Method for preventing tin from drifting away in formic acid atmosphere

Abstract

The invention relates to the technical field of electronic packaging and semiconductor manufacturing, in particular to a method for preventing tin drifting in formic acid atmosphere. In the prior art, tin formate is easily generated in the process of reducing tin by formic acid, and the tin formate is difficult to completely consume after sublimating into a gas phase, so that the tin element drifts away and is subjected to mass loss, and the product quality and the production stability are further influenced. The problem cannot be effectively solved by the existing air blowing method and the like. By adding the noble metal catalyst into the reaction system, the chemical reaction path is changed, and the generation of tin formate is effectively prevented, so that the drifting of tin is reduced, the process stability and the product quality are improved, and the production cost and the environmental pollution are reduced. The method has the advantages of being simple, effective, stable in process, environmentally friendly, remarkable in economic benefit and the like.

Description

Technical Field

[0001] The invention relates to the technical field of electronic packaging and semiconductor manufacturing, and in particular to a method for preventing tin from drifting in a formic acid atmosphere. Background Art

[0002] Tin is widely used in industrial production, but it is easily affected by oxidation. Formic acid is a common gas-phase reducing agent. The size of formic acid gas molecules is 60 angstroms, and the reduction activity temperature range is 150-250°C. It is suitable for various scale structures and matches the melting temperature of most solders. Using formic acid to reduce tin is very common in industrial production, especially in the fields of electroplating industry, semiconductor manufacturing, chemical synthesis, and catalyst preparation. In these applications, formic acid is usually used as a reducing agent to reduce tin oxides to metallic tin or tin compounds to achieve specific chemical conversions or industrial process requirements.

[0003] In order to alleviate the problems caused by the sublimation of tin formate, a variety of methods have been used in the prior art, among which the most common is air blowing technology. Air blowing technology refers to the use of high-speed airflow to blow sublimated tin formate and other tin compounds away from the reaction area. This method reduces the dispersion and deposition of tin by physical means, thereby reducing the mass loss of tin and the impact on the product. However, the effect of this method is limited and cannot fundamentally prevent the generation and sublimation of tin formate. In addition, the air blowing effect is uncontrollable in some cases, and may be affected by the intensity, direction and environmental conditions of the airflow, resulting in the instability of the control effect, which brings new challenges. It is necessary to seek more effective technical solutions to fundamentally solve the problems of tin formate sublimation and tin element dispersion in the process of formic acid reduction of tin, improve process efficiency, ensure product quality, and reduce production costs and environmental impacts. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a simple, efficient and environmentally friendly solution. By adding metal catalysts such as Pt, the chemical reaction pathway is changed, the reaction between formic acid and tin is prevented, and the generation and dispersion of tin formate is effectively suppressed. The generation mechanism of tin formate is that in a formic acid atmosphere, formic acid will decompose to form formate (-COOH), which will form an intermediate product tin formate (Sn(COOH)2) with tin oxide, and it will not react completely in the subsequent process, which will lead to the dispersion of tin. After adding the Pt metal catalyst, most of the formic acid is directly decomposed into carbon dioxide (CO2) and hydrogen free radicals under the action of the catalyst. Instead of forming formate and tin formate, which react with hydrogen ions (H + ), the hydrogen radicals showed higher reduction activity. The hydrogen radicals then reacted directly with tin oxide, effectively preventing the formation of tin formate.

[0005] The invention relates to a method for preventing tin from drifting in a formic acid atmosphere. The key lies in adding metal catalysts such as Pt during the process of reducing tin with formic acid to change the chemical reaction pathway and reduce the generation and drift of tin formate.

[0006] Taking Pt catalyst as an example, the following steps are included:

[0007] When Pt is added as a catalyst to the reaction system, the chemical reaction path changes:

[0008] S1: adding a noble metal catalyst into the reaction system;

[0009] S2: catalyzes the direct decomposition of formic acid into carbon dioxide and hydrogen radicals;

[0010] S3: Hydrogen radicals react with themselves to generate hydrogen, or combine with oxygen and hydrogen radicals adsorbed on the surface to generate water vapor;

[0011] S4: Hydrogen radicals react directly with tin oxide to avoid the formation of tin formate, thereby maintaining the stability of tin and the controllability of the process and reducing the dispersion of tin.

