Substrate Plating Uniformity via Dual-Face Current Control
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Solution Overview
Problem
The conventional electrolytic plating method results in variations in the thickness of the plating layer near the clamp member, leading to unreliable connections due to uneven plating, as the plating layer forms not only on the scheduled regions but also on the clamp member, causing a lower plating rate in the vicinity.
Innovation Solution
A substrate plating method where a first resist film is formed on one face with openings over plating-scheduled regions and a second resist film on the opposite face exposing a feeding layer, with the substrate held by clamp members contacting these feeding layers, and a higher current supplied between the second face and its electrode compared to the first face, allowing current deflection and uniform plating layer growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a current is supplied between an electrode and a substrate held with a clamp member in a plating bath, then a plating layer is formed on the substrate surface, but the plating layer has a variation in thickness in the plane of the substrate due to lower plating rate near the clamp member
Solution Approach 1:
The invention applies different current values to different regions of the substrate by supplying current between the first face and first electrode, and between the second face and second electrode. This allows local control of plating rate - higher current to the second face compensates for the plating suppression near the clamp member contact regions, achieving uniform plating layer thickness across the substrate plane
Solution Approach 2:
Instead of attempting to increase plating rate at the center of the substrate, the invention applies higher current to the opposite face (second face) where the clamp member contacts. This inverted approach compensates for the localized suppression effect by balancing the electrical field distribution, resulting in uniform plating thickness
2Ease of operation
If the substrate is held with a clamp member during plating, then the substrate can be securely positioned, but the plating layer forms on the clamp member causing lower plating rate in the vicinity
Solution Approach 1:
The invention changes the electrical parameter (current value) supplied to different faces of the substrate. By supplying a higher current value to the second face than to the first face, the plating rate near the clamp member contact regions is compensated, achieving uniform plating thickness while maintaining the clamp member in place for substrate holding stability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method reduces the variation in plating layer thickness across the substrate, enhancing the reliability of external connection terminals by ensuring a more uniform plating layer thickness, particularly near the clamp members.
Implementation Method 1
Electrolytic plating is a conventional method for forming a plating layer on a substrate. When a current is supplied between the substrate surface and the electrode in the plating bath, a plating layer is formed on the plating-scheduled regions of the substrate surface through the resist film as a mask.
Implementation Method 2
forming a plating layer on the plating-scheduled region of the first face while using the first resist film as a mask under conditions in which a value of current supplied between the second face of the substrate and the second electrode is larger than a value of current supplied between the first face of the substrate and the first electrode
Data Source
AI summary
A substrate plating method includes forming a first resist film exposing a first feeding layer on a first face of a substrate; forming a second resist film exposing a second feeding layer on a second face of the substrate opposite to the first face; holding the substrate with a clamp member in such a manner that the clamp member is in contact with the first feeding layer and the second feeding layer, and arranging a first electrode in opposed relation with the first face and a second electrode in opposed relation with the second face; and forming a plating layer on a plating-scheduled region of the first face under conditions in which a value of current supplied between the second face and the second electrode is larger than a value of current supplied between the first face and the first electrode.