Removable Cover for Underfill Fillet Control in Multichip Modules

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Solution Overview

Problem

Conventional multi-chip module manufacturing is limited by the constraints imposed by underfill material fillets, which restrict the minimum spacing between semiconductor chips, thereby limiting miniaturization and increasing signal latency and power consumption due to resistive losses.

Innovation Solution

A method involving a removable cover positioned on the interposer to constrain lateral underfill flow, allowing for narrower chip-to-chip spacing by forming a narrow underfill fillet proximate the sidewall of the semiconductor chip, thereby reducing electrical pathways and improving latency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional underfill dispensing method is used, then underfill material forms fillets that extend beyond chip periphery, but this increases minimum spacing between chips and limits miniaturization

Engineering Contradiction:

Improveunderfill fillet width controlVSAvoidchip-to-chip spacing

Core Design Contradiction:

Manufacturing precisionVSLength of moving object

Solution Approach 1:

A removable cover is introduced as an intermediary element between the underfill material and the surrounding environment. The cover acts as a temporary barrier that confines underfill flow to a predetermined region during dispensing, preventing excessive lateral migration. After underfill curing, the cover is removed, allowing the narrow fillet to remain without obstruction. This mediator enables precise control of fillet dimensions without permanently obstructing the chip surface.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The removable cover is positioned on the interposer before underfill dispensing, establishing predetermined boundaries for underfill flow in advance. This preliminary action defines the acceptable fillet width region before the underfill material is applied, ensuring that the fillet will not extend beyond the desired narrow dimensions. The cover is removed only after underfill curing, maintaining the confined geometry throughout the critical bonding process.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If wider chip spacing is maintained to accommodate underfill fillets, then manufacturing is simpler, but electrical pathway length increases causing higher latency and power consumption

Engineering Contradiction:

Improveunderfill dispensing simplicityVSAvoidsignal latency

Core Design Contradiction:

Ease of manufactureVSLoss of time

Solution Approach 1:

The removable cover serves as a temporary mediator that enables narrow chip spacing by confining underfill flow during dispensing. It allows the manufacturing process to achieve precise fillet control without requiring complex dispensing equipment or multi-step processes. The cover is removed after curing, leaving the narrow spacing configuration intact, thus reducing electrical pathway length and signal latency while maintaining manufacturing feasibility.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If underfill material is allowed to flow freely, then complete gap filling is achieved, but fillet width increases requiring larger chip spacing

Engineering Contradiction:

Improvegap filling completenessVSAvoidunderfill fillet area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The removable cover acts as a mediator that confines underfill flow to the gap region between the chip and interposer, preventing lateral overflow. It allows complete gap filling to occur within the confined space, ensuring reliability through thorough gap penetration while simultaneously limiting the fillet area to only what is necessary for sealing the gap. The cover is removed after curing, leaving a minimal fillet area that does not require additional chip spacing.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This approach enables a significant reduction in the minimum spacing between semiconductor chips, leading to shorter electrical pathways, decreased latency, and enhanced electrical performance.

Implementation Method 1

The underfill migrates laterally between the chip and the interposer and, upon thermal cure, produces a fillet that extends beyond the periphery of the semiconductor chip

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentEP2614521B1Method of assembling a multichip module with underfilled semiconductor chip

Publication Date: 2018.01.24 ATI TECHNOLOGIES ULC

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AI summary

A method of manufacturing is provided that includes placing a removable cover (195, 195 ', 195 ") on a surface (215) of a substrate (120). The substrate includes a first semiconductor chip (1 10) positioned on the surface. The first semiconductor chip includes a first sidewall (170). The removable cover includes a second sidewall (200) positioned opposite the first sidewall. A first underfill (155) is placed between the first semiconductor chip and the surface wherein the second sidewall provides a barrier to flow of the first underfill. Various apparatus are also disclosed.