. This is because copper balls are 5-10 times more conductive than solder balls, and their thermal conductivity is better than traditional ball grid array package (BGA) solder balls.

Therefore, it is necessary to take advantage of copper balls in three-dimensional space (3D) packaging to develop copper core balls with copper balls as the core and better solderability to meet the needs of advanced processes.

In view of this, the applicant of this case based on his many years of R & D experience in related fields, conducted in-depth discussions on the aforementioned shortcomings, and actively sought solutions based on the aforementioned needs. After a long period of hard research and multiple tests, he completed this invention.

The main object of the present invention is to provide a method for preparing a copper core solder ball with excellent solderability.

In order to achieve the above-mentioned purpose, the method for preparing copper core solder balls for high-end electronic packaging according to the present invention is prepared through the following steps: A. Copper ball preparation: The piezoelectric vibration process, the wire remelting process or the cold heading grinding process are used. Copper pellets or copper wires are made into copper balls. B. Surface treatment: The copper balls are ground and slightly acid-etched to improve the surface roughness of the copper balls. C. Anti-oxidation treatment: The surface of the copper balls is subjected to anti-oxidation treatment to maintain the luster of the surface of the copper balls. D. Screening treatment: The roundness and size of copper balls after oxidation treatment are screened. E. Electroplating treatment: The surface of the copper balls after being screened is subjected to acid etching treatment. After the acid etching treatment is completed, the surface of the copper balls is plated with an electroplating layer. During the electroplating process, the accompanying balls and copper are also added. Balls are plated together, and copper-cored solder balls can be obtained after the plating is completed. F. Secondary anti-oxidation treatment: The copper-cored solder ball that has been electroplated is subjected to a second anti-oxidation treatment, and the electroplated layer is maintained in solderability. G. Finished product screening: The final roundness and size screening of the copper cored solder balls that have been treated with secondary oxidation resistance, and the copper cored solder balls suitable for electronic packaging can be obtained after the screening is completed.

The method for preparing a copper core solder ball for high-level electronic packaging according to the present invention has the advantage that the anti-oxidation treatment can ensure the solderability of the copper core solder ball plating layer.

It is expected that the purpose, effects, features, and structure of the present invention can be understood in more detail. The preferred embodiments are described below with reference to the drawings.

Please refer to FIG. 1 first. FIG. 1 is a schematic flowchart of a method for preparing a copper core solder ball for high-end electronic packaging according to the present invention.

The method 1 for preparing copper core solder balls for high-level electronic packaging according to the present invention is prepared through the following steps: A. Copper ball preparation 11: using a piezoelectric vibration process, a cutting and remelting process, or a cold heading grinding process to remove copper particles or copper The silk is made of copper balls, and the purity of the copper balls is more than 99.9%. B. Surface treatment 12: The copper balls are ground and slightly acid-etched to improve the surface roughness of the copper balls. C. Anti-oxidation treatment 13: The copper balls after the surface treatment 12 are subjected to anti-oxidation treatment, so as to maintain the luster of the copper ball surface, and at the same time prevent the copper balls from oxidizing after a long period of storage to cause obvious color differences on the surface. D. Screening 14: The roundness of copper balls after anti-oxidation treatment 13 is screened, and the roundness of each copper ball needs to be less than 0.03, and then the size of the copper balls is screened. The size needs to be between 1 ~ 900 between. E. Plating treatment 15: The surface of the copper balls after the screening treatment 14 is subjected to acid etching treatment. After the acid etching treatment is completed, the surface of the copper balls is plated with an electroplating layer, and an accompanying plating is added during the plating process. The ball is electroplated together with the copper ball, and the copper-core solder ball can be obtained after the electroplating is completed. F. Secondary anti-oxidation treatment 16: The copper-cored solder balls that have completed the electroplating treatment 15 are subjected to the second anti-oxidation treatment. The purpose is to keep the electroplated layer solderable and prevent the electroplated layer from being oxidized, which may cause re-soldering of electronic packages. Problems with poor welding occurred. G. Finished product screening 17: Final screening of copper-cored solder balls that have undergone secondary oxidation treatment 16. The copper-cored solder balls must have a true roundness of less than 0.03, and the size must be between 10 and 1000. In between, when the screening is completed, copper-core solder balls suitable for electronic packaging can be obtained.

In the above steps, special attention should be paid to the difference in the size of the copper balls produced by the piezoelectric vibration process, the shredding remelting process, or the cold heading grinding process used in the copper ball preparation 11.

The screening process 14 is to control the roundness and size of the copper balls to meet the processing requirements, and to enable the subsequent plating process 15 to better control the thickness of the plating layer and help reduce the defect rate of subsequent processing.

