阅读说明：本技术 一种锡镀液、其制备方法和应用 (Tin plating solution, preparation method and application thereof ) 是由 王溯 孙红旗 于 2019-03-15 设计创作，主要内容包括：本发明公开了一种锡镀液、其制备方法和应用。本发明锡镀液的组合物原料,以锡镀液为1L计,其包括如下用量的组分：30～120g/L的甲磺酸锡；60～300g/L的甲磺酸；0.1～100mg/L的聚维酮K45；0.01～10mg/L的低分子聚醚,所述低分子聚醚为双胺酚醚和/或马来酰亚胺基聚乙二醇单甲醚；和水。本发明的锡镀液在不含氟化表面活性剂的情况下也可用于为倒装芯片封装体在金属类UBM层上形成锡类焊料凸点,成本较低,工艺简单；其在电流效率方面有利,不产生金属间化合物层中的破裂和凸点内的空隙,可以用于形成平整性高和高度波动小的凸点,适用于高速电镀。(The invention discloses a tin plating solution, a preparation method and application thereof. The raw materials of the composition of the tin plating solution of the invention are counted by taking 1L of the tin plating solution, and the composition comprises the following components by weight: 30-120 g/L of tin methane sulfonate; 60-300 g/L of methanesulfonic acid; 0.1-100 mg/L of povidone K45; 0.01-10 mg/L of low molecular polyether, wherein the low molecular polyether is bisphenol ether and/or maleimide polyethylene glycol monomethyl ether; and water. The tin plating solution can be used for forming tin solder bumps on the metal UBM layer for the flip chip packaging body under the condition of not containing fluorinated surfactant, and has the advantages of low cost and simple process; it is advantageous in terms of current efficiency, does not cause cracks in the intermetallic compound layer and voids in the bump, can be used for forming a bump having high flatness and small height fluctuation, and is suitable for high-speed plating.)

1. The tin plating solution is characterized by comprising the following components in parts by weight based on 1L of tin plating solution: 30-120 g/L of tin methane sulfonate; 60-300 g/L of methanesulfonic acid; 0.1-100 mg/L of povidone K45; 0.01-10 mg/L of low molecular polyether, wherein the low molecular polyether is bisphenol ether and/or maleimide polyethylene glycol monomethyl ether; and water.

2. The tin plating solution according to claim 1, wherein the amount of tin methanesulfonate used is 40 to 110 g/L;

and/or the dosage of the methanesulfonic acid is 70-280 g/L.

3. The tin plating solution according to claim 1, wherein the amount of tin methanesulfonate used is 45 to 100 g/L;

and/or the dosage of the methanesulfonic acid is 75-250 g/L.

4. The tin plating solution according to claim 1, wherein the povidone K45 is used in an amount of 0.5 to 50 mg/L;

and/or the dosage of the low molecular polyether is 0.05-5 mg/L.

5. The tin plating solution according to claim 1, wherein the povidone K45 is used in an amount of 1 to 10 mg/L;

and/or the dosage of the low molecular polyether is 0.1-1 mg/L, and the low molecular polyether is preferably bisphenol ether.

6. The tin plating solution of any of claims 1 to 5, wherein the tin plating solution is comprised of the following components in the following amounts, based on 1L of tin plating solution: 30-120 g/L of tin methane sulfonate; 60-300 g/L of methanesulfonic acid; 0.1-100 mg/L of povidone K45; 0.01-10 mg/L of low molecular polyether, wherein the low molecular polyether is bisphenol ether and/or maleimide polyethylene glycol monomethyl ether; and water.

7. The tin plating solution of any of claims 1 to 5, wherein the tin plating solution further comprises an additive.

8. A method of preparing a tin plating solution according to any one of claims 1 to 7, comprising the steps of: mixing the components of the tin plating solution;

preferably, the tin plating solution is filtered by a cylinder filter with micron-sized pore diameter after being mixed;

more preferably, the pore size is 0.2 to 6 μm.

9. Use of a tin plating solution as claimed in any one of claims 1 to 7 in the formation of solder bumps in a flip chip.

10. The use according to claim 9, characterized in that said use comprises the following steps:

1) electroplating a silicon wafer with a copper or copper/nickel plating solution, the silicon wafer having a protective layer exposing the electrode pad and an under bump metal layer;

2) forming a copper or copper/nickel column on the under bump metal layer;

3) and electroplating the copper or copper/nickel column by using the tin plating solution within 12h after the copper or copper/nickel column is formed, thereby forming the solder bump.

