Dispensing nozzles are designed for accurate dispensing of the glue onto the substrate which helps to prevent inconsistent epoxy problems like tailing, bridging, voids and insufficient epoxy coverage. This enables our customers to achieve superior dispensing performance. The complete set of nozzles and adaptors is available for all types of bonders in the market.

The dispensing tools can be designed for ESEC, ASM or any other Die-Attach machine.

In many cases, it is essential to use customized and adjustable adaptors. MPP has developed a manufacturing process that ensures that its adaptors are accurate, thus preventing leakage and allowing for a smooth dispensing process.

In general, dispensing can be defined as transfer of fluid from a container (typically in syringe) to a substrate in a form of pattern or calculated volumes to host a die or component. In electronics industry, there are various methods that have evolved to keep up with the rapid development of manufacturing need for adhesives and conductive epoxies in a wide array of packaging assemblies.

Over the years, dispensing applications have expanded to other areas needed for new types of packaging encapsulation techniques. A wide variety of fluid materials with different viscosity are being used, from solder paste, conductive adhesives and damming compound to fluxes, thermal paste and underfills.

Stamping:

Sometimes known as daubing or pin transfer, this method involves dipping a compliant tool into a reservoir of liquid material then transferring the adhering liquid onto a substrate. This method is frequently used to attain very small dots. However, the process is considered slow as compared to other methods especially if the application requires multiple dots dispensing. To increase throughput, gang (multiple) stamping tool can be employed to stamp an array of dots simultaneously. Grid type stamping tool is also available to print a large area.

Stencil Printing:

Stencil printing is the fastest and most efficient way of applying adhesive to a large area in mass production runs. In this method, a patterned stencil is placed over the substrate and a squeegee force the material through the stencil apertures onto the substrate. This may become complicated when the stencil apertures become so small that the material can no longer print effectively.

Jet-dispensing:

Non-contact jet-dispensing is one of the newer methods in dispensing technologies. Shots of fluid are fired onto the substrate in a non-contact process. Since dispensing dots are typically restricted to one specific size during a run, larger volumes are achieved by accumulating multiple dots. By moving the jet head during deposition, required patterns can be formed.

Nozzle or Needle Dispensing:

In this method, time and air pressure is commonly used to push the fluid through a needle or nozzle to form single dot or multiple dot patterns over the substrate. Over the years, various dispensing platforms with programmable pumps and valves, such as auger and piston have been developed to achieve unique patterns or volumes using single needle or special tapered nozzle. These platforms could either be stand-alone dispensing equipment or integrated on those new pick and place machines.

In the realm of micro-dispensing application, the challenge takes place on methods to achieve small volumes or dots of 200 microns (8mils) and below with high repeatability. Among the methods that have been developed, the ideal approach at present would still be dispensing nozzle using auger screw or piston pumps. As for the nozzle, micro-dispensing requires small orifice with tighter tolerance. Smooth internal finishing is also an important factor to enhance fluid flow.

 

Nozzle or Needle Dispensing Tools In this method, time and pressure is commonly used to push the fluid through a needle or nozzle to form single dot/line or multiple dot/line patterns over a substrate. Over the years, various dispensing platforms such as Auger and piston have been developed. We distinguish 2 different techniques depending on the dispensing accuracy and equipment capability : • Static Dispensing • Programmable Dispensing Static Dispensing Tools The advantage of these tools in comparison to the programmable dispensing tools is the throughput. In one shot, a defined pattern is quickly generated and the volume dispensed is finely adjustable on the pump/ valve setting parameters. The epoxy paste is dispensing through needles or through a nozzle having usually a cross groove on the face. The body of the tool is to be adapted to a specific die bonder type or directly to a standard syringe. Programmable Dispensing Tools The nozzle or needle tip is used as a written pen to dispense a specific epoxy pattern. The layout and necessary dispensed volume is calculated on the die bonders, based on the die size and desired bond line thickness. A few examples are shown hereafter From left to right : Cross, Double Y and Asterisk The valid size range for the Cross layout can extends form 2 to 25mm for square dice. For smaller dimensions, single dots are dispensed. The nozzles are also used to dispense volume of material like glob top and flip chip underfill.

 

Nozzle Types Even if the traditional single needle with plastic holder is quite popular, the nozzle construction is more sophisticated and gives better results due to a wiser inner tapered hole. The nozzle outer geometry is here again dependent on the equipment on which it is mounted. Some types are more common and are compatible on different dispenser types. This is the more the case in the Surface Mount Technology rather than in the Die Bonder field. The Luer Lock thread allows the nozzle to be directly connected to a common syringe tip. The material of the nozzle or needle was for a long time restricted to stainless steel. However, with the dot size shrinkage requirement, alternative material needed to be developed especially for hole diameters of 0.15mm and below. The ceramic is the material of choice for those applications especially if the inner hole is molded and well polished. The advantages are longer tool life, reduction of paste clogging as well as ease of cleaning and improved fluid flow. The soft solder dispensing is made with comparable nozzle technique or through a process known as “spanking”. Here, the solder is melted from a wire and dispensed on the target. The Spank tool, with a shallow front cavity, is placed over the solder volume and defines a specific wetted area.

Conclusion: You have seen a short description of many different tools to handle a device and dispense a fluid. Each process and application offers a wide range of possibilities in the selection of an appropriate tool. Due to the large range of base materials as well as options in the finishing of the tools, there is almost an infinite performance behavior. Fortunately, most of them will comply to the standard requirement and give satisfaction to the user. In other more stringent situations, a more focused approach need to be implemented The best results are then obtained by working closely with a partner able and willing to support his customer in the search of excellence.

 

出處: http://www.mpptools.com/MicroPoint/Templates/showpage.asp?DBID=1&LNGID=1&TMID=87&FID=1525

http://www.epakelectronics.com/spt_epoxystampinganddispensingtools.htm

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