Lead Frame Dicing Hole Layout for Uniform Package Sizing
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Solution Overview
Problem
Conventional lead frame assemblies experience misalignment and size variations in chip packaging devices due to offset positioning holes during the encapsulation process, leading to inaccurate dicing and inconsistent device sizes.
Innovation Solution
A lead frame assembly comprising a conductive lead frame body with through holes, an encapsulant unit, and dicing positioning units, where the dicing positioning units are formed with an adhesive layer and smaller dicing positioning holes within the through holes, defining precise dicing lines to ensure accurate alignment and uniform size during the dicing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If positioning holes are formed on the outer frame portion during the etching process, then the dicing process can be conducted, but misalignment and offset between positioning holes and encapsulating layer occur leading to imprecise dicing
Solution Approach 1:
The patent forms dicing positioning holes through the encapsulating layer after injection molding, rather than pre-forming positioning holes on the lead frame during etching. This preliminary action of creating positioning features after encapsulation ensures that the positioning holes are accurately aligned with the encapsulating layer, eliminating misalignment issues that occur when positioning holes are formed earlier in the process.
Solution Approach 2:
The patent introduces an intermediary structure (the dicing positioning holes formed through the encapsulating layer) that mediates between the encapsulation process and the dicing process. These positioning holes serve as accurate reference markers that are inherently aligned with the encapsulating layer, enabling precise dicing without direct dependency on the lead frame's outer frame positioning.
2Productivity
If conventional positioning holes are used, then the dicing process can proceed, but extrusion of encapsulating material results in offset between positioning holes and encapsulating layer
Solution Approach 1:
The patent performs the positioning hole formation as a preliminary action immediately after injection molding, while the encapsulating material is still in its formed state. By punching or drilling positioning holes through the encapsulating layer at this stage, the holes are created with precise alignment to the encapsulating layer geometry, preventing any subsequent offset that would occur if positioning were attempted after encapsulation completion.
3Ease of manufacture
If dicing is conducted with offset positioning holes, then chip packaging devices can be separated, but the devices exhibit great difference in size
Solution Approach 1:
The patent creates a feedback mechanism where the dicing positioning holes formed through the encapsulating layer serve as accurate reference markers that provide real-time alignment information during the dicing process. This feedback ensures that the dicing blade follows the correct path, maintaining consistent spacing and producing chip packaging devices with uniform sizes, eliminating the size variations caused by offset positioning holes.
Data Source
AI summary
A lead frame assembly includes a lead frame body, an encapsulant unit, and dicing positioning units. The lead frame body includes lead frame units, an outer frame portion extending around the lead frame units, and through holes formed on the outer frame portion. The encapsulant unit includes a lower encapsulating portion, and an upper encapsulating portion formed on the lower encapsulating portion. The dicing positioning units are respectively located at the through holes, and each includes an adhesive layer which partially fills a corresponding one of the through holes and which is formed with at least one dicing positioning hole. The dicing positioning units define at least one first dicing positioning line and at least one second dicing positioning line.