PCBA Soft Shell In-Mold TPU Bonding for Waterproof Durability
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Solution Overview
Problem
Existing soft PCBA manufacturing methods result in products that are thick, poorly bonded, and lack effective waterproof, moisture-proof, and leakage-proof performance due to the use of 3M adhesive, leading to short service life and ease of aging.
Innovation Solution
An in-mold injection molding process for a PCBA soft material involving preheating a PET thin film, printing patterns, laminating a UV adhesive with a Flexible Printed Circuit (FPC) board, and injecting Thermoplastic Polyurethane (TPU) resin into a mold cavity to form a durable and water-resistant mobile phone protective shell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If 3M adhesive is used to bond FPC to injection-molded protective shell, then bonding is achieved, but service life is short and aging occurs easily
Solution Approach 1:
The patent changes the bonding method from chemical adhesive (3M adhesive) to physical bonding through in-mold injection molding. The TPU material is injected at controlled temperature (180-220°C) and pressure to bond the FPC to the protective shell, eliminating adhesive aging issues while maintaining strong bonding durability
Solution Approach 2:
The patent replaces the chemical bonding system (adhesive) with a mechanical/thermal bonding system (in-mold injection molding). The TPU material is melted and injected to physically bond the components, providing mechanical strength and thermal stability without chemical degradation
2Ease of manufacture
If flannelette material is used to cover the product, then coverage is achieved, but product thickness increases making it inconvenient to use
Solution Approach 1:
The patent uses a thin TPU film injected through the injection molding process to cover and protect the FPC board. This thin film provides the necessary coverage and protection while maintaining product thinness and convenience, replacing the thick flannelette material
Solution Approach 2:
The patent combines the coverage function and protective function into a single TPU layer injected during the molding process. This integrated approach eliminates the need for separate thick covering materials while achieving both coverage and protection in one thin layer
3Ease of manufacture
If FPC board is assembled with adhesive method, then assembly is achieved, but waterproof, moisture-proof and leakage proof performance is poor
Solution Approach 1:
The patent uses TPU (Thermoplastic Polyurethane) as a composite material that provides both structural bonding and protective functions. The TPU material inherently provides waterproof, moisture-proof, and leakage-proof properties while serving as the bonding medium, eliminating the need for separate adhesive layers that compromise sealing
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
The process enhances the appearance and durability of the product, improves bonding strength, and provides enhanced waterproof and moisture-proof performance, addressing the limitations of existing methods.
Implementation Method 1
preheating a Polyethylene Terephthalate (PET) thin film: baking the PET thin film in a baking oven for 3 to 5 min at 60 to 120° C.
Implementation Method 2
laminating the printed PET thin film with the FPC board, then performing UV light curing drying
Implementation Method 3
injecting Thermoplastic Polyurethane (TPU) resin through an injection hole, so that the diaphragm A is on an outer side of a product mobile phone protective shell
Implementation Method 4
scraping a layer of adhesive on a printing ink side in step 5), and placing the prepared FPC board laminated diaphragm in the baking oven for curing, where the temperature is 80 to 120° C., and the time is 0.5 to 1.5 h
Data Source
AI summary
The present disclosure provides an in-mold injection molding process for a Printed Circuit Board Assembly (PCBA) soft material, including the following steps: 1) preheating a Polyethylene Terephthalate (PET) thin film; 2) printing patterns; 3) preparing a diaphragm A; 4) laminating a diaphragm on a Flexible Printed Circuit (FPC) board; 5) scraping printing ink; 6) scraping an adhesive; 7) preparing an inner diaphragm B; and 8) placing prepared diaphragm A and FPC board laminated diaphragm in a mold cavity of an injection mold of a Haitian 130T injection molding machine, preheating injection mold to 30° C., and injecting Thermoplastic Polyurethane (TPU) resin through an injection hole, so that diaphragm A is on an outer side of a product mobile phone protective shell, FPC board laminated diaphragm is on an inner side of the product mobile phone protective shell, and temperature of the TPU resin is at 180° C.