Sinhon thiourea | Applications of thiourea in electroplating

Thiourea, also known as thiourea (CAS number: 62-56-6), is generally a colorless orthorhombic crystal. Due to the presence of lone pair electrons on sulfur and ammonia atoms in thiourea molecules, they can form coordination compounds with various metal ions, but the coordination constants are generally small. It is worth noting that due to the special affinity of sulfur atoms in thiourea for precious metals, it often forms stable coordination compounds with precious metals, making it widely used in electroplating and chemical plating of precious metals. And thiourea is a small molecule with good coplanarity, so it is easy to firmly adsorb on the metal surface, thereby changing the electronic structure of the metal surface. This property makes it widely used in the field of electroplating additives.

As a coordinating agent

The sulfur atoms in the new thiourea molecules are prone to form stable coordination compounds with metal ions such as Au, Ag, Zn, Cu, and Pb. For example, the coordination compound ion formed by thiourea and Ag+is [Ag (H: NCSNH:),]+, with a stability constant of 13.1M '; The coordination compound ion formed with Au+is [Au (H2NCSNH2) 2]+, with an instability constant of 4.2 × 10 ^ -235.

As a stabilizer

Thiourea can exert its stabilizing effect by forming stable coordination compounds with certain specific metal ions. For example, in chemical nickel plating, copper, nickel phosphorus alloys, and tin immersion, thiourea can play a stabilizing role.

At present, thiourea has been applied in electroplating zinc, copper, silver, and copper gold alloys, as well as chemical copper plating, nickel, nickel phosphorus alloys, and various tin alloys, and serves as a coordinating agent, stabilizer, or additive in various plating solutions. Sinhon Chemical uses softened water to produce thiourea, strictly controlling the content of thiocyanate, heavy metals, calcium ions, etc. The thiourea grade reaches electronic and pharmaceutical standards.

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