This application is related to U.S. application entitled Tray With Flat Bottom Reference Surface filed on the same date as this application, having attorney reference 0067810/0303882 which is expressly incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to trays for use in carrying components such as semiconductors, and more particularly to a tray having flat datum surfaces and configured to avoid calibration variations due to mold injector pin burrs imposed on the tray during manufacture.
2. Description of the Related Art
Small components such as semiconductors are often stored or shipped in molded plastic trays similar to tray 10 shown in FIGS. 1A and 1B. In the molding production operation, ejector pins are used to push/eject the tray from the mold casing. Burrs are caused from molten plastic filling the circumferential gap between the ejector pin and the ejector pin hole. Slight protrusions can also occur if the ejector pin is not level with the part surface. Part ejection is a forceful process, and the pressure of the pins on the tray leaves burrs/marks/blemishes on the tray surfaces. These burrs cause variations in the effective tray thickness and as a result trays cannot be stacked with a consistent height or degree of flatness. The burrs cause errors in calibration of automated tray handling equipment, and equipment for picking and placing components in tray component packets. Removal of burrs would involve additional and expensive machining or manual processes, and generally is not practical.
FIG. 1A is a perspective top view of a prior art tray 10 showing ejector pin marks/burrs 12 left after ejecting the tray 10 from a mold. FIG. 1B is a perspective bottom view of the tray 10 showing ejector pin marks 14. For stacking of trays such as tray 10 and for calibration of automated tray handling equipment for use in handling trays of the design shown in FIGS. 1A and 1B, it is necessary to use surfaces 16 and 18 as reference surfaces. The burrs 12 and 14 cause problems in the calibration. For example, since burrs 14 would not be consistent from one tray to another, the height of surface 20 would also be less certain from one tray to another, and from one side of a tray 10 to another side of the tray. These distorted/inaccurate reference surfaces limit the ability of automatic machines to accurately pick and place components in the tray. The burrs 12 and/or 14 also cause an uncertainty in the height and straightness of a stack of trays 10, causing problems with automatic stack handling equipment, as well as problems with shipping containers and clips.
It is an advantage of this invention in that it provides a component tray that has improved reference surfaces.
It is a further advantage in this invention in that it adds bosses to a bottom surface of a tray so as to avoid uncertain contacts due to burrs.
It is a still further advantage of this invention in providing a tray that in use maximizes the accuracy of calibration of automated equipment.
It is another advantage of this invention in providing a tray that can be stacked accurately.
It is another advantage of this invention in providing a tray wherein ejector pin blemishes do not affect stacks and calibration.
In one embodiment of the present invention, a component tray includes a component housing portion having a plurality of component pockets, with each pocket opening to a component housing top surface. The tray has a contacting surface which makes contact with a mating surface upon which the tray is placed, such as an equipment handling base, or a contacting surface of another tray if trays are stacked. In one embodiment the contacting surface is on a flange surrounding the component housing portion defining a perimeter of the tray. A flange top surface in one embodiment is below the component housing top surface. A plurality of bosses extend downward from a flange bottom surface, and are designed to be positioned in dis-alignment with burrs caused by contact of mold ejector pins with flange bottom and top surfaces. The height of the bosses is designed to exceed the height of burrs, so as to avoid contact of the burrs with any surface upon which the tray is set. A bottom cavity in each tray provides clearance for a tray component housing of another tray upon which it is stacked.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a perspective top view of a prior art tray;
FIG. 1B is a perspective bottom view of the prior art tray of FIG. 1A;
FIG. 2A is a perspective top view of a tray according to the present invention;
FIG. 2B is a perspective bottom view of a tray according to the present invention.
FIG. 3A is a top perspective view of two trays of the present invention in position to be stacked;
FIG. 3B is a bottom perspective view of the trays of FIG. 3A;
FIG. 4 is a planar view of a tray illustrating more clearly the principle of the present invention;
FIG. 5 shows three trays stacked; and
FIG. 6 illustrates using bosses attached to a base to determine an accurate reference surface for picking and placing components in tray pockets.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
While the present invention will be described herein with reference to particular embodiments thereof, a latitude of modifications, various changes and substitutions are intended, and it will be appreciated that in some instances some features of the invention will be employed without a corresponding use of other features without departing from the spirit and scope of the invention as described with respect to the preferred embodiments set forth herein.
