GB2499792A

GB2499792A - Electronic device comprising an electronic die, a substrate integrated waveguide (SIW) and a flip-chip ball grid array package

Info

Publication number: GB2499792A
Application number: GB1203405.4A
Authority: GB
Inventors: Herve Merlet; Philippe Le Bars
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2012-02-28
Filing date: 2012-02-28
Publication date: 2013-09-04
Anticipated expiration: 2032-02-28
Also published as: GB2499792B; GB201203405D0

Abstract

An electronic device comprises an electronic die 110 such as a power amplifier mounted via conductive bumps 114, 114', 114" on a dielectric substrate 112, and a waveguide 111 integrated in the dielectric substrate 112. It comprises a conductive projection 120 extending in the substrate integrated waveguide 111 and electrically connected to the electronic die 110 through at least one conductive bump 114'. The conductive projection may be a blind metalized hole extending into the dielectric of the substrate. In addition, the electronic device may have several conductive bumps 114 surrounding the conductive projection which are electrically connected to the top 117 and/or bottom 118 metal plate associated with the substrate integrated waveguide. The substrate integrated waveguide may have at the input end 120 the conductive projection 120 and at the other end an antenna lens 113. The electronic device may be used to provide a low-loss transition between the electrical output of a power amplifier and the electromagnetic field associated with the microwave antenna lens 113. The device may typically operate in the 50-70GHz region.

Description

1

Electronic device comprising an electronic die and a substrate integrated waveguide, and flip-chip ball grid array package

5 The present invention concerns an electronic device comprising an electronic die and a substrate integrated waveguide SIW.

It also concerns a flip-chip ball grid array comprising such an electronic device.

As a general way, the present invention concerns the connection 10 between an electronic die or integrated circuit chip and an electromagnetic waveguide.

The field of the invention is the interconnection between a radiofrequency die and an antenna, and also covers the field of transmission between several electronics components.

15 Communication devices are increasingly numerous today and require ever greater quality of service. Indeed, such devices meet a growing need on the part of users for reliable systems with high recording capacity, that are user friendly and offer high image quality. These may be for example digital cameras or high-definition digital camcorders including hand-held cameras or shoulder cameras. 20 When images (for example video images or still pictures) are being viewed on a display device such as an HD (high-definition) television set for example, the data bit rates brought into play for the transmission of data between the imaging device and the display devices are very high, in the range of some gigabits per second, owing to the nature and very high resolution of the information 25 transmitted. This is also the case when data are transmitted between the imaging device and a storage device.

Thus, for example, in order to prevent any loss of quality between a digital camera or a DVD-Blue-Ray player and an HD television set when viewing images, the use of a digital wire link such as an HDMI (high-definition multimedia

2

interface) cable may prove to be necessary because such a cable transfers high-definition non-compressed multimedia data.

However, establishing a wire link in order to set up a connection between a camera and a television set is not always easy.

5 One known approach to overcoming these drawbacks lies in setting up a wireless connection between the television set and the camera, providing a degree of simplicity as regards the installation of the hardware for the user. Achieving this simplicity of implementation calls for wireless connectivity means making it possible to support data bit rates of the order of 5 gigabits per second. 10 Current Wi-Fi systems work in the 2.4 GHz and 5 GHz radio bands and do not enable such bit rates to be attained. It would therefore seem to be necessary to use communications systems in a radio band of higher frequencies to obtain bit rates of this order, for example the radio band around 60 GHz.

Using an extensive bandwidth, 60 GHz radio communications systems 15 are particularly well suited to transmitting data at very high bit rates, especially high-definition audio/video type data. The range of such communications systems is therefore of the order of some meters.

Furthermore, in this carrier frequency band, the attenuation of the radio signal in air is great, due especially to the presence of water and oxygen molecules 20 in the air.

In practice, in order to obtain high radio communications quality (i.e. communications with a low bit error rate) and to obtain sufficient radio range between two devices (for example a camera and a television set) using a radio band of this kind without having to transmit at unauthorized power levels, the 25 above-mentioned physical characteristics make it necessary for these devices to have directionally (or selectively) configured antennas with positive gain enabling line of sight (LOS) transmission of data.

