Lead Frame Recesses Enhance Encapsulant Adhesion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional lead frame devices face issues with poor adhesion between silver wires and the copper-based lead frames, leading to complications in manufacturing and potential damage during electroplating, as well as peeling of the encapsulating layer due to inadequate adhesion to the substrate.
Innovation Solution
A lead frame device design featuring a metallic outer frame with recesses in the leads and a gap around the die pad, filled with an insulating polymer encapsulant, which enhances adhesion between the encapsulating layer and the leads, and serves as a mask for electroplating, eliminating the need for additional masking materials and reducing the risk of scratches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protecting layer is attached to the bottom surface prior to electroplating, then adhesion during electroplating is improved, but the manufacturing process becomes more complicated and requires additional scrapping steps
Solution Approach 1:
The patent removes the protecting layer from the manufacturing process entirely. The bottom surface of the lead frame device is electroplated directly without attaching any protecting layer, thereby eliminating the complexity of attachment and scrapping steps while maintaining adhesion quality through direct electroplating on the copper substrate
Solution Approach 2:
The bottom surface of the lead frame device serves its own function as the electroplating substrate without requiring an external protecting layer. The copper-based alloy bottom surface directly receives the electroplating treatment, making the process self-sufficient and eliminating additional manufacturing steps
2Ease of manufacture
If the encapsulating layer is applied directly to the lead frame device, then the manufacturing process is simplified, but the encapsulating layer peels off due to poor adhesion
Solution Approach 1:
The patent applies local quality by forming recesses at specific locations on the leads where encapsulant adhesion is critical. These recesses are strategically positioned to enhance bonding between the encapsulant and leads, while the rest of the lead surfaces maintain their original properties for electrical functionality
Solution Approach 2:
The recesses are formed on the leads before the encapsulation process. This preliminary action creates predetermined adhesion zones that ensure the encapsulating layer bonds properly to the leads during subsequent encapsulation, preventing peeling without complicating the manufacturing process
3Device complexity
If wires are bonded to the lead frame device without electroplating, then the manufacturing process is simpler, but the adhesion between silver wires and copper lead frame is poor
Solution Approach 1:
The patent applies local quality by electroplating only specific portions of the leads with noble metal-containing materials. The electroplating is localized to the regions where wire bonding occurs, providing enhanced adhesion for silver wires where needed, while leaving other portions of the leads as copper-based alloy for their original functions
Solution Approach 2:
Instead of electroplating the entire lead frame device, the patent applies partial electroplating only to the necessary bonding areas. This partial action provides sufficient adhesion improvement for wire bonding while avoiding the complexity and cost of complete electroplating
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 design improves the reliability of the chip package by ensuring strong adhesion between the encapsulant and the encapsulating layer, preventing peeling and allowing for reliable electroplating without additional masking, thus enhancing the manufacturing process and reducing damage to the lead frame devices.
Implementation Method 1
The encapsulant is filled in the recesses of the leads and the gap around the die pad, thereby improving the adhesion between an encapsulating layer and leads
Implementation Method 2
A lead frame device design featuring a metallic outer frame with recesses in the leads and a gap around the die pad, filled with an insulating polymer encapsulant, which enhances adhesion between the encapsulating layer and the leads, and serves as a mask for electroplating
Data Source
AI summary
A lead frame device includes a metallic outer frame member, a lead frame package preform, and an encapsulant. The metallic outer frame member includes a pair of spaced apart longitudinal and transverse sections. The lead frame package preform includes at least one die pad surrounded by the metallic outer frame member such that a gap is formed around the die pad within the metallic, and a plurality of spaced apart leads. Each of the spaced apart leads has a first portion connected to the metallic outer frame member, a second portion proximal to and spaced apart from the die pad, a top surface, and a recess indented from the top surface. The encapsulant is filled in the recess. The disclosure also provides a lead frame device assembly.