Vacuum Assist

Picking up microparts when mechanical tweezers just won’t do

Here’s a riddle: Without touching them, how do you pick up small, delicate parts, such as those with ultrafine finishes or tiny, electronic components sensitive to electrostatic discharge? Answer: With vacuum tweezers.

These devices don’t have much in common with that old Hoover in the front hall closet. Although vacuum tweezers share some of the same characteristics as that clunky dinosaur, many VTs are precise, scientific instruments that no laboratory or cleanroom can do without.

Why not use mechanical tweezers? For starters, it’s pretty easy to drop something with mechanical tweezers, especially a micropart, which is one of the areas where VTs shine. And because of the mechanical forces involved, you can easily damage fragile surfaces or shapes with mechanical tweezers.

Vacuum tweezers excel at picking up things that shouldn’t be touched: temperature- or moisture-sensitive biological specimens, micromachined parts requiring inspection or assembly, surface-mount electronics, computer chips and optics. (They’re also good for stamps and coins, and even dead moths and butterflies!)

They can’t pick up everything, though. Because they operate via suction, they’re not much good at lifting heavy things. And the size of the part is limited by the diameter of the nozzle tube—pick too large a nozzle and you might spend the afternoon disassembling the vacuum pump to look for your parts. In general, however, VTs can handle parts as small as 100µm across.

Ted Pella’s benchtop vacuum tweezers system. Image courtesy Ted Pella.

How they work

VTs come in a variety of shapes and sizes. They function by creating a difference in atmospheric pressure—the same phenomenon that drives windy days and hurricanes.

There are almost as many ways of powering VTs as there are VT models, including batteries (both rechargeable and disposable), portable vacuum pumps and in-house vacuum systems. You can also plug some VTs into a wall outlet or even use good-old hand power. Interestingly, vacuum tweezers—which are low-pressure devices—can even run off compressed air.

Because vacuum tweezers are handheld devices, they are all relatively small, about the size of a fountain pen (although they may be attached to a much larger system). And they’re relatively cheap. Many VTs cost just a few dollars, and even an industrial-grade vacuum tweezers with its own vacuum generator can be had for under $1,000.

So which one’s the right tool for the job? That depends on several factors, such as available budget, quantity of objects to be picked up and what you need to grab—material, weight and shape should all be considered before purchasing a vacuum tweezers. Fortunately, most VTs are available with a broad range of nozzles, or tips, so you can easily pick up a variety of products with the same tool.

In its simplest form, a VT closely resembles that red aspirator bulb you used to use to clean your kid’s nose when he or she had a cold. And this basic VT doesn’t cost much more than that drugstore device, either—bulb units with electrostatic discharge (ESD)-safe tips can be found online for as little as $15.

Tom Mealey, executive vice president of vacuum tweezers manufacturer Virtual Industries Inc. in Colorado Springs, Colo., explained that his company’s Bulb-Vac is ideal for low-volume placement of IC chips onto computer boards, and is simple to use. When the bulb is squeezed, air is forced out of the bulb. The rubber tip is then placed on a flat surface—the chip, in this case—and the bulb is relaxed to draw the air back in, picking up the part. A second squeeze of the bulb releases the part.

Similar to the Bulb-Vac is Virtual Industries’ Pen-Vac, a self-contained, manually powered and inexpensive vacuum tweezers. A Pen-Vac kit that includes four tips goes for about $50. More elegant than the Bulb-Vac or its smaller cousin, the Handi-Vac, the Pen-Vac is operated by a push-button on the side of its plastic or aluminum body. Because of its static-dissipative tip, the Pen-Vac is ideal for handling IC chips and surface-mount electronics as small as 3mm across.

Need to move a lot of ICs? The next rung up on the price ladder is the Stealth-Vac, which operates on compressed air or nitrogen, and costs about $100. Mealey warned that it’s very important to use filtered air on these units; otherwise, the small venturi pump (which creates the vacuum) inside the unit can become clogged or damaged by dirt in the air lines or wayward compressor oil.

The Stealth-Vac is Virtual’s most powerful unit. It’s suitable for high-volume or industrial use, and is especially good at picking up products that otherwise might be difficult to grab, such as those with rough or irregular surfaces. And, said Mealey, the Stealth-Vac is simple to use—just touch the part to pick it up and depress a small button on the side of the VT to release it.

Similar in function and capacity to the Stealth-Vac is Pisco USA’s Air Pincette. The Air Pincette is offered in two styles, the VTA and VTB. The VTA Air Pincette is actuated by covering a small hole at the front of the device, while the VTB requires pressing a button.

“The restrictions depend on the size and weight of the object, but the Air Pincette can pick up almost any small object,” said Brian Boike, customer service representative at Pisco’s Elmhurst, Ill., facility. “I’ve had customers use them for everything from microchips to Ping-Pong balls.”

In some work areas, such as cleanrooms and wafer-handling operations, long hoses are impractical since they can collect stray dirt particles. In these operations, battery-powered VTs are the norm. They are also used in applications where manual dexterity is vital. One example of a battery-powered VT is Virtual Industries’ Porta-Vac. Although substantially more expensive (upwards of $1,500), the Porta-Vac can handle large, flat parts—media disks, solar panels and wafers for ICs—in a cleanroom environment. In this application, the Porta-Vac is the weightlifting champion of the VT world. It is capable of lifting an incredible 500g—roughly the weight of a family-sized can of pork and beans.