More particularly, antennas of this type, known as "smart antennas" or "programmable antennas" are used to reach the distances required by the audio 30 and video applications between the camera and the television set.

3

A smart antenna is formed by a network of radiating elements distributed on a given support. To cover n directions, n radiating elements are necessary with their feeder. The huge number of fed lines of radiating elements makes difficult the realization in respect of the signal phase, amplitude, etc..., and 5 in term of cost, miniaturization and performances.

To feed the radiating elements, substrate Integrated Waveguide (SIW) is a technology for guiding electromagnetic waves adapted for very short wavelengths (corresponding to the 60 GHz frequency band) in term of integration and miniaturization. In the context of the design of an antenna based on a 10 Luneburg lens, SIW technology is typically used for transporting electromagnetic waves out of a MMIC (Monolithic Microwave Integrated Circuit) generating the waves.

In its principle, the SIW comprises a dielectric substrate, such as a printed circuit board. Metal plates cover the top and bottom faces of the dielectric 15 substrate. A channel through the dielectric substrate is defined by plating the sides of the dielectric substrate or by providing two rows of spaced-apart plated vias, or posts.

The SIW are used to link the RF electronic components such as RF-IC or Flip-Chip or MMIC to an antenna element.

20 In an IEEE paper document "Cost-Effective 60-GHz Antenna Package with End-Fire Radiation for Wireless File-Transfer System", IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 58, NO. 12, DECEMBER 2010, Ryosuke Suga, Member, IEEE, Hiroshi Nakano, Yasutake Hirachi, Life Member, IEEE, Jiro Hirokawa, Senior Member, IEEE, and Makoto Ando, Fellow, 25 IEEE, a cost-effective antenna package was proposed providing the end-fire radiation from the open-ended post-wall waveguide built into the side of the package. However, the transition described in this document comprises wire bonding between an electronic die and a micro-strip line, then between the micro-strip line and a Substrate Integrated Waveguide SIW.

4

In the milli-wave domain, at 60GHz and above, these technologies to connect one electronic die to one antenna have some limitations. Even with an industrial process, it is very difficult to perfectly control the wire bond length, the wire bond position or the wire bond soldering.

5 The length of the wire bond creates parasitic factors (resistance,

inductance, capacitance) changing the impedance and thus the adaptation. This variation in the adaptation is detrimental to the return loss parameters (S11), but also deteriorates the transmission yield between the IC die and the antenna (or other electronics components).

10 Moreover, at each different implementation of the electronic die, the adaption has to be fine-tuned once again.

As a general rule, each transition between the electric field and the electromagnetic field, comprising several interconnections, creates losses in the signal quality, and losses of power.

15 The invention aims to mitigate at least one of the foregoing drawbacks.

The present invention is directed to providing an electrical and electromagnetic transition solution and to forming a transition between an IC die and a Substrate Integrated Waveguide SIW which is cost effective and contributes at the miniaturization of an electronic device, without jeopardizing quality.

20 To that end, according to a first aspect, the present invention concerns an electronic device comprising an electronic die mounted via conductive bumps on a dielectric substrate, and a waveguide integrated in said dielectric substrate.

According to the invention, the electronic device comprises a conductive projection electrically connected to said electronic die through at least one

25 conductive bump and extending in said substrate integrated waveguide.

Thus, the transition between an electronic device and a substrate integrated waveguide is formed directly by the conductive projection, adapted to convert electrical signals received from the electronic die into electromagnetic signals radiated in the substrate integrated waveguide.

30 By using only a conductive projection, the transition between the electric

5

domain and the electromagnetic domain is performed with a good adaptation of impedance.

Thus, the size and shape of the conductive projection, and for example the diameter and the length of a cylindrical projection, can be determined to have a 5 good impedance adaptation with the output or input of the electronic die and to obtain a good transfer of the electrical power into an electromagnetic power.

Moreover, the conductive projection is easy to assemble with the electronic die through a conductive bump. This kind of connection allows a minimum of losses in the transition between the electronic die and the substrate 10 integrated waveguide.

In order to expand the dimensions of the conductive projection and thus facilitate manufacturing, the conductive projection is connected to several conductive bumps of said electronic die.

