The method of preparing fine solder powder (ultra-micro solder powder)

There are various ways to prepare fine solder powder, and five commonly used methods are described below:

I. Gas atomisation method

Principle:

The molten liquid flowing through the nozzle is broken up and atomised into fine droplets using a high speed airflow.

The droplets are cooled and solidified during the settling process to form powder particles, which are sorted to obtain ultra-fine tin powder.

Features:

High crushing efficiency and high output.

The products are mostly oval, with rough surface, high oxygen content and wide powder size distribution.

Nitrogen consumption is high and costly.

Satellite ball sticking band is serious, particle size sorting is difficult.

II. Centrifugal atomisation method

Principle:

Using the centrifugal force generated by the high-speed rotation of the turntable, the molten metal droplets are thrown out and atomised into powder, which is cooled and solidified to obtain ultra-micro tin powder after sorting.

Features:

The product has good sphericity, small oxidation, and the particle size is easy to control.

The atmosphere is relatively easy to control.

The equipment has high rotational speed and high requirements for heat resistance and wear resistance of the motor.

Equipment cost is relatively high.

Due to the limitation of high speed motor, the particle size of powder is mainly concentrated in 10-50um, and the harvest rate of ultra-fine tin powder is low.

III. Ultrasonic atomisation method

Principle:

Using the vibration and cavitation effects of ultrasound, molten metal droplets are atomised into fine droplets on an ultrasound transducer.The droplets cool and solidify in the air to form spherical powder particles.

Features:

1 Controllable powder particle morphology and size, highly spherical, uniform particle size and narrow distribution.

2Powder particles purity and oxygen content is low.

3Simple equipment and process, convenient operation, stable and controllable product quality.

4 Low energy consumption, high utilisation, low cost, environmental protection and energy saving.

5 Restricted by ultrasonic power, low harvesting rate of ultrafine powder, small output, capacity may not be able to meet the large-scale market demand.

IV.  Conventional melt dispersion

Step-by-step overview:

1 Melt the solder alloy in a high temperature resistant vegetable and/or animal oil.

2 The melt is fed into another pre-set oil at a temperature at least 20°C above the liquid phase line temperature.

3 Stirring is carried out and the melt is subjected to a number of shearing processes by means of a rotor and a stator to form a dispersion comprising solder beads and oil.

4 The solder beads are separated from the dispersion with the aid of subsequent precipitation.

Features:

The method is effective in refining and homogeneously dispersing the alloy composition and removing undesired reaction products such as oxides and slag.

It is suitable for the preparation of fine welding powders with a specific diameter range (e.g. 2.5 to 45 μm).

V. Liquid-phase moulding preparation technology

Principle:

Combining the principles of shear emulsification and ultrasonic cavitation effect, fine solder powders are prepared by liquid phase forming technology.

Features:

1Can prepare super micro welding powder above T6.

2 Good powder form, uniform and controllable particle size, low oxygen content.

3 Solved the problem of low yield of ultrasonic atomisation process, and has achieved large-scale mass production.

Fitech co.ltd adopts the liquid phase moulding powder making technology, and the super micro solder powder made by this technology has the following advantages:

1. Fine particle size and uniform distribution: due to the use of advanced ultra-micro liquid-phase moulding technology, without the need for back-end sorting, the particle size of the ultra-micro tin powder is uniformly distributed, making its physical and chemical properties more stable.

2. Thin and dense oxide film: the particle size of the ultra-micro tin powder decreases, which directly leads to a significant increase in its specific surface area, and only by controlling the size and density of the oxide film can we guarantee the performance of the ultra-micro solder powder.

3. Good sphericity: Ultra-micro solder powder is made of fine metal droplets solidified in high-temperature liquid medium, driven by the surface energy of the droplets, the fine droplets solidify into a true roundness sphere with minimum surface tension, achieving lower surface area, no sorting process at the back-end, eliminating surface damage to the powder, and lower oxygen content, better stability.

4. Small particle size and good uniformity: due to the small particle size, can be more amount of solder paste as well as a smaller volume to achieve the transfer of solder paste, to achieve different sizes of solder joints, to meet the needs of different solder joint size.

5. Improvement of electrical and thermal conductivity: with a low oxygen content of ultra-micro solder powder matching the appropriate flux, to achieve good wetting welding, resulting in IMC metallurgical connection, to ensure its high electrical and thermal conductivity in the field of electronic packaging, welding and other areas.

6. Easy to process and apply: Ultra-micro solder paste prepared by ultra-micro solder powder has good fluidity and dispersion, with a wide process window, thus improving processing performance and product quality.

7. Environmental protection and energy saving: the use of advanced dispersion moulding technology and equipment greatly improves the harvesting rate of super-micro solder powder, which can achieve low energy consumption and low emission production.

8. Good stability: Due to its special preparation process and surface treatment, Coating process of the powder has better oxidation resistance and stability.

It is because of this powdering technology that the formulated Fitech solder paste has been widely used in the fields of micro photoelectricity, SIP integrated packaging, semiconductor packaging, etc., and has received unanimous praise from the industry.