Through-Hole Electroplating Using PR Pulsed Current
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Solution Overview
Problem
Conventional electroplating methods face challenges in efficiently filling through-holes with a metal film of uniform thickness, particularly for diameters between 30 μm to 300 μm, leading to prolonged processing times and potential void formation.
Innovation Solution
An electroplating method involving a three-stage process using PR pulsed current, where the first stage forms a uniform metal film, the second stage blocks the central portion of the through-hole using a forward and reverse current alternately, and the third stage completes filling with a current value equal to or greater than the forward-current value of the second stage, along with agitation of the plating solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional electroplating method is used to fill through-holes with metal film, then the through-hole can be filled with metal film, but the processing time becomes excessively long for through-holes with diameter of 150 μm to 300 μm
Solution Approach 1:
The patent applies periodic action by using pulsed current with alternating forward and reverse polarity. The forward current deposits metal film while the reverse current dissolves it, creating a periodic plating-dissolution cycle that accelerates filling of large-diameter through-holes compared to continuous direct current plating.
Solution Approach 2:
The patent changes the electrical parameters by switching between forward and reverse current modes, adjusting current density and pulse width dynamically. This parameter variation enables control over deposition rate and film quality, resolving the contradiction between fast filling and void prevention.
2Manufacturing precision
If conventional electroplating method is used to fill through-holes, then metal film is deposited, but voids may form in the metal film during the filling process
Solution Approach 1:
The periodic alternation between forward current (deposition) and reverse current (dissolution) prevents void formation by continuously redistributing metal ions and preventing premature closure of the through-hole opening, ensuring uniform film thickness throughout the filling process.
Solution Approach 2:
The patent inverts the conventional approach by applying reverse current after forward current, causing dissolution of previously deposited metal. This inverted sequence prevents voids by maintaining open pathways for ion transport and ensuring uniform deposition before closing the hole.
3Productivity
If PR pulsed current with forward and reverse current is used to fill through-hole, then the central portion can be blocked up faster, but the forward-current value must be reduced compared to conventional plating current
Solution Approach 1:
The patent uses periodic pulsed current where the forward current (at reduced value) deposits metal and the reverse current dissolves it, creating a net accumulation effect that blocks the central portion faster than continuous low-current plating, while avoiding the voids caused by high continuous current.
Solution Approach 2:
The forward current phase performs preliminary metal deposition that prepares the pathway for faster central blocking, while the subsequent reverse current phase enhances this effect by dissolving surface deposits and promoting uniform inward growth, achieving faster blocking than either current mode alone.
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 securely fills through-holes with a metal film in a shorter time and prevents void formation, ensuring uniform thickness and efficient filling across a wide range of diameters.
Implementation Method 1
supplying a plating current between the substrate and anodes to perform a first plating process, a second plating process, and a third plating process
Implementation Method 2
blocking up a central portion of the through-hole with the metal film
Implementation Method 3
using a PR pulsed current constituted by a forward current used in metal deposition and a reverse current used in metal dissolution which are generated alternately
Implementation Method 4
a reverse current used in metal dissolution which are generated alternately
Data Source
AI summary
There is provided an electroplating method for a through-hole. The method includes: a first plating process, a second plating process, and a third plating process. The first plating process is a plating process of forming a metal film with a uniform thickness in the through-hole to reduce a diameter of the through-hole, the second plating process is a plating process of blocking up a central portion of the through-hole with the metal film using a PR pulsed current, and the third plating process is a plating process of completely filling the through-hole with the metal film using the plating current whose value is equal to or larger than a forward-current value of the PR pulsed current used in the second plating process.