According to a feature, the conductive projection is soldered to at least 15 one conductive bump.

In practise, said conductive projection is a blind metalized hole extending in the dielectric substrate.

In order to improve the transition between the electronic die and the substrate integrated waveguide, the conductive projection is connected to a power 20 amplifier integrated in said electronic die.

According to another feature, several conductive bumps surrounding said conductive projection are electrically connected to a top metal plate and/or a bottom metal plate constituting respectively a top face and/or a bottom face of said substrate integrated waveguide.

25 Therefore, the conductive bumps surrounding the conductive projection are at the ground potential corresponding to the potential of the conductive faces defining the waveguide in the dielectric substrate.

In order to avoid electrical coupling between the conductive projection and the ground, an insulated area is provided around said conductive projection. 30 In a practical way, the substrate integrated waveguide comprises one

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input end receiving said conductive projection and one output end connected to a lens of an antenna.

The electronic device is well adapted for transporting electromagnetic waves out from an electronic die to an antenna comprising a lens.

5 This kind of electronic device with this transition contributes to the miniaturisation of the electronic device.

According to a second aspect, the present invention concern a flip-chip ball grid array package, comprising at least one electronic die mounted via conductive bumps on a dielectric substrate, and a waveguide integrated in said

10 dielectric substrate.

According to the invention, a conductive projection is electrically connected to said at least one electronic die through at least one conductive bump and extends in said substrate integrated waveguide.

The flip-chip ball grid array package has features and advantages that

15 are similar to those described above in relation to the electronic device.

In a specific application, adapted to interconnect two electronic dies, flip-chip ball grid array package comprises two electronic dies mounted via conductive bumps on a dielectric substrate, and at least one waveguide integrated in the dielectric substrate.

20 Two conductive projections extend in the at least one substrate integrated waveguide and are respectfully electrically connected to said two electronic dies through at least one conductive bump.

Other particularities and advantages of the invention will also emerge from the following description.

25 In the accompanying drawings, given by way of non-limiting examples:

- Figure 1 is a cross section view of a flip-chip ball grid array package according to a first embodiment of the invention;

- Figure 2 is a schematic top view of the flip-chip ball grid array package shown in Figure 1;

30 - Figure 3 is a schematic top view of a flip-chip ball grid array package

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according to another configuration of the first embodiment;

- Figure 4 is a schematic top view of a flip-chip ball grid array package according to a second embodiment of the invention;

- Figure 5 is a perspective view of a real implementation of an 5 electronic device according to an embodiment of the invention;

- Figure 6 is a curve illustrating the S11 parameter representing the return loss in dB of the implementation shown in Figure 5;

- Figure 7 is a cross section view of a flip-chip ball grid array package according to a third embodiment of the invention; and

10 - Figure 8 is a schematic top view of the flip-chip ball grid array package shown in Figure 7.

A first embodiment of a flip-chip ball grid array package will be described here-below as represented in Figure 1.

In this embodiment, by way of a purely illustrative example, this 15 application concerns an RF module comprising one electronic die 110, a waveguide 111 integrated in a dielectric substrate 112 and a dielectric lens 113 of an antenna.

Thus, Figure 1 illustrates an embodiment to feed an antenna based on a dielectric lens 113 by a high frequency signal transported by the electromagnetic 20 waveguide 111.

In this embodiment, the electronic die is a RF-IC die mounted on the dielectric substrate 112.

In a flip-chip ball grid array package or flip-chip BGA package, the term "flip-chip" refers to an electronic component or semiconductor device that can be 25 mounted directly onto a dielectric substrate in a "face-down" manner.

Electrical connection is achieved through conductive bumps 114 built on the surface of the electronic die 110.

During mounting, the electronic die 110 or chip is flipped on the dielectric substrate 112, with the conductive bumps 114 being precisely positioned 30 on their target location.

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The conductive bumps 114 serve various functions:

- to provide an electrical connection between the electronic die 110 (or chip 110) and the dielectric substrate 112;

- to provide thermal conduction from the chip 110 to the dielectric 5 substrate, thereby helping dissipate heat from the chip;

- to act as spacer for preventing electrical shorts between the electronic die or chip circuit and the dielectric substrate circuit; and

- to provide mechanical support to the electronic die 110.

