PCB – Precision Glue Dosing

Rush PCB understands that high quality products require highly precise component placements on their printed circuit boards (PCBs). However, in traditional PCB assembly, there is typically a high amount of wastage because of fluctuations in glue viscosity, inconsistent height of the dispensing needle, and variable amounts of glue.

The effect of this variability is that assemblers often have to scrap expensive components, resulting in slowing production lines that hit the bottom line. Additionally, these variables also make the gluing process rather operator-intensive, further adding to the production time and costs.

Problems with Glue-Dosing

There can be several problems with glue-dosing. One of the most common issues is constant dripping of glue. Usually, there are three causes for this—very thin glue, large air pressure, large needle diameter.

Very thin glue may drip constantly, and the solution is to replace it with a thicker glue. A large air pressure may also force the glue to drop continuously, and this can be solved by reducing the pressure.

It is very important to use the correct diameter for the dispensing needle. If the diameter is too large, the glue can drip continuously. On the other hand, with a small diameter needle, the valve may start dripping once it is closed. This is because the small diameter needle causes a back pressure to build up. Rush PCB recommends using a tapered oblique needle to reduce back pressure.

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Precision Glue-Dosing Solutions

To eliminate most of the above variables from their production environment, Rush PCB uses fully automated turnkey glue-dosing solutions. Driven by precise vision and motion systems, the turnkey solution is self-calibrating as it applies an identical amount and pattern of glue to every component. Not only does this process simplify the operator’s tasks, it also ensures repeatability, while reducing scrap. In turn, we at Rush PCB, transfer the cost reduction to the customer, resulting in lower quotes.

One of the biggest challenges during PCB assembly is applying microscopic amounts of epoxy glue efficiently in precise parallel lines. Irrespective of production cycles being short or long, there is a high possibility that the regular process of glue application may turn inconsistent or go wrong.

For instance, there are chances that the alignment or positioning of the surface mount devices (SMDs) might change slightly, there may be too much glue, the dispensing needle may be somewhat lower, higher, or offset from the previous PCB, there may be inadequate glue, the glue may be of a different viscosity, and so on.

To reduce the impact of the above variables, we at Rush PCB have installed an automated system in our production environment. This ensures a perfect alignment of the plate and glue-dispensing needle, while keeping them the same distance apart all the time.

The automated system consists of two high-resolution vision camera systems, and a mechanism for imparting precise motion, operating on smart software. The combination helps to keep the distance between the plate and the glue-dispensing needle to within ±5 microns on the three axes. Additionally, a volumetric glue-dispensing system ensures that only the required volume of glue dispenses to each part.

The system also has a recipe handler that helps with product changeovers. It allows the operator to reconfigure the system quickly by simply entering the new value such as glue type, speed, start/stop positions, and height.

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Benefits of Precision Glue-Dosing

There are several advantages to Rush PCB when using an automated system for precision glue-dosing. As the entire system is fully automated, the process is entirely operator independent. Moreover, the system ensures a repeatable operation providing uniform product quality and takt time.

The turnkey glue-dosing system being self-calibrating, it does not require the operator to intervene periodically, thereby eliminating time-consuming stoppages. Moreover, the operator does not require training in calibrating the system.

The automatic dosing system dispenses glue volumetrically, ensuring application of precise amounts of glue.

Applications of Precision Fluid-Dosing Systems

Apart from attaching SMDs to PCBs for quality assembly, Rush PCB uses the precision glue-dosing system in other applications involving fluid dispensing. These involve applications such as:

Large IC Failure Protection with Underfill

While assembling large ICs such as PoP, BGA, and CSP, it is necessary to underfill them to prevent failure. Densely populated boards require tight keep-out zones with small, narrow fillets. A high degree of precision is necessary with applying underfill to these components to augment quality, speed, and productivity.

Adhesives for Thermal Management

Several components dissipate heat when operating, and require thermal management to keep them within safe operating temperatures. Most such components use heatsinks with heat-conducting adhesives in between the heat-producing IC and the heatsink. The heat-conducting adhesive helps to transfer the heat from the component to the heatsink. For proper application, the fluid-dosing system must dispense the heat-conducting adhesive in exact volumes and in a thin profile. The automated system helps in dispensing the adhesive in the right consumable combinations and speed.

Please contact Rush PCB for all your precision assembly requirements. Please visit the Rush PCB website, or call now for an instant quote.