Patent Application
20070056138
1. Field of the Invention
The present invention generally relates to a high volume brush cleaning apparatus which is used in the fabrication of electronic components and, in particular, for the removal of unwanted ceramic debris generated in the sizing of a larger ceramic substrate laminate such as unfired greensheets into smaller members.
2. Description of Related Art
The fabrication of electronic components is very complex and costly and requires a number of steps which must be performed with a high degree of precision. The steps range from the making of the electronic components substrate to the forming and plating of metallic features on the substrate to form the finished product. Because of the extremely small size and complexity of the electronic component circuitry, debris including dust and other particles cannot be tolerated in or on the product and extreme measures have been taken by the industry to overcome this problem such as the use of clean rooms and ultra filtered chemicals and wash solutions.
Electronic components cover a wide range of products from semiconductor chips made from semiconductor wafers, multilayer ceramic substrates, printed circuit boards, and the like. While the present invention can be used in the fabrication of electronic components in general, the following description will be specifically directed for convenience to the fabrication of multilayer ceramic substrates for which the problem of debris and dust are particularly troublesome.
In general, conventional multilayer ceramic substrates are formed from ceramic greensheets which are prepared by mixing a ceramic particulate, a polymer binder, plasticizers and solvents. This composition is spread or cast to form ceramic sheets or slips from which the solvents are subsequently volatilized to provide coherent and self-supporting flexible greensheets. After blanking and punching, the greensheets are screened with a metallic paste to form current patterns and to fill vias and then stacked, laminated, and fired at temperatures sufficient to drive off the polymeric binder resin and sinter the ceramic particulate together into a densified multilayer ceramic substrate product.
In one process, a plurality of similar unfired ceramic greensheets would be formed and stacked in a conventional manner to form a ceramic substrate laminate. The laminate will then be sized by cutting or sawing into smaller ceramic substrate laminates. When sintered, the ceramic substrate laminates will form fully functioning multilayer ceramic products.
As with any sawing or cutting operation, particles will be generated which are on or get attached to the ceramic surface and which must be removed or the resulting product will be defective. This debris is in the form of particles and ceramic strips which are left behind in the sizing process.
Bearing in mind the problems and deficiencies of prior art, it is therefore and object of the present invention to provide an improved method for the removal of unwanted debris including ceramic debris from electronic components such as chips and multilayer ceramic substrates (MLC's) particularly unfired greensheets.
Another object of the present invention is to provide a high volume brush cleaning apparatus for cleaning the surfaces of electronic components such as chips, wafers, unfired ceramic greensheets and MLC products to remove debris and other particulate matter.
The above and other objects, which will be apparent to those skilled in art, are achieved in the present invention which is directed to a high volume vacuum brush for removing debris and cleaning the surface of an electronic component such as an unfired ceramic greensheet, fired ceramic greensheet, semiconductor wafer, and the like comprising:
a housing member having a hollow interior and an opening at its upper end for attachment to a vacuum source and at the other opposed bottom end one or more sweeping member (brush) openings defining rows running substantially parallel along the bottom end of the housing member holding a plurality of downwardly extending bi-directional sweeping members mounted within the openings with the free end of the sweeping members extending below the plane of the bottom end and one or more through suction openings interspaced between the rows and also preferably on the outer side of each sweeping member end row for communication of the spaces between the rows and on each side of the end rows with the vacuum source.
In another aspect of the invention a high volume vacuum brush is provided for removing debris and cleaning the surface of an electronic component such as unfired ceramic greensheets, fired ceramic greensheets, semiconductor wafers, and the like comprising:
a housing member having an interconnected top, front, rear, and side walls and an open bottom defining a hollow interior, with the top having an opening for attachment to a vacuum source;
a brush retainer housing member having a top and a bottom sized to fit in the open bottom of the housing member, the bottom of the brush retainer housing having one or more sweeping member openings defining rows running substantially parallel along the length of the brush retainer housing for holding a plurality of downwardly extending bi-directional sweeping members mounted within the openings with the free end of the sweeping members extending below the plane of the bottom of the brush retainer housing and one or more through suction openings interspaced between the rows and also preferably on the outer side of each sweeping member end row for communication of the spaces between the rows and on each side of the end rows with the vacuum source.
In another aspect of the invention the housing member is preferably rectangular and with curved corners and a curved top and the sweeping member openings in the brush retainer housing member are dovetailed to securely hold the sweeping members which are formed with a corresponding dovetail shape. The sweeping members may be easily inserted and removed from the brush retainer housing member.
In another aspect of the invention the sweeping members are elongated and made from compressed nylon bristles.
In a further aspect of the invention the suction openings are a slot running along the length of the brush retainer housing member with the slot being narrower at the bottom end to increase the velocity of the air at the substrate surface being sucked into the slot by the vacuum source. This provides a high volume and high velocity vacuum and improves the efficiency of the debris removal from the surface of the electronic component.
