Mold Chase Slot Design for Fluid Ejection Die Flash Control
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Solution Overview
Problem
The formation of epoxy molding compound (EMC) flash on contact pads during the manufacturing of fluid ejection devices is a significant issue, leading to defects and reduced device reliability.
Innovation Solution
The use of an upper mold chase with a slot forming feature that covers ink feed holes and includes hold-down structures to reduce the cantilever length between the end of the feature and the fluid ejection die, minimizing the space and applying downward forces to eliminate EMC flash on contact pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an upper mold chase is used to cover ink feed holes during EMC application, then EMC flash on contact pads is reduced, but the complexity of the molding process increases
Solution Approach 1:
The upper mold chase is segmented into distinct functional features: slot-forming features that define fluid access paths, and separate hold-down structures positioned at end portions of the die. This segmentation allows each feature to independently perform its function - the slot features control EMC access to ink feed holes while hold-down structures apply localized pressure to prevent flash at contact pad areas.
Solution Approach 2:
The upper mold chase acts as an intermediary tool between the EMC application process and the die structure. It mediates the molding process by physically blocking EMC from reaching ink feed holes through slot features, and by applying controlled pressure through hold-down structures to prevent flash formation at critical contact pad regions.
2Reliability
If hold-down structures are added to reduce cantilever length, then EMC flash is eliminated, but the mold chase structure becomes more complex
Solution Approach 1:
Hold-down structures are strategically positioned at specific end portions of the die where contact pads are located. This local application of hold-down force concentrates the structural reinforcement exactly where needed to prevent EMC flash, rather than requiring uniform reinforcement across the entire mold chase structure. The local quality approach maintains simplicity in non-critical areas while providing enhanced support at critical locations.
3Object-generated harmful factors
If the slot forming feature length is reduced to less than 1.5mm from die end, then EMC flash on contact pads is minimized, but manufacturing precision requirements increase
Solution Approach 1:
The slot-forming features are designed with predetermined dimensions and positioning relative to the die structure before the molding process begins. By establishing the slot length to be less than 1.5mm from the die end in the mold chase design phase, the patent preliminarily configures the geometry to prevent EMC flash formation, eliminating the need for post-molding adjustments or complex real-time control during manufacturing.
Data Source
AI summary
A method includes applying a mold chase to a fluid ejection die to at least partially define at least one cavity. The mold chase includes a feature to contact a fluid ejection portion of the fluid ejection die, and at least one structure separate from the feature to contact a first end portion adjacent a first end of the fluid ejection die. The method includes filling the at least one cavity with a mold compound to produce a molded carrier for the fluid ejection die.