Technical Field

The invention relates to a tin plating solution, a preparation method and application thereof.

Background

The conductive interconnection bumps of the flip chip have wide application in wafer level packaging processes. These interconnect bumps serve as electrical and physical connections for the semiconductor component to the printed wiring board. Tin/lead alloys are commonly used to form solder bumps; however, due to the toxicity of lead, the industry has attempted to find acceptable lead-free pure tin or tin alloys that can be readily co-deposited.

In bump electroplating, the problem of bump thickness uniformity and the problem of voids are the two most important problems, and the industry is dedicated to developing a plating solution or an additive for solving the two problems. Patent CN105316711A discloses a tin alloy plating solution for solder bumps containing perfluoroalkyl surfactants, a tin plating solution for forming solder bumps of flip chip package, the tin plating solution containing tin methane sulfonate, silver methane sulfonate, methane sulfonic acid, fluorinated surfactants, aromatic polyoxyalkylene ether and water. The tin plating solution is advantageous in terms of current efficiency, does not cause cracking in an intermetallic compound (IMC) layer or voids in a bump, can be used for forming a bump having high flatness and small height fluctuation, and is suitable for high-speed plating. However, the present invention clearly indicates that the tin plating solution must contain fluorinated surfactant which is complicated to prepare to achieve the above-mentioned effects.

Therefore, how to reduce the cost and simplify the process while solving the problems of bump thickness uniformity and voids becomes an urgent technical problem to be solved in the field.

Disclosure of Invention

The invention aims to overcome the defects that the thickness of a solder bump formed by using tin electroplating solution is uniform and the gap is small only by using fluorinated surfactant in the prior art, and provides a tin electroplating solution, a preparation method and application thereof. The tin plating solution of the invention can form solder bumps with uniform thickness and no gaps under the condition of not using fluorinated surfactant, thereby simplifying the preparation process of tin plating solution.

The invention solves the technical problems through the following technical scheme:

the invention provides a tin plating solution, which comprises the following components in parts by weight based on 1L of the tin plating solution: 30-120 g/L of tin methane sulfonate; 60-300 g/L of methanesulfonic acid; 0.1-100 mg/L of povidone K45; 0.01-10 mg/L of low molecular polyether, wherein the low molecular polyether is bisphenol ether and/or maleimide polyethylene glycol monomethyl ether; and water.

In the present invention, the amount of the tin methanesulfonate is preferably 40 to 110g/L, and more preferably 45 to 100 g/L.

In the present invention, the amount of the methanesulfonic acid is preferably 70 to 280g/L, and more preferably 75 to 250 g/L.

In the present invention, the amount of the povidone K45 is preferably 0.5 to 50mg/L, and more preferably 1 to 10 mg/L.

In the present invention, the amount of the low molecular weight polyether is preferably 0.05 to 5mg/L, and more preferably 0.1 to 1 mg/L.

In the present invention, the low molecular weight polyether is preferably a bisaminophenol ether.

In the present invention, the tin plating solution is preferably free of fluorinated surfactant.

In the invention, the tin plating solution is 1L, and the tin plating solution preferably comprises 30-120 g/L tin methanesulfonate; 60-300 g/L of methanesulfonic acid; 0.1-100 mg/L of povidone K45; 0.01-10 mg/L of low molecular polyether, wherein the low molecular polyether is bisphenol ether and/or maleimide polyethylene glycol monomethyl ether; and water.

In the present invention, the tin plating solution of the present invention preferably contains various additives conventional in the art in addition to the above-mentioned components; the additive is preferably one or more of an accelerator, an inhibitor, a defoamer, an organic antioxidant and a grain refiner; the antioxidant is preferably one or more of phenol, hydroquinone and resorcinol.

The invention also provides a preparation method of the tin plating solution, which comprises the following steps: mixing the above components.

Wherein, the mixing is the conventional operation in the field, and a stirring method is generally adopted; preferably, the prepared tin plating solution is filtered by a cylinder filter with micron-sized pore diameter; more preferably, the pore size is 0.2 to 6 μm. Wherein the filtering through the cartridge filter is to remove precipitates or impurities that hinder the formation of the solder alloy bumps.

