WO2013029222A1

WO2013029222A1 - Method and structure for reducing body static voltage

Info

Publication number: WO2013029222A1
Application number: PCT/CN2011/079016
Authority: WO
Inventors: Kek Hing Kow
Original assignee: Esd Technology Consulting & Licensing Co., Ltd
Priority date: 2011-08-26
Filing date: 2011-08-26
Publication date: 2013-03-07
Also published as: CN203596968U

Abstract

A method for reducing body static voltage is provided, which comprises sewing a highly conductive attachment (1) partially, selectively or full length into a chosen section(s) of a static dissipative strip (2) with its exposed portion facing the ESD floor. A structure for reducing body static voltage is also disclosed.

Description

METHOD AND STRUCTURE FOR REDUCING BOD Y STATIC

VOLTAGE

FIELD OF THE INVENTION

The present invention relates to body static voltage reduction. More specifically, the invention relates to a method and structure for reducing body static voltage.

BACKGROUND OF THE INVENTION

It is popular and well known in the Electrostatic discharge (ESD) control industry that the use of ESD shoes for the drainage of harmful static charge from body to ground is one of an important measures in the combat against ESD in a typical ESD- sensitive electronics manufacturing environment.

The use of ESD shoe straps, shoe grounders or heel strap are also a popular option for those who are wearing normal shoes or street shoes entering into a Electrostatic Protected Area (EPA) in a typical microchip production work place.

Patent no. US Patent 4812948, US Patent 4249226 and PI 2010000262 disclose the drainage of static charge from body to ground using static dissipative straps wrap around a shoe or a static dissipative loop incorporated into a shoe.

However, all these static dissipative straps and static dissipative loops have limitation in bringing down the body static voltage to a safe level of 50 to 60 volts or less in a typical standard static dissipative flooring to protect the electrostatic sensitive electronics devices from the risk of ESD damage as per the new recommendation highlighted in the Industrial Council on ESD Target Levels (USA).

To overcome the problem, one skilled in the art may improve the electrical conductivity of the material by the incorporation of more conductive filler in the material composition of the static dissipative strap, shoe grounder or static dissipative loop in an attempt to lower the body to ground electrical resistance to cut down the body static voltage.

However, the incorporation of a higher dosage of conductive filler not only cause material brittleness issue, it also cause sloughing or flaking of micro particles which is of high concern especially in a cleanroom manufacturing environment in the production of highly sensitive microchips.

Other alternative solutions may also exist, such as the application of special conductive coating on floor to improve the electrical property of the flooring. However, conductive coating on floor possesses its own shortcomings like durability issue, high cost of regular re-coating and other high repair and maintenance cost, etc.

Therefore, further research and development work is needed to provide better alternative or more effective and economical method to control body voltage to a safer level to protect the microchip during manufacturing process from the electrostatic discharge (ESD) damage.

SUMMARY OF THE INVENTION

A method and structure which can be used for reducing body static voltage with simple design and low cost, substantially as shown in and/or described in connection with at least one of the drawings, as set forth more completely in the claims, providing an alternative solution lacking in prior technology.

The invention disclosed herewith is a method for reducing body static voltage, which comprises sewing a highly conductive attachment partially, selectively or full length into a chosen section(s) of a static dissipative strip with its exposed portion facing the ESD floor. In the above-mentioned method for reducing body static voltage, the method further comprises sewing the conductive attachment at a designated location that dose not come into direct contact with the human body.

In the above-mentioned method for reducing body static voltage, the electrical property of the conductive attachment is less than l*10e5 ohm.

In the above-mentioned method for reducing body static voltage, the electrical property of the conductive attachment is less than l *10e3 ohm.

In the above-mentioned method for reducing body static voltage, the electrical property of the conductive attachment is less than l*10el ohm.

In the above-mentioned method for reducing body static voltage, the conductive attachment is made of metal.

A structure for reducing body static voltage is also disclosed herenin, which comprises a static dissipative strip and a highly conductive attachment partially, selectively or full length sewn into a chosen section(s) of the static dissipative strip with its exposed portion facing the ESD floor.

In the above-mentioned structure for reducing body static voltage, the highly conductive attachment is at a designated location that does not come into direct contact with the human body.

In the above-mentioned structure for reducing body static voltage, the conductive attachment is metallic thread or conductive wire.

In the above-mentioned structure for reducing body static voltage, the static dissipative strip is a shoe grounder.

