METHOD AND APPARATUS FOR INTEGRATING SPARK GAP INTO SEMICONDUCTOR PACKAGING

Abstract

The present invention is a spark gap protection capable of integrating into multiple layer semiconductor substrate packaging. The initial gap in the spark gap is solid and it can be converted into air, meaning gaseous, and the air gap is achieved by having the gap initially be filled with a solid and then running a voltage through the spark gap so that the gap explodes and the solid is replaced by an air cavity.

Claims

1. A spark gap apparatus comprising; a first electrode and a second electrode forming an electrode pair that is encapsulated in a semiconductor packaging epoxy plastic with glass bead filling and operationally spaced to form a gap between the first electrode and the second electrode that is 12 microns or less apart; where the first electrode electrically connects to a ground and the second electrode electrically connects to an input/output, and the spark gap is embedded in a multi-layer epoxy plastic substrate suitable for integrated circuit packaging.

2. The spark gap of claim 1, where in the gap of the spark gap apparatus is a pre-sparked tuned combusted cavity spark gap.

3. The spark gap apparatus of claim 1, further comprising a plurality of electrode pairs.

4. The spark gap of claim 2, wherein the gap of at least one of the electrode pairs is a combusted cavity gap.

5. The spark gap of claim 2, wherein the electrodes of the electrode pairs each come to an angular point that points to the electrode they are paired with.

6. The spark gap of claim 2, wherein the electrodes have a rounded shape.

7. The spark gap of claim 2, wherein the electrodes are copper.

8. The spark gap of claim 2, wherein the electrodes are plated with a nickel, nickel phosphorus, an alloy of nickel Iron or a titanium plating.

9. The spark gap of claim 2, where in the spark gap is on the same layers and at least one trace or other embedded components such as inductors, capacitors, resistors.

10. The method of making a spark gap apparatus comprising; taking a spark gap apparatus comprising; at least one first electrode and at least one second electrode forming at least one electrode pair that is encapsulated in a semiconductor packaging epoxy plastic with glass bead filling and operationally spaced to form a gap between the first electrode and the second electrode that is 12 microns or less apart; where the first electrode electrically connects to a ground and the second electrode electrically connects to an input/output, and the gap is filled with the semiconductor packaging epoxy plastic; creating an initial electrostatic discharge between the first electrode and the second electrode so that the semiconductor packaging epoxy plastic which fills the gap combusts and forms a combusted cavity gap reaching the first electrode and the second electrode.

11. The method of claim 10, wherein the resulting combusted cavity gap has a tuned frequency.

12. The method of making a spark gap claim 11, wherein the first electrode and the second electrode of the electrode pairs each come to an angular point that points to the electrode they are paired with.

13. The method of making a spark gap claim 11, wherein the first electrode and the second electrode of the electrode pairs have a rounded shape.

14. The method of making a spark gap claim 11, further comprising creating one electrostatic discharge event per electrode pair until the semiconductor packaging epoxy plastic of the gap for every electrode pair is replaced with a combusted cavity gap.

15. The method of making a spark gap claim 10, wherein after all of the electrode pair gaps are replaced with a combusted gap at least one future electrostatic event occurs across at least one combusted gap.

16. The method of making a spark gap claim 10, wherein the electrodes are plated with a nickel, nickel phosphorus, an alloy of nickel Iron or a titanium plating.

17. The method of claim 10, wherein the spark gap is co-built on the same layers and with the same materials as other traces and other embedded components such as inductors, capacitors, resistors.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0049] FIG. 1A Is a top-down cross-sectional view of a single electrode pair embodiment with a epoxy plastic filled gap.

[0050] FIG. 1B Is a side cross-sectional view of a single electrode pair embodiment with a epoxy plastic filled gap.

[0051] FIG. 2 Is a top-down cross-sectional view of a single electrode pair embodiment with a combusted cavity air gap.

[0052] FIG. 3 Is a top-down cross-sectional view of a single electrode pair embodiment with a combusted cavity air gap where the electrodes are heavily damaged.

[0053] FIG. 4 Is a top-down view of a variety of electrode head shapes

[0054] FIG. 5 Is a top-down cross-sectional view of a single plated electrode

[0055] FIG. 6 Is a top-down cross-sectional view of a spark gap with three electrode pairs where the epoxy plastic they are embedded in has a higher breakdown voltage than the gas of the combusted cavity gap as an initial spark is arcing across a gap.

