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Integration of foil sensors – there is something for every requirement.

Gluing & Bonding

During glueing, a full-surface or partial connection is made between the surfaces of the foil sensor and the component. The adhesion of the two elements is created with the help of an adhesion promoter, which, in contrast to laminating, is applied as a solid element or in liquid form.

For the production of a stable bond using solid adhesives, an appropriate contact pressure is required. With liquid adhesives, on the other hand, curing can be carried out by using temperature, UV light or on the basis of a chemical 2-component activation, depending on the adhesive system.

The advantage for laminating is that a foil sensor can also be applied to three-dimensional component surfaces.  

Conclusion: An adhesive bond offers the possibility of applying a foil sensor to the surface of a three-dimensional component even at a later date.  It is possible to use transparent / optical adhesive systems to enable further optical control by the foil sensor. 

Guideline and examples

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“Foilsensor – Sticking & Bonding“

Lamination

During lamination, a full-surface connection is created between the surfaces of the foil sensor and the component. The adhesion of the two elements is created with the help of an adhesion promoter. A distinction is made between hot laminating and cold laminating. Cold lamination occurs when the two joining elements (foil sensor + component) and the bonding agent are pressed together under a defined pressure. In the case of hot lamination, next to pressure, temperature is required to melt and activate the bonding agent. 

Conclusion: Cold lamination is relatively easy to implement, but the adhesive strength is lower than with hot lamination. In addition, cold lamination is not permanently heat stable (the adhesive strength decreases significantly above 70°C ). The water absorption capacity is also increased with cold lamination. Hot laminating provides higher adhesive strength and stability, but the hot lamination process is more extensive due to temperature input and higher contact pressures (in the range of 20KN) 

Guideline and examples

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“Foilsensor – Laminat“

Injection molding

During casting or injection moulding, the foil sensor is integrated on or in a plastic component. Casting takes place in a pressureless process (e.g. vacuum casting), which means that the foil sensor is placed in a mould and liquid plastic material is filled into the mould without pressure. Injection moulding also involves the introduction of plastic material into a tool/mould, whereby the plastic material is filled in under pressure.

Regardless of the process, there are different integration possibilities for the foil sensor. 

Back injection:
For back injection, the foil sensor is positioned against the wall of the mould. The filled-in plastic material only hits one side of the foil sensor, which means that the other side of the foil sensor forms the surface of the plastic body. It should be noted that the material pairing of the foil material of the foil sensor and the potting or injection molding material must be compatible to achieve good adhesion.  

Section over-moulding:
When over-moulding, the foil sensor is partially enclosed in plastic. In this way, holding elements can be realized. This possibility of over-moulding is particularly interesting if the material pairing of the foil material of the foil sensor and the encapsulation or injection moulding material are not compatible and thus back-moulding is not possible. 

Rivets moulding: 
In the case of rivets moulding, partial foil openings are already included in the design of the foil sensor layout. These openings (Vias) are used for the entire structure of the foil sensor, from the carrier foil to the final surface. The foil sensor is placed in the mould and filled with plastic from one side, in the same way as for back injection. Through the vias in the foil sensor plastic material can flow through and thus form a type of “rivet”. By injecting the casting material through the vias of the foil sensor, a form-fit and force-locking connection is created.   

Over-moulding:
During over-moulding, the foil sensor is completely enclosed with plastic material during the moulding process. This over-moulding is only partially possible because the foil sensor must be held in position in the mould. If a suitable material pairing of foil sensor material and plastic material is selected, a “media density – “dense overmoulding” Wall bushing can be achieved. This is used, for example, to integrate foil sensors in pipes and ducts.

In the case of unfavourable material pairings, a “tight” over-moulding can also be realised by applying a bonding agent or sealing element to the foil sensor in advance. 

Conclusion:
Especially the integration of a foil sensor into injection molded components in the manufacturing process (injection molding process – “In Mold Sensors”) is an economically attractive possibility for sensor integration. The material pairing of foil material of the foil sensor and injection moulding material is particularly relevant for a permanently stable connection.

The introduction of a foil sensor into the injection moulding process is not trival. We as accensors work with the specialists for foil sensor integration of the Erwin Quarder Group

Are you interested in foil sensors which are integrated into a plastic component. Please feel free to contact us.

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Guideline and examples

“Foilsensor – Injection molding“

Assembling

There are two different procedures for assembling and mounting. Sandwitch assembling is a force-locked assembly form in which the foil sensor is fixed between two elements in a force-locked manner. For instance, in process monitoring, foil sensors can be inserted into a sealing flange via sandwitch assembling. 

During eyelet assembly, a positive and non-positive connection is created. Here the film sensor is constructed in such a way that special eyelets are imaged on or on the film material. The foil sensor is mounted to the fixed point via these eyelets, for example with the help of screws.

Conclusion:
Assembling is a very simple way of integration. It opens up the possibility to integrate foil sensors into existing systems.   

Guideline and examples

“Foilsensor – Injection molding“

Welding

During welding, an inseparable and material-tight connection is created between the film sensor and the component. The welded connection is the most stable connection, especially for long-term integration. 

In order to enable welding, the foil sensor must be equipped with a sufficiently large welding area. It must be ensured that welding is only possible outside the sensor and supply line area, otherwise the sensor will be damaged. There are different methods of welding, such as ultrasonic welding, laser welding, heat-impulse welding, convection welding, resistance welding or induction welding (and some more). 

Conclusion:
Welding is the most sustainable integration principle wjen it comes to strength and stability against external influences. In addition, no further foreign material is introduced during welding, which could be critical, especially when it comes to compatibility with certain measuring media (such as blood or drinking water).  

Guideline and examples

“Foilsensor – Injection molding“

Electrical contacts

In the electrical contacting of foil sensors, a distinction is made between detachable and non-detachable electrical connections. The detachable electrical connections are further subdivided into whether the electrical connection can be detached once, can be detached a few times or can be stably detached several times.

The contacting of the foil sensors can be made with the help of electronic standard components, we as accensors also offer our own contacting standard. 

Conclusion:
Depending on the application the contacting of the foil sensor can be done in different ways. Standard contacting elements and contacting processes known from conventional electronics production can still be used. 

Guideline and examples

“Foilsensor – Injection molding“