As miniaturization progresses further, increasingly small, sensitive components need to be joined. However, with increased functionality comes an increased mix of materials and higher quality requirements. This makes it necessary for joining methods to ensure that miniature components are reliably bonded. In many cases, adhesive bonding is the ideal solution to meet the requirements relating to material diversity and application size. The bonding of small components, in turn, requires accurate application of tiny amounts of adhesive.

Furthermore, companies often seek to reduce costs, mainly by speeding up their production processes. The challenges to be faced by microdispensing technology are thus clearly defined: ever-smaller amounts of adhesive need to be dispensed at ever increasing precision and speed.

The printing industry has already shown how this can be achieved. Yesterday’s dot-matrix printers were extremely slow in transferring ink to paper by making contact with it. The development of inkjet systems contactlessly dispensing placing tiny ink droplets without touching paper has significantly increased both speed and resolution.

Jetting beats needle application

These advantages can also be used for adhesive dispensing, specifically when jetting adhesive droplets. The time-consuming process of placing a dispensing needle onto the substrate for application, as is done with traditional dispensing, is no longer necessary, resulting in a time advantage that directly reflects in higher throughput.

Position tolerances of components in the Z-direction are irrelevant when jetting since the adhesive droplet has no needle to determine its position at dispensing. Consequently, the risk of a needle colliding with the component does not exist in jetting mode, so there is no need to perform camera measurements before and after the application process.

A jet valve’s closing mechanisms prevent unwanted dripping as can happen with needle valves, thus avoiding dragging of the adhesive. Also compared to needle dispensing, jetting also dispenses materials at much lower quantities, thus facilitating precision.

To put it simply, you can opt for needle dispensing if you have mere milligrams of adhesive to be dispensed with maximum precision. You may prefer jetting, however, if you would like to maximize production efficiency or seek to achieve ultimate miniaturization.

Pneumatic or piezo?

In the latter case, you can choose between two driving systems for your dispensing unit. They use either pneumatic actuators or piezoelectric ceramic actuators. Through the years, piezo valves had an advantage over pneumatic valves in their robustness, operating costs, and ability to process higher-viscosity or highly filled materials.

DELO-DOT PN5: The new microdispensing valve

DELO is the only adhesive manufacturer that develops its own jet valves. For its DELO-DOT PN5 | DELO-DOT PN5 LV microdispensing valves, the company relies on a pneumatic actuator system. In contrast to conventional pneumatic or piezo actuators, the new system does not use any sliding or frictional elements. It is extremely robust and has an exceptionally long service life of up to one billion dispensing cycles.

Compared to its predecessor, DELO-DOT PN3, the new valve features increased jet performance. It allows for adhesives to be dispensed in significantly smaller quantities. Certain products can even be jetted permanently in quantities of 1 nl.

Even materials that are more difficult to dispense such as high-viscosity and highly filled adhesives, can be dispensed in tiny amounts: With the DELO MONOPOX AC268, a nickel-filled adhesive commonly used for RFID chips, droplet sizes as small as 300 µm have been achieved. Average weight came in at just under 8.2 µg, which equates to a single 8 cm strand of hair.

This all is made possible thanks to an optimized fluid system geometry and two different piston types, one for very small dispensing amounts and one for small to medium drop sizes.

Easy maintenance

With its modular design, the actuator is completely separate from the resistant fluid system which, in turn, can be completely dismantled. This allows complete and easy cleaning of all components that come in contact with adhesives and the relevant areas are easily accessible without any special tool. To keep system downtime to a minimum, for example when changing the adhesive, it is possible to replace the fluid system entirely. Single components such as the chemical-resistant stainless steel fluid system body, nozzles—available in different diameters and geometries—and the nozzle heater are available separately and can quickly be exchanged by the user onsite without any supervising specialists or prior training. This is rarely the case with comparable devices and maximizes the availability of the new jet valve.

The redesigned nozzle heater guarantees permanently stable temperatures and viscosity conditions for the dispensing material. The built-in thermal insulation of the heater ensures that only the part at the valve which carries the material is heated, thus reducing the time during which sensitive dispensing media are exposed to a defined thermal load.

Plug & play installation

Especially in high-throughput systems, components must maximize space efficiency in its design. The compact outer dimensions of the DELO-DOT PN5 LV valve (as little as 68 mm × 19 mm × 90 mm), combined with a media supply that can be positioned at a 90-degree angle, allow you to adapt it to small installation spaces and easy integration into production systems. Mounted on a movable axis, its low weight of less than 240 g is ideal for high travel speeds and guarantees you a maximum dispensing frequency of up to 400 Hz in burst mode.

Once installed you will find that the microdispensing valve is quite easy to use. Many parameters can be read from a PCL, which is not the case with a mechanical system.

The advantages of jetting

• Increased Throughput: Jetting eliminates the time required to position a needle onto the substrate, allowing for faster adhesive application. This results in higher production efficiency and throughput since the process can be executed without direct contact.
• Adaptability to Component Tolerances: Jetting is not affected by position tolerances in the Z-direction. Since there is no physical contact with a needle, variations in component height do not affect the dispensing process, reducing the risk of needle collision and the need for pre- and post-application measurements.
• Reduced Risk of Contamination and Dripping: Unlike most needle dispensing, jetting utilizes a closing mechanism that prevents unwanted dripping and dragging of adhesive, enhancing the cleanliness and precision of the application.
• Flexibility and Precision: Jetting allows for the dispensing of smaller quantities of adhesive with high precision and can handle a wide range of viscosities. The modular design and components of jetting systems such as DELO-DOT PN5 provide further flexibility, enabling quick and easy adjustments or replacements, which are advantageous in maintaining production continuity.