Removable Backside Protective Layer for Semiconductor Package Molding
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Solution Overview
Problem
Semiconductor packages face challenges such as mold flashing and solder defects during manufacturing, leading to reduced effectiveness and increased costs due to debris under the leadframe tape causing mold flashing and improper solder placement resulting in short circuits.
Innovation Solution
A removable protective layer is attached to the leadframe, which forms recesses after curing, preventing mold flashing and allowing closer lead and die pad placement, reducing the risk of solder overlap and short circuits by providing a barrier for solder flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a removable protective layer is attached to the leadframe, then mold flashing is prevented and manufacturing precision is improved, but device complexity increases
Solution Approach 1:
A removable protective layer is applied to the leadframe before the molding process to prevent mold flashing. This preliminary protective action ensures that the leadframe surface is protected during molding, and the protective layer can be removed afterward to reveal clean, flash-free leads and die pads.
Solution Approach 2:
The removable protective layer serves as an intermediary between the mold and the leadframe. It temporarily occupies the space where mold flashing would occur, preventing the molding compound from adhering to the leadframe surface, and is subsequently removed to leave a clean surface.
2Reliability
If leads and die pads are placed farther apart, then solder overlap and short circuits are reduced, but area utilization decreases
Solution Approach 1:
The protective layer is strategically positioned to extend beyond the edges of the leads and die pads, creating an overhang that acts as a physical barrier. This converts the potential harm of solder overflow into a beneficial feature, as the overhanging protective layer captures and contains the solder within recesses, preventing short circuits while allowing closer component placement.
3Reliability
If the protective layer extends beyond lead and die pad edges, then solder overflow is contained, but material usage increases
Solution Approach 1:
The protective layer is applied with varying thickness in different regions. It extends beyond the edges of leads and die pads only where needed to contain solder overflow, while maintaining minimal thickness elsewhere. This localized extension optimizes solder containment while minimizing material consumption.
Data Source
AI summary
A semiconductor package formed utilizing a removable backside protective layer includes a leadframe, a die pad, leads and a molding compound around them. The first surface of the die pad and leads are exposed to an external environment by the plurality of recesses. The recesses are formed by coupling a removable backside protective layer to the leadframe before applying the molding compound. After the molding compound is applied and cured, the backside protective layer is removed to expose the first surface of the die pad and the first surfaces of the leads so the semiconductor package may be mounted within an electronic device. The removable backside protective layer protects the die pad and the leads from mold flashing and residue when forming the semiconductor package during the fabrication process.