Copper Lead Frame Conversion Coating for Mold Compound Adhesion
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Solution Overview
Problem
Existing semiconductor package manufacturing techniques often result in delamination between the mold compound and the die pad or conductive members, leading to diminished structural and functional integrity due to inadequate adhesion.
Innovation Solution
A method involving the formation of a conversion coating solution with salts of zirconate and vanadate, or a copper tungsten layer, to chemically anchor the mold compound to the copper lead frame, enhancing adhesion through chemical bonding with the lead frame's surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional manufacturing techniques are used without conversion coating, then the manufacturing process is simpler, but the adhesion strength between mold compound and lead frame is insufficient leading to delamination
Solution Approach 1:
The copper lead frame surface is pre-treated with a conversion coating solution containing zirconate and vanadate salts before mold compound application. This preliminary chemical treatment creates a reactive surface layer that enhances subsequent adhesion, preventing delamination without requiring complex manufacturing changes
Solution Approach 2:
The surface chemistry of the copper lead frame is modified by immersing it in a conversion coating solution. This changes the surface parameters by creating a chemically reactive layer with hydroxyl groups that can form strong bonds with the mold compound, thereby improving adhesion strength
2Reliability
If the copper lead frame is immersed in conversion coating solution with zirconate and vanadate salts, then the adhesion strength is significantly increased, but the manufacturing process becomes more complex
Solution Approach 1:
A conversion coating layer acts as an intermediary between the copper lead frame and the mold compound. This intermediate layer contains hydroxyl groups that chemically bond to both the copper substrate and the mold compound, ensuring reliable structural integrity while maintaining a manageable manufacturing process
Solution Approach 2:
The copper lead frame is transformed into a composite structure with a copper core and a conversion coating shell containing zirconate, vanadate, and hydroxyl groups. This composite structure provides enhanced adhesion properties and structural reliability
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 described method significantly increases the adhesion strength between the mold compound and the lead frame, reducing delamination and improving the structural and functional integrity of the semiconductor package.
Implementation Method 1
chemically anchor the mold compound to the copper lead frame, enhancing adhesion through chemical bonding with the lead frame's surface
Implementation Method 2
immersing the cleaned copper lead frame in the conversion coating solution; forming an assembly by coupling a semiconductor die to the copper lead frame, coupling the semiconductor die to a lead of the copper lead frame, applying a mold compound onto at least a portion of the outer surface of the copper lead frame, and curing the mold compound
Data Source
AI summary
In examples, a method of forming a semiconductor package comprises forming a conversion coating solution comprising a salt of a vanadate, a salt of a zirconate, or both with a complexing agent; cleaning a copper lead frame, wherein the cleaned copper lead frame comprises copper oxide on an outer surface thereof; immersing the cleaned copper lead frame in the conversion coating solution; rinsing the copper lead frame; and forming an assembly by coupling a semiconductor die to the copper lead frame, coupling the semiconductor die to a lead of the copper lead frame, applying a mold compound onto at least a portion of the outer surface of the copper lead frame, and curing the mold compound. An adhesion strength at an interface between the mold compound and the at least the portion of the outer surface of the copper lead frame is increased relative to a same assembly formed without immersing the copper lead frame in the conversion coating solution.