Patent Application
20090108053
The invention relates to electronic semiconductor devices and manufacturing. More particularly, the invention relates to apparatus, systems, and methods useful in semiconductor device manufacturing processes for placement of an array of solder balls onto a surface.
The use of various forms of BGA (ball grid array) packages for semiconductor integrated circuits has become fairly common in the arts. A standard approach to manufacturing BGA packages is to firmly attach solder balls to solder pads (or electrodes) arranged on a receiving surface, such as a BGA substrate. Such a manufacturing process typically includes solder ball placement, semiconductor device placement, and subsequent reflow. Solder ball placement involves aligning the solder balls with the positions of the solder pads and placing the solder balls onto these positions. The device is typically placed on the solder balls. Reflow is a process in which solder balls melt, reflow, and harden onto the solder pads of the substrate to create the electrical couplings between the semiconductor device and the substrate.
Current methods and systems for solder ball placement usually involve sweeping or rolling solder balls onto a template approximately corresponding to the arrangement of the receiving surface, usually an array arranged in a grid. A pick-up head is generally used to pick up the solder balls from the template, move them into position over the receiving surface, and release them onto their respective positions, e.g., on contact pads, on the receiving surface for subsequent reflow.
Pick-up heads used for solder ball placement typically use a vacuum force to hold the solder balls against a bearing surface. When the pick-up head is properly positioned, the vacuum force may be interrupted in order to release the solder balls. Although relatively successful in terms of solder ball handling, problems remain with the vacuum pick-up heads currently used in the arts. The vacuum pick-up heads used for handling solder balls include a precision-machined bearing surface configured to match a particular solder ball array pattern and solder ball size. Individual solder ball recesses are provided in precise locations integrated into the bearing surface for receiving each solder ball of the array. Each recess is in turn served by a vacuum port. The vacuum ports must be precisely located within each of the recesses, and must be significantly smaller than the solder ball size in order to prevent the solder ball from being pulled into the vacuum chamber of the pick-up head, and to prevent the solder ball from being damaged by contact with the rim of the port where it meets the recess. The precision machining required, sometimes including holes in the bearing surface of 60 micrometers in diameter or smaller, makes pick-up heads used in the arts costly and time-consuming to manufacture. Machining problems are sometimes compounded by efforts to use materials particularly suited for semiconductor processing equipment, such as certain types of stainless steel or other alloys requiring slow milling speeds and low feed rates. This is particularly problematic in light of the fact that any given pick-up head may be used only for a particular solder ball array configuration, and for only a very limited range of solder balls sizes.
Due to these and other technological challenges, improved solder ball placement tools and related methods would be useful and advantageous in the arts. The present invention is directed to overcoming, or at least reducing the effects of one or more of the problems with the present state of the art.
In carrying out the principles of the present invention, in accordance with preferred embodiments thereof, the invention provides improved solder ball placement tools with enhanced efficiency and adaptability for various solder ball sizes and solder ball array patterns.
According to one aspect of the invention, apparatus for positioning solder balls in a desired array on a surface includes a vacuum head body configured to direct a vacuum force through a permeable vacuum plate enclosing a vacuum chamber. A stencil adjacent to the outer surface of the permeable vacuum plate includes numerous solder ball niches configured to capture solder balls when a vacuum force is applied through the vacuum chamber. The vacuum head is adapted for positioning over a supply of solder balls, capturing a number of solder balls, repositioning over a surface for receiving solder balls, and releasing the solder balls onto the surface.
According to another aspect of the invention, in a preferred embodiment, solder ball positioning apparatus includes a porous metallic permeable vacuum plate.
According to another aspect of the invention, in a particular preferred embodiment, solder ball positioning apparatus includes a sintered metal permeable vacuum plate.
According to another aspect of the invention, a preferred embodiment includes solder ball positioning apparatus having a stencil made from etched metal.
According to yet another aspect of the invention, a preferred embodiment of a solder ball positioning system includes a moveable vacuum head with a body configured to direct a vacuum force through a vacuum chamber. A permeable vacuum plate encloses the vacuum chamber. Also included in the system are interchangeable stencils for individual attachment adjacent to the vacuum plate. Each stencil includes solder ball niches configured to capture solder balls for positioning by the moveable vacuum head.
The invention has advantages including but not limited to providing versatile, adaptable, and efficient solder ball placement tools for use in semiconductor device manufacturing processes, which may provide tool preparation efficiencies, and decreased costs. These and other features, advantages, and benefits of the present invention can be understood by one of ordinary skill in the arts upon careful consideration of the detailed description of representative embodiments of the invention in connection with the accompanying drawings.
The present invention will be more clearly understood from consideration of the following detailed description and drawings in which:
References in the detailed description correspond to like references in the drawings unless otherwise noted. Descriptive and directional terms used in the written description such as first, second, top, bottom, upper, side, etc., refer to the drawings themselves as laid out on the paper and not to physical limitations of the invention unless specifically noted. The drawings are not to scale, and some features of embodiments shown and discussed are simplified or amplified for illustrating the principles, features, and advantages of the invention.
The invention provides solder ball positioning apparatus, systems, and methods for placement of solder balls useful in semiconductor device manufacturing processes. Referring primarily to
The solder ball niches 24 are preferably more-or-less cylindrical apertures perforating the stencil 20 and configured to capture solder balls 26 (not part of the invention). Now referring primarily to
An alternative overview of apparatus and systems 10 for solder ball placement is shown in the exploded bottom perspective view of
The methods and systems of the invention provide one or more advantages including but not limited to providing solder ball placement tools useful in the semiconductor device manufacturing arts with adaptable, efficient, and cost-effective characteristics. While the invention has been described with reference to certain illustrative embodiments, those described herein are not intended to be construed in a limiting sense. For example, variations or combinations of steps or materials in the embodiments shown and described may be used in particular cases without departure from the invention. Various modifications and combinations of the illustrative embodiments as well as other advantages and embodiments of the invention will be apparent to persons skilled in the arts upon reference to the drawings, description, and claims.
