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Indium Bump Plating - Discussion on Microbumps Using Low-Melting Point Solder Materials

Hello, this is TZ from the Sales Department.

We have recently received an order from a domestic sensor manufacturer for a 300mm face-up electroplating system for indium bump formation processes.

Indium, which has properties of both metal and semiconductor, plays an important role as a material in semiconductor devices.

This time, our face-up system has been adopted for depositing solder materials on fine patterns used in advanced semiconductor chips.

In this blog, we will introduce the characteristics and applications of indium.

Indium's Low Melting Point, Flexibility, and Remarkable Electrical Properties

Indium has the following characteristics:

  • Low Melting Point : It has a low melting point (156.7 deg C), melting at a lower temperature than many other metals.

  • Flexibility : It has a soft properties even at low temperatures. It has a high affinity with glass and ceramics, ensuring good adhesion.

  • Electrical Properties : As a compound semiconductor, it exhibits excellent electrical properties not achievable with silicon.

These characteristics make it suitable for the following applications:

  • Soldering : Indium and indium-tin alloys are widely used as soldering materials. They are particularly suitable for low-temperature soldering and for soldering between different materials.

  • Display Technology : Indium tin oxide (ITO) is used as a transparent conductive film in the manufacture of liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays. This allows for both transparency and conductivity, making it ideal for display wiring.

  • Solar Cells : Indium is known as a raw material for CIS (copper-indium-selenium) and CIGS (copper-indium-gallium-selenium) compound solar cells.

  • Semiconductor Devices : Compound semiconductors containing indium, such as InP (indium phosphide) and InN (indium nitride), are used in high-frequency communication devices and optical devices.

Thus, the properties and applications of indium play a crucial role in the field of various electronic devices and renewable energy.

Innovative application of indium plating in fine patterns: Possibilities for solder joint technology with low melting point and flexibility

In the process of mounting semiconductor chips and electronic components on printed circuit boards, solder material is used for the terminals of the chips.

Normally, solder balls are mounted or solder paste is screen-printed, but when the pitch between terminals becomes narrow, such as in advanced semiconductor chips, from a few tens of µm to a few µm, these methods become difficult to use.

Electroplating is suitable for depositing a film of solder material on such fine patterns.

In fact, the electrode formation process for advanced semiconductor chips employs a method for forming microbumps called copper (Cu) pillars by electroplating.

In the case of Cu pillar bumps, a layered structure of copper/nickel/tin-silver (Cu/Ni/Sn-Ag) is formed by electroplating.

Similarly, indium can also form fine patterns on a base metal film using electroplating. Electroplating solutions for indium are commercially available from various plating chemical manufacturers.

When soldering multiple stacked chips, using solder metals with different melting points allows for sequential soldering in the order of highest to lowest melting point.

Indium is a suitable material for solder due to its slightly lower electrical resistance and higher thermal conductivity compared to tin.

In addition, internal stress occurs due to the difference in coefficient of thermal expansion(CTE) between the chip and the resin substrate caused by heat treatment during the manufacturing process andn heat generated by the chip during the product use. If internal stress concentrates in the solder joint, it can cause cracks and lead to disconnection.

By using indium, a soft metal with a low melting point, it is possible to create highly reliable electronic device products that are less likely to disconnection even under harsh environments.

Delivered Electroplating Equipment for 300mm Wafer Indium Bumps

This time, the electroplating equipment for 300mm wafer indium bumps is the same model as the electroplating equipment previously delivered for SnAg solder plating applications.

In the bump formation process, the narrower the pitch and the thinner the film thickness, the more significantly film thickness variation affects yield. By adopting a face-up electroplating system, which excels in film thickness uniformity, high yield can be expected even for sensor products with a large number of terminals over a wide area.

When it comes to micro bump plating processes using indium or tin-based low melting point solder materials tailored to your needs, think of "Tosetz"!

Our company manufactures in response to various customer requirements. Please consider us when planning to introduce electroplating equipment.

We have also published the following related articles, so please take a look.

"Micro-wiring Formation Technology for High Frequencies Required in 5G and 6G Communication Systems"

"Electrode Formation Technology for Power Device Products"

"Proposal for Electroplating Equipment Products for Contract Plating Manufacturers"

For those interested in Tosetz, please visit:


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