GB2527135A

GB2527135A - A reversible adhesive for the disassembly of electronics components at disposal or repair of a portable/wearable device

Info

Publication number: GB2527135A
Application number: GB1410649.6A
Authority: GB
Inventors: Andreas Timothy Bilicki
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-06-14
Filing date: 2014-06-14
Publication date: 2015-12-16
Also published as: GB201410649D0

Abstract

An adhesive that allows articles such as components of an electrical device, to be bonded and de-bonded comprising a thermoplastic adhesive 3 capable of bonding articles and a ferromagnetic material 2 that is in thermal contact with the thermoplastic 3, where by the ferromagnetic material is heated by induction heating which melts the thermoplastic allowing the adhesive to bond or to de-bonded as required. Preferably the ferromagnetic material 2 is a layer or particles positioned between layers of thermoplastic material, or dispersed within the thermoplastic. The ferromagnetic particles may be uniform or vary in particle size, when different sized particles are used in two adhesive bonds, the application of an inductive heat at frequency to heat the particles will allow one of the adhesive bonds to be sufficiently heated to de-bond the adhesive and remove an article while the particles in other adhesive bond are not sufficiently heated to soften or melt and hence maintain the bond between the articles bonded by the second adhesive. Alternatively thermoplastics of different melting points may be used in two or more adhesive bonds to allow adhesives to be de-bonded under the application of various induction heat.

Description

A reversible adhesive for the disassembly of electronics components at disposal or repair of a portable/wearable device.

DESCRIPTION

Technical Field

This invention relates to a composite adhesive which can be selectively heated through external stimuli, namely induction, and delaminated without affecting other components in the bonded object. The composite adhesive is formed of a ferrous sheet or particle mixed with a thermoplastic with adhesive bonding properties and the ability to tack to high structural strength. The use of an induction heater operating at frequencies within the kHz to Mhz range induces eddy currents and heating through the Joule eRect in the lerrous material. The heating of the ferrous materials locally increases the temperature through thermal conduction, bringing the adhesive above its glass transition temperature Tg. and in some cases above its melting point Tm. This change of state from solid to viscous or liquid breaks bonds near the contact surface, allowing for easy disassembly.

The variation in ferrous materials sheet or particle size, combined with inversely proportional variations in frequency. allow for selective heating and separation.

Backround The creation of portable and wearable electronic devices, such as smartphones which incorporate an increasing number of electronic components. deliver a high number of functions whilst reducing in size, has led to a shift in fastening methods. Screws have progressively been replaced by high-contact strength adhesive tapes which allow for an overall thinner product profile and easier to automate mass manufacture. However these changes have made the devices harder to disassemble for recycling or repair.

This is all the more important when taking into account the raw material and economical value contained in the electronic components in the form of purified and processed rare e»=nth or precious metals. Recycled c-waste metals are typically several times richer and purer than equivalent mined ores.

Currently, very few allernatives to the hand disassemhly of wearable and portable dectronie devices exist. This leads to the loss of valuable material which is questionable on an economical and environmental level, consider ng the demand under which these materials are, especially in the electronic-devices industries.

Induction heating is a well-known technology, which is widespread both in industrial settings and in the home. However it is eulTently used mainly to heat for welding, brazing, forging or sealing purposes, and not for the disassembly of adhesives.

Disclosure of the Invention

The present invention proposes a new way of selectively disassembling components in wearable portable electronic devices, such as mobile telephones, including smartphones. This is (lone through the application of a magnetic field alternating polarity at high frequency by a custom induction heater to a composite adhesive containing ferrous material particles or sheets of different volumes. The application of such a field induces eddy currents and generates heat in the felTous parts, through effects similar to resistance in a wire (the Joule effect). It is important to note that typically, the required frequency to inductively heat a ferrous metal is inversely proportional to the volume of material heated; that is to say that the smaller the particle-size, the higher the frequency required.

The heating of the ferrous part will locally heat the adhesive through thermal conduction, bringing its temperature above its Tg or Tm. depending on particle size. This change in viscosity and state will generate bubbles at the interface between component and adhesive, breaking the chemical bonds made there, thus allowing for simple disassembly.

The adhesive is composed of a thermoplastic adhesive material, for example toughened acrylic flexon, polyvinyl acetate or cyanoacrylates. and felTomagnetic material in thermal contact with the thermoplastic; the ferromagnetic material may be iron, magnetite or steel-based (stainless ideally) and may he in the form of particles.

The invention comprises of two parts: a composite adhesive and a custom induction heater.

The induction heater outputs a magnetic field alternating polarity at a frequency in the kHz to Mhz range. The device itself would run using a power supply (using mains power), an inverter, an inductor coil, typically made of copper, The adhesive is composed of a thermoplastic adhesive and a ferrous material in the form of sheet sections or particle shape. Through the application of differently sized ferrous materials within the adhesive, a series ol tapes with homogenous particle sizes can he obtained. These will then react to different applied inductive frequencies, allowing for selective heating. This is to say that different tapes could be used to attach different components in a single device, and could be heated using their respective frequencies individually to separate only the desired component.

This type of system could be used in any form of assembly which assembles non-ferrous materials, and may need to be separated after having formed a strong bond. The invention could be used especially for assemblies where the joint concerned is near the surface of the object. It could have applications in the wearable and portable electronics industries, modular devices and internet of things' products for instance. It could also be used for detailing or finishing detail-joining on assemblies.

This could typically be used to allow for the point-of-collection disassembly of electronic devices for waste-stream separation and recycling.

