Heater Chip Reflow Bonding for Head Suspension Wiring
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Solution Overview
Problem
Existing reflow bonding methods are inefficient and costly, as they require large furnaces or expensive pulse heat power sources to effectively join wiring members together, which is not met by existing Japanese Unexamined Patent Applications.
Innovation Solution
A reflow bonding method using a heater chip with a nickel-film-coated pressing face to heat and press one of the bonding parts from behind, allowing the solder to reflow and bond the wiring members together, while protecting the heater chip from oxidation and maintaining heat conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large reflow furnace is used for reflow bonding, then the solder can be melted and wiring members can be joined, but the equipment becomes large and complex
Solution Approach 1:
The patent divides the reflow bonding process into localized heating zones using multiple heater chips positioned at different locations (first heater chip for solder bump heating, second heater chip for solder joint heating). This segmentation allows the bonding process to be performed in a compact manner without requiring a large furnace, while still achieving reliable solder reflow and wiring member joining.
Solution Approach 2:
The patent introduces heater chips as intermediary heating elements that directly contact or closely approach the solder and wiring members. These heater chips act as localized heat sources that transfer thermal energy efficiently to the bonding interface, eliminating the need for large-scale radiant heating from a furnace and enabling compact equipment design.
2Device complexity
If a pulse heat power source and heater chip are used for reflow bonding, then the bonding can be performed with smaller equipment, but expensive facilities are required
Solution Approach 1:
The heater chips are designed to be directly heated by induction heating coils, allowing them to self-generate the required heat for bonding without requiring complex pulse heat power sources. The heater chips' ferromagnetic material properties enable them to convert electromagnetic energy directly into heat through hysteresis loss, simplifying the power supply system and reducing manufacturing costs.
Solution Approach 2:
The patent replaces the mechanical contact-based heating system (requiring direct contact between heater and workpiece) with an electromagnetic induction heating system. The induction heating coils generate alternating magnetic fields that induce eddy currents in the ferromagnetic heater chips, which then self-heat without mechanical contact. This substitution eliminates the need for expensive pulse heat power sources while achieving the same bonding effect.
3Device complexity
If the heater chip pressing face is not protected, then the structure remains simple, but the heater chip oxidizes and loses heat conductivity
Solution Approach 1:
The heater chip pressing face is constructed as a composite structure with a ferromagnetic base material (for induction heating) covered by a oxide-resistant coating layer (for protection). This composite design allows the heater chip to simultaneously achieve effective induction heating through its ferromagnetic properties and long-term oxidation resistance through the protective coating, maintaining heat conductivity over extended service life.
Solution Approach 2:
The oxide-resistant coating on the heater chip pressing face creates a protective barrier that effectively isolates the base material from oxidative environments. This coating acts as an inert protective layer that prevents oxygen from reaching and oxidizing the ferromagnetic material, thereby maintaining the heater chip's heat conductivity and structural integrity during repeated heating cycles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables efficient and cost-effective bonding of wiring members by maintaining heat conductivity and extending the service life of the heater chip, ensuring proper bonding without the need for large furnaces or expensive equipment.
Implementation Method 1
heating and pressing one of the first and second bonding parts from behind with a pressing face of a heater chip so that the solder is heated and reflows
Implementation Method 2
The nickel film protects the heater chip, which is not in contact with the solder, from oxidization damage
Implementation Method 3
melting the plated solder with heat, and solidifying the molten solder to bond the first and second wiring members together
Data Source
AI summary
A reflow bonding method easily bonds first and second wiring members together by reflowing solder arranged on at least one of first and second bonding parts that are defined on the first and second wiring members, respectively. The method includes positioning the first and second wiring members so that the first and second bonding parts face each other with the solder interposed between them and heating and pressing one of the first and second bonding parts from behind with a pressing face of a heater chip so that the first and second bonding parts lie one on another and so that the solder is heated and reflows to bond the first and second wiring members together.