Interleaf Identification for Leadframe Verification
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Solution Overview
Problem
Existing methods for identifying leadframes during IC assembly, such as stamping or etching, are inadequate as they do not reliably convey lead finish information and can alter the geometry of leadframe sheets, while ink printing on metal surfaces is ineffective due to rapid drying, leading to mixing of part numbers and finishes from different suppliers during assembly.
Innovation Solution
Incorporating interleaf members with indicia between leadframe sheets that identify part numbers and finishes, allowing for verification during assembly, using materials like lint-free paper or plastic film with machine-readable codes, and removing the interleaf members for verification by the assembly machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If stamping or etching is used to identify leadframes, then part number identification is achieved, but lead finish information is lost and geometry is altered
Solution Approach 1:
The identification system is segmented into two separate components: the leadframe itself and the interleaf member. The interleaf carries both the part number and lead finish information, while the leadframe remains unaltered. This segmentation allows complete identification information to be preserved without modifying the leadframe geometry.
Solution Approach 2:
The interleaf member acts as an intermediary carrier for identification information. Instead of directly marking the leadframe (which would alter its geometry), the interleaf serves as a mediator that holds the part number and lead finish data, and is temporarily associated with the leadframe during assembly.
2Loss of information
If ink printing is used on leadframe surface, then identification is achieved, but drying time is excessive causing smudging
Solution Approach 1:
The interleaf member serves as an intermediary substrate for ink printing. Since the interleaf is typically paper or porous material, ink dries quickly on its surface compared to metal leadframe surfaces. This resolves the drying time issue while still providing durable identification information.
Solution Approach 2:
Instead of printing directly on the leadframe, the identification information is copied onto the interleaf member. The interleaf becomes a duplicate carrier of the identification data, allowing optimal printing conditions to be used without compromising the leadframe itself.
3Loss of information
If part numbers are printed on box lid only, then identification is maintained, but mixing of leadframes from different suppliers occurs during assembly
Solution Approach 1:
The identification system is segmented so that each individual leadframe in the stack is associated with its own identification information on the interleaf, rather than relying on a single box lid label. This ensures that even when boxes are mixed or lids removed, each leadframe's identity is preserved through its corresponding interleaf.
Solution Approach 2:
The system incorporates verification feedback mechanisms where the assembly machine reads the part number from the interleaf and verifies it against the required part number. This feedback loop prevents incorrect leadframes from being used, ensuring identification accuracy even when multiple suppliers' leadframes are handled.
Data Source
AI summary
A method of making an IC device includes providing a stack of leadframe sheets each including a plurality of leadframes and an interleaf member interposed between adjacent ones of the leadframe sheets. The interleaf members include indicia that identifies the leadframes sheets. The stack of leadframe sheets is loaded onto an assembly machine. A first interleaf member is removed from the first leadframe sheet. The first leadframe sheet is transferred onto a mounting surface of the assembly machine. Semiconductor die are attached to leadframes on the first leadframe sheet. The method can include reading the indicia from the first interleaf member to determine a part number and lead finish for the first leadframe sheet, verifying the part number for the first leadframe sheet by comparing to a build list, and transferring the first leadframe sheet onto a mounting surface of the assembly machine only if the part number is verified.