The electroplating methods used in the electroplating process 15 include chemical plating, vibration plating, rolling plating, etc., and different plating methods are used to match copper balls of different sizes. The size of the accompanying ball used in the electroplating process must be the same as There are obvious differences between copper balls and copper-cored solder balls after electroplating, in order to quickly screen and separate copper-cored solder balls and co-plated balls after electroplating. Among them, the most suitable material for the co-plated balls is tin balls.

In addition, the plating layer plated on the copper balls in the electroplating treatment 15 may be pure metal (for example: pure tin, pure gold, pure nickel, etc.), alloy (for example: tin-lead alloy, ordinary alloy, low alpha radiation alloy, etc.) And composite plating (for example, nickel plating and pure tin composite plating). In addition, it should be noted that if the plating layer is a composite plating layer, a thickness of about 1 to 10 will be plated during the plating process. Nickel, and then coated with a thickness of about 5 to 100 Tin.

To sum up, the method for preparing copper core solder balls for high-end electronic packaging of the present invention has the following advantages: 1. The plating layer can select the most appropriate metal as the plating layer according to different types of electronic packages. 2. The anti-oxidation treatment can maintain the solderability of the electroplated layer, and avoid the oxidation of the electroplated layer after long-term storage, which will cause the problem of poor soldering during the reflow of the electronic package.

Therefore, the present invention has excellent progress and practicability in similar products. At the same time, after reviewing domestic and foreign technical information on such structures, it was found that no identical or similar structure exists before the application in this case. Patent applications that have met the "creative", "suitable for industrial use", and "progressive" requirements should be filed in accordance with the law.

However, the above are only preferred embodiments of the present invention. For example, any other equivalent structural changes applied to the description of the present invention and the scope of patent application should be included in the scope of patent application of the present invention.

1‧‧‧ Method for preparing copper core solder ball for high-level electronic packaging of the present invention

11‧‧‧ Copper Ball Preparation

12‧‧‧ surface treatment

13‧‧‧Anti-oxidation treatment

14‧‧‧ Screening

15‧‧‧Plating treatment

16‧‧‧ secondary oxidation treatment

17‧‧‧ Finished product screening

FIG. 1 is a schematic flowchart of a method for preparing a copper core solder ball for high-level electronic packaging according to the present invention.

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Claims (9)

A method for preparing copper core solder balls for high-level electronic packaging, which is prepared through the following steps: A. Copper ball preparation: using piezoelectric vibration process, cutting and remelting process or cold iron grinding process to make copper particles or copper wire Copper balls; B. Surface treatment: copper balls are ground and slightly acid-etched; C. Anti-oxidation treatment: The copper balls after the surface treatment are subjected to oxidation treatment to maintain the luster of the copper ball surface; D. Screening treatment: The copper balls after oxidation treatment are screened for roundness and size. Among them, the roundness of the copper balls selected in the screening process is less than 0.03; E. Plating treatment: the screened copper balls The surface is acid-etched first. After the acid-etching treatment is completed, the surface of the copper ball is plated with an electroplating layer. During the electroplating process, the accompanying ball and copper ball are added together to plate, and the copper core can be obtained after the plating is completed. Solder balls; F. Secondary anti-oxidation treatment: The copper-cored solder balls that have been plated are subjected to a second anti-oxidation treatment; G. Finished product screening: Copper-cored solder balls that have been subjected to secondary anti-oxidation treatment Roundness and size filtering and get applied to Cu core solder balls sub-package. The method for preparing copper core solder balls for high-end electronic packaging according to item 1 of the claim, wherein the purity of the copper balls in the preparation of the copper balls is above 99.9%. The method for preparing copper core solder balls for high-end electronic packaging according to item 1 of the claim, wherein the size of the copper balls selected in the screening process is between 1 and 900 μm. The method for preparing copper core solder balls for high-end electronic packaging according to item 1 of the claim, wherein the plating layer in the electroplating process may be any one of pure metal, alloy and composite metal. The method for preparing copper core solder balls for high-end electronic packaging according to item 5 of the claim, wherein the pure metal is any one of pure tin, pure gold, and pure nickel. The method for preparing a copper core solder ball for high-end electronic packaging according to item 5 of the claim, wherein the alloy is any one of tin-lead alloy, ordinary alloy, and low-alpha radiation alloy. The method for preparing a copper core solder ball for high-end electronic packaging according to claim 5, wherein the composite metal is a composite metal of nickel and tin. The method for preparing copper core solder balls for high-end electronic packaging according to item 1 of the claim, wherein the roundness of the copper core solder balls selected for the finished product screening is less than 0.03. The method for preparing copper core solder balls for high-end electronic packaging according to item 1 of the claim, wherein the size of the copper core solder balls selected by the finished product screening is between 10 and 1000 μm.