Component Management

Liquid pressure-sensitive adhesives for electronics

5th November 2020
Alex Lynn

DELO has developed adhesives that have similar properties to (double-sided) adhesive tapes but are applied in liquid form. This helps users save time and costs in the production process. The liquid pressure-sensitive adhesives can be dispensed accurately and once the components have been joined, they can be further processed immediately in a fully automated process.

The adhesives are particularly suitable for electronic applications such as smartphone speakers or display frames.

Adhesive tapes are used for numerous bonding applications in the electronics industry. Their advantage is the immediate adhesion after two components have been pressed together. However, adhesive tapes have two major disadvantages. The first is: When using small or complex tape geometries, automated handling becomes very time-consuming or even impossible due to the low stiffness of the carrier material and the high adhesive force.

The second is that structures with a low fill factor, like those found in frame bonding, involve a large amount of waste from cutting the geometric shapes, which increases component costs.

The liquid pressure-sensitive adhesives from DELO now open up new possibilities. They are dispensed in liquid form directly onto the component and then irradiated by UV light. This creates a tacky surface, which is characteristic for tapes. Since the adhesive reaches its initial strength immediately after the second component is pressed on, the bonded assembly can be processed directly and without any fixing devices. This is a great advantage over many standard liquid adhesives.

The entire process, from precise dispensing even on tiny components or three-dimensional geometries to irradiation and mechanical pressing, can be fully automated. This makes the liquid pressure-sensitive adhesives particularly suitable for high-output production.

Depending on the requirements, users can choose liquid pressure-sensitive adhesives with different chemical bases. The acrylate-based adhesive DELO PHOTOBOND PS4130 has very similar properties to typical adhesive tape in terms of flexibility, peel resistance and strength.

It is particularly suitable for adhesive applications with short cycle times and moderate requirements on final strength. Thanks to its excellent damping properties and low outgassing values, DELO PHOTOBOND PS4130 is already being used, for example, in the assembly of smartphone speakers.

The epoxy-based adhesive DELO KATIOBOND PS6372, on the other hand, was developed specifically for structural bonding applications requiring high strength. Once the initial strength has been achieved by pressing on the components, the assembly can be processed immediately, with the strength of the bonded joint increasing afterwards.

When fully cured, DELO KATIOBOND PS6372 achieves compression shear strengths of over 30MPa on aluminium and over 10MPa on FR4. Its high resistance to temperature and media makes it also suitable for automotive applications.

The special features of DELO's liquid pressure-sensitive adhesives are discussed in detail in the whitepaper entitled ‘Liquid Pressure-sensitive Adhesives’.

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