Substrate Package Via Interconnects Without Post-Mold Grinding
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Solution Overview
Problem
Legacy MIS-BGA packaging techniques face challenges in achieving fine line and spacing (FLS) of copper traces due to the need for grinding and surface treatment, which limits the ability to mass produce traces with widths and spacings less than 15 microns, and negatively impacts the reliability and structural stability of the package.
Innovation Solution
The proposed solution involves forming one or more pads and traces on a substrate with a sacrificial element that decomposes to gas upon thermal treatment, allowing for the formation of vias without the need for grinding, using compression molding to ensure the sacrificial element is flush with the mold compound, and employing high precision techniques for precise alignment and decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If grinding and surface treatment processes are used to expose vias in legacy MIS-BGA packages, then via formation is achieved, but manufacturing complexity increases and reliability decreases
Solution Approach 1:
The via openings are formed before the mold compound is applied. The DFR is patterned and copper is plated to create vias while the substrate is still accessible, eliminating the need for subsequent grinding or surface treatment to expose the vias.
Solution Approach 2:
Instead of forming vias through the mold compound by grinding after molding (traditional approach), the invention inverts the sequence by forming vias first on the substrate, then applying the mold compound over them. This eliminates the harmful grinding step while achieving the same via exposure function.
2Manufacturing precision
If two lithography steps are used to create pads and via metal separately, then precise via formation is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The invention combines the pad formation and via formation into a single lithography step. The DFR is patterned to define both the pad openings and via openings simultaneously, and a single copper plating process fills both types of openings, eliminating the need for separate lithography and plating steps.
Solution Approach 2:
The DFR pattern serves multiple functions: it defines both pad locations and via locations, and the subsequent copper plating process simultaneously creates both pad structures and via structures. This multi-functional approach reduces the number of process steps while maintaining precision.
3Ease of operation
If grinding is performed to expose embedded vias, then via accessibility is improved, but structural stability deteriorates
Solution Approach 1:
The vias are formed and made accessible before the mold compound is applied. The copper plating creates via structures that are already accessible and functional before molding, eliminating the need for post-molding grinding to expose them.
Solution Approach 2:
Instead of embedding vias in the mold compound and then grinding to expose them (traditional sequence), the invention inverts the sequence by forming accessible vias first, then covering them with mold compound. This eliminates the grinding step while maintaining via accessibility for subsequent processing.
4Manufacturing precision
If multiple DFR stripping processes are used, then complete via exposure is achieved, but manufacturing time and complexity increase
Solution Approach 1:
The DFR is completely removed after via formation while the substrate is still accessible, ensuring complete via exposure before the mold compound is applied. This preliminary removal eliminates the need for subsequent stripping steps after molding.
Solution Approach 2:
Instead of applying mold compound first and then attempting to remove DFR through it (requiring multiple stripping steps), the invention inverts the sequence by removing DFR completely before molding. This single stripping step achieves complete via exposure without compromising productivity.
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 the creation of MIS-BGA packages with FLS less than 15/15 microns, increasing the number of input/output ports without increasing cost or z-height, while enhancing reliability and reducing manufacturing complexity by eliminating the need for grinding and multiple DFR stripping processes.
Implementation Method 1
A sacrificial element may be provided on at least one of the pads. A mold compound may be compression molded onto the package such that the face of the sacrificial element is generally flush with the face of the mold compound. The package may then be thermally treated such that the sacrificial element cleanly decomposes to gas to form a via.
Data Source
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AI summary
Embodiments herein may relate to providing, on a pad coupled with a carrier panel, a sacrificial element. Embodiments may further relate to providing, on the pad, a mold compound, wherein the mold compound is at least partially adjacent to the sacrificial element. Embodiments may further relate to removing, subsequent to the providing of the mold compound, the sacrificial element to form a via in the mold compound to at least partially expose the pad. Other embodiments may be described and/or claimed.