Copper Surface Roughening for BOT Package Delamination Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor packaging methods face challenges in achieving strong mechanical interlocking and adhesion between conductive layers and molding underfill (MUF) due to thermal stress and delamination issues, particularly in bump-on-trace (BOT) packages, where small gaps and material mismatches lead to cracking and reliability concerns.
Innovation Solution
A surface treatment process involving a chemical bath with specific concentrations of NaClO2, NaOH, and Na3PO4 to create a roughened CuO nanowire surface on conductive layers, enhancing mechanical interlocking, combined with the use of complex compounds like thiol or trimethyl phosphite for improved chemical bonding, which increases adhesion strength and reduces delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a smooth conductive layer surface is used in BOT packaging, then the manufacturing process is simpler, but the mechanical interlocking and adhesion strength with MUF is insufficient, leading to delamination under thermal stress
Solution Approach 1:
The conductive layer surface is pre-treated with a chemical solution containing NaClO2, NaOH, and Na3PO4 before MUF application to create a roughened surface with nanowire structures. This preliminary surface modification enables strong mechanical interlocking with MUF, preventing delamination under thermal stress while maintaining manufacturing feasibility
Solution Approach 2:
The surface morphology of the conductive layer is fundamentally changed from smooth to roughened with nanowire structures through chemical treatment. This parameter change in surface topology dramatically increases the mechanical interlocking capability with MUF, transforming the adhesion mechanism from weak chemical bonding to strong mechanical anchoring
2Reliability
If conventional surface treatment is used on conductive layers, then the process is simpler, but cracking occurs in solder bumps or solder balls due to thermal stresses
Solution Approach 1:
The conductive layer undergoes preliminary chemical treatment to develop a roughened surface with nanowire structures before subsequent packaging steps. This pre-established surface morphology provides stress distribution capability that prevents crack initiation and propagation in solder bumps and balls under thermal cycling, enhancing reliability without complicating the overall manufacturing flow
Solution Approach 2:
The surface roughness parameter of the conductive layer is fundamentally transformed through chemical treatment, creating a nanowire structure that acts as a stress buffer. This parameter change enables the surface to absorb and distribute thermal stresses, preventing the concentration of stresses that would otherwise cause cracking in the solder interconnects
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 surface treatment significantly enhances mechanical interlocking force between conductive layers and MUF, doubling the adhesion strength and improving reliability under thermal stress conditions, as demonstrated by increased bonding interface strength and reduced delamination in experimental results.
Implementation Method 1
the substrate with the integrated circuit die is submerged into a chemical solution. The chemical solution roughens a surface of the conductive layer to form a roughened surface
Implementation Method 2
the use of complex compounds like thiol or trimethyl phosphite for improved chemical bonding, which increases adhesion strength
Data Source
AI summary
A surface treatment and an apparatus for semiconductor packaging are provided. A surface of a conductive layer is treated to create a roughened surface. In one example, nanowires are formed on a surface of the conductive layer. In the case of a copper conductive layer, the nanowires may include a CuO layer. In another example, a complex compound is formed on a surface of the conductive layer. The complex compound may be formed using, for example, thiol and trimethyl phosphite.