There are many known processes for mounting an electronic die 110 via 10 conductive bumps 114 on the dielectric substrate 112, which will not be described in detail below.

In summary, an assembly process comprises a step of depositing solder at suitable locations on the electronic die and a step of subjecting the electronic die mounted on the dielectric substrate to a temperature sufficient to melt the solder 15 and form the interconnection via conductive bumps.

Next this electric device is mounted via several balls 115 on the application electronic board or the Printed Circuit Board PCB 116.

Such a PCB 116 designed for a specific application links all the necessary components like resistors, capacitors, inductors and other integrated 20 circuits.

These components are located on the top side and on the bottom side of the PCB 116.

The die bumps 114 are disposed under the electronic die 110 as a matrix of die bumps 114 with a regular pitch p between the die bumps 114. The 25 balls 115 in the Ball Grid Array are also located as a matrix of balls 115 with a defined pitch P.

The pitch p of the die bumps 114 is equal for example to 150 pm and the pitch P of the balls 115 in the BGA is equal to 500 pm.

These values are just indicative and not limitative.

30 In the embodiment shown in Figure 1, the high frequency signal is

9

transported by an electromagnetic waveguide to an antenna based on the dielectric lens 113.

A part 112A of the dielectric substrate 112 is kept for the low frequency signal of the electronic die 110 as usual.

5 Another part 112B of the dielectric substrate 112 is dedicated at the high frequency signal.

A SIW 111 is integrated in this said another part 112B to transport an electromagnetic signal to illuminate the lens 113 constituting the antenna.

Thus, the dielectric substrate 112 comprises a lens mounting area, 10 which corresponds to an output end 111 b of the SIW 111, for feeding the lens 113 with an electromagnetic signal.

For example, the dielectric material of the substrate 112 has a permittivity value of 2.94 and low loss performance.

The SIW 111 is defined by two metal plates, a top metal plate 117 and a 15 bottom metal plate 118 extending respectively on two opposite sides of the dielectric substrate 112.

The end wall and the lateral sides of the SIW 111 are in this embodiment made by traversing posts 119 (see also Figure 2).

The transition between the electronic die 110 and the SIW 111 is 20 constituted of a conductive projection 120 extending in the SIW 111 and electrically connected to the electronic die 110.

This conductive projection 120 thus constitutes a radiating element adapted to transfer electrical power into electromagnetic power in the SIW 111.

The conductive projection 120 extends at an end of the SIW 111, 25 constituting an input end 111a opposite to the output end 111b.

In this embodiment, as clearly shown also in Figure 2, the conductive projection 120 is electrically connected to the electronic die 110 through one conductive bump 114'.

Thus, the output or the input of the electronic die 110 is directly 30 connected to the SIW 111 with a conductive bump 114' and a coaxial probe

10

provided by the conductive projection 120 integrated in the dielectric substrate 112.

Consequently, there is only one connection between the electronic die 110 and the lens 113 of the antenna.

The conductive projection 120 is made for example of a blind metalized 5 hole (or post or so-called blind via) into the dielectric substrate 112.

Its shape and size are determined to provide good impedance adaptation with the output or input of the electronic die 110 and to provide good transfer of the electrical power into electromagnetic power.

For example, the conductive projection 120 can be connected to a 10 power amplifier (not shown) integrated in the electronic die 110.

Depending on the size, the diameter and the length of the conductive projection 120, the die input or output impedance has to be equal to the equivalent impedance of the conductive projection 120. This aim is achieved by using equivalent usual components integrated on the die, as capacitors, inductors, 15 resistors.

These usual components are for example formed in the integrated circuit technology by metal strips (for inductors or resistors) or by pads (for capacitors).

The other conductive bumps 114 not linked to the conductive projection 20 120 are connected to other signals delivered by the electronic die 110.

The conductive bumps 114" around the conductive bump 114' connected to the conductive projection 120 are at ground potential (referred to as "G" in Figure 1).

In this arrangement of conductive bumps 114, the conductive bumps 25 114" around the conductive bump 114' connected to the conductive projection 120 are located in the matrix at the points adjacent to the conductive bump 114' connected to the conductive projection 120.

