A New Neutral pH Tin Electroplating Process for Acid Sensitive Electronic Components

摘要

Most chip capacitors and some chip resistors are manufactured with ceramic dielectric materials that are subject to attack by strongly acidic plating solutions. Also, some copper based termination pastes lose adhesion strength during the plating operation. The most common tin electroplating solution designed for this industry operates at a pH between 3.0 and 4.0. This pH range has proven very satisfactory for the passive components industry over the past 20 years. However, new ceramic dielectric material formulations, and new copper termination pastes, are more sensitive to the tin plating electrolyte. A new tin plating process has been developed that operates at a pH range of 6.5 to 7.0 to reduce the chemical attack rate on these materials. This paper describes the conditions under which the new plating process is operated: current density range, temperature range, and chemical component range. Solderability characteristics of the tin deposits will be tested by wetting balance. A comparison of the new neutral pH plating bath against several different tin plating electrolytes will examine the attack rates on LTCC materials and copper termination pastes.