Wire Bond Encapsulation Profiling for Printhead Clearance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The encapsulation of wire bonds between a circuit board and an integrated circuit die poses challenges due to the high profile of the encapsulant bead, which obstructs active surfaces like inkjet printheads, and the non-uniformity of the encapsulant bead shape, leading to inefficient use of wafer real estate and reduced die production.
Innovation Solution
Raising the chip mounting area relative to the conductor mounting area, combined with techniques such as plastic deformation of wire bonds and profiling the encapsulant bead using a blade, to reduce the height and profile of the encapsulant, allowing closer proximity of active surfaces without contact and improving encapsulant control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the encapsulant bead is made to extend 500-600 microns proud of the contact pads to fully encapsulate the wire bonds, then the wire bonds are protected and strengthened, but the active surface of the die cannot be brought into close proximity with another surface
Solution Approach 1:
The support structure introduces a vertical dimension by providing a raised chip mounting area. This elevation separates the chip mounting plane from the conductor mounting plane, allowing the encapsulant bead to extend horizontally to protect wire bonds while the vertical raise maintains clearance for the active surface to approach another surface closely.
Solution Approach 2:
The support structure is segmented into distinct functional areas: a chip mounting area raised relative to conductor mounting areas. This segmentation allows different regions to serve different purposes - the raised area protects wire bonds through encapsulation while maintaining the necessary clearance for active surface operations.
2Ease of manufacture
If the encapsulant bead sides are not straight due to variations in pressure and needle speed, then the encapsulation process is simpler, but valuable wafer real estate is wasted and the number of dies that can be fabricated is reduced
Solution Approach 1:
The support structure provides localized raised areas specifically positioned to accommodate encapsulant beads. This local structural modification allows non-uniform encapsulant deposition without compromising overall packaging quality, as the raised areas are strategically placed only where wire bond encapsulation is needed, preserving wafer real estate for additional dies.
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 reduces the encapsulant bead height above the active surface, enabling closer proximity of functional elements like inkjet nozzles to the paper path, increases die density, and maintains the integrity of the wire bonds, enhancing the operational efficiency and compactness of integrated circuit packaging.
Implementation Method 1
pushing on the wire bond to collapse the arc and plastically deform the wire bond; and releasing the wire bonds such that the plastic deformation maintains the wire bond in a flatter profile shape
Implementation Method 2
moving the profiling blade across the bead before the bead of encapsulant has cured to reshape the bead profile
Data Source
AI summary
A method for profiling a bead of encapsulant extending along an edge of a die mounted to a supporting structure, by depositing a bead of encapsulant onto wire bonds along the edge of the die, positioning a profiling surface over the die at a predetermined spacing from the die, moving the profiling surface across the bead before the bead of encapsulant has cured to reshape the bead profile and, curing the bead of encapsulant. The invention has found that the encapsulant can be effectively shaped by a profiling surface without stripping the encapsulant from the wire bonds. The normally convex-shaped upper surface of the encapsulant bead can be pushed to one side of the bead with the profiling surface. With a lower encapsulant bead, the active surface can be brought into closer proximity with another surface without making contact. For example, the nozzle array on a printhead IC can be 300 microns to 400 microns from the paper path. By collapsing or flattening the wire bond arcs before applying and profiling a bead of encapsulant, the nozzle array on the printhead IC can be less than 100 microns from the paper path.