Drill Structure With Assist Relief Surfaces For PCB Drilling
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Solution Overview
Problem
Conventional micro drills used in printed circuit boards suffer from high contact area between cutting faces and the board, leading to surface finish degradation and reduced service life due to frequent breakage.
Innovation Solution
The drill structure features chamfered drill blades with assist relief surfaces, continuous cutting edges, and helical grooves, reducing contact area and enhancing cutting ability, with assist relief surfaces tilted towards the shank part to decrease breakage and improve surface finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional micro drill cutting structure with primary and secondary relief surfaces is used, then the drill can perform basic cutting function, but the contact area between cutting faces and board is large causing frequent breakage and poor surface finish
Solution Approach 1:
The relief surfaces are segmented into three distinct zones: primary relief surface, secondary relief surface, and assist relief surface. Each surface serves a specific function in chip evacuation and cutting, reducing the contact area between the cutting faces and the board, thereby decreasing the likelihood of breakage and improving service life.
Solution Approach 2:
Different regions of the drill blade are given different geometric properties. The assist relief surface is specifically designed with a predetermined angle relative to the drill axis to optimize chip discharge in specific areas, while the primary and secondary relief surfaces maintain their traditional functions. This localized optimization reduces contact area without compromising overall cutting performance.
2Manufacturing precision
If conventional micro drill cutting structure is used, then the drill can maintain structural simplicity, but the surface finish of drilled holes deteriorates due to large contact area and frequent breakage
Solution Approach 1:
The relief surfaces are divided into three segments (primary, secondary, and assist relief surfaces) with distinct geometric characteristics. This segmentation allows each surface to perform its specific function optimally, resulting in improved surface finish while maintaining manageable structural complexity through systematic design.
Solution Approach 2:
The geometric parameters of the relief surfaces, particularly the angle of the assist relief surface relative to the drill axis, are optimized to achieve the desired surface finish. By adjusting these parameters, the patent improves manufacturing precision without requiring fundamentally complex device architecture.
3Length of moving object
If micro drills are made longer to drill stacked PCBs, then the drilling depth capability increases, but the chip discharge capability becomes insufficient
Solution Approach 1:
The flutes are designed with optimized helical geometry and the relief surfaces are segmented to work together in a coordinated chip evacuation system. This segmentation allows chips to be progressively moved from the cutting zone through the flutes, maintaining effective chip discharge capability even in longer drill configurations for stacked PCB drilling.
Solution Approach 2:
The patent utilizes the helical dimension of the flutes in conjunction with the three-dimensional geometry of the relief surfaces to create an effective chip discharge pathway. This multi-dimensional approach to chip evacuation maintains productivity in longer drills by efficiently removing chips along the helical path rather than relying solely on linear flute length.
Data Source
AI summary
A drill structure includes a shank part and a flute part arranged on one end of the shank part. A chisel edge is formed on the front end of the flute part and two drill blades with tilt directions toward the shank part are symmetrically formed on the two sides of the chisel edge. Every drill blade includes: a primary relief surface with a cutting edge, a first connecting edge and a first chamfering edge, a secondary relief surface with a knife-back edge, a second connecting edge, a second chamfering edge and an outer edge, and an assist relief surface. The second connecting edge joins to the first connecting edge, and the second chamfering edge connects with the first chamfering edge. The assist relief surface, which tilts toward the shank part the, is extend from the first chamfering edge and the second chamfering edge. This drill structure can improve the surface finish of the drilling hole.