Another noteworthy vacuum tweezers is the aspirette, a product from Hirschmann Inc. in Louisville, Ky. According to the manufacturer, the aspirette is a battery-powered alternative to manual tweezers. Designed to move laboratory slides, coverslips and similar items, Hirschmann’s offering is an ergonomically designed, one-button approach to picking up delicate items weighing less than 50g, and is also available in antistatic versions.

But what about really small parts, say anything under 1⁄8"? This is the area where VTs excel. Unlike mechanical tweezers, with a VT you’ll never be crawling on the floor looking for lost parts again. If you’re on a limited budget, most VTs do a fine job with small parts.

Virtual Industries’ high-strength Porta-Wand vacuum tweezers lifting an electronics substrate. Image courtesy Virtual Industries.

Those with larger budgets can order a Virtual Industries continuous-vacuum electric benchtop unit that would be the envy of any electronics-assembly technician, small-parts inspector or anyone working with large quantities of micro components. The units come with automatic shutoff and optional foot-switch activation, and are ideal for high-volume, small-parts handling.

Ted Pella Inc., Redding, Calif., offers a simple, low-cost benchtop unit. Designed for small, lightweight materials, the 520-series Vacuum Pick-Up is limited to parts weighing 70g or less and comes with tips capable of holding components from 0.4" across down to 0.02".

Tip tips

Like a car without a steering wheel, a VT is nothing without the right tip. Tip materials include Buna-N (rubber) cups for picking up parts with large flat surfaces, heat-resistant Torlon for high-temperature parts, ESD-safe Acetal tips for electronic components, economical Delrin tips for everyday use—and the list goes on.

There are many sizes and shapes to choose from as well. “For example, when handling flat substrates such as wafers, solar cells or flat panels, the tips themselves are flat,” said Mealey. “These tips require a constant vacuum source to overcome leakage between the substrate being handled and the pickup tip itself.” To this end, Virtual’s Stealth-Wand can be equipped with several paddle-like tips, one of which resembles a flattened donut, and can be used for lifting wafers up to 12" across.

Virtual Industries makes tips for vacuum tweezers that can pick up parts as small as 100µm. Image courtesy Virtual Industries.

Cup-shaped tips—in straight or angled versions—are good for handling a range of workpiece materials, weights and geometries.

For picking up miniature springs, Swiss-machined or microformed parts, optical fibers and tiny surface-mount electronics, users can choose from ESD-safe Delrin tips.

When handling parts smaller than 1⁄8", a small-part tip is recommended, according to Mealey. “The business end of the small-part tip typically has a conical point ending in a flat area with a hole drilled through the center. The holes vary in size from 0.060" to 0.003". The smallest tip easily handles 100µm parts.” Mealey warned that, because of the limited airflow with a tip this small, a constant vacuum source should be used.

If none of the off-the-shelf tips mentioned so far fit your needs, VT manufacturers will be happy to quote a custom tip for you. Best of all, tip changeover is simple on all systems—just twist the old tip off and stick a new one on.

So if you’re having a problem picking something up, reach for a VT and suck it up. µ

Contributors

Hirschmann Inc.
(502) 240-0287
www.hirschmann-inc.com

Integra Biosciences Corp.
(603) 578 5800
www.integra-biosciences.com/us

Pisco USA Inc.
(630) 993-3500
www.pisco.com

Ted Pella Inc.
(530) 243-2200
www.tedpella.com

Virtual Industries Inc.
(719) 572-5566
www.virtual-ii.com

Lifting liquid samples with Pipetboy Pro devices. Image courtesy Integra Biosciences.

The wet or dry option

While standard vacuum tweezers are great for picking up small objects, they can’t suck up water. Enter the Pipetboy Pro, a specialty product designed by Integra Biosciences Corp. for accurate “pipetting” of serological liquids, which, to us non-scientific folks, is a little like what your kid does at McDonald’s when he puts a finger over the end of his straw and lifts a tube full of orange soda to his mouth.

With North American headquarters in Hudson, N.H., Integra offers laboratory tools for liquid handling, media preparation, sterilization and cell cultivation. According to Dr. Lydiane Saucède, product manager at Integra Biosciences AG in Switzerland, the Pipetboy Pro is an ergonomic, handheld device that provides for productive and accurate handling of a variety of liquids up to 100ml in volume.

Hirschmann's aspirette vacuum tweezers kit with an assortment of small nozzles. Image courtesy Hirschmann.

For users who need to handle liquids one day and “untouchable” dry materials the next, Integra has taken the Pipetboy Pro one step further by offering an accessory, the Pipetboy vacuum tweezers. Capable of lifting up to 50g, it’s ideal for microscope slides, cover slips, small optics, electronics and biological specimens.

The illuminated and battery-powered Pipetboy vacuum tweezers set comes with a stainless steel tip and interchangeable rubber cups, from 3mm to 10mm in diameter.

—K. Hanson