The ground is the potential of the top metal plate 117 and the bottom metal plate 118 constituting the SIW 111, together with the traversing posts 119 30 constituting the end and the side wall of the SIW 111.

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The lens 113 comprises a shield 113a which is also electrically linked to the ground by the top and the bottom metal plates 116, 117.

Figure 2 is the top view of this particular embodiment with the BGA substrate 112, the electronic die 110 and the lens 113 without the shield 113a to 5 better see the SIW 111.

The conductive bumps 114, 114', 114" and the traversing posts 119 are shown by representing the parts above as transparent.

In this embodiment, the conductive bumps 114" connected to ground potential are also aligned with the traversing posts 119.

10 In another embodiment, as shown in Figure 3, the conductive bumps

114" connected to ground potential are not aligned with the traversing posts 119 defining the end wall and the lateral sides of the SIW 111.

Moreover, in this embodiment, the conductive projection 120 is connected to several connected bumps 114' of said electronic die 111.

15 Thanks to this feature, the size, and for example the diameter, of the conductive projection 120 can be expanded, in order to facilitate the industrial process for forming the blind metalized hole.

In this embodiment, for example, the conductive projection 120 is ^ connected to four conductive bumps 114'.

20 In a practical way, the conductive projection 120 is soldered to at least one conductive bump 114'.

Consequently, the conductive bumps 114' can be connected to the conductive projection 120 during the assembly process of the electronic die 110 and the dielectric substrate 112 as disclosed previously.

25 In order to avoid electrical coupling with ground potential of the conductive projection 120 connected to the conductive bumps 114', an insulated area 121 is provided around the conductive projection 120.

The insulated area is provided for example by chemical etching when using the PCB technology. The metal between the post constituting the conductive

30 projection 120 and the top metal plate 117 is removed to form an insulated area

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121 around the conductive projection 120.

For example, the insulated area 121 is an insulator ring as shown in figure 2.

The internal diameter of the insulator ring 121 is for example equal to 5 200 pm and the external diameter is for example equal to 400 pm.

In the embodiments disclosed in Figures 2 and 3, the SIW 111 comprises one input end 111a receiving the conductive projection 120 and one output end 111b connected to the lens 113 of the antenna.

These embodiments are well adapted to transfer electromagnetic signal 10 to the lens 113 from an electronic die 110.

Another embodiment is also disclosed in Figure 4.

Of course, this embodiment is only an example of several combinations which can be performed on the basis of the electronic device described previously.

In this example, a multi-beam antenna can be realized. 15 A flip-chip ball grid array package 400 comprises a dielectric substrate

412 and an electronic die 410.

The dielectric substrate 412 is provided with several lens mounting areas 430, and in this embodiment with four lens mounting areas 430 located on each side of the dielectric substrate 412 which is substantially rectangular. 20 Each lens mounting area 430 is adapted to house a lens 413 in order to form a multi-beam antenna (in Figure 4 only three lenses 413 are shown in order to see a free lens mounting area 430).

As previously disclosed, the electronic die 410 is mounted in a flip-chip arrangement on the dielectric substrate 412, with several SIWs 411 adapted to 25 transfer electromagnetic signals to each lens 413.

In this embodiment, only by way of example, each lens 413 is connected to two SIWs 411 in order to create two radiation beams 431, 432.

Each beam 431, 432 corresponds to one of the two SIWs 411.

As also disclosed previously in relation to Figure 1, this flip-chip ball grid 30 array package 400 can be mounted on a PCB to be interconnected with other

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electronic components.

Figure 5 is a perspective view of a real implementation of the electronic device as described in Figure 1.

A simulated model of the transition between the electronic die 110 and 5 the SIW 111 is shown, the conductive projection 120 extending into the SIW 111 integrated in the dielectric substrate 112.

The conductive projection 120 is connected to a conductive bump 114' which is a spherical bump.

The diameter of the spherical conductive bump 114' is equal to about

10 100 (jm.

In this simulation, the conductive projection 120 has a cylindrical shape with diameter equal to about 200 pm. in order to avoid discontinuity with the spherical bump diameter.

As shown in Figure 6, this simulated model has a good return loss 15 parameter S11, that is less than -6dB which is acceptable in term of yield.

