Overmolded Electronic Assembly Backplate Cavity Underfill
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current overmolded electronic assemblies face challenges in reducing size and cost while ensuring adequate support during the overmolding process, which can lead to damage to solder joints and hinder effective heatsinking of high-power devices.
Innovation Solution
A double-sided substrate is mounted to an aluminum backplate using an acrylic adhesive, with flip-chips on the heatsink side for enhanced thermal conductivity, and thermal films like Indium films are used between flip-chips and the backplate, along with cavities in the backplate to allow underfilling with overmold material, providing robust support and reducing stress on solder joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-sided substrate is used with a backplate providing rigidity, then the assembly has adequate support during overmolding, but the product form factor increases and cost increases
Solution Approach 1:
The patent transitions from a single-sided substrate arrangement to a double-sided substrate arrangement, utilizing both surfaces for component mounting. This dimensional change allows the same functional components to be packed into a smaller footprint, reducing the product form factor while maintaining adequate support through the backplate structure during overmolding.
2Volume of moving object
If flip-chips are located on the side of the PCB opposite the backplate, then the assembly can be compact, but heatsinking the flip-chips becomes more difficult
Solution Approach 1:
The patent inverts the conventional arrangement by mounting flip-chips on the side of the PCB that is in contact with the backplate (heatsink side) rather than on the opposite side. This inversion places the heat-generating components directly adjacent to the heatsinking surface, significantly improving thermal conductivity and heatsinking effectiveness while maintaining a compact assembly size.
3Reliability
If the PCB area is increased to accommodate single-sided component placement, then adequate support is provided, but cost increases
Solution Approach 1:
The patent utilizes both sides of the PCB substrate for component mounting, effectively doubling the usable area without increasing the PCB footprint. This approach reduces the required PCB area and backplate size, thereby lowering material costs and manufacturing expenses while maintaining adequate support through the backplate structure.
4Volume of moving object
If a double-sided PCB is used to reduce assembly size, then the form factor decreases, but the PCB is not as well supported during overmolding, leading to potential damage to solder joints
Solution Approach 1:
The patent incorporates a backplate structure that is positioned and secured to the PCB before the overmolding process. This preliminary action provides pre-established mechanical support and rigidity to the PCB during overmolding, preventing deflection and protecting solder joints from damage while enabling the use of a compact double-sided PCB configuration.
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 configuration reduces the size and cost of the assembly, enhances heatsinking, and minimizes damage to solder joints by distributing stress and improving substrate support during the overmolding process, leading to increased package density and manufacturing yield.
Implementation Method 1
A double-sided substrate is mounted to an aluminum backplate using an acrylic adhesive
Implementation Method 2
thermal films like Indium films are used between flip-chips and the backplate
Implementation Method 3
cavities in the backplate to allow underfilling with overmold material
Data Source
Figure 1~1A
Figure 2~2A
Figure 3
AI summary
A technique for manufacturing an electronic assembly (300) includes a number of steps. Initially, a backplate (302) with a cavity (319) formed into a first side of the backplate (302) is provided. Next, a substrate (304) with a first side of an integrated circuit (IC) die (306A) mounted to a first side of the substrate (304) is provided. The IC die (306A) is electrically connected to one or more of a plurality of electrically conductive traces formed on the first side of the substrate (304). The substrate (304) includes a hole (320) approximate an outer edge of the IC die (306A). The first side of the substrate (304) is then positioned in contact with at least a portion of the first side of the backplate (302). The IC die (306A) is positioned within the cavity (319) with a second side of the IC die (306A) in thermal contact with the backplate (302). The substrate (304) and at least a portion of the backplate (302) are overmolded with an overmold material (350), which enters the cavity (319) through the hole to substantially underfill the IC die (306A) and substantially fill an unoccupied portion of the cavity (319).