Sometimes a screening application cannot be solved by simply placing the product on the sieve surface and allowing the screener to do its job. While a round screener is meant to separate product by particle size, sometimes this simple process can cause problems or damage the product. Recently, a customer inquired about fine mesh ultrasonic sieving of his solder powder. While I am no expert in the production of solder powder, I do know solder powder is generally a very spherical powder (see pic below) and sieves very well when applying ultrasonic to the screen surface.If the solder powder spends too much time on the screen surface, the spheres can be damaged or they can oxidize. Particle size separation is also very critical. More difficult-to-sieve powders fall into different categories based upon size:
- Type 4 (-400 +635 mesh)
- Type 5 (-500 mesh)
- Type 6 (-635 mesh)
- Type 7 and 8 can be sieved, but the process is very slow
So my customer asked for a standard lab demo to try and sieve his Type 4, 5 and 6 solder powder. Our small lab models use 8” or 12” diameter sieves equipped with our HK Ultrasonic Sieving System. Just as I thought, he called after a couple weeks of working with the demo and said the lab unit was very efficient at sieving the powders, but the length of time the powder spent on the sieve surface damaged his spheres. He asked for my thoughts and I explained to him the ultrasonic was the key but we need to remove the covers off the screen surface in a much quicker time frame while still removing all if the fines.
My suggestion was to try our Model HK Incline. The HK Incline is a very unique ultrasonic sieving system that utilizes rectangular screen frames and no mechanical vibration. We designed the HK Incline to rely strictly on the pulsing of the ultrasonic energy to move the powder down the screen surface. So here is how it works: You load a small hopper/feeder with your powder and a small electromagnetic feeder feeds the powder onto our special ultrasonic rectangular sieve frames. While the sonics is pulsing on/off, the powder is moving down the screen surface. The fines pass through the sieve either on to a second mesh or into a fines collection funnel. The over sized materials are discharged off the ends of the screen frames into collection containers. What I like about this style of equipment is the ability to adjust the feed rate and product yield. There is a little bit of “black magic” on our end in designing the screen frames and adhering the sieve material to the frames but the end result is a very efficient ultrasonic screening system. There is a product data sheet at the end of this article – I could not find my pictures of the unit. The HK Incline Ultrasonic System is not for every application… If you have a powder that agglomerates or does not flow well – the HK Incline will not be effective. But if you have a fine, free-flowing powder such as solder spheres or other atomized powders, the HK Incline could be your ticket. As for my customer……He tried the HK Incline and loved it!
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Image: Example of materials for this screening solution