Electroless Pd Plating with Rare Earths for Wire Bonding
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Solution Overview
Problem
Electroless Ni/Pd/Au plating films exhibit deteriorated wire bondability after high-temperature thermal history, such as reflow treatment, which affects the connection success rate in wire bonding.
Innovation Solution
An electroless palladium plating solution containing a Palladium compound, a reducing agent, a complexing agent, and at least one selected from Ge and rare earth elements, specifically La, Ce, Sm, and Y, is used to form a Pd plating film that suppresses the formation of a Pd—Au solid solution on the Au plating film surface, maintaining excellent wire bondability even after high-temperature thermal history.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electroless Ni/Pd/Au plating films are used, then wire bondability is excellent before high-temperature thermal history, but wire bondability is significantly deteriorated after high-temperature thermal history in reflow treatment
Solution Approach 1:
The invention changes the compositional parameters of the Pd plating solution by adding specific rare earth elements (La, Ce, Sm, or Y) at controlled concentrations (0.01-5 g/L). This compositional modification prevents Pd diffusion into the Au layer during thermal history, thereby maintaining wire bondability after reflow treatment while preserving the original plating film structure
Solution Approach 2:
Rare earth elements act as intermediary substances that inhibit the direct interaction and diffusion between Pd and Au atoms during high-temperature thermal history. These rare earth elements form a barrier or modify the diffusion pathway, preventing the formation of Pd-Au solid solutions that would otherwise deteriorate wire bondability
2Productivity
If Pd plating film thickness is reduced to meet miniaturization requirements, then density is enhanced, but wire bondability after thermal history is compromised
Solution Approach 1:
By modifying the Pd plating solution composition with rare earth elements, the invention enables the use of thinner Pd films that maintain their protective and functional properties after thermal history. The rare earth element additives enhance the thermal stability of thin Pd films, allowing miniaturization while preserving wire bondability
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
The electroless Pd plating solution with Ge and rare earth elements ensures excellent wire bondability after high-temperature thermal history, outperforming conventional solutions by inhibiting solid-dissolution and maintaining bondability with a film thickness equivalent to or less than that of a conventional Au plating film.
Implementation Method 1
a reducing agent
Implementation Method 2
a complexing agent
Implementation Method 3
electroless Pd plating solution
Data Source
AI summary
An object of the present invention is to provide an electroless Pd plating solution which enables formation of a Pd plating film forming a plating film having excellent wire bondability even after a high-temperature thermal history. An electroless Pd plating solution of the present invention includes: a Palladium compound, a reducing agent, a complexing agent, and at least one selected from a group consisting of Ge and rare earth element.