Implant Housing Header Molding with Heat-Activated Polyurethane Film
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Solution Overview
Problem
The existing methods for forming headers on implantable medical devices using liquid media like 2-part epoxy resins or silicone adhesives are difficult to automate, involve high costs due to mechanical rework, and require long curing times, while differential pressure molding is complex and temperature management is challenging.
Innovation Solution
A method involving a thermally activatable connecting film, such as a polyurethane film, is applied to the housing surface, allowing injection molding of a header directly onto the housing, forming a sealed composite without additional joining steps, using thermoplastic polyurethane and titanium components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If liquid media (2-part epoxy resins or 2-part silicone adhesives) are used for bonding header to housing, then adhesion between components is achieved, but automation difficulty increases and mechanical rework is required
Solution Approach 1:
The patent changes the state of the adhesive from liquid to solid film form, and from room-temperature curing to heat-activated bonding. The thermoplastic polyurethane film is applied in solid form and activated by heating during injection molding, eliminating the difficulties of handling and automating liquid adhesive application.
Solution Approach 2:
The patent replaces the chemical bonding process of liquid adhesives with a physical bonding process using heat-activated thermoplastic film. The thermoplastic film melts and bonds to both surfaces through thermal activation during injection molding, eliminating the need for chemical curing processes.
2Productivity
If 2-part epoxy resins or 2-part silicone adhesives are used for bonding, then adhesion is achieved, but curing time increases to hours
Solution Approach 1:
The patent changes the curing mechanism from slow chemical reaction at room temperature to rapid thermal activation. The thermoplastic polyurethane film bonds within seconds when heated to melting temperature during injection molding, reducing curing time from hours to seconds.
3Strength
If inserts with plasma polymer layers are heated to melting temperature in injection mold, then bonding to thermoplastic header is achieved, but temperature management complexity increases
Solution Approach 1:
The patent extracts the complex temperature management requirement by changing the bonding approach. Instead of heating inserts to melting temperature, the thermoplastic polyurethane film is activated by the heat of the injected thermoplastic material itself, eliminating the need for separate heating circuits for the inserts.
Solution Approach 2:
The injected thermoplastic material serves dual purposes: it forms the header structure and simultaneously provides the heat needed to activate the thermoplastic polyurethane film for bonding. The process uses the energy already present in the system rather than requiring external heating for the bonding function.
4Strength
If inserts with plasma polymer layers are heated in injection mold, then bonding is achieved, but cycle time increases
Solution Approach 1:
The patent merges the bonding function with the injection molding process itself. The thermoplastic polyurethane film is activated during the injection cycle by the hot material, so bonding occurs simultaneously with header formation rather than as a separate heated step, reducing cycle time.
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 approach enables a media-tight connection between the header and housing, allowing automated assembly and reducing process steps, eliminating the need for manual rework and additional bonding, thus improving efficiency and reducing costs.
Implementation Method 1
injection molding of the header by filling the cavity with a thermoplastic material, such that the connecting film bonds to said surface and to the thermoplastic material
Implementation Method 2
the thermally activatable connecting film forms a duromer (e.g., in the seconds range) under low heat and exhibits good adhesion to both partners
Implementation Method 3
injection molding of the header by filling the cavity with a thermoplastic material
Implementation Method 4
the thermally activatable connecting film is a thermally activatable polyurethane film
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a method for forming a header (1) on a housing (2) of an implantable medical device (100), the method comprising: providing a housing (2) having a surface (2a) to which the header (2) is to be connected, wherein a thermally activatable connecting film (3) is arranged on said surface (2a), arranging the housing (2) with respect to a mold (6) for injection molding such that said surface (2a) with the connecting film (3) thereon delimits a cavity (60) of the mold (6), and injection molding of the header (2) by filling the cavity (60) with a thermoplastic material, such that the thermally activatable connecting film (3) bonds to said surface (2a) and to the thermoplastic material.