Multi-Size Cavity Die Attach for Low-Resistance Semiconductor Packaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional die attach solutions using metal particle-filled polymers face significant thermal and electrical resistance issues, which are exacerbated by temperature-induced stresses in solder die attach processes, limiting their effectiveness in compact, high-current electronic systems.
Innovation Solution
A semiconductor device with a metal substrate featuring a through-hole aperture and multi-size cavity, where a semiconductor die with a back side metal layer is directly attached to the substrate using an electroplated metal die attach layer, enhancing thermal conductivity and mechanical stability while avoiding voiding issues associated with Sn-Cu intermetallic formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal particle-filled polymer die attach adhesive is used, then electrical and thermal pathways are provided, but significant thermal and electrical resistance occurs
Solution Approach 1:
The patent changes the material parameter from polymer-based adhesive to electroplated metal layer, fundamentally altering the thermal and electrical conductivity properties. The electroplated metal layer provides direct metal-to-metal contact, eliminating the high resistance inherent in polymer-filled adhesives.
Solution Approach 2:
The patent employs a composite structure combining electroplated metal layers with the semiconductor die and substrate, creating a multi-layer composite assembly that optimizes both thermal and electrical pathways while minimizing resistance through direct metal contact interfaces.
2Reliability
If solder die attach is used, then back side electrical contact is achieved with good thermal and electrical resistance performance, but the process causes temperature-induced stresses to the semiconductor die's metal interconnect
Solution Approach 1:
The patent changes the process temperature parameter by using electroplating at lower temperatures compared to solder reflow processes. This eliminates the high temperature-induced stresses on metal interconnect while achieving equivalent or superior thermal and electrical performance through direct metal contact.
Solution Approach 2:
The patent replaces the thermal-mechanical soldering process with an electrochemical deposition process. Instead of using heat and mechanical pressure to bond solder, the patent uses electroplating to deposit metal layers that provide direct electrical and thermal contact without the harmful thermal stresses.
3Strength
If conventional die attach adhesive is used, then mechanical attachment is provided, but thermal conductivity is limited
Solution Approach 1:
The patent creates a composite structure where the electroplated metal layer serves dual functions: providing mechanical attachment strength through direct bonding to the substrate while simultaneously establishing high-conductivity thermal pathways. This eliminates the thermal conductivity limitation of polymer-based adhesives.
Solution Approach 2:
The electroplated metal layer performs multiple functions simultaneously: it provides mechanical attachment, establishes electrical contact, and creates high-conductivity thermal pathways. This multi-functionality replaces the need for separate adhesive materials that could only provide mechanical bonding with poor thermal conductivity.
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 significantly increases thermal conductivity by one to two orders of magnitude over conventional methods, provides low electrical resistance, and improves mechanical stability by eliminating voids and reducing temperature-induced stresses.
Implementation Method 1
the die attach adhesive generally comprises a polymer such as a polyimide or an epoxy-based adhesive. Silver is often added in particle flake form as a filler to the polymer to raise both the electrical conductivity and the thermal conductivity
Implementation Method 2
Silver is often added in particle flake form as a filler to the polymer to raise both the electrical conductivity and the thermal conductivity
Implementation Method 3
a back side metal (BSM) layer thereon that is directly attached onto the metal substrate by an electroplated (plated) metal die attach layer
Data Source
AI summary
A semiconductor device includes a metal substrate including a through-hole aperture having a multi-size cavity including a larger area first cavity portion above a smaller area second cavity portion that defines a first ring around the second cavity portion, where the first cavity portion is sized with area dimensions to receive a semiconductor die having a top side with circuitry coupled to bond pads thereon and a back side with a metal (BSM) layer thereon. The semiconductor die is mounted top side up with the BSM layer on the first ring. A metal die attach layer directly contacts the BSM layer, sidewalls of the bottom cavity portion, and a bottom side of the metal substrate.