GB2150918A

GB2150918A - Packaging tubes for electronic components

Info

Publication number: GB2150918A
Application number: GB08332526A
Authority: GB
Inventors: F Flat A Yun Kai Lee; Stanley Kwok
Original assignee: Peak Plastic & Metal Prod
Current assignee: Peak Plastic & Metal Prod
Priority date: 1983-12-06
Filing date: 1983-12-06
Publication date: 1985-07-10
Also published as: GB2150918B; GB8332526D0

Abstract

An antistatic plastic packaging tube - notably for DIL-encapsulated electronic components - includes a transparent window 20 which is configured as a lens 22 to give a magnifying effect and so assist in reading any information printed on the electronic components' encapsulation. The tube is manufactured by extruding opaque antistatic and transparent materials from respective feed screws through an orifice to form a composite tube which is then formed to the required cross section in a die. <IMAGE>

Description

SPECIFICATION Packaging tubes for electronic components This invention relates to packaging tubes used for holding electronic components in transit and to a method of producing such tubes. In particular, although not exclusively, the invention is concerned with carrier tubes for components in dual-in-line (DIL) encapsulation.

In the electronics industry it is often necessary to pack and transport large numbers of components encapsulated in DIL encapsulation, the majority being integrated circuits (I.C.'s). DIL encapsulation consists of a fairly flat rectangular body in which the I.C. or other component(s) is encapsulated, with short connecting leading pins descending from the two longer sides of the encapsulation.

It is customary for the component type number, or other identifying information to be printed on the top face of the body, opposite the pins. It is also customary for component identifying information to be printed on other less common types of encapsulation.

To pack and transport these DIL encapsulated components there are currently provided hollow elongate carrier tubes which generally have a cross section which is substantially trapezoidal with an inward projection from the longer parallel side of the trapezium. The components are slid into the tube straddling this projection. Such packaging tubes may be required to have an antistatic property to protect the electronic components from possible damage by static electricity building up on the tube. This antistatic action can be provided by the incorporation of carbon black into the plastics material from which the tube is formed, but this renders the tube opaque.

Our co-pending U.K. application 83.10536 discloses packaging tubes formed from opaque plastic (pvc is used) and incorporating a clear plastics window which enables the components to be seen. The cross section of the tube is such that components cannot touch the window. In our co-pending application this is achieved by locating the window in an outward projection beyond adjacent wall regions. In U.S. patent 4327832, components are prevented from touching a window by means of inward projections at either side of the window.

The provision of windows in packaging tubes for other encapsulations is also known from U.K. patent application 2081226A.

These prior disclosures have provided windows which were mainly flat, and were of uniform thickness.

According to the present invention, a window in a plastic packaging tube for electronic components is configured as a lens to give a magnifying effect and so assist in reading any information printed on the electronic components' encapsulation.

Suitably the lens is formed by configuring the window with at least one convex arcuate surface, arranged so that the lens will face towards the printed area of electronic components when these are packed in the tube. Preferably opposite surfaces of the window are both convex to provide a biconvex barrel lens. It is appropriate for such arcuate surface(s) to be at least approximately symmetrical about a plane which will be normal to the printed area on the components' encapsulation.

When the packaging tube is for DIL encapsulated components, and incorporates an internal projection, it is appropriate for the lens to face substantially towards this, so that when components straddle and rest on the internal projection, the lens will face their printed area.

It is desirable to prevent contact between components and the window, and preferred forms of the invention provide a packaging tube for electronic components of predetermined form, the tube comprising opaque antistatic material and having at least one window of light transmitting material providing along the length of the tube means for seeing electronic components in the tube, the shape and size of the tube correlative to said electronic components of predetermined form being such as to prevent contact between said components and said light transmitting material when said components are packed inside the tube, characterised in that the window has at least one arcuate surface, so that the window is a lens arranged to face towards a surface of the said electronic components of predetermined form when packed inside the tube.

In a preferred arrangement the window is in an outward projection from the packaging tube. A preferred form of tube for DIL encapsulated components is a hollow elongate tube of substantially quadrilateral overall cross-section with two opposed parallel sides, there being an identation along the length of the tube in a first said parallel side to provide an internal projection to be straddled by electronic components in the tube. An outward projection incorporating the said window is then preferably provided in the second said parallel side. The overall cross-section may be trapezoid, with the first said parallel side being longer than the said second. An alternative quadrilateral overall cross-section is rectangular.

The invention also embraces a method of making a packaging tube, comprising the steps of forming streams of molten opaque antistatic material and light transmitting material, and advancing these streams by means of respective feed screws, feeding the streams to different parts of a passage leading to an extrusion orifice, letting them merge in the passage and extruding them together as a tube with a window having relatively thicker and thinner parts which form a lens, or are subsequently deformed to form a lens.

The tube can conceivably be extruded in its required final shape, but it is preferred to extrude it with a relatively simple cross-section, and shape this further while it is still soft, notably by passage through a die.

We prefer to use PVC as the tube material, incorporating carbon black to provide the antistatic property, because of the greater rigidity of PVC which enables the thickness of the tube body to be reduced as compared with the thickness necessary when polystyrene or polypropylene is used.

Our co-pending U.K. application 83.10536 describes the possibility of including a second window in the tube. The packaging tubes of this invention may incorporate an additional window if desired which may be flat or a lens. The disclosure of the above co-pending application is incorporated herein by reference. An additional window can be provided by extruding an additional stream of light transmitting material, as disclosed in that application, and if it is to be a lens the additional window should be extruded with relatively thicker and thinner regions as for the first window.

Embodiments of the present invention, given by way of example, will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of one end portion of a packaging tube; Figure 2 is a somewhat diagrammatic cross-section of the tube of Figure 1; Figures 3 and 4showfurther possible cross-sections for tubes embodying the present invention; Figure 5 is a sectional view of an extruder head used in producing the packaging tubes of Figures 1 and 2; Figure 6 is a sectional view along the line I-I of the extruder head shown in Figure 5; Figure 7 is an end view of the extruder head die shown in Figure 6 looking in the direction of arrow X; Figure 8 shows a die for producing packaging tubes in association with the extruder head shown in Figure 5; and Figure 9 is a sectional view on line Il-Il of the die shown in Figure 8.

Referring first to Figure 1 of the drawings, the packaging tube shown is an elongate tube formed of extruded plastic. The tube has a uniform cross-section and as can be seen from Figure 2 this cross-section comprises a side 2, shown at the top, mutually includin sides 4,6, a side 8 parallel to the side 2, but longer, and a projection 10 of rectangular section which extends into the tube from the longer parallel side 8. The sides 2,4, 6,8, define substantially a trapezium shape. The tube is used to carry DIL encapsulated integrated circuits 12 (Figure 2). These are packed into the tubes straddling the projection 10 so that the body 14 of the encapsulation rests on the projection 10 and the connecting pins 16 lie at each side of it. After filling, the integrated circuits are retained in the packaging tubes by pins inserted through holes punched at each end of the tube, e.g. as at 17.

The tube shown in Figures 1 and 2 is primarily formed from rigid PVC which incorporates carbon black thus giving the tube an antistatic property but at the same time rendering it opaque. This opaque PVC is shown shaded in Figure 2 and forms the margins 18 ofthe top wall, the base 8, the inward projection 10 and the inclined walls 4, 6. Thus these are a single-wall, conductive, carbonized part.

The central portion of the top 2 is an outward projection 20 formed of PVC from which the carbon black is absent, so that the PVC material is clear. This is shown without shading in Figure 2. It provides a transparent, non-conductive windowthrough which integrated circuits in the packaging tube can be seen. Across almost the entire top of the projection the window has arcuate upper and lower surfaces, providing a biconvex barrel lens 22. identifying information printed onto the top surface 24 of the components 12 can be viewed through this lens 22, which faces the components' top surfaces 24. Because of the lens the information is seen enlarged in the direction transverse to the long axis of the components, and this gives an aid to reading it.

The projection 20 has short sides 26 and these merge tangentially into the margins 18 at the top of the tube. Because the transparent plastic is confined to the projection 20, the encapsulated components 12 in the tube cannot touch the transparent plastic. They are held away from it by the inside faces ofthe margins 18. A further feature of this tube cross section is that the tubes will stack with the projection 20 of one fitting into the recessed area 9 (at the base of the projection 10) of another.

This packaging tube can be extruded from PVC with carbon black as the anti-static material, or it can be made from the more conventional materials polystyrene or polypropylene as alternatives to PVC.

Figures 3 and 4 show further possible cross sections which have a generally similar shape to that of Figure 2. In each case anti-static material is shown shaded while window material is shown without shading. The anti-static material can in each case be rigid PVC incorporating carbon black.

In Figure 3 small inward projections 30 of opaque plastic are provided at each side of the window, and these hold components away from the transparent material of the window. In Figure 4 the lens 22 is at the same level as the margins 18, although of course it extends above and below the margins 18 because of its greater thickness. Components are held away from the inside face of the lens 22 by the inward projections 30 which are provided at each side of the lens 22. They are dimensioned such that their extremities 32 lie slightly further into the tube than the centre of the inside are 34 of the lens, and consequently components 12 touch these extremities of the inward projections before they can reach the non-conductive lens 22.

Figures 5 to 7 show apparatusforforming the tube of Figures 1 and 2. This apparatus has two main screws for extruding plastics material. The screw 41 is for clear PVC, the screw 42 is for opaque PVC incorporating carbon black as conductive antistatic material.

These two different plastics material are advanced along respective tubes 43,44 within which the screws 41,42 operate to deliver streams of each material in a molten state. The tube 44 delivers directly into a prolongation of it 46 which is of the same diameter. Within this prolongation there is a central mandrel 48 supported on a web 50, while on the opposite side of the mandrel to this web there is a tube 52 which is connected to the tube 43 by a duct 54 as shown. The mandrel incorporates an air vent 56.

The downstream part of the mandrel 48 is surrounded by an extrusion die 58, held in place by a large forged nut 60. The die and mandrel together define an annular extrusion orifice. The die may be heated.

Molten opaque plastic is driven forward by the screw 42 from the tube 44 into the prolongation 46. Molten clear plastic is driven by the screw 41 through the duct 54 and out of the tube 52 to form a clear stream withir the stream of opaque plastic. The streams of molten plastic merge without mixing and are extruded together through the orifice as a circular tube with a transparent sector 61 and a much larger opaque sector 62 as shown by Figure 7. The size of the tube 52 and the feed rates of the two screws 41, 42 are arranged so as to give sectors 61,62 of the desired size.

Although this detail is not shown in the general view provided by Figure 5, the extrusion orifice, and preferably also at least the outer part of the duct 52 are shaped as shown by Figures 6 and 7. Consequently, in the extruded tube the clear sector 61 has a central thickened region 64 which is almost circular and projects both out of and into the extruded tube. It has thinner regions 66 at either side which have the same thickness as the uniform thickness of the opaque sector 62.

The circular tube 67 produced by the apparatus of Figures 5 to 7 is then formed to the shape required by a die as shown in Figures 8 and 9.

The tubular extrusion is fed into the die 70 while it is still hot enough to be soft, and within the die it is deformed to the final tube shape 68. The die 70 is cooled with water which passes through tubes 72.

Preferably the water is supplied at a temperature of from 3 to 70C. A vacuum or partial vacuum is connected to tubes 74 to assist in forming the final tube shape 68. As shown by the cross-sectional view in Figure 9, this subatmospheric pressure applied via tubes 74 is used to suck the tube against the sides and particularly the edges of the die 70. The tubes 74 are connected to the die cavity 75 by narrow passages 76 which enter the die cavity particularly at positions along the edges of the die cavity.

Within the die 70 the thickened region 64 of the extruded tube spreads laterally somewhat to form the required shape of the lens 22.

In the extrusion apparatus of Figure 5 the relative feed rates of the two streams of molten plastic are appropriately controlled so as to give an appropriately small width to the transparent sector 61 of the extruded tube 67, which in turn has the resu It that the transparent material is confined within the projection 20 of the final tube.

The cavity 75 of the die 70 should of course have a shape appropriate to the tube shape being made. As stated the shape shown is that for the tube of Figures 1 and 2.

A conceivable alternative to the use of the die 70 would be for the molten plastic to be extruded directly into the final cross section through an extrusion die of appropriate shape.

For all of the tubes described above the antistatic PVC containing carbon black can for example be formed by compounding the following materials in the proportions by weight stated: PVC powder 67% Carbon Black 30% Stabilizer 1.5% Lubricant 0.5% Processing Aid 1% The carbon black used must of course be conductive so that no static electricity can accumulate on the parts of the surface of the tube formed from it.

The general thickness of the tube walls, i.e. the thickness of the opaque walls, preferably lies between 0.014 and 0.060 inches, with a greater thickness for the thickest part of the lens. (wall thicknesses are somewhat exaggerated in the drawings).

Claims

1. A plastic packaging tube for electronic components, having a window for viewing components contained in the tube, characterised in that said window is configured to provide a lens therein to magnify the view of a region of said components.

2. A packaging tube according to claim 1 wherein the window has at least one convex arcuate surface.

3. A packaging tube according to claim 2 wherein opposite surfaces of the window are both convex.

4. A packaging tube according to any one of claims 1 to 3 wherein the window is elongate and the lens is a barrel lens extending along the length of the elongate window.

5. A packaging tube for electronic components of predetermined form, the tube comprising opaque antistatic material and having at least one window of light transmitting material providing along the length of the tube means for seeing electronic components in the tu be, the shape and size of the tube correlative to said electronic components of predetermined form being such as to prevent contact between said components and said light transmitting material when said components are packed inside the tube, characterised in that the window has at least one arcuate surface, so that the window provides a lense arranged to face towards a surface of the said electronic components of predetermined form when packed inside the tube.

6. A packaging tube according to any one of the preceding claims having an elongate internal projection to be straddled by components with DIL encapsulation, wherein the said lense faces substantially towards said projection.

7. A packaging tube according to any one of the preceding claims wherein the window is in an outward projection from the remainder of the packaging tube.

8. A packaging tube according to any one of the preceding claims for DIL encapsulated components, which tube is a hollow elongate tube of substantially quadrilateral overall cross-section with two opposed parallel sides, there being an indentation along the length of the tube in a first said parallel side to provide an internal projection to be straddled by electronic components in the tube, with the said window being provided in the second said parallel side.

9. A packaging tube according to any one of the preceding claims, made from pvc and incorporating carbon black to give antistatic ron-window areas.

10. A method of making a packaging tube according to any one of the preceding claims comprising the steps of forming streams of molten opaque antistatic material and light transmitting material, and advancing these streams by means of respective feed screws, feeding the streams to different parts of a passage leading to an extrusion orifice, wetting them merge in the passage and extruding them together as a tube with a window which is so shaped as to provide a lense or which is subsequently deformed to provide a lens.

11. A method according to claim 10 wherein the tube is initially extruded in a shape other than its final shape, with the window having relatively thicker and thinner parts, the extruded tube thereafter being deformed to the required final shape during which deformation the window is deformed to the required lens configuration.

12. A plastic packaging tube substantially as any described herein with reference to any of Figures 1 to 4 of the drawings.

13. A method of making a packaging tube substantially as herein described with reference to the drawings.