When implementing present method and structure for reducing body static voltage, it is interesting to note that improved body static voltage is achieved simply by adding a conductive attachment, without the need of doing any additional design or additional work that may lead to other problems such as material brittleness issue, considerable cost, etc. Accordingly, the invention possesses high commercial attractiveness as it can effectively drain static charge from body to ground readily and safely, so as to reduce body static voltage in a simple and cheap way yet ensuring human safety in an ESD environment.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate one or more embodiments of the invention and, together with the written description, serve to explain the principles of the invention. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment, and wherein:

Figure 1 is a diagram of a strip with conductive attachment such as a conductive thread according to an embodiment of the present invention;

Figure 2 is a diagram of a strip with conductive attachment such as a conductive wire according to an embodiment of the present invention;

Figure 3 is a diagram of a strip with a conductive attachment such as a conductive wire according to another embodiment of the present invention;

Figure 4 is a diagram of measuring the body static voltage according to an embodiment of the present invention;

Figure 5 is a structure diagram of a shoe with a conductive attachment in its grounding strip according to an embodiment of the present invention;

Figure 6 is a structure diagram of a boot with a conductive attachment in its grounder according to an embodiment of the present invention;

Figure 7 is a structure diagram of a shoe with a conductive attachment in its heel strap according to an embodiment of the present invention;

Figure 8 is a structure diagram of a conductive attachment such as a conductive wire according to another embodiment of the present invention;

Figure 9 is a structure diagram of a grounding roller with a conductive attachment according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Referring to the drawings, like numbers indicate like components throughout the views.

Figure 1 is a diagram of a strip with conductive attachment 1 such as a conductive thread according to an embodiment of the present invention. Refering to Figure 1, the conductive thread 1 can be sewn in a single or any pattern of lines as long as the thread 1 is exposed and facing the ESD floor as shown in Figure 1. The conductive thread 1 can be sewn partially, selectively or full length into a chosen section(s) of the strip 2, loop or heel strap outside the shoe located underneath the bottom of the shoe. Such desirable location(s) of the metallic thread sewn also helps in eliminating the possibility that the metallic thread will come into contact with the body of a person to cause risk of electrical hazard as a safety precaution.

Figure 2 is a diagram of a strip with conductive attachment 1 such as a conductive wire according to an embodiment of the present invention. Figure 3 is a diagram of a strip with a conductive attachment 1 such as a conductive wire according to another embodiment of the present invention. Refering to Figure 2 and 3, a conductive wire 1 may be used to incorporate into the chosen portion of the static dissipative strip that is beneath the bottom of the shoe. As highlighted earlier, this will help in eliminating the possibility that the metallic wire to come into direct contact with the body of a person to cause risk of electrical hazard as a safety precaution. The shape or layout of the conductive wire may be obvious for the skilled in the art, and Figure 2 and 3 are only for the purpose of illustration but not limitation. In an embodiment, the electrical property of the thread or wire chosen is less than Ixl0e5 ohm, preferably less than Ixl0e3 ohm, more preferably less than lxlOelohm when measured according to ANSI/ESD STM 11.11 (USA). More preferably, metallic thread or metallic wire may be used in the current invention.

Before the body static voltage walking test ANSI/ESD STM 97.2 was carried out, body-to-ground electrical resistance was checked and measurement was made using the design in Figure 1. It was found that the body-to-ground electrical resistance measured as per the method in Figure 4 remains unchanged before and after the strip being sewn on with the conductive attachment.

Figure 4 is a diagram of measuring the body static voltage according to an embodiment of the present invention. Refering to Figure 4, the body static voltage readings were taken before and after the modification using ANSI/ESD STM 97.2 (USA) body static voltage walking test using Personal Volt Meter (Electrometer WT 5000) sold by Wolfgang Warmbier (Germany) and the result was tabulated in table 1 as follows.

Table 1

It was surprisingly discovered that the strip with the sewn-on conductive thread or conductive wire design consistently registered a significant drop in body static voltages compared to the non-conductive attachment design. It is not exacting known why it behaves that way as there is no change in the body electrical resistance to ground in both the cases. It may probably due to the improved electrical contact at a point where the modified strip touches the ESD floor which causes fast transfer of the static charge although there was no difference in body-to-ground electrical resistance.

This unique static voltage reduction technique can be used in various area such shoe straps, shoe grounders, heel straps, grounding rollers and ESD boots, etc.

Figure 5