Vented BGA Adhesive Channel for Cleaner Solution Barrier
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Solution Overview
Problem
Vented BGA packages allow corrosive aqueous cleaner solutions to ingress, limiting them to 'no-clean' solder flux and processes due to ineffective rinsing through small vents, preventing the use of clean flux and aqueous washing.
Innovation Solution
A method reconfigures vented BGA packages by applying a continuous adhesive bead around the perimeter to create a channel through pressure relief vents to a polarity through-hole, allowing for elevated temperature reflow with clean or no-clean flux, followed by sealing to prevent aqueous cleaner solution contact with internal conductors during washing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vents are formed in the adhesive to prevent pressurization during reflow, then the lid can expand without separating from the substrate, but corrosive cleaner solutions can ingress through the vents making rinsing ineffective
Solution Approach 1:
The invention segments the venting function from the sealing function by creating separate pathways: pressure relief vents allow gas escape during reflow, while the continuous adhesive bead creates a sealed channel that directs cleaner solution away from internal conductors. This segmentation resolves the contradiction by allowing both pressure relief and corrosion protection.
Solution Approach 2:
The continuous bead of adhesive acts as an intermediary element that serves dual purposes: it creates a sealed pathway for pressure relief while simultaneously forming a barrier against corrosive cleaner solution ingress. The adhesive mediator protects internal conductors while maintaining the venting function.
2Object-affected harmful factors
If a continuous bead of adhesive is applied around the perimeter to seal the gap, then a cleaner solution barrier is formed, but the complexity of the adhesive application process increases
Solution Approach 1:
The continuous adhesive bead performs multiple functions simultaneously: it seals the gap between lid and substrate, creates a channel for pressure relief, forms a barrier against cleaner solution ingress, and provides mechanical bonding. This multi-functionality reduces overall process complexity despite the continuous application requirement.
Solution Approach 2:
The invention changes the parameter of adhesive application from discrete beads to a continuous bead, fundamentally altering how the adhesive functions. This parameter change enables the adhesive to form both seals and channels, simplifying the overall design while maintaining protection against cleaner solution ingress.
3Stress or pressure
If vents are made small to prevent excessive pressure loss, then pressure relief is maintained, but rinsing effectiveness is reduced allowing cleaner solution to remain inside
Solution Approach 1:
The invention segments the venting and rinsing functions into separate pathways: small pressure relief vents maintain pressure control while the continuous adhesive bead creates a sealed channel that directs rinsing solution flow. This segmentation allows both functions to operate optimally without compromising each other.
Solution Approach 2:
The continuous adhesive bead acts as an intermediary that creates a controlled pathway for both pressure relief and rinsing solution flow. It mediates between the small vents that maintain pressure and the rinsing process that requires effective solution flow, allowing both to function effectively.
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
Enables the use of both clean and no-clean flux with aqueous washing processes, effectively removing flux residue while protecting internal components from corrosive solutions, enhancing the adaptability and reliability of BGA packages.
Implementation Method 1
The continuous bead and discrete beads define a channel through the pressure relief vents to the polarity through-hole
Implementation Method 2
Surface tension causes the molten solder to hold the package in alignment with the PWB, at the correct separation distance, while the solder cools and solidifies
Data Source
AI summary
A vented BGA package is reconfigured by first applying a continuous bead of adhesive around the perimeter of the package to seal the gap between the lid and substrate. The continuous bead defines a channel through the pressure relief vents to a polarity through-hole in the lid. The BGA package is reflow soldered to a PWB at an elevated temperature using solder flux, clean or no-clean. The IC die achieves elevated temperature pressure relief through the pressure relief vents along the channel and out the polarity through-hole. After reflow a seal is applied to plug the polarity through-hole. The PWB is washed in an aqueous cleaner solution to remove flux residue. The continuous bead of adhesive and the seal form a cleaner solution barrier that prevents the solution from contacting conductors inside the package. The seal may be removed or left intact depending on the operating environment.