The patent's inventors are Byars, Jonathan (
This patent was filed on
From the background information supplied by the inventors, news correspondents obtained the following quote: "The present invention generally relates to ultrasonic bonding and more particularly to a support structure used for securing a semiconductor device during the bonding.
"As global markets demand smaller power semiconductor devices for mobile application at lower costs, manufacturers seek to improve the process and make it as efficient as possible. These cost reduction strategies involve using less raw copper material. This forces the creation of highly populated lead-frames used to transport the semiconductor packages through the front-end manufacturing process. Highly populated lead-frames contain many rows and columns of semiconductor devices connected to a matrix by small and thin tie bars. Because of the density of the devices on the lead-frame and their inherently small sizes, properly constraining the packages during the large ultrasonic wire or ribbon bonding process becomes very difficult. Poor clamping leads to an unreliable process and poor quality parts.
"FIG. 1 shows one type of conventional clamping that uses an array of thin flexible clamp fingers 102 (only one shown) to constrain specific points on a lead-frame 104 during ultrasonic bonding. Lead-frame 104 is constrained by the spring action of clamp fingers 102. Clamp fingers 102 are designed to flex a specific amount during the clamping operation to ensure even clamping force along lead-frame 104 in the presence of tolerance stack up between components. Due to the flexibility of the clamp fingers, a large amount of tip deflection occurs over the surface of lead-frame 104 (shown by the portion between the two arrows). This movement combined with the high force applied to the clamps can damage the lead-frames by leaving visible marks on the frames. As a result, the placement of the clamps are constrained to areas encapsulated in the final package or areas that are cut away and not included in the final package (for cosmetic reasons). Clamp placement may also be constrained to places on the lead-frame large enough to handle the deflection of the clamp fingers. Furthermore, the use of small and light clamp fingers to secure specific points on the lead-frame can cause unwanted resonance problems during bonding due to the many modes of the clamp fingers in the frequency spectrum close to the bonding frequency. This can cause instability and inconsistency in the bonding process as well as rendering an application impossible to bond with a given set of tooling.
"Thus, there is a need for a way to bond lead-frames without the disadvantages of conventional clamping discussed above."
Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "According to one embodiment, a device for supporting a semiconductor device comprises a base, and a compliant layer over the base, wherein the compliant layer secures the semiconductor device to a window clamp during a bonding process. The device further includes a protective layer over the compliant layer in one embodiment. For example, the semiconductor device may be a lead frame carrying semiconductor dice, and the compliant layer and the protective layer are separated into a plurality of portions over the base in different embodiments.
"In another embodiment, a clamping system for securing a semiconductor device comprises a base; a compliant layer over the base; and a window clamp that secures the semiconductor device to the compliant layer during a bonding process. In one embodiment, a protective layer is added over the compliant layer.
"A further embodiment is a device for supporting a semiconductor device comprising a window clamp; and a compliant layer over the window clamp, wherein the compliant layer secures the semiconductor device to a support during a bonding process. A protective layer, such as metal, may be added over the compliant layer.
"In yet another embodiment, a method for securing a semiconductor device during a bonding process comprises moving a window clamp to a lead frame; moving a supporting device to the lead frame; and compressing a compliant material on the supporting device against the lead frame. The method may further include pressing a protective layer on the supporting device against the lead frame. In one embodiment, moving the window clamp occurs before moving the supporting device and compressing the compliant material.
"These and other features and advantages of the present invention will be more readily apparent from the detailed description of the embodiments set forth below taken in conjunction with the accompanying drawings."
For the URL and additional information on this patent, see: Byars, Jonathan; Copperthite, Theodore J.. Semiconductor Device Support for Bonding. U.S. Patent Number 8720767, filed
Keywords for this news article include: Semiconductor,
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