Wire-Bonded Metal Clip Joints for Small Semiconductor Bond Pads
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Solution Overview
Problem
Conventional solder technologies face challenges in attaching metal clips to small bond pads on semiconductor dies, particularly due to pad contamination, residue issues, and limited process windows for clip placement alignment, leading to yield and performance losses.
Innovation Solution
The method involves aligning a metal clip's bonding region with a semiconductor die's bond pad and forming wire bonds through openings in the clip's bonding region, creating a solder-free joint between the clip and the bond pad, and optionally forming additional wire bond or solder joints for enhanced security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solder technology is used to attach metal clips to small bond pads, then the attachment process can be completed, but pad contamination and residues from cleaning occur
Solution Approach 1:
The patent extracts the harmful solder material from the bonding process and replaces it with wire bonds. The metal clip is attached to the bond pad through wire bonds that pass through openings in the clip, eliminating solder paste application and the associated contamination and residue problems while maintaining reliable electrical and mechanical connection.
Solution Approach 2:
The patent introduces wire bonds as an intermediary element between the metal clip and the bond pad. Instead of directly soldering the clip to the pad, the wire bonds serve as a mediator that connects the two components through the openings in the clip, avoiding direct contact between solder and the bond pad surface.
2Manufacturing precision
If conventional wire and wedge bond technologies are used with small bond pad openings, then wire bonds can be formed, but dented passivation and wire lift-off occur
Solution Approach 1:
The patent performs preliminary alignment by positioning the metal clip over the bond pad with its openings precisely aligned before forming the wire bonds. The clip acts as a pre-positioned template that guides the wire bond formation process, ensuring that wires are bonded to the correct locations on the passivation layer without causing dents or lift-off.
Solution Approach 2:
The patent creates localized bonding zones through the openings in the metal clip. Each opening provides a controlled local area where wire bonds are formed, concentrating the bonding action in specific locations rather than across the entire bond pad surface. This localized approach prevents excessive force from damaging the passivation layer.
3Area of stationary object
If small Cu clips are used for gate pad connections, then the gate pad opening size is limited, but this limits the size of the gate pad opening for Cu clips
Solution Approach 1:
The patent designs the metal clip with multiple openings that can accommodate wire bonds of various sizes and configurations. The clip structure itself is universal and can be used with different bond pad sizes and types (source, gate, drain), while the wire bond diameter and number can be adjusted to match the specific application requirements, providing flexibility without limiting the opening size.
4Measurement precision
If tight clip placement alignment is required for source/gate area, then yield and performance are improved, but the process window for alignment becomes small leading to yield losses
Solution Approach 1:
The patent incorporates alignment features on the metal clip such as tabs or protrusions that engage with corresponding features on the substrate or leadframe. These features provide mechanical feedback during the placement process, guiding the clip into the correct position and providing tactile or visual feedback to the placement equipment to ensure accurate alignment within the required tolerance window.
Solution Approach 2:
The patent includes preliminary alignment features built into the metal clip structure that are designed to self-align with corresponding features on the substrate or leadframe during the placement process. This preliminary mechanical alignment reduces the reliance on precise positioning control and expands the effective process window for accurate clip placement.
Data Source
AI summary
A semiconductor package includes: a semiconductor die attached to a leadframe and having a first bond pad at a side of the semiconductor die facing away from the leadframe; a metal clip having a first bonding region attached to the first bond pad of the semiconductor die by a plurality of first wire bonds which extend through a plurality of first openings in the first bonding region of the metal clip, the plurality of first wire bonds forming a joint between the metal clip and the first bond pad of the semiconductor die; and a joint between the plurality of first wire bonds and the metal clip at a side of the metal clip facing away from the semiconductor die. Additional semiconductor package embodiments and related methods of manufacture are also described.