Wafer Level Chip Scale Package Thick Bottom Metal Support
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Solution Overview
Problem
Conventional wafer level chip scale packages (WLCSP) lack mechanical support and optimized thermal performance, and the exposure of the back surface metal contact results in poor moisture resistance and mechanical protection.
Innovation Solution
A method for creating a molded wafer level chip scale package with a thick bottom metal, involving the formation of through vias, insulation layers, and a conductive material connection to the back surface, along with a lead frame and package material to provide mechanical support and improved heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the chip is thinned to reduce substrate resistance and package thickness, then the package size and resistance are improved, but the chip becomes more prone to breaking and damage
Solution Approach 1:
The patent applies beforehand cushioning by forming a thick bottom metal layer and providing mechanical support structures before the chip thinning process. This pre-established support system prevents chip breakage during and after thinning, allowing the chip to be thinned to the required thickness without compromising mechanical integrity.
Solution Approach 2:
The patent uses composite materials by combining the thinned chip with a thick bottom metal layer and package material to create a hybrid structure. The composite construction provides both the thin profile needed for low resistance and the mechanical strength required to prevent breakage, resolving the contradiction between thickness reduction and strength maintenance.
2Ease of manufacture
If the back surface metal contact is exposed to achieve simple structure, then manufacturing is easier, but moisture resistance and mechanical protection deteriorate
Solution Approach 1:
The patent introduces an intermediary package material that covers and protects the exposed back surface metal contact. This intermediary layer acts as a barrier against moisture and mechanical damage while maintaining the simplicity of the manufacturing process, thus resolving the contradiction between ease of manufacture and moisture resistance.
3Device complexity
If conventional packaging methods are used to simplify the package structure, then device complexity is reduced, but thermal performance and mechanical support are insufficient
Solution Approach 1:
The patent replaces the conventional mechanical packaging structure with a optimized thermal structure featuring a thick bottom metal layer that serves as a heat sink. This substitution improves thermal performance by providing a low-resistance thermal path while maintaining relatively simple device complexity, as the same metal layer serves both structural and thermal functions.
Data Source
AI summary
A method for forming a wafer level chip scale (WLCS) package device with a thick bottom metal comprising the step of attaching a lead frame comprising a plurality of thick bottom metals onto a back metal layer of a semiconductor wafer including a plurality of semiconductor chips having a plurality of bonding pads formed on a front surface of each chip, each thick bottom metal is aligned to a central portion of each chip; a plurality of back side cutting grooves are formed along the scribe lines and filled with a package material, the package material are cut through thus forming a plurality of singulated WLCS package devices.