The invention also provides application of the tin plating solution in forming solder bumps in a flip chip. Said application preferably comprises the following steps:

1) electroplating a silicon wafer with a copper or copper/nickel plating solution, the silicon wafer having a protective layer exposing the electrode pad and an under bump metal layer;

2) forming a copper or copper/nickel column on the under bump metal layer;

3) and electroplating the copper or copper/nickel column by using the tin plating solution within 12h after the copper or copper/nickel column is formed, thereby forming the solder bump.

The copper or copper/nickel plating solution described in step 1) is preferably a copper or copper/nickel plating solution that is conventional in the art, for example, the copper plating solution may be a plating solution comprising copper sulfate, sulfuric acid, hydrochloric acid, water, and optionally additives. Copper plating solutions are commercially available; the plating operation is preferably a plating operation conventional in the art.

The plating operation in step 3) is preferably a continuous plating operation as is conventional in the art, and a continuous plating operation of 12 hours can minimize intermetallic adhesion caused by formation of an oxide film on the surface of copper or nickel or generation of cracks and defects between metal layers.

The operation of electroplating the tin plating solution in step 3) may be performed by any suitable process known in the art, and thus specific conditions thereof will not be described herein. For example, the operation of the electroplating for forming the solder bump is performed under the condition that the silicon wafer on which the copper pillar is formed on the under-bump metal layer serves as a cathode and an inert metal electrode (for example, a platinum electrode or a platinized electrode) serves as an anode; preferably, the electroplating operation is performed at 3A/dm²～20A/dm²At a current density of (a); more preferably, the electroplating is performed at 10A/dm²～19A/dm²High-speed electroplating is carried out under the current density of the electroplating solution;

as known to those skilled in the art, solder reflow is typically performed after the solder bumps are formed.

The above preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention without departing from the common general knowledge in the art.

The reagents and starting materials used in the present invention are commercially available.

The positive progress effects of the invention are as follows: the inventionThe tin plating solution can prevent the generation of cracks in the intermetallic compound layer and the formation of voids in the bump, reduce the height fluctuation of WID and WIW bumps, improve the current efficiency of the plating process, and obtain the effect of high-speed plating even in the range of (10A/dm)²～19A/dm²) A flip chip package having excellent plating properties.

Drawings

FIG. 1 is an X-ray void-free map after solder reflow of example 1.

Fig. 2 is an X-ray voided image of comparative example 1 after solder reflow.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

1. Formation of copper pillars

And forming a copper column on the lower metal UBM layer of the copper salient point of the flip chip semiconductor packaging body. Specifically, the catalyst contains CuSO₄·5H₂O、H₂SO₄、HCl、H₂Commercial copper sulfate based bath of O and additives (SYS2310, Shanghai Xinyang semiconductor Co., Ltd., China) was stirred at room temperature and 10A/dm²Electroplating a 12 inch patterned wafer and forming copper pillars until the height of the copper pillars reaches 10 μm; copper electroplating is performed according to manufacturer's recommendations and thus a brief description of the electroplating conditions is given herein.

2. Preparation of tin plating solution

The components were mixed with stirring and filtered through a cartridge filter having a pore size of 1 μm, to thereby prepare a tin plating solution. Tin plating solutions for examples 1 to 10 as shown in Table 1 and comparative examples 1 to 14 as shown in Table 2 were prepared in this manner.

TABLE 1 tin plating bath composition parameters for the examples

TABLE 2 composition parameters of each comparative plating bath

3. Application of tin plating solution in forming solder bump

The tin plating solutions of each example and comparative example were each electroplated on the copper pillar within 12h after the copper pillar was formed on the 12-inch patterned wafer, thereby forming a solder bump. The electroplating is carried out at 13A/dm by adopting a continuous electroplating process which is conventional in the field²While stirring the tin plating solution at room temperature. After heating to 240 c at a rate of 2 c/min and cooling at a rate of 3 c/min, solder reflow was performed. Analysis at 13A/dm by SEM electron microscope and X-ray imaging before and after solder reflow²And (3) electroplating the formed solder bump at the current density of (a). The parameters of the solder bumps formed by the examples and the comparative examples are shown in the following table 3.

TABLE 3 parameters of solder bumps