Through-Mold Interconnect Venting for Ball Lifting Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Advanced packaging architectures face ball lifting issues due to moisture outgassing from capillary underfill materials, which exert high vapor pressure on solder balls through constrained vias, leading to electrical opens and yield loss, especially in tight spacing conditions where increasing drill diameter is not feasible.
Innovation Solution
Incorporating vents alongside through mold interconnects (TMIs) to allow moisture to escape through the mold layer without passing through the package substrate, thereby reducing vapor pressure on solder balls and preventing ball lifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the TMI drill diameter is increased to provide more space for outgassing moisture, then ball lifting is reduced, but mechanical integrity of the mold is compromised and warpage increases
Solution Approach 1:
The through mold opening is segmented into two separate openings: a first opening that provides access to the solder ball and a second opening (vent) that provides an outgassing path. This segmentation allows the drill diameter for the first opening to remain small (maintaining mechanical integrity) while the second opening provides dedicated outgassing space (preventing ball lifting).
Solution Approach 2:
The outgassing function is extracted from the first opening (which must remain small for mechanical integrity) and assigned to a separate second opening. This allows the first opening to maintain its constrained diameter for structural support while the second opening handles the outgassing function independently.
2Reliability
If the TMI drill diameter is increased to reduce vapor pressure on solder balls, then ball lifting is prevented, but the spacing constraint with the die is violated requiring ablation of CUF material
Solution Approach 1:
The single large drill opening is segmented into two separate openings with different functions. The first opening maintains the original constrained diameter and position, while the second opening is positioned away from the die to provide outgassing without requiring ablation of CUF material or violation of spacing constraints.
Solution Approach 2:
The solution moves from a single-dimensional approach (increasing drill diameter) to a two-dimensional approach (adding a second opening at a different position). This allows outgassing functionality to be added without increasing the diameter of the first opening, thus maintaining compliance with die spacing constraints.
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
The vented TMIs maintain mechanical integrity and electrical performance by providing an outgassing path that does not compromise the package's structural integrity or require redesigning conductive layers, effectively preventing ball lifting and improving yield.
Implementation Method 1
outgassing of moisture absorbed by the package organic materials (particularly outgassing by a capillary underfill (CUF) material) in the first package
Implementation Method 2
outgassing of moisture absorbed by the package organic materials exerts a high vapor pressure on the solder balls
Data Source
AI summary
Embodiments disclosed herein include electronic packages. In an embodiment, an electronic package comprises a package substrate, a first die electrically coupled to the package substrate, and a mold layer over the package substrate and around the first die. In an embodiment, the electronic package further comprises a through mold opening through the mold layer, and a through mold interconnect (TMI) in the through mold opening, wherein a center of the TMI is offset from a center of the through mold opening.