Referring now to FIGS. 2A and 2B, a component tray 22 is shown that has been formed in a mold. The tray 22 has a component housing portion 24 containing a plurality of component pockets 26 opening to top surface 28. A flange 30 extends around the housing portion 24, defining the perimeter of the tray 22. The flange 30 has a flange top surface 32, and a bottom surface 34 shown in FIG. 2B. The flange alternatively can be of other configurations, for example the flange could extend less than completely around the housing, or could be in segments, such as only on two opposite sides of the housing. The flange top surface 32 can alternatively also be of different heights, including above, below or equal to the top surface 28 of the housing 24. FIG. 2A illustrates a particular embodiment wherein surface burrs/blemishes 36 are shown on the top surface 32 caused by mold ejector pins when the molded tray 22 is ejected from the mold. FIG. 2B is a bottom perspective view of the tray 22 of FIG. 2A, and also shows burrs/blemishes 38 formed as a result of the pressure of mold ejector pins on the flange bottom surface 34. Although FIGS. 2A and 2B show burrs on both the top and bottom flange surfaces, the spirit of the present invention also includes trays having burrs on just a top or bottom surface.
According to one embodiment of the present invention, the tray 22 has bosses 40 extending from the flange bottom surface 34 to a height that is high enough to prevent the burrs 38 from contacting a surface on which the tray is placed. More generally, the present invention includes bosses on any surface for preventing contact of burrs/blemishes with any surface. In one embodiment, the bosses are greater than twice an expected height of the burrs/blemishes so that when the trays are stacked, one on another, any burrs facing each other do not interfere with each other i.e. in the case of burrs on the flange bottom surface of an upper tray in a stack and any burrs on the flange top surface of a bottom tray. This is shown, and will be described more clearly in reference to FIG. 5. In this way, the bosses solve the problem of the burrs/ejector pin marks interfering in stacking and calibration operations. In the various figures, only a few of the bosses and burrs are labeled with numbers for ease of illustration. Generally, a boss is shown on the flange bottom surface 34 between every two burrs. The present invention, however, also includes other arrangements including fewer or greater numbers of bosses, and/or bosses of other configurations. The number of bosses required is only a sufficient number placed so as to assure tray stability when placed in contact with a mating surface.
FIGS. 3A and 3B illustrate two trays of the present invention placed one over the other as in preparation for stacking. FIG. 3A shows the fact that a plurality of trays 22 processed/molded by the same mold or molds of the same design, will have ejector pin marks/burrs 36 and/or 38 in alignment with each other as indicated by line 44 (FIG. 3A) when the trays 22 are placed in an aligned, stacked position as shown. FIG. 3B is a bottom view of the two trays of FIG. 3A, and shows bosses 40, designed as described above in one embodiment so as to have a height that is greater than twice the expected or actual height of the ejector pin marks/burrs 36 and 38 so that when the trays are stacked, the two burrs facing each other, one burr 36 on the flange top surface and one burr 38 on the flange bottom surface, do not touch each other. This can be seen clearly in reference to FIG. 5. In the case where burrs are only on the top or bottom, but not both, the required minimum height of the bosses need only be greater than the height of the burrs on the single surface.
Line 48 indicates that the bosses 40 of the two trays 22 are in alignment. According to the present invention, the bosses are positioned so as not to be in alignment with the ejector pin marks 36 or 38. Line 50 indicates the alignment of the ejector pin marks 38. Contact between the two trays is made by contact of the surfaces 52 of the bosses 40 with the flange top surface 32 (FIG. 3A). In the event that burrs are on both the top and bottom of the tray, the burrs 36 and 38 of one tray do not make contact with another tray when stacked because the height of the bosses 40 is more than the combined height of burrs 36 and 38.
