Mold Flash Removal Using Acid Etching for Semiconductor Packages
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Solution Overview
Problem
Current methods for removing mold flash from semiconductor packages, such as adhesive tape and laser ablation, are costly, time-consuming, and can lead to contamination and poor solderability, while plasma etching results in silica residue and charred material, making them inefficient and costly.
Innovation Solution
A method involving a mold flash removal apparatus that uses an acid solution to selectively remove excess encapsulation material from unmolded surfaces of molded substrates, with the acid solution comprising a mixture of nitric and sulfuric acid, and optional scrubbing or oscillating mechanisms to enhance removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If adhesive tape is used to mask the bottom surface during molding, then mold flash formation is minimized, but manufacturing cost increases and additional processing steps are required
Solution Approach 1:
The leadframe substrate itself serves as the masking element through its side walls that extend beyond the molded surface. The substrate's own structural features (side walls and ledges) are utilized to prevent mold flash without requiring external masking materials or additional processing steps.
Solution Approach 2:
The masking function is extracted from the leadframe body and implemented through dedicated structural features (side walls and ledges) that are integral to the leadframe design, eliminating the need for separate masking components.
2Object-affected harmful factors
If adhesive tape is attached to the bottom surface, then mold flash is prevented, but contamination occurs and solderability deteriorates
Solution Approach 1:
The leadframe substrate's own side walls and ledges serve as the masking mechanism, eliminating contamination from external masking materials and preserving the solderability of the bottom surface.
3Object-affected harmful factors
If adhesive tape is used for masking, then mold flash is minimized, but manufacturing cost increases
Solution Approach 1:
The leadframe substrate's inherent structural features (side walls and ledges) provide the masking function, eliminating the need to purchase and apply external masking materials, thereby reducing manufacturing costs.
4Manufacturing precision
If laser ablation is used to remove mold flash, then mold flash is removed, but processing time increases and manufacturing cost increases
Solution Approach 1:
The side walls and ledges are formed during the molding process itself, performing the masking action preliminarily to prevent mold flash formation in the first place, thereby eliminating the need for subsequent removal operations.
5Manufacturing precision
If plasma etching is used to remove mold flash, then mold flash is removed, but silica residue and charred material are generated
Solution Approach 1:
The masking structure prevents mold flash formation during molding, eliminating the need for post-processing removal operations that would generate harmful residues.
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 method effectively removes mold flash without damaging the semiconductor package, improving solderability and reducing manufacturing costs by avoiding additional processing steps and contamination, while allowing for controlled removal and recycling of the acid solution.
Implementation Method 1
contacting the unmolded surfaces with the acid solution for a sufficient time to remove the excess encapsulation material
Data Source
AI summary
A method is provided for removing excess encapsulation material from unmolded surfaces of a molded substrate including semiconductor packages by utilizing an acid solution. The method comprises the steps of mounting the substrate to a holding device with the unmolded surfaces facing an acid source for supplying an acid solution, contacting the unmolded surfaces with the acid solution for a sufficient time to remove the excess encapsulation material from the unmolded surfaces while substantially avoiding contact with molded surfaces thereof, and thereafter removing the substrate from contact with the acid solution.