Handling miniature parts is becoming more challenging for manufacturers since many parts continue to get smaller even as they increase their levels of integration and functional complexity. These miniature parts are being incorporated in a growing number of electronic products, including cellular telephones, pacemakers, hearing aids, and even viewing glasses.
Manufacturers faced with handling smaller parts rely on the aid of automated equipment, such as systems that can place electronic parts as small as a 01005 resistor (0.010 x 0.005-in.) with accuracy and speed. Still, some parts, because of their odd shapes or sensitive surfaces, must be placed by hand. Some can be handled by means of a mechanical tweezer, and tweezer manufacturers may even offer to work with an engineering staff to create a tweezer profile suited to the profile of the part to be handled. Of course, with such customization the cost of the tweezer can increase significantly. Also, if an assembly person drops such a tool, the tip profile is easily damaged and the custom tweezer may be rendered worthless.
Various new tools are available that can support the assembly of a wide variety of miniature and odd-sized electronic parts without need of creating a customized tweezer tip. As an example, the Vacuum-Tweezer tool from Virtual Industries is well suited for many of these applications. Unlike a mechanical tweezer with its two gripping surfaces, the vacuum tweezer employs only a single conical point at the tip. The tip has an orifice opening that is connected to a vacuum source. The source maintains a low-pressure vacuum at the top that is used to grip anything coming in contact with the tip. The tool is operated by means of a handle with a control button.
Single Gripping Tip
There are several advantages to using a tool that has only a single gripping tip. First of all, there is no mechanical squeezing of the gripped part that could cause breakage or other mechanical damage to a fragile item. Secondly, once a part is gripped by the vacuum at the tip, it stays on the tip and is released only when the operator presses the release control button on the vacuum tweezer handle.
Also, vacuum tweezers help to eliminate the "zing effect" that can plague picking and placing of small parts with mechanical tweezers. This effect occurs when a part is picked with mechanical tweezers, it slides off one of the tweezer tips, and is lost somewhere across the assembly work floor, never to be seen again. Small parts can be expensive, with lost parts adding to the total cost of assembly for a product. In addition, a vacuum tweezer makes it possible to grip a part from the side, from the top, or from any protruding feature. In contrast to a mechanical tweezer, two opposing flat surfaces are not required to grip the part.
To provide several examples of instances where the use of a vacuum tweezer benefitted an assembly process, in one case, an engineer was picking miniature ball bearings from a container of loose bearings. The miniature bearings were then placed into a tiny race as part of assembling a completed bearing. Gripping the loose bearings with a mechanical tweezer posed a challenge, made worse by the "zing effect" for bearings that were first gripped but then lost.
Fortunately, this assembly process was greatly simplified with the purchase of a vacuum tweezer having a tip with an opening slightly smaller than the outside diameter of the ball bearing. In use, the vacuum tweezer tip was plunged into the container of ball bearings and gripped the first bearing it contacted. The ball bearing was then placed into the race and the zing effect was totally eliminated.
Another example of the effectiveness of vacuum tweezers for some applications involved the handling of microelectromechanical-systems (MEMS) devices. MEMS devices are miniature circuits that may include such functions as accelerometers, gyroscopes, digital compasses, inertial modules, pressure sensors, humidity sensors, and microphones at the die level. The micromachined features on the top surface of a MEMS device can be easily damaged with improper handling, and mechanically gripping a MEMS die from the sides can damage the die. But with the correct small-part-tip and vacuum-source the vacuum-tweezer easily grips the MEMS device from the edge of the die as part of an effective assembly process.
Implementation of vacuum tweezers for placement of electrical or mechanical parts can cover a wide range of parts. Vacuum tweezer tips range in size from the 0.75-in. diameter rubber suction cup down to the model VSPT0803 vacuum tweezer tip, with a 0.003-in. (75µm) orifice for handling extremely small parts.
Contact: Virtual Industries, Inc., 2130 Victor Place, Colorado Springs, CO 80915 719-572-5566 fax: 719-572-5504 E-mail: firstname.lastname@example.org Web: http://www.virtual-ii.com