Semiconductor Package Standoff Structure for Sensor Cavity Height

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Solution Overview

Problem

Conventional semiconductor packages for image sensor chips often result in uneven or non-uniform cavity heights due to adhesive flow issues, which can lead to reliability problems such as damage to wire bonds from insufficient clearance.

Innovation Solution

A semiconductor package design that includes a standoff structure on the cap bond region, configured to maintain a predefined cavity height between the protective cover and the sensor region, using a combination of adhesive and rigid studs to ensure uniformity and prevent contact with wire bonds or the sensor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If adhesive is used to attach the cover to the die, then the cover can be attached to the die, but the cavity height becomes uneven or non-uniform due to adhesive flow

Engineering Contradiction:

Improveattachment strengthVSAvoidcavity height uniformity

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The adhesive attachment process is segmented into two distinct functions: (1) adhesive is applied only to the peripheral bond pads to provide attachment strength, and (2) standoff structures are placed in the center of the cavity to maintain uniform height. This segmentation prevents adhesive from flowing into the center and creating height variations, while still achieving secure attachment at the periphery.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Standoff structures are introduced as intermediary elements between the die and the cover. These standoffs act as mechanical mediators that maintain a predetermined uniform cavity height, preventing direct contact between the adhesive and the center region, thereby ensuring height uniformity while the adhesive provides peripheral attachment.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If adhesive flow is not controlled, then the attachment process is simple, but wire bonds may be damaged due to insufficient cavity clearance

Engineering Contradiction:

Improveattachment process simplicityVSAvoidwire bond integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Standoff structures are placed on the die surface before the cover is attached. This preliminary action establishes the minimum cavity height requirement before adhesive application, ensuring that even if adhesive flows, it cannot reduce the cavity clearance below the standoff height, thereby protecting wire bonds from damage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The standoff structures serve as a cushioning mechanism that prevents excessive adhesive flow from compromising wire bond clearance. By having these height-maintaining structures in place beforehand, the system is cushioned against the potential harmful effect of adhesive flow, ensuring reliable wire bond protection.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS11670521B2Reliable semiconductor packages for sensor chips

Publication Date: 2023.06.06 UTAC HEADQUARTERS PTE LTD

AI summary

A method for forming a semiconductor package is disclosed. The method includes providing a package substrate having a die attach region with a die attached thereto. A protective cover is disposed over a sensor region of the die and attached to the die by a cover adhesive. The protective cover is supported by a standoff structure disposed on the die and below the protective cover. An encapsulant is disposed to cover the package substrate while leaving the top package surface exposed.