US20050077205A1

US20050077205A1 - Tray with flat bottom reference surface

Info

Publication number: US20050077205A1
Application number: US10/682,788
Authority: US
Inventors: James Pylant; Scott Bradley
Original assignee: Peak Plastic and Metal Products International Ltd
Current assignee: Peak Plastic and Metal Products International Ltd
Priority date: 2003-10-08
Filing date: 2003-10-08
Publication date: 2005-04-14
Also published as: WO2005036588A2; WO2005036588A8; WO2005036588A3

Abstract

A molded component tray includes a component housing portion having a plurality of component pockets. The tray has a flange around 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 flange bottom surface includes recessed areas positioned in alignment with mold ejector pins which may contact the flange bottom surface, and alternatively in alignment with mold ejector pin marks on the flange top surface. The depth of the recesses is greater than the height burrs left by the ejector pins, thereby leaving the tray bottom surface free of burrs caused by ejector pins. Alternatively, when one tray is stacked on top of another, the recesses in the bottom of an upper tray can be positioned to allow clearance for ejector pin marks on the top of the flange of a lower tray.

Description

RELATED APPLICATIONS

This application is related to U.S. Application entitled Bare Die Tray With Flat Datum Surface filed on the same date as this application, bearing attorney reference 0678100301344 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 pockets. 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 on 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 the burrs are not consistent from one tray to another, the height of surface 20 is 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 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.

SUMMARY

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 recessed areas for contact with mold ejector pins so as to avoid uncertain contacts due to burrs, and therefore provides a flat datum surface.
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 stacking of trays and calibration.
In one embodiment of the present invention, a molded component tray includes a component housing portion having a plurality of component pockets. The tray has a flange around 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 flange bottom surface includes recessed areas positioned in alignment with mold ejector pins which may contact the flange bottom surface, and alternatively in alignment with mold ejector pin marks on the flange top surface. The depth of the recesses is greater than the height of burrs left by the ejector pins, thereby leaving the tray bottom surface free of burrs caused by ejector pins. Alternatively, when one tray is stacked on top of another, the recesses in the bottom of an upper tray can be positioned to allow clearance for ejector pin marks on the top of the flange of a lower tray.

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 the tray of FIG. 2A according to the present invention;
FIG. 2C is an enlargened section view from FIG. 2B;
FIG. 3 shows two trays stacked, with recesses in the tray bottom flange surface; and
FIG. 4 shows two trays stacked, with recesses in the flange top surface.

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. The component pockets 26 are for holding small components, such as semiconductor devices. 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 shows burrs/blemishes 36, which may or may not occur on the surface 32. The burrs/blemishes 36 shown in FIG. 2A raised from the top surface 32 may be due to 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 pressure of mold ejector pins.
According to the present invention, recesses 40 are formed along the bottom surface 34 to be in alignment with the burrs/blemishes 36 and/or 38, which in a particular embodiment are caused by ejector pins used for removing the tray from a mold. For example, if the mold is designed for ejector pins to push on the bottom of a tray for the purpose of ejecting the tray from the mold, the recesses are configured to be in alignment with the ejector pins and at a diameter somewhat greater than the pins so that the pins make their mark on the bottom of the recesses 40. The depth of the recess need only be in excess of the height of the burr/mark 38 left by the ejector pins.
In the event that burrs exist on the top surface 32, such as ejector pins used to press on the top surface 32 of the tray, then the recesses 40 in the bottom surface are designed to provide corresponding clearance for the burrs 36 on the top surface, so as to allow a flat mating surface 32 for a tray bottom surface 34 in the event that the trays are stacked.
A recess 40 can therefor provide a recess bottom surface upon which to apply an ejector pin, or/and the recess 40 can serve to provide clearance for a burr/mark on a mating top surface when trays are stacked.
FIG. 2C is an enlargened section A taken from FIG. 2B to show recesses and burrs more clearly.
The recesses 40 of FIG. 2B are shown as an example of the concept of the present invention. The invention also includes recesses of other configurations and positions to allow clearance for burrs/blemishes in any mating surface that the tray may be set upon. For example, in the event that trays are stacked, a recess in surface 34 may be included to allow clearance for any raised mark in the surface 32 of a lower tray. A raised mark for example, could be caused by an ejector pin, or it could for example be a company symbol/logo or a part number, etc.
As a further alternate embodiment, one or more recesses can be placed in the top surface 32, to provide recess bottom surfaces for ejector pins that may be applied to the top surface 32, or as a recess to provide clearance for an ejector pin mark on a tray bottom surface when trays are stacked. It should be noted however, that placing a recess only on the top surface does not provide a flat reference surface on the bottom of a tray, which would be a problem for the bottom tray of a stack if there are marks on the bottom surface.
FIG. 3 is a cross sectional view of two trays 42 and 44 stacked one upon the other, and illustrates the use of recesses 46 to achieve a flat bottom reference surface 48, for example on tray 42 to sit on the top surface 50 of tray 44, and the flat bottom surface 48 on tray 44 to sit on a base surface 54. FIG. 3 shows how the recesses 46 provide clearance for burrs 56 on the top surface 50 of tray 44, as well as provide recess bottom surfaces 58 for the application where contact with ejector pins causes burrs 60.
FIG. 4 shows two trays 62 and 64 stacked, wherein the trays have recesses 66 in the top flange surface 68 to provide a recess bottom surface 70 for receiving ejector pins that leave a mark/burr 72.
The present invention also includes trays with recesses in both the top and bottom surfaces for providing clearance for any type of surface burrs/blemishes, such as ejector pin marks or raised lettering, logos, etc. in a mating 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.

Claims

1. A tray comprising:

a molded tray including

a component housing having a plurality of pockets for holding components; and

a tray surface having a plurality of recesses, each recess for recessing a burr on a bottom surface of said recess below said tray surface.

2. A tray as recited in claim 1 wherein said burr is caused by contact of a mold ejector pin with said bottom surface.

3. A tray as recited in claim 1 wherein said tray has a flange, and said tray surface includes a flange surface.

4. A tray as recited in claim 3 wherein said tray surface includes a flange top surface.

5. A tray as recited in claim 3 wherein said tray surface includes a flange bottom surface.

6. A tray comprising:

a tray for holding a plurality of semiconductor devices, said tray including

a component housing having a plurality of pockets for holding said semiconductor devices; and

a flange surrounding said housing, said flange having a flange surface with a plurality of recesses formed therein for providing clearance for a burr on a mating surface for contacting said flange surface.

7. A tray as recited in claim 6 wherein said flange surface is a flange bottom surface, and said mating surface is a flange top surface of a second tray upon which said tray is to be placed.

8. A tray as recited in claim 7 wherein said burr is caused by contact of a mold ejector pin with said flange top surface of said second tray.

9. A method of tray manufacture comprising:

forming a plurality of recesses in a tray for holding semiconductors devices using a mold; and

applying a mold ejector pin to a recess bottom surface of a said recess for ejecting said tray from said mold.

10. A method as recited in claim 9 wherein said tray includes a flange, and at least one of said recesses is in a flange top surface.

11. A method as recited in claim 10 wherein said tray includes a flange, and at least one of said recesses is in a flange bottom surface.