METHOD OF CONTROLLING CONCENTRATION OF PLATING LIQUID

摘要

PURPOSE:To automatically control the Ni concn. of a plating liquid always at a normal value by comparing the measured value of the Ni ion concn. of the plating liquid with the values of 1st, 2nd memories by utilizing the memories storing plural sets of measurement data and by replenishing the plating liquid in accordance with the difference thereof at the time of controlling the Ni ion concn. in the electroless Ni plating liquid. CONSTITUTION:The 1st memory and 2nd memory which can successively store (n) pieces of the Ni ion concn. are previously provided at the time of the electroless plating of Ni. Whether the measured value of the Ni ion concn. during the plating operation is within or out of the rage of permissible errors is decided from the average value of the n pieces of the data of the 1st memory. The measured value is inputted to the 1st memory and the average value is calculated in case of the former. A pump 6 of a plating replenishing liquid tank 5 is controlled by this value in a controller 7. The value is inputted as an abnormal value to the 2nd memory in case of the latter. The contents of the 1st memory and substd. with the contents of the 2nd memory when (n) pieces of the abnormal values are continuously inputted to the 2nd memory and the fluctuation in the data thereof is within the permissible errors. The pump 6 of the plating replenishing liquid tank 5 is thereafter controlled by the average value thereof, by which the Ni ion concn. of the plating liquid in a plating cell 1 is maintained at the prescribed value.