[0012] Preferably, in step S1, most of the formic acid is directly decomposed into carbon dioxide and hydrogen radicals under the action of the Pt catalyst instead of generating formate;

[0013] Preferably, in step S3, the hydrogen radical reacts with itself to generate hydrogen gas;

[0014] Preferably, in step S3, the hydrogen radicals combine with the oxygen-hydrogen radicals adsorbed on the surface, which is conducive to the rapid extraction of oxygen from the surface to generate water vapor;

[0015] Preferably, in step S4, hydrogen radicals exhibit higher reduction activity than hydrogen ions and can directly react with tin oxide, thereby effectively avoiding the formation of tin formate, maintaining the stability of tin and the controllability of the process.

[0016] The specific chemical reaction can be expressed as:

[0017]

[0018] SnO+2H→Sn+H2O (4) Compare the following reaction process with tin oxide in formic acid atmosphere without Pt catalyst:

[0020] The specific chemical reaction can be expressed as:

[0021] HCOOH (g) →-COOH (ads) +OH (ads) (1)

[0023] -COOH (ads) →CO2+H+e - (2)

[0025] H+H→H 2(g) (3)

[0027]

[0028] Sn(COOH)2→Sn+H2+2CO2 (5) The reaction process is:

[0030] 1. Formic acid is adsorbed on the surface of tin and decomposed into hydroxide ions and formate ions;

[0031] 2. As the temperature rises, the formate ions further decompose into hydrogen ions, carbon dioxide and water;

[0032] 3. Some hydrogen ions react with themselves to generate hydrogen;

[0033] 4. Hydrogen ions combine with hydroxyl groups adsorbed on the surface, which is conducive to the rapid extraction of oxygen from the surface and the generation of water vapor;

[0034] 5. Adsorption, dissociation and oxidation of formate esters, in which water vapor is generated and tin oxide is reduced.

[0035] The present invention has the following beneficial effects:

[0036] 1. Simplified operation: This method does not need to rely on complex physical means such as air blowing, reduces additional cleaning and processing steps, simplifies the process flow, and is easy to implement and control.

[0037] 2. Improve efficiency: By introducing metal catalysts such as Pt, the reaction mechanism is changed, the reaction between formic acid and tin is effectively prevented, the formation of tin formate is inhibited, and the problems of tin formate sublimation and tin element dispersion are solved from the reaction path, thereby improving the stability of the process and the quality of the product.

[0038] 3. Environmental friendliness: The present invention reduces the risk of environmental pollution, improves the working environment and the health conditions of operators, and provides a more environmentally friendly production solution by effectively inhibiting the generation and dispersion of tin formate.

[0039] 4. Significant economic benefits: Due to the effective suppression of tin dispersion, the present invention reduces the loss of tin materials and reduces the cost of raw materials. In addition, simplified operation and improved process stability reduce the probability of failure and rework during production, further reducing production costs and improving overall economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a diagram of the reaction process without adding a Pt catalyst in one embodiment of the present invention;

[0041] Figure 2 It is a diagram of the reaction process when a Pt catalyst is added in one embodiment of the present invention; DETAILED DESCRIPTION

[0042] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0043] In this technical solution, Sn corresponds to the metal element tin, and Pt corresponds to the metal element platinum. Figure 1 to Figure 2 ,like Figure 2 The principle of the present invention is shown, Figure 1 As a control group without adding Pt catalyst, the present embodiment provides a method for preventing tin from drifting in a formic acid atmosphere, comprising the following steps:

[0044] S1: adding a noble metal catalyst into the reaction system;

[0045] S2: catalyzes the direct decomposition of formic acid into carbon dioxide and hydrogen radicals;

[0046] S3: Hydrogen radicals react with themselves to generate hydrogen, or combine with oxygen and hydrogen radicals adsorbed on the surface to generate water vapor;

[0047] S4: Hydrogen radicals react directly with tin oxide to avoid the formation of tin formate, thereby maintaining the stability of tin and the controllability of the process and reducing the dispersion of tin.

[0048] The invention effectively prevents the generation and dispersion of tin formate by introducing metal catalysts such as tin and tin oxide, thereby improving process stability and controllability, protecting the integrity of tin materials and product quality, and reducing environmental pollution and bringing significant economic benefits.

[0049] The key points of this technical solution are as follows:

[0050] 1. Use of metal catalysts such as Pt: The introduction of metal catalysts such as Pt is a key technical point of the present invention. Pt and other catalysts can change the chemical reaction path of formic acid on the tin surface, so that formic acid is directly decomposed into carbon dioxide and hydrogen free radicals. The hydrogen free radicals directly participate in the reduction reaction, thereby avoiding the formation of tin formate.

[0051] 2. Preventing the formation and dispersion of tin formate: The present invention effectively prevents the formation and further decomposition of tin formate by using catalysts such as Pt, thereby protecting the integrity and quality of the tin material and improving the stability of the process.

[0052] 3. Improve the controllability and efficiency of the process: The introduction of metal catalysts such as Pt can change the chemical reaction process of formic acid reduction of tin, thereby improving the stability and controllability of the process.

[0053] 4. Improve product quality and stability: Preventing the formation and dispersion of tin formate can avoid the negative impact of tin residues on product quality and stability. The purity and smoothness of the product surface are protected, and the effect of chemical reaction and adhesion are improved.

[0054] 5. Protect the environment and reduce pollution: By preventing the formation and dispersion of tin formate, the loss of raw materials is reduced, the pollution and harm to the environment are reduced, and environmental protection requirements are met.

[0055] 6. Significant economic benefits: By effectively inhibiting the drift of tin, the present invention reduces the loss of tin materials and reduces the cost of raw materials. In addition, simplified operations and improved process stability reduce the probability of failure and rework during production, further reducing production costs and improving overall economic benefits.

[0056] The above disclosure is only a preferred embodiment of the method for preventing tin from drifting in a formic acid atmosphere of the present invention. Of course, this cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for preventing tin from drifting in a formic acid atmosphere, characterized in that: The following steps are involved: S1: adding a noble metal catalyst into the reaction system; S2: catalyzes the direct decomposition of formic acid into carbon dioxide and hydrogen radicals; S3: Hydrogen radicals react with themselves to generate hydrogen, or combine with oxygen and hydrogen radicals adsorbed on the surface to generate water vapor; S4: Hydrogen radicals react directly with tin oxide to avoid the formation of tin formate, thereby maintaining the stability of tin and the controllability of the process and reducing the dispersion of tin.

2. A method for preventing tin from drifting in a formic acid atmosphere as claimed in claim 1, characterized in that: The atmosphere of the reaction system is formic acid atmosphere.

3. A method for preventing tin from drifting in a formic acid atmosphere as claimed in claim 1, characterized in that: The reaction system includes but is not limited to tin and its alloy materials, and Cu, Ag and their alloy materials commonly used in semiconductor bonding are all within the scope of the claims of this patent.

4. A method for preventing tin from drifting in a formic acid atmosphere as claimed in claim 1, characterized in that: The process is highly scalable and applicable to substrate materials of different sizes and shapes, including but not limited to silicon wafers, metal substrates and plastic substrates, and the stability and controllability of the process are improved by controlling the reaction conditions.

5. A method for preventing tin from drifting in a formic acid atmosphere as claimed in claim 1, characterized in that: The chemical reaction process is changed to reduce the generation and sublimation of tin formate.

6. A method for preventing tin from drifting in a formic acid atmosphere as claimed in claim 1, characterized in that: The addition of catalysts can also reduce production energy consumption and costs.

7. A method for preventing tin from drifting in a formic acid atmosphere as claimed in claim 1, characterized in that: The amount of the noble metal catalyst added is optimized according to the volume of the reaction system and the required reaction rate to ensure efficient catalytic effect. The noble metal catalyst can be platinum, palladium, rhodium or a mixture thereof. The particle size and distribution of the catalyst have a significant effect on the catalytic efficiency. The method of adding the noble metal catalyst to the reaction system includes but is not limited to direct impregnation, chemical vapor deposition or physical vapor deposition.

8. A method for preventing tin from drifting in a formic acid atmosphere as claimed in claim 1, characterized in that: By real-time monitoring of the temperature, pressure and gas composition in the reaction system, the reaction conditions are dynamically adjusted to maintain the optimal reaction environment.

9. A method for preventing tin from drifting in a formic acid atmosphere as claimed in claim 1, characterized in that: Implementation of the process reduces environmental impact due to reduced emissions of hazardous gases and reduced material waste through recovery and reuse of by-products.

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