In a still further aspect of the invention the vacuum brush is specifically used to clean unfired ceramic substrates which have been sized and which contain debris and other particulate matter resulting from the sizing operating or other operation from which the unfired ceramic greensheets have been exposed.
In another aspect of the invention a method is provided for cleaning the surface of electronic components such as unfired ceramic greensheets, fired ceramic greensheets, semiconductor wafers, and the like comprising positioning the surface of the electronic component to be cleaned, contacting the free ends of the sweeping members of the brush with the surface of the component and moving the vacuum brush of the invention substantially transverse to the axis of the sweeping members back and forth over the surface of the substrate while the vacuum is activated to remove debris and particulate matter from the surface of the substrate.
The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:
One brush apparatus of the invention employs a brush retainer housing whose interior has smooth and rounded surfaces to alleviate the chance of any ceramic build up in the housing. A brush retainer for insertion into the housing has slots that secure the brushes and the brushes can be easily slid in/out of the brush retainer. A dovetail is preferred in the grooves of the retainer, which is used to retain dovetailed brushes which typically have a tapered metal shank. Different material brushes in any combination can be used at the same time. The brush retainer also has longitudinal slot through openings, preferably which run the length of the brush. These slots are preferably employed between and on all sides of the brush. The through slots allow the vacuum to remove the unwanted ceramic debris.
The brush retainer housing has a high volume area chamber so that the vacuum air drawn through the slots rapidly removes ceramic debris on the substrate surface.
Referring now to
A brush retainer shown as numeral 18 is also shown rectangular in shape with curved edges and is sized to fit within brush retainer housing typically as a force-fit or snap fit holding the brush retainer 18 within the interior of housing 12. The brush retainer has opposed longitudinal walls 20a and 20b and opposed side walls 20c and 20d. The thickness of the brush retainer is such that it only partially fits into brush retainer housing 12 so that the bottom surface 20f is essentially flush with the bottom surface 14f of the brush retainer housing 12. The upper surface 20e of the brush retainer is below the upper surface 14e of the brush retainer housing leaving an air space above the brush retainer so that the vacuum can suck air through openings 22a-22d in the brush retainer 18 into the brush retainer housing 12 and into the vacuum source 30.
The brush retainer 18 is shown having longitudinal dovetailed grooves 23a-23c, having a dovetail portion 24a-24c and a straight portion 24a′-24c′, extending the length of the brush retainer housing. The grooves only extend partly into the brush retainer housing to the desired depth and brushes comprising a plurality of bristles are shown generally as numeral 26a-26c have a dovetail portion 28a-28c and a straight portion 28a′ and 28c′. The dovetail portion 28a-28c would be inserted into its respective groove 24a-24c. The brush retainer 18 is also shown having longitudinal through openings 22a-22d where 22b-22c are interspaced between the brushes 26a, 26b and 26c with a preferred design as shown having additional longitudinal openings 22a and 22d on the periphery of the brush retainer housing outside the outside brushes 26a and 26c.
An assembled vacuum brush apparatus is shown in
Referring to
Any suitable brush or sweeping member may be used in the brush apparatus of the invention with a particularly preferred brush being made from compressed nylon. Also materials such as camel hair, polypropylene and other plastic fibers may likewise be used. A suitable compressed nylon brush is made by Precision Brush Company with the name Nylon P/N 4855. This brush is necessarily resilient at its free end and preferably comprises a plurality of bristles (strands) as is well known in the art. The thickness of the strands may vary and it is typically about 2 mil to 10 mil. The dovetail portion of the brush member is typically encased in a metal or other sleeve (such as with a paint brush) to contain the bristles.
In another embodiment, the sweeping members may be a resilient solid material which would act like a squeegee. Nylon or other suitable material may be used.
The components of the brush apparatus are preferably made from a plastic such as Delrin. Any suitable plastic or other material may be employed.
It is an important feature of the invention for the preferred brush assembly shown in
Use of the brush apparatus has been found to efficiently remove debris such as ceramic particles from the surface of electronic components such as unfired greensheets.
The brush retainer housing has a high volume area chamber above the brush retainer so that the vacuum air drawn through the slots makes for rapid removal of any foreign ceramic debris on the substrate surface. Typically, the brush apparatus is about 4 inch×1.5 inch and 6 inch overall high. The brushes are about 0.625 inch to 0.750 inch high and 0.125 inch thick at the top and 0.1 inch at the free end. The slots are typically 0.125 inch wide. The above sizes may vary widely depending on the application.
While the present invention has been particularly described, in conjunction with a specific preferred embodiment, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications, and variations as falling within the true scope and spirit of the present invention.
Thus, having described the invention, what is claimed is:
