WO2005091352A1 - Packaging of microelectronic, optoelectronic and other devices - Google Patents

Abstract

A chip or the like is packaged by being sealed between first and second package elements. The package elements are created by impressing dispensing a liquid polymer into a mould cavity and impressing the chip, or another object of equivalent shape, into a polymer body by hot or cold embossing. The polymer body may comprise a liquid polymer dispensed into a mould cavity, the liquid polymer being cured by heat or radiation such as UV. Multiple chips may be enclosed in a single package.

Description

"Packaging of Microelectronic, Optoelectronic and Other Devices"

This invention relates to the packaging of devices such as microelectronic and optoelectronic devices, microfluidic devices and MEMS.

Conventional microelectronic packaging techniques include hermetic ceramic packages (e.g. multilayer and pressed ceramic packages) , metal can packages, and plastic packages. Typical plastic packaging methods include transfer moulding, in which plastic is injected into a mould cavity formed around the device. These conventional techniques tend to be complex, expensive and time-consuming.

Optoelectronic devices generally comprise a die including optical waveguides which have to be accurately aligned with optical fibres attached to the device for providing external optical connections to the device. Some of these devices also have additional electrical connections. This attached device is then mounted in an elaborate metal box. This is also a complex, expensive and time-consuming process. This manufacturing process is a low yielding process .

Similar considerations apply to microfluidic devices and MEMS.

Where a number of devices are required to be interconnected for the purposes of an end product, it is conventional for the devices to be individually packaged and for the individually packaged devices to be mounted on a printed circuit board or the like which provides the required connections between the devices.

The present invention seeks to provide improved packaging methods and improved packaged products.

The present invention provides a method of packaging a micro component, which component comprises a chip with one or more elongate connecting elements attached to and extending therefrom, the method comprising: (a) providing an object having the same physical dimensions as a predetermined working envelope of the chip to be packaged; (b) providing a body of a polymer whose physical characteristics can be altered by application of heat or exposure to radiation, the polymer body having a length and width greater than those of the chip; (c) forming an impression of part of the object in the polymer body by embossing the object into a surface of the body and applying heat or radiation, thereby forming a first packaging element; (d) removing the object from the first packaging element; (e) repeating steps (b) and (c) with the object reversed to form a second packaging element; and (f) securing a component to be packaged between the first and second packaging elements.

From another aspect, the invention provides a packaged micro component comprising a chip with one or more attached elongate connecting elements, the chip being surrounded by a package comprising first and second package elements, the first and second package elements being separately formed and integrated together around the chip.

Preferred features and advantages of the invention will be apparent from the following description and from the claims.

Embodiments of the present invention will now be described, by way of example only, with reference to the drawings, in which: Fig. 1 shows, in diagrammatic cross-sectional side view, a series of steps in forming a package in one embodiment of the invention; Fig. 2a is a similar view illustrating one step of an alternative embodiment; Fig. 2b is a perspective view of a package element produced in the alternative embodiment; Fig. 3a is a schematic perspective view of a component used in another embodiment of the invention; Fig. 3b illustrates a packaging element produced in this embodiment; and Fig. 3c shows the resulting packaged component of this embodiment.

Referring to Fig. 1, the method of this embodiment starts with the creation of a mould 10 (Step 1) , which comprises a body defining a mould cavity 12 open at a planar upper surface 14. The mould 10 may be a re-usable mould for example of metal or silicon; alternatively it may be a disposable mould which is itself formed by a moulding process such as injection moulding.

In Step 2, the mould cavity 12 is filled with a liquid or viscous flowable polymer 16. The polymer 16 is one which may be cured by heat or by radiation, preferably UV radiation. Suitable polymers are well known to those in the art and include a UV curable resin, epoxy, glue, adhesive, resist, silicone, acrylate or acrylic material.

A component 18 is then presented (Step 3) to the polymer-filled mould 10, and in Step 4 is embossed or pressed into the cured polymer. The embossing may be performed first and the polymer 16 then cured, or the component 18 may be embossed into the polymer 16 when it is in a partially cured condition.

Once the polymer is fully cured, the component 18 is removed from the cured polymer, and the cured polymer is removed from the mould 10 as a lower embossed package element 20 (Step 5) .

Steps 1-5 are then repeated, but with the component 18 inverted, to produce an upper package element 22 (see Step 6) .

The component 18 is then positioned between the upper and lower package elements 20,22 which are sealed together to form an encapsulated component 24.

The component 18 of the foregoing example comprises a microelectronic or optoelectronic chip 26 with attached electrical leads and/or optical fibres 28. As described, the same component 18 is used for embossing the upper and lower package elements 20,22 and then encapsulated between them. However, it is equally possible, and may be preferred, to use an object other than the chip which is to be encapsulated. For example, a chip of the same type which has failed tests of electrical or optical function may be used as a model or template to produce package elements for encapsulating healthy chips. Alternatively, the upper and lower package elements may be embossed using a tool or shim made specially for the purpose, and which has no electrical or optical circuitry.

In the preferred embodiment as described above, the mould cavity 12 has a length and width greater than those of the chip 26 by an amount chosen to provide a suitable encapsulation size, and the depth of the mould cavity is such that the leads/fibres 28 will sit on the planar upper surface.

The procedure is similar to cold embossing (in the case where the polymer is cured by radiation such as UV) or hot embossing (where the polymer is cured by . heat) and known apparatus as used in hot embossing and cold embossing may be used in carrying out the present invention.

The invention may also be used to package more than one chip in a single package. This is illustrated in Fig. 2. Fig. 2a shows a mould 30 having a mould cavity 32. The cavity 32 is filled with a liquid polymer 34 and a model 36 is embossed into the polymer surface. The model 36 comprises two parts 38 representing two chips, external leads or fibres 40, and interconnecting leads or fibres 42. (For ease of illustration only a single lead or fibre is shown in each location, but it will be understood that typically multiple leads or fibres are used.)

After curing, the polymer is removed to form a package element 44 as seen in Fig. 2b. The interconnecting lead or fibre 42 has formed a channel 46 which can be used to align separate leads or fibres from individual chips received in package element cavities 48. It will be understood that the channel 46 is shown exaggerated in size in Fig. 2.

In a modification of the foregoing embodiments, the step of dispensing a liquid or viscous polymer into a mould may be dispensed with. Instead, there is provided a block or body of a solid polymer which softens when heated sufficiently to allow the pattern object to be embossed into it, or which is sufficiently soft in its initial state to allow the pattern object to be embossed into it and then hardens under the influence of heat or radiation. "Solid" in this context is used to means non- flowable and may include materials which, at ambient temperatures, are initially resilient or plastic. The individual blocks could be pre-moulded or could, for example, be cut from a bar or reel of polymer material.

In the preferred embodiment described, heat or radiation is applied while embossing or impressing the object into the polymer. In some cases the properties of the polymer may be such that the uncured polymer can retain the embossed shape temporarily, allowing the application of heat or radiation to be done as a separate step after removing the object. The use of a process akin to hot or cold embossing allows additional features to be incorporated. As is well known, hot and cold embossing using known apparatus can produce highly accurate physical features down to nano scale. Fig. 3 shows one example of the use of this.

Fig. 3a shows a simplified representation of a device 50 which includes a chip 52 having electrical connecting leads 54. The chip 52 has areas 56 sensitive to analytes, typically liquids, applied thereto. The chip 50, or a model simulating it, is used as before to create first and second packaging elements one of which is seen at 60 in Fig. 3b. The packaging element 60 includes a cavity 62 for receiving the chip 52 and channels 64 corresponding to the leads 54. In addition, an embossing tool which is used to emboss the chip 52 into the polymer is also provided with means for forming channels 66. In the final packaged device as seen in Fig. 3c, the channels 66 form fluid conduits for communicating analytes to the chip 52.

It will be understood that, although described particularly with reference to microelectronic and optoelectronic circuits, the invention is also applicable to other micro devices fabricated in similar ways, such as microfluidic devices (in which case the leads/fibres may be wholly or partially substituted by fluid conduits) and micro electro- mechanical systems (MEMS) . In such applications, it may be appropriate to perform the embossing steps with an object which is not precisely the same shape as the chip which is eventually packaged, in order to provide one or more spaces in the immediate vicinity of the chip. For example, a MEMS may require an empty volume into which a moving part may extend as it moves. Therefore , the object used as the embossing model or tool may define a volume which is effectively a defined working envelope of the chip, i.e. the chip plus adjacent volumes.

It is also possible for the method to include one or more additional embossing steps in order to produce further features in the mating surfaces of the package elements. As is well known in the art, available embossing apparatus is capable of forming such features down to a nano scale.

Claims

1. A method of packaging a micro component, which component comprises a chip with one or more elongate connecting elements attached to and extending therefrom, the method comprising: (a) providing an object having the same physical dimensions as a predetermined working envelope of the chip to be packaged; (b) providing a body of a polymer whose physical characteristics can be altered by application of heat or exposure to radiation, the polymer body having a length and width greater than those of the chip; (c) forming an impression of part of the object in the polymer body by embossing the object into a surface of the body and applying heat or radiation, thereby forming a first packaging element; (d) removing the object from the first packaging element; (e) repeating steps (b) and (c) with the object reversed to form a second packaging element; and (f) securing a component to be packaged between the first and second packaging elements.

2. The method of claim 1, in which the polymer body is provided by the preliminary steps of: providing a mould having an open mould cavity with a length and width greater than those of the chip; and dispensing into the mould cavity a liquid or viscous polymer which is curable by heat or radiation.

3. The method of claim 2, in which the heat or radiation is applied to the polymer at the same time as said embossing takes place.

4. The method of claim 1, in which said polymer body is a solid body formed of a polymer which softens under application of heat to permit embossing.

5. A method according to any preceding claim, in which the object used to form the packaging elements is the component to be packaged.

6. A method according to any of claims 1 to 4, in which the object used to form the packaging elements is a component comprising a chip and attached connecting elements similar to the component to be packaged, but where the object is not itself packaged.

7. The method of claim 2, in which the depth of the mould cavity is such that the connecting elements attached to the chip rest, when the component is pressed into the surface of the liquid resin, on a planar upper surface of the mould adjacent the mould cavity.

8. The method of any of claims 1 to 3, in which the object is an object other than a microelectronic or optoelectronic component but having similar dimensions and surface topography to the chip to be packaged.

9. The method of any of claims 1 to 3, in which the object is an object other than a microelectronic or optoelectronic component but having dimensions equating to the chip to be packaged plus one or more predefined working spaces in the immediate vicinity of the chip.

10. The method of any preceding claim, in which the component to be packaged is a microelectronic or optoelectronic component and the connecting elements comprise electrical leads and/or optical fibres.

11. The method of any preceding claim, in which a plurality of objects, each having a shape corresponding to the working envelope of a component to be packaged, are impressed into a single polymer body, thereby to produce packaging elements for enclosing plural components within single package.

12. The method of any preceding claim, in which at least one of the embossing steps also forms physical features additional to the shape of the chip in the surface of the polymer body.

13. The method of claim 12, in which said physical features form fluidic channels in the respective packaging element.

1 . A packaged microelectronic, optoelectronic or microfluidic component or a MEMS produced by the method of any preceding claim.

15. A packaged micro component comprising a chip with one or more attached elongate connecting elements, the chip being surrounded by a package comprising first and second package elements, the first and second package elements being separately formed and integrated together around the chip-.

16. A component according to claim 15, in which said first and second package elements are formed by embossing.

17. A component according to claim 15 or claim 16, in which a plurality of chips are secured within a single pair of first and second package elements.

18. A component according to any of claims 15 to 17, in which the package has one or more fluidic channels communicating with the or each chip.