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Introduction： The core logic of semiconductor packaging is to firmly secure the chip first, and then precisely connect the circuits. Many attribute packaging defects, electrical abnormalities, gold wire sagging, poor bonding and offset issues to Wire Bond equipment parameters. Nevertheless, in mass production, the vast majority of wire bonding failures originate from upstream Die Bond flatness and LeadFrame positioning stability. Precision tooling for supporting, pressing and thermocompression forming serves as the core hardware linking these two processes to secure packaging yield. Suzhou ECLEN Electronic Technology Co., Ltd. is dedicated to the R&D and manufacturing of packaging precision tooling for semiconductor LeadFrames and substrates.From a mass production perspective, this article introduces the process sequence: Die Bonding → Pre-treatment → Wire Bond Thermocompression Bonding.It focuses on the core functions and production value of thermocompression tooling, positioning fixtures and precision components applied in LeadFrame wire bonding scenarios. I. Core Upstream Packaging Process: Die Bonding (chip mounting) is the first critical procedure in chip packaging.Its core objective is to accurately, evenly and firmly attach individual diced bare dies to designated areas of LeadFrames or substrates, laying the foundation for subsequent wire bonding and molding processes.The flatness after die bonding, adhesive thickness and die offset directly determine the forming stability of subsequent Wire Bonding. 1. Complete Die Bond Process Flow Wafer expanding → Ejector pin lifting → Die pick-up by collet → Adhesive dispensing / Pre-form → Alignment & Bonding → Pre-curing 1）. Wafer Expansion & Separation: The diced wafer is stretched via wafer expanding to evenly space individual dies for easy pick-up and prevent scratches on die mirror surfaces. 2）. Precision Die Pick-up: Ejector pins lift individual dies precisely. Vacuum collets pick dies vertically to avoid inclined picking and positional offset. 3）. Substrate Adhesive Dispensing: Silver epoxy or non-conductive die attach adhesive is accurately dispensed onto the die pad area of LeadFrames, featuring consistent adhesive volume, no overflow and minimal voids. 4）. Alignment & Bonding: Machine vision alignment accurately presses dies into target positions to control X/Y offset, angular deviation and bonding thickness. 5）. Pre-curing & Shaping: LeadFrames with mounted dies are transferred to the preheating station for preliminary curing, preventing die shifting and edge warpage. 2. Key Mass Production Control Parameters • Die mounting offset accuracy: ≤±0.02 mm • Die attach adhesive thickness uniformity: 0.03~0.06 mm, thickness variation ≤0.015 mm • Die warpage: ≤0.02 mm (Avoid single-side suspension which causes unstable wire bonding) • Pre-curing condition: 120~135℃ / 60~90 s • Post-curing bonding strength: Withstand thermal shock during wire bonding and high-pressure impact in molding without die delamination 3. Common Mass Production Defects of Die Bond (Directly Affect Subsequent Wire Bonding) • Die offset and angular tilt: Result in shifted bonding positions, missing bonds and offset cold joints in the subsequent wire bonding process. • Uneven die attach adhesive thickness & local voids: Uneven stress distribution on dies leads to micro-shift of chips and bond peeling under ultrasonic vibration during wire bonding. • Edge adhesive overflow: Adhesive contaminates bonding pads and blocks gold wire bonding, resulting in mass scrap. • Warped and suspended die: Uneven bonding pressure causes one sound bond and one cold joint. Core Conclusion Die bonding lays the foundation. An uneven foundation inevitably leads to unstable wire bonding.To achieve high Wire Bond yield, the top priority is to guarantee absolute flatness of LeadFrames and dies through tooling optimization and process control. II. Inter-process Treatment: Post Die Bond Pre-treatment (Preparations Prior to Wire Bonding) Wire bonding cannot be carried out immediately after Die Bond. Standardized pre-treatment is mandatory, which also serves as a critical transitional stage where tooling delivers its value: 1. Full Curing: Constant temperature curing at 150℃ for 2 hours to fully cure the die attach adhesive, release bonding stress and prevent die displacement under high temperature during wire bonding. 2. Plasma Cleaning: Remove micro oil contaminants and particles on bonding pads and die surfaces, improve adhesion of gold wire bonding, and reduce the risk of cold joints and bond lifting.
3. Panel Positioning via Tooling: Load the entire panel of LeadFrames into dedicated carrier tooling to correct frame warpage and deformation, and ensure consistent flatness of the whole panel. III. Core Focus: Wire Bond Gold Wire Bonding Process (LeadFrame Application Scenario) Wire Bond (interconnect bonding) is the core process for chip circuit interconnection. With the combined effect of thermocompression, ultrasonic energy and bonding force, ultra-fine gold or copper wires are bonded at one end to chip bonding pads and the other end to LeadFrame leads, realizing electrical conduction between the chip and external circuits. Compared with wire bonding on substrates, LeadFrame wire bonding is more challenging. LeadFrames are thin and prone to deformation, with dense leads and susceptibility to warpage under heat. Therefore, extremely high precision is required for tool positioning, supporting, thermal insulation and compression. 1. Standard Wire Bond Process Flow Tool loading → Hot stage preheating → First bond (ball bond on chip) → Loop forming → Second bond (wedge bond on frame) → Inspection & unloading 1）. Tool Loading & Positioning: Load the full LeadFrame panel into thermocompression wire bonding tooling for precise limiting, clamping and leveling to eliminate frame deformation. 2）. Constant-temperature Preheating: Preheat the tooling together with frames to narrow temperature difference and reduce bonding stress. 3 ）. First Bond (Ball Bond): Form free-air ball via electronic flame-off, then bond the gold ball onto chip pads by ultrasonic thermocompression. 4 ）. Wire Loop Forming: The equipment controls the trajectory to form loops with uniform height and regular curvature. 5）. Second Bond (Wedge Bond): The tail of gold wire is thermocompression bonded onto LeadFrame lead pads. 6）. Visual Inspection: Inspect bond morphology, loop height, offset, wire sagging and short-circuit defects. 2. Key Mass Production Process Parameters (Specially for LeadFrame) • Bonding temperature: 130~150℃(Low-temperature thermocompression for frames to prevent frame deformation and thermal damage to chips) • Ultrasonic power: 60~90 mW (Adjust according to wire diameter) • Bonding force: 40~70 g • Loop height: 80~150 μm (Standard for mass production, fine-tuned based on product specifications)
• Bonding time: 15~25 ms for the first bond; 20~30 ms for the second bond
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