The invention is described in more detail in the following drawings, looking at examples shown below: Figure 1 shows a side view of a composite tape.

Figure 2 shows an assembly with two types of composite adhesive and the induction heater.

Figure 3 shows an assembly with two types of adhesive on an induction heater, one adhesive being selectively heated.

Figure 4 shows the same assembly as shown in Figure 3. the coniponents joined by the heated adhesive separated out.

In Figure 1 the tape is seen as a cross-section sulTounded a non-stick support. 1. The adhesive is in the middle. 3, and the ferrous material is at its core, 2. The non stick support is removed before bonding.

In Figure 2 we see a cross-section view of a smartphone-assembly consisting of a screen, 4, a printed circuit hoard, 6. and a casing, 8. These components are joined by two composite adhesives: one with large ferrous particles, 5, and one with smaller ferrous particles, 7. It is placed on an induction heater, 9.

In Figure 3 the same assembly shown in the previous Figure is being heated by a low-frequency program run on the induction heater. 9. At this frequency the composite adhesive with large ferrous particles is being heated up, 5.

In Figure 4, the same assembly shown in the previous Figure has been disassembled, with the heated large ferrous particle composite adhesive. 5. having delarninated from the screen, 4, and the printed circuit hoard, 6.

Two components were bonded together by an adhesive a thermoplastic material and a ferromagnetic material in thermal contact with the adhesive. The ferromagnetic material can he in the form of particles that can he heated by induction heating at a narrow range of frequencies to cause the thermoplastic material to soften or melt and allowing separation of the components. The induction frequencies for a given particle size and ferromagnetic material can be easily discerned by a skilled person, but examples of the particle size of spring steel and their associated induction frequencies are: Ferromagnetic Material Sheet Size Induction Frequency Spring steel 20 mm2 100 kHz Spring Steel 120mm2 70 ld-Iz

Claims

CLAIMS1. An adhesive configured to bond articles together, e.g. components of an electrical device, which adhesive comprises a thermoplastic adhesive material capable of bonding the articles and a ferromagnetic material in thermal contact with the thermoplastic material, the arrangement being such that the ferromagnetic material can be heated by induction heating. thereby heating the thermoplastic material to above its softening or melting point and so allowing the articles to be separated.
2. An adhesive as claimed in claim 1, which comprises a hyer of ferromagnetic material sandwiched between laycrs of thermoplastic material.
3. An adhesive as claimed in claim 2, wherein the layer of ferromagnetic material comprises ferromagnetic particles.
4. An adhesive as claimed in claim 1, which compnses fcrromagnetic particles dispcrsed within thermoplastic material.
5. An adhesive as claimed in claim 3 or claim 4, wherein the ferromagnetic particles are of a consistent size, whereby they are heated by induction at a single frequency.
6. An adhesive as claimed in any one of claims 3 to 5, wherein the ferromagnetic particles have a particle size in the rangc of 1 pm to 10 mm range.
7. An adhesive as claimed in any preceding claim that is in the form of a tape or sheet, e.g. a sheet having a shape corresponding to the shape of the opposed surfaces of the components to be bonded.
8. A method of bonding articles together, e.g. components of an electrical device, which method comprises: a. placing between the articles an adhesive that comprises a thermoplastic adhesive material and a ferromagnetic material in thermal contact with the thermoplastic material, and b. heating the adhesive before or after placement until the thermoplastic material is at a temperature above its softening or melting point and c. allowing the adhesive to cool to bond the articles together.
9. A method as claimed in claim 8. wherein the adhesive is heated by induction heating.
10. A method of dc-bonding articles, e.g. components of an electrical device, which articles are bonded together by an adhesive that comprises a thermoplastic adhesive material and a ferromagnetic material in thermal contact with the adhesive, wherein the method comprises: applying induction heating to the ferromagnetic material to cause the thermoplastic material to solien or mcli, thereby dc-bonding the articles and allowing them to he separated.
11. A method of claim 10, wherein some articles are bonded together by a first adhesive and others by a second adhesive, which adhesives each comprises a thermoplastic adhesive material and ferromagnetic particles and wherein the size of the particles in the first adhesive is different from the size of the particles in the second adhesive.wherein and the method comprises applying induction heating to the articles at a frequency that heats the particles in the first adhesive such that the thermoplastic adhesive material in the first adhesive is softened or melted hut the particles in the second adhesive are not heated sufficiently to cause (he thermoplastic adhesive material in (he second adhesive to be softened or melted, thereby allowing the articles bonded by the first adhesive to be separated while maintaining the bond between the articles joined by the second adhesive.
12. A method of claim 10, wherein sonic articles are bonded together by a first adhesive and others by a second adhesive, which adhesives each comprises a thermoplastic adhesive material and ferromagnetic particles and wherein the melting or softening point of the thermoplastic material in the first adhesive is different from the inciting or softening point of the thermoplastic material in the second adhesive, wherein and the method comprises applying induction heating to the device to heat the particles in the adhesives to an extent such that the thermoplastic material in the first adhesive is softened or melted but the thermoplastic material in the second adhesive is not. 11 ereby allowing the arUdes bonded by Ue first adhesive to be separated while maintaining the bond between the articles joined by the second adhesive.
13. A method as claimed in any one of claims 8 to 11, wherein the adhesive is as claimed in any one of claims ito 7.
14. A device comprising components that are bonded together by an adhesive, which adhesive comprises a thermoplastic material and a ferromagnetic material in thermal contact with the thermoplastic material.
15. A device as claimed in claim 14, wherein the adhesive is as claimed in any one of claims ito 7.