Study of a dipping method for flip-chip flux coating

• Flow process is analyzed by using two indicators including reflective area ratio and flow velocity.
• Stably reflective area ratio of glue is associated with gluing speed instead of viscosity.
• Different gluing speed changes the amount of the glue transferred to the groove.
• Flow velocity of glue is related with gluing speed, a greater gluing speed leads to greater maximum flow velocity.
• Larger gluing speed gives greater inertial force to the glue.

A dipping method for flux coating is proposed in the paper. Flow process of the flux transferred into the groove is investigated by using an optical detection means. Flow process influenced by gluing speed and viscosity is analyzed by using two indicators including reflective area ratio and flow velocity. Experimental result shows that stably reflective area ratio of glue is associated with gluing speed instead of viscosity; and it decreases with the increase of gluing speed in a same viscosity. The reason is that different gluing speed changes the amount of the glue transferred to the groove. Flow velocity of glue is related with gluing speed, a greater gluing speed leads to greater maximum flow velocity at the same viscosity, which may be due to larger gluing speed gives greater inertial force to the glue. Real chip experiments verified the feasibility of this method.