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Electronic Materials

In the field of electronic materials, our research is focused on the development of soldering materials to mount electronic components on printed circuit boards. In recent years, electronic devices such as mobile phones have been getting smaller, faster and more sophisticated, and there has been a need to use environmentally friendly products that do not contain substances harmful to the environment. Against the back ground of these responsibilities, we are working to develop soldering materials by concentrating on the concept of " Clean & Fine", where " clean " means environmentally friendly and " fine " means miniaturization and performance.

Image : Electronic Materials

MS Series :De-activation function Lead-free solder paste

Strong Activation during reflow. De-activation after reflow

Image : Strong Activation during reflow. De-activation after reflow

Tin based lead-free solder cannot achieve such wettability as conventional tin-lead eutectic solder. Although a strong activator is needed for lead-free solder paste, if such material remains after reflow, reliability problems, such as corrosion and migration, will arise. Lead-free solder paste of Harima Chemicals can realize good solderability and high reliability in no-clean soldering process by our unique deactivation function. Since activity can be lost after reflow, though the strong activator is contained in flux. In other words, it is lead-free solder paste which has higher activity as RA (Rosin Activated) paste during reflow and higher reliability as RMA (Rosin Mildly Activated) paste after reflow.

Deactivation Function

Image : Deactivation Function

The activator, the amine hydrohalide, is decomposed by heating at the beginning of reflow process to generate hydro halide. The generated hydrohalide reacts with a metal oxide, and purifies a metal surface. At the same time, hydrohalide (ionic bond) reacts with the deactivator to be carbon and halogen covalent compound. The reliability of flux residue is improved by changing into covalent compound from ionic substance.

Reason of Strong Activity needed for lead-free Soldering

Image : Reason of Strong Activity needed for lead-free Soldering

Since the deoxidization ratio of tin oxide is much lower as compared with lead oxide, it can be said that tin is a metal very difficult to be purified. Another obstacle for tin based alloy to achieve better wetting is this alloy shows higher surface tensions as compared with the conventional solder. So, if tin based lead-free alloy is used, there is a tendency to have less wettability compared with the conventional tin-lead eutectic alloy.

Soldering Quality

Image : Soldering Quality

In the soldering IC lead edge which is apt to get less wettability in case of using RMA paste, good solderability equivalent to conventional RA solder can be secured by deactivation function.

SS Series (SUPER SOLDER): Solder precoating

SUPER SOLDER alloy formation mechanism

Our SUPER SOLDER technology forms solder alloys chemically by utilizing differences in metal ionization tendency. In the case of a mixture of metallic tin and an ionic lead compound, the lead deposits on the surface of metallic tin particles through a substitution. Consequently, the deposited lead diffuse into a metallic tin particle to form a tin-lead alloy particle.

Image : SUPER SOLDER alloy formation mechanism

Application to lead-free solders

SUPER SOLDER technology can also be applied to various lead-free solder compositions For example, as depicted in the figure below, tin-silver and tin-silver copper alloys can be formed by the combination of ionic compounds and metals, respectively.

Image : Application to lead-free solders

Whole surface printing method

SUPER SOLDER enables to apply the unique screen-print precoating technology, whole surface printing method. The accuracy of the paste printing precision is not required so that SUPER SOLDER demonstrate excellent fine pitch capability with good mass productivity.

Image : Whole surface printing method

Solder-dam precoating Method

For fine-pitch area array substrates, solder bumps with minimal height variations are formed by a solder dam precoating method involving a DFR lithography process.

Image : Solder-dam precoating Method

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