MEMS Package Structure with Exposed Bumps for Reliable Connections
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Solution Overview
Problem
Conventional MEMS package fabrication methods face electrical connection failures due to position deviation of bonding wires caused by mold flow of the encapsulant, which affects the alignment of exposed wire ends and subsequent electrical connections.
Innovation Solution
A package structure and fabrication method where first bumps are strategically positioned on the second conductive pads, either distant from or proximate to the wire ends of bonding wires, ensuring that even if the encapsulant mold flow causes position deviation, the bumps remain exposed at predetermined positions for reliable electrical connections, avoiding the failure of electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an encapsulant is formed to encapsulate the lids, bonding wires, conductive pads and metal layers, then the MEMS elements are protected and encapsulated, but the mold flow of the encapsulant causes position deviation of the bonding wires, leading to electrical connection failure
Solution Approach 1:
The patent applies preliminary action by forming the encapsulant before the bonding wires are completely positioned and connected. The encapsulant is formed in advance to establish a stable base structure, and then the bonding wires are bonded to conductive pads on the encapsulant surface. This sequence prevents the encapsulant's mold flow from causing position deviation of the bonding wires, as the wires are positioned after the encapsulant has set, thereby maintaining electrical connection reliability while avoiding position precision issues.
2Ease of manufacture
If the bonding wires are positioned and connected before encapsulation, then electrical connections can be established, but the subsequent encapsulant mold flow causes deviation of wire positions, affecting alignment with conductive pads
Solution Approach 1:
The patent reverses the conventional sequence by applying preliminary action to form the encapsulant first, creating a stable platform with conductive pads before performing wire bonding. This eliminates the problem of mold flow causing wire position deviation, as the encapsulant is already cured and dimensionally stable when the wires are positioned and connected, ensuring both ease of manufacture and high alignment precision.
Data Source
AI summary
A package structure having an MEMS element includes: a chip having at least an MEMS element and a plurality of first conductive pads; a lid disposed on the chip to cover the MEMS element and having a plurality of second conductive pads formed thereon; a plurality of bonding wires electrically connecting the first and second conductive pads; a plurality of first bumps disposed on the second conductive pads, respectively; an encapsulant formed on the chip to encapsulate the lid, the bonding wires, the first and second conductive pads and the first bumps while exposing the top surfaces of the first bumps; and a plurality of circuits formed on the encapsulant and electrically connecting to the exposed first bumps, thereby avoiding the conventional drawback of electrical connection failure caused by position deviation of bonding wires due to mold flow of the encapsulant.