[0056] FIG. 7 Is a top-down cross-sectional view of a spark gap with three electrode pairs where the epoxy plastic they are embedded in has a higher breakdown voltage than the gas of the combusted cavity gap with an initial spark turning the gap receiving the initial spark into a gas gap.

[0057] FIG. 8 Is a top-down cross-sectional view of a spark gap with three electrode pairs where the epoxy plastic they are embedded in has a higher breakdown voltage than the gas of the combusted cavity gap with a spark crossing an initial combusted cavity.

[0058] FIG. 9 Is a top-down cross-sectional view of a spark gap with three electrode pairs where the epoxy plastic they are embedded in has a higher breakdown voltage than the gas of the combusted cavity gap with the electrodes of initial cavity broken and a spark crossing a second epoxy plastic filled gap.

[0059] FIG. 10 Is a top-down cross-sectional view of a spark gap with three electrode pairs where the epoxy plastic they are embedded in has a higher breakdown voltage than the gas of the combusted cavity gap with the second gap now being a combusted cavity and a spark crossing that cavity.

[0060] FIG. 11 Is a top-down cross-sectional view of a spark gap with three electrode pairs where the epoxy plastic they are embedded in has a higher breakdown voltage than the gas of the combusted cavity gap with the electrodes of the second gap now being heavily damaged and a spark crossing the last epoxy plastic filled gap.

[0061] FIG. 12 Is a top-down cross-sectional view of a spark gap with three electrode pairs where the epoxy plastic they are embedded in has a higher breakdown voltage than the gas of the combusted cavity gap with the second gap now being a combusted cavity and a spark crossing that cavity.

[0062] FIG. 13 Is a top-down cross-sectional view of a spark gap with three electrode pairs where the epoxy plastic they are embedded in has a higher breakdown voltage than the gas of the combusted cavity gap with the electrodes of the last gap now being heavily damaged.

DETAILED DESCRIPTION

[0063] In the present invention, a spark gap is embedded in semiconductor epoxy plastic. An initial voltage discharge event, such as an electrostatic discharge (ESD), will cause the gap material of the spark gap to explode. The electrodes of the spark gap are made strong enough to survive an explosion. The exploded material of the spark gap will leave a combusted cavity that is roughly shaped. The combusted cavity can serve as what can be referred to as an air or gas gap as it will be filled with gas from the explosion or environment or both. The survival of the electrodes and the creation of a combusted cavity allows the spark gap to handle multiple ESD events.

[0064] FIG. 1A and FIG. 1B depict an elegant embodiment of the present invention: a spark gap apparatus 100 which is a spark gap comprised of at least two electrodes 10, one electrode is connected to an I/O 111 and the other electrode is connected to a ground 112, between the electrodes there is a gap 20 that is twelve microns or less across, and a semiconductor packaging epoxy plastic 30 encapsulates the spark gap. This forms a spark gap completely embedded in a semiconductor packaging epoxy plastic 30. There is no cavitythe gap between the electrodes is a solid epoxy plastic. The spark gap is able to be incorporated into semiconductor packages on the leading edge of minimization as well as the leading edge of multi-layer packaging as apparatus 100 also occurs on a micron-scale and incorporates the epoxy plastic packaging. Further due to their location connecting electrodes to the IC is a simple procedure.

[0065] FIG. 1A shows a top-down cross-section of the spark gap and FIG. 1B shows a side-view cross-section of the same spark gap. Therefore, it can be seen that the spark gap 100 is entirely encapsulated by semiconductor packaging epoxy plastic. This gives the embodiment its elegance, as it is able to integrate into a wide variety of semiconductor packages cheaply and quickly. The invention is highly compatible with Ajinomoto epoxy plastics, and the preferred embodiment of the present invention incorporates black build-up film as the epoxy plastic 30. However, a wide variety of epoxy plastics may be utilized by the present invention.

When a high voltage event, for example, an electrostatic discharge, occurs a spark is generated across the gap 20 and that spark can violently explode any epoxy plastic 30 in gap 20 leaving a gas gap as shown in FIG. 2. The gas gap can be referred to by three names, combusted cavity, gas gap, and air gap. After or by the explosion, the combusted cavity may be filled with air, carbon dioxide, or other gases that form as a result of the spark reaction. By controlling the properties of the electrodes 10 and the epoxy plastic 30 the creation of a gas gap can in this manner can be beneficial and be tuned to provide a specific level of ESD voltage protection. The benefits include a low-cost, tunable, and simple gas gap that can handle multiple discharge events. Further, in embodiments with rows of electrode pairs, the order of the spark gap discharges can be controlled.
Packaging epoxy plastics can have different breakdown voltages as there are a wide variety of packing epoxy plastics possible so there are a wide range of epoxy plastic breakdown voltages available.
In preferred embodiment of the invention, an epoxy plastic, for example, an epoxy plastic with a breakdown at 900 volts at 12 microns, an ESD event with a high enough voltage to cause the breakdown and to explode the epoxy plastic may be triggered on purpose before the spark gap is to be used. The resulting explosion leaves behind an air gap between the two electrodes which, for example, has a voltage breakdown of approximately 300 volts. In this example, the spark gap can now protect the semiconductor IC that will be later attached to the substrate against ESD events with voltages of 300 or higher which is about 600 volts lower than the epoxy plastic that originally filled the gap.
With reference to FIG. 2, it can be seen that the combusted cavity gap 25 may reach the ends of the electrodes 10. There are several design elements that are taken in various embodiments of the present invention to improve the survivability of the electrodes 10. The first design element is the shape of the electrode in FIG. 2 the electrode comes to a rounded point. The rounded point is more resistant to the explosion that occurred in the gap 25, but still provides some directional influence on the spark. Other electrode shapes can be implemented, and several are shown in FIG. 4 where 11 is a sharp-angled point, 12 is a rounded angle, 13 is a rounded electrode, and 14 is a flat surface. More shapes may be made, and the angles and angle softness may vary among embodiments
A second design element is the material of the electrodes 10. The electrodes 10 are copper. Copper is preferred used for its low impedance. The resistance of the electrode to damage can be further controlled, by a third design element: plating the electrodes 10, which is shown in FIG. 5 where 15 is the initial electrode material and 16 is the plated material. The electrodes may be plated with a stronger metal including titanium, steel alloy, or nickel. (A copper electrode is especially suited for being plated with nickel as nickel will prevent copper ions from interacting with the gap.) Plating helps to ensure that the spark gap can operate over multiple ESD events even as the epoxy plastic of the gap material is blown out leaving a combusted cavity gap 25 as shown in FIG. 2. The plating of the electrode can also enable more angled electrode shapes by adding structural strength to the electrode with a weaker shape such as a thin and sharp point.
Further, when epoxy plastic explodes, the size of the combusted cavity left behind tends to be in the micron range. Thus, using metal electrodes, shaping the electrodes, reinforcing them by plating, or doing all three to the electrodes, helps keep the combusted cavity within the confines of the spark gap.
The design of the electrodes and the placement of the electrodes in the semiconductor epoxy plastic enable a spark gap to handle higher voltages than otherwise and survive multiple discharge events while being small enough to be relevant as semiconductor technology continues to miniature as well as being backward compatible into a wide variety of semiconductor packaging designs and types. The preferred embodiment of the present invention is capable of incorporation directly into multi-layer semiconductor substrate packaging. Because of, but not limited to, the size, ease of manufacturing, level of protection, and location of the spark gap, this invention reduces the required die size and cost of ESD protection while increasing the survivability of the IC over multiple ESD events.

Example Embodiments

[0066] An elegant embodiment and the stages of its life cycle (the point from when the spark gap apparatus is made to when it is no longer operable) are shown by FIG. 1A, FIG. 2, and FIG. 3. As shown by FIG. 1 the spark gap 100 contains one electrode pair of electrodes 10 and is embedded fully in epoxy plastic at the start of its lifecycle. The second life cycle stage is shown in FIG. 2 and occurs after an initial ESD event. In this stage, a combusted cavity 25 in the epoxy plastic 30 will present the medium that the spark will travel through. The third and final life cycle stage of the spark gap occurs after the electrodes melt or are damaged so that they are no longer operable.
The transition from the first stage to the second stage occurs after an initial discharge event. This event can be triggered by a user or manufacturer of the spark gap on purpose to transition the spark gap to the second stage or it can be left for happenstance in the daily life of the system. A user may wish to transition to the second stage as this will ensure a specific breakdown voltage and enable the spark gap to protect against lower voltages. In the first stage, a partial discharge may occur, and this may delay the transition into the second stage giving the first state the ability to handle multiple discharges. In embodiments where there are multiple electrode pairs each pair will have its own lifecycle.
In the second stage, multiple ESD events may occur until the electrodes are melted or damaged in some manner so as to be inoperable. Once inoperable the third stage entered and is shown in FIG. 3 where the electrodes 10 are now heavily damaged. A heavily damaged electrode is one that will no longer take a spark within a voltage threshold to be useful for protecting the device. This transition from a second stage to a third stage is important when considering more sophisticated embodiments.
In this elegant embodiment of the invention shown in FIG. 1A-FIG. 3, the electrodes forming the gap may have any of the above discussed shapes, but the rounded angle shape as shown is currently preferred. A rounded angle shape will be able to survive more ESD events than a sharply angled point. In this embodiment, the electrodes may be, but are not limited to copper or nickel. The use of copper or nickel gives the electrodes strength. To further increase the strength of the electrodes they may be plated with nickel, nickel iron alloy, a steel alloy, titanium, or material with similar properties. Many configurations of a single electrode pair may be made without exceeding the scope of the invention.
Embodiments can include multiple electrode pairs per spark gaps. One such embodiment is shown in FIG. 6, where there are three electrode pairs, electrode pair 110, electrode pair 120, and electrode pair 130. Each electrode pair has a gap 210, 220, and 230 associated with it and all electrodes connect to either a ground 300 or an input/output 350. The electrode pairs 110, 120, and 130 form a row of electrodes. By incorporating multiple electrode pairs into a single spark gap the longevity of the spark gap is increased without a significant increase in cost. This embodiment is embedded in semiconductor epoxy plastic 30 and all gaps 210, 220, and 230 consist at the stage shown in FIG. 6 as a solid semiconductor epoxy plastic.
In the preferred embodiment, the spark gap is embedded in epoxy plastic thus the first discharge will be over solid epoxy plastic. However, the order in which the electrode pairs discharge across the gap after an initial electrode pair completes the transition to the second stage of the lifecycle is primarily determined by the semiconductor epoxy plastic. When the semiconductor epoxy plastic the gas gap it will run through its life cycle stages before the next electrode pair is triggered. When the semiconductor epoxy plastic has a lower breakdown voltage than air each epoxy plastic electrode will transition into the second stage before the air gap will be utilized.
In the embodiment denoted by FIG. 6, where the epoxy plastic 30 has a higher breakdown voltage than a potential combustion cavity gap, the first electrode pair to hold a spark will be an electrode pair that has a epoxy plastic gap and this is shown in FIG. 6 as a spark occurs between electrode pair 110. After this spark occurs the next discharge will occur in the combusted cavity 210 as shown by FIG. 8. This air gap 210 is designed to continue to take a plurality of ESD events and it will do so until as shown by FIG. 9 its associated electrode pair 110 becomes damaged and inoperable. At this point a surviving electrode pair having a solid epoxy plastic gap will receive the next ESD event, as shown in FIG. 10, and as such the ESD protection the whole spark gap apparatus offers will be temporarily raised to that of the epoxy plastic. As shown in FIG. 11, the new combustion cavity gap 220 created by the spark in FIG. 10 will receive discharge events. Once the electrode pair receiving the discharge, here 120, has been damaged the new electrode pair, here 130, will receive the spark. The new combustion cavity 130 shown in FIG. 12 will continue to receive the spark until the electrode pair 130 become damaged as shown in FIG. 13. Once the final pair of electrodes is damaged and can no longer receive an ESD event the spark gap will no longer be to protect against such events. Therefore, from FIG. 6-FIG. 13 it can be seen that when the spark gap of the present invention with a plurality of electrode pairs is embedded into a epoxy plastic that has a higher breakdown voltage than air at 12 microns or less that each individual electrode pair is used up before the next one begins to receive ESD events.
In the preferred embodiments the electrode pairs are to be spaced 12 microns or less apart. However, in alternative embodiments they may be spaced greater than 12 microns apart. The distance the electrodes are apart affects the breakdown voltage over the gap, by increasing the distance the electrodes are apart there is an increase in the amount of material in the gap and thus the needed voltage to breakdown the gap is increased.
The electrodes may be created by electroplating and the epoxy plastic placed by ordinary means.
Because of, but not limited to, the size, ease of manufacturing, level of protection, and location of the spark gap, this invention reduces the required die size and cost of ESD protection while increasing the survivability of the IC over multiple ESD events.

[0067] The drawings and figures show multiple embodiments and are intended to be descriptive of particular embodiments but not limiting with regard to the scope or number, or style of the embodiments of the invention. The invention may incorporate a myriad of styles and particular embodiments. All figures are prototypes and rough drawings: the final products may be more refined by one of skill in the art. Nothing should be construed as critical or essential unless explicitly described as such. Also, the articles a and an may be understood as one or more. Where only one item is intended, the term one or other similar language is used. Also, the terms has, have, having, or the like are intended to be open-ended terms.