Lead Frame Warpage Control via Localized Work Affected Layer
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Solution Overview
Problem
The warpage of lead frames occurs due to unbalanced residual stresses caused by the removal of work affected layers from one side, leading to manufacturing challenges in maintaining flatness and stability.
Innovation Solution
A lead frame design with a work affected layer existing region at the front end of protruding portions and a non-existing region on the plate surface, along with controlled etching to balance residual stresses by removing the work affected layer from the plate's surface, ensuring balanced surface areas of work affected layers on both sides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the work affected layer is removed from one side of the metal material, then the surface quality and flatness are improved, but the residual stresses become unbalanced causing warpage
Solution Approach 1:
The patent applies local quality by creating different surface conditions in different regions of the lead frame. Specifically, the plate portion has the work affected layer removed to improve surface quality, while the protruding portion retains the work affected layer to maintain residual stress balance. This localized differentiation allows simultaneous achievement of surface flatness improvement and warpage reduction.
Solution Approach 2:
The lead frame is segmented into two functional regions: a plate portion and a protruding portion. The plate portion undergoes work affected layer removal for surface quality, while the protruding portion preserves the layer for stress balance. This segmentation allows different surface treatments in different areas, resolving the contradiction between flatness improvement and stress balance.
2Stability of the object's composition
If the work affected layer is retained on both surfaces, then the residual stress balance is maintained, but the surface quality and flatness are compromised
Solution Approach 1:
Instead of uniformly retaining the work affected layer on both surfaces, the patent applies local quality by selectively removing the layer from the plate portion while retaining it on the protruding portion. This localized approach allows surface flatness improvement where needed while maintaining stress balance where required.
Data Source
AI summary
A lead frame includes a plate portion provided with a first surface and a second surface, the second surface being opposite to the first surface; a protruding portion integrally formed with the plate portion to be protruded from the first surface of the plate portion, wherein a surface of the lead frame includes a work affected layer existing region at which a work affected layer is formed, and a work affected layer non-existing region at which a work affected layer is not formed, wherein a front end surface of the protruding portion is the work affected layer existing region, wherein a region of the first surface at which the protruding portion is not formed is the work affected layer non-existing region, and wherein the second surface of the plate portion includes the work affected layer non-existing region.