A planar side view of a tray 54 is shown in FIG. 4 that is simplified for ease of illustration by showing fewer bosses and marks. The present invention, however, includes any number of burrs and bosses in any configuration wherein the bosses provide a contact surface and prevent the contact of burrs with surfaces on which the tray is placed. The tray 54 according to the present invention has a component pocket housing 56 with a plurality of component pockets similar to the tray 22 of FIGS. 2 and 3, but for ease of illustration are not shown in this figure. The housing 56 is surrounded by a tray flange 58, having a flange top surface 60 and a flange bottom surface 62, both surfaces being orthogonal to the view of FIG. 4. For illustration, three burrs/marks 64 are shown made by ejector pin contact with the flange top surface 60, and three ejector pin marks/burrs 66 are shown as made by ejector pin contact with the flange bottom surface 62. The marks 64 on the top surface 60 may be in alignment with the marks 66 on the bottom surface 62 as indicated by line 68. Other configurations wherein the burrs are not in alignment are also included in the present invention, wherein bosses are used to avoid contact of the burrs with surfaces. Four bosses 70 are shown extending from the flange bottom surface 62. The bosses 70 as shown and according to the present invention are not aligned with the burrs/marks 64 or 66. The height “h1” of the bosses 70 in one embodiment is greater than twice the anticipated or actual height “h2” of the burrs/marks. With this boss height, the bottom surfaces 72 of the bosses can therefore make contact with a surface on which the tray is set, including the flange top surface of another tray and prevent contact of the burrs on the flange bottom surface of a first tray making contact with a burr on the flange top surface of a second tray on which the first tray is stacked. This will be shown more clearly in FIG. 5. In another embodiment, the height of h1 of the bosses is simply greater than the height of the burrs 66 on the flange bottom surface, allowing the tray to be placed on a flat reference surface 73 without the burrs 66 touching the surface 73. As noted above, this boss height is also adequate if there are burrs on only the top or bottom, but not both surfaces.
According to a method of the present invention, the tray 54 is set on a base surface 73. The housing surface 75 can be accurately calibrated due to the accuracy and reproducibility of the contact between the boss reference surfaces 72 and the base 73. This is an improvement over the prior art trays wherein the burrs 66 would contact the surface 73. In automated equipment for example, the base 73 can be a part of the equipment. A tray according to the present invention allows accurate calibration of the surface 75 and thereby accurate calibration for handling the tray 54, and for picking and placing components in component pockets that open to the surface 75; for example component pockets 26 as shown in FIG. 2A.
FIG. 5 shows three trays 77 in a stacked arrangement. Note that each tray 77 generally has a bottom pocket 74 providing clearance for a component housing 76 of a tray upon which it is stacked. The bosses 70 are high enough to prohibit contact of the burrs with a surface, and as shown between the two opposing burrs 64 and 66, and therefore the bosses of an upper tray make contact with the flange top surface of the tray upon which it is set, and as a result provide an accurate stack. FIG. 5 also illustrates placing a stack of trays 79 on a base surface 81, which can be a surface for example of calibrated tray handling equipment. The accurate position of the trays as described above due to the bosses, allows accurate calibration of automated tray handling equipment.
FIG. 6 shows an alternate embodiment wherein bosses 78 are attached to a base 80, such as a part of automated equipment for tray handling and/or for picking and placing components in component pockets of a tray 82. Similar to the description above, the bosses 78 are designed to have a height greater than the height of otherwise interfering burrs 84 caused by pressure from ejector pins during a tray molding process. The embodiments described above all show bosses and burrs on flanges of trays. The present invention also includes as an alternate embodiment trays with burrs and bosses at other locations on trays. The present invention also includes bosses on trays of other configurations. For example, the tray may or may not have a flange, or the flange area could be of different heights in relation to the surface 75 of the housing 56 of FIG. 4. These and other combinations/configurations of trays using bosses to avoid contact of burrs and/or blemishes with surfaces are included in the spirit of the present invention. Although the above description describes in detail the use of bosses to avoid burrs caused by mold ejection pins from contacting a surface on which a tray is set, or contacting a surface of a second tray stacked upon a first tray, the present invention also includes the use of bosses as described above for avoiding contact of any other kind of surface burr/blemish with a surface. For example, a burr/blemish could be a raised logo or a part number formed on a surface.
While the present invention has been described herein with reference to particular embodiments thereof, a latitude of modifications, various changes and substitutions are intended in the foregoing disclosure, and it will be appreciated that in some instances some features of the invention will be employed without a corresponding use of other features without departing from the spirit and scope of the invention as set forth in the appended claims.