Indeed, as shown in Figure 6, the return loss parameter S11 less than -7dB within the frequency band comprised between 59 and 64 GHz.

Another embodiment is also disclosed in Figures 7 and 8.

In this embodiment, a flip-chip ball grid array package 700 comprises 20 two electronic dies 710 mounted via conductive bumps 714 on a dielectric substrate 712.

At least one SIW 711 is integrated in the dielectric substrate 712.

As shown in Figure 8, in this embodiment, by way of non-limitative example, the flip-chip ball grid array package 700 comprises four SIWs 711 25 extending between two electronic dies 710.

As shown in Figure 7, each SIW 711 extends between two electronic dies 710, with traversing posts 719 defining the end walls of each electronic die 710.

Two conductive projections 720 extend in the SIW 711 and are 30 electronically connected respectively to the electronic dies 710 through a

14

conductive bump 714'.

Thus, the SIW 711 plays the role of a usual electrical link extending between two electronic dies 710 in order to interconnect them.

For example, the power output of an amplifier of the electronic dies 710 5 is connected directly to one or several conductive bumps 714' soldered on the conductive projection 720.

The current can be shared between several conductive bumps 714' and therefore the losses due to the transition between the electronic dies 710 are decreased.

10 For each electronic die 710, the conductive projection 720 corresponds to an input or an output of the electrical signal.

As previously disclosed for the first embodiment, the dielectric substrate 712 is mounted via an array of balls 715 to a PCB 716 in order to be connected to other electrical elements.

15 The electronic device according to the invention provides an excellent impedance match over a wide bandwidth. It is cost effective and easy to manufacture with a conventional industrial process.

The various embodiments described above are only examples for performing the present invention.

20

15

Claims

1. An electronic device comprising an electronic die mounted via conductive bumps on a dielectric substrate, and a waveguide integrated in said

5 dielectric substrate, characterized in that said electronic device comprises a conductive projection electrically connected to said electronic die through at least one conductive bump, said conductive projection extending in said substrate integrated waveguide.

2. An electronic device according to claim 1, characterized in that said

10 conductive projection is connected to several conductive bumps of said electronic die.

3. An electronic device according to any one of claims 1 or 2, characterized in that said conductive projection is soldered to at least one conductive bump.

15

4. An electronic device according to any one of claims 1 to 3,

characterized in that said conductive projection is a blind metalized hole extending in said dielectric substrate.

5. An electronic device according to any one of claims 1 to 4, characterized in that said conductive projection is connected to a power amplifier

20 integrated in said electronic die.

6. An electronic device according to any one of claims 1 to 5, characterized in that several conductive bumps surrounding said conductive projection are electrically connected to a top metal plate and/or a bottom metal plate constituting respectively a top face and a bottom face of said substrate

25 integrated waveguide.

7. An electronic device according to any one of claims 1 to 6, characterized in that an insulated area is provided around said conductive projection.

8. An electronic device according to any one of claims 1 to 7,

30 characterized in that said substrate integrated waveguide comprises one input end

16

receiving said conductive projection and one output end connected to a lens of an antenna.

9. A flip-chip ball grid array package, comprising at least one electronic die mounted via conductive bumps on a dielectric substrate, and a waveguide

5 integrated in said dielectric substrate, characterized in that a conductive projection is electrically connected to said at least one electronic die through at least one conductive bump and extends in said substrate integrated waveguide.

10. A flip-chip ball grid array package according to claim 9, characterized in that it comprises two electronic dies mounted via conductive

10 bumps on a dielectric substrate, and at least one waveguide integrated in said dielectric substrate, and in that two conductive projections extend in said at least one substrate integrated waveguide and are respectively electrically connected to said two electronic dies through at least one conductive bump.

11. A flip-chip ball grid array package substantially as hereinbefore

15 described with reference to, and as shown in, Figures 1 and 2.

12. A flip-chip ball grid array package substantially as hereinbefore described with reference to, and as shown in, Figure 3.

13. A flip-chip ball grid array package substantially as hereinbefore described with reference to, and as shown in, Figure 4.

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14. A flip-chip ball grid array package substantially as hereinbefore described with reference to, and as shown in, Figures 7 and 8.