阅读说明：本技术 一种SnBi无铅复合焊料的制备方法 (Preparation method of SnBi lead-free composite solder ) 是由 严继康 顾鑫 甘有为 白海龙 周国琼 赵玲彦 吕金梅 滕媛 解秋莉 陈东东 徐凤 于 2019-09-29 设计创作，主要内容包括：本发明涉及一种SnBi无铅复合焊料的制备方法,属于焊料技术领域。本发明将Cu<Sub>6</Sub>Sn<Sub>5</Sub>纳米颗粒和SnBi焊锡粉加入到熔锡炉中,匀速升温至200~250℃并保温直至SnBi焊锡粉熔化得到熔体A；熔体A在搅拌条件下保温处理25~35min,随炉冷却至室温得到复合焊料。本发明纳米Cu<Sub>6</Sub>Sn<Sub>5</Sub>颗粒抑制界面层化合物的正向生成反应,以有效降低合金界面层化合物及其附近出现微裂纹的几率,纳米Cu<Sub>6</Sub>Sn<Sub>5</Sub>颗粒组成接近焊料组成,尤其是界面层化合物的组成,则纳米Cu<Sub>6</Sub>Sn<Sub>5</Sub>颗粒与焊料的晶界共格情况更好,结合会更紧密,有利于提升宏观性能。(The invention relates to a preparation method of SnBi lead-free composite solder, belonging to the technical field of solder. In the invention, Cu 6 Sn 5 Adding the nano particles and the SnBi soldering tin powder into a tin melting furnace, raising the temperature to 200-250 ℃ at a constant speed, and preserving the temperature until the SnBi soldering tin powder is melted to obtain a melt A; and (3) carrying out heat preservation treatment on the melt A for 25-35 min under the stirring condition, and cooling to room temperature along with the furnace to obtain the composite solder. The invention relates to nano Cu 6 Sn 5 The particles inhibit the positive generation reaction of the interface layer compound so as to effectively reduce the probability of microcracks appearing in the alloy interface layer compound and the vicinity thereof, and the nano Cu 6 Sn 5 The grain composition is close to the solder composition, especially the composition of the interface layer compound, and then the nano Cu 6 Sn 5 The grain boundary coherent condition of the particles and the solder is better, the combination is tighter, and the macroscopic performance is favorably improved.)

1. A preparation method of SnBi lead-free composite solder is characterized by comprising the following specific steps:

(1) mixing Cu ₆Sn ₅Adding the particles and the SnBi soldering tin powder into a tin melting furnace, raising the temperature to 200-250 ℃ at a constant speed, and preserving the temperature until the SnBi soldering tin powder is melted to obtain a melt A;

(2) and (3) carrying out heat preservation treatment on the melt A for 25-35 min under the stirring condition, and cooling to room temperature along with the furnace to obtain the composite solder.

2. The method for preparing the SnBi lead-free composite solder according to claim 1, wherein the method comprises the following steps: bi content in the melt A in the step (1)15.0-20.0wt% of nano Cu ₆Sn ₅The content of the particles is 0.5-1.0 wt%.

Technical Field

The invention relates to a preparation method of SnBi lead-free composite solder, belonging to the technical field of electronic packaging.

Background

The electronic industry is one of the most rapidly developing industries, especially the promotion of automation and intellectualization, and electronic equipment is taken as the most important control element, and the assembly process of the electronic equipment plays a decisive role in the quality of electronic products. The lead-free solder alloy is used as the most basic material of an electronic assembly process, the performance of the lead-free solder alloy is one of the focuses of electronic packaging process attention, and the excellent wettability can effectively reduce the problems of insufficient solder, missing solder and the like generated in the welding process.

On the other hand, the electronic products are being miniaturized and miniaturized at present, and the required welding solder is less and less, so that the performance of the solder has higher requirements, the solder alloy is required to have excellent welding performance, and the quality after welding is ensured. The appearance of the IMC layer of the welding interface has important influence on the quality after welding, and due to the particularity of welding materials, the intermetallic compound layer formed on the welding interface is often uneven, so that the reliability of a welding joint is reduced, the appearance of the welding interface is controlled, and the welding interface with moderate, even and smooth thickness is obtained, which is also the target pursued by solder developers.

Interfacial layer compound Cu formed between tin solder and copper plate ₆Sn ₅Is easy to be inThe aging process is abnormally large, and the growth process of the aluminum alloy is mainly formed by the combination of several Sn and Cu atoms which are bonded into one Cu ₆Sn ₅When molecular, the volume of the system will decrease, when Cu is in large amount ₆Sn ₅When formed in this manner, microcracks and micropores at the interface layer ensue; and Cu ₆Sn ₅There is a phase change point during solidification, causing internal stresses that can also lead to additional microcracks in the solder joint after the solder solidifies.

When high melting point refractory metal nanoparticles are added, because the nanoparticles are lighter than the melt, the melt is very easy to oxidize, and the nanoparticles have poor wettability with solder, the nanoparticles and the melt are always separated by a thicker oxide film, which results in that the nanoparticles hardly enter the melt when the nanoparticles are directly added into the melt.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a preparation method of SnBi lead-free composite solder, which adopts IMC primary compound as a nano additive to improve the reliability of the solder and improve the microstructure, welding performance and mechanical property of the alloy; and Cu is added in the invention ₆Sn ₅In time, Cu due to segregation ₆Sn ₅A large amount of particles appear at the interface layer, the raw materials required by the growth of the interface layer are directly provided, the bonding of Sn and Cu is greatly reduced, the probability of microcracks caused by the growth of the compound of the interface layer is effectively reduced, and Cu is artificially introduced ₆Sn ₅In solder, 6Cu +5Sn → Cu ₆Sn ₅Will be inhibited. Solder-added Cu ₆Sn ₅After the nano particles, the growth of the alloy interface structure is also inhibited.

The invention adds Cu ₆Sn ₅The nanometer particles refine the alloy structure, inhibit abnormal growth of alloy grains and improve the reliability of the solder, and Cu is added ₆Sn ₅The nano particles are original products of the welding spots, thereby facilitating the recovery of the subsequent welding flux, reducing the pressure of impurity removal during the recovery, and the Cu ₆Sn ₅Addition of Cu suppresses ₆Sn ₅The generated chemical process is beneficial to improving the alloy reliability;

a preparation method of SnBi lead-free composite solder comprises the following specific steps:

(1) mixing Cu ₆Sn ₅Adding the particles and the SnBi soldering tin powder into a tin melting furnace, raising the temperature to 200-250 ℃ at a constant speed, and preserving the temperature until the SnBi soldering tin powder is melted to obtain a melt A;

(2) and (3) carrying out heat preservation treatment on the melt A for 25-35 min under the stirring condition, and cooling to room temperature along with the furnace to obtain the composite solder.

In the step (1), the content of Bi in the melt A is 15.0-20.0wt%, and the nano Cu is ₆Sn ₅The content of the particles is 0.5-1.0 wt%.

The IMC primary compound is used as a nano additive to improve the reliability of the solder and improve the mechanism of the alloy micro-structure, the welding performance and the mechanical property: additive Cu ₆Sn ₅As the original compound of the solder joint interface layer, when it is attached to the interface layer Cu ₆Sn ₅Local tissue surface generation of 6Cu +5Sn → Cu ₆Sn ₅The chemical reaction will be inhibited to some extent (Cu is generated in the positive direction) ₆Sn ₅Is inhibited) and Cu is introduced ₆Sn ₅Can be used as the existing raw material required by the growth of an interface layer, thereby reducing the production of Cu ₆Sn ₅The stress induced; and due to Cu ₆Sn ₅The high surface energy of the nano particles leads the nano particles to be easily adsorbed on the surface of the interface layer compound, so that the growth driving force of the interface layer compound is reduced; in addition, higher melting point Cu ₆Sn ₅The nanoparticles provide a non-uniform nucleation core during solder solidification, improving solder nucleation capability, thereby refining solder structure and inhibiting growth thereof. When the size of the alloy structure is reduced, the surface energy of the alloy structure is increased, so that the melting point of the alloy after the structure is refined is reduced. When the grain size is refined, the energy required for the initiation of the dislocations within the grains will rise significantly,thereby improving the mechanical property of the solder. In addition, Cu introduced ₆Sn ₅The particles are in coherent match with the original interface layer compound, so the bonding force between the nanoparticles and the interface layer compound is stronger. As described above, Cu ₆Sn ₅The addition of the nano particles is beneficial to the improvement of the reliability, the weldability and the mechanical property of the solder.

The invention has the beneficial effects that:

(1) the invention introduces Cu ₆Sn ₅The particles contain Cu element, which is beneficial to improving the electric conductivity and the thermal conductivity of the solder;

(2) the invention adds Cu ₆Sn ₅The nano particles are used for refining an alloy structure, inhibiting abnormal growth of crystal grains in a matrix and inhibiting microcracks of an interface layer so as to improve reliability;

(3) the invention adds Cu ₆Sn ₅Interface layer Compound Cu after nanoparticles ₆Sn ₅The forward generation reaction of the solder is inhibited to a certain degree, and the growth speed of the interface layer compound is reduced, which is beneficial to improving the reliability of the solder;

(4) the invention relates to nano Cu ₆Sn ₅The composition of the particles is close to that of the interface layer compound, the bonding condition of the particles and the welding spot structure is better, the abnormal growth of the interface layer is inhibited by the nano phase, and the additive Cu is added ₆Sn ₅The solder is a welding spot primary compound, is beneficial to the recovery of the solder in the later period, and is beneficial to reducing the pressure of impurity removal during the recovery of the solder;

(5) the method has the advantages of convenient operation, simple process, cost saving, no impurity introduction and no pollution to the environment.

Drawings

FIG. 1 is a gold phase diagram of a substrate SnBi20 of example 1;

FIG. 2 is a gold phase diagram of the composite solder of example 1.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments, but the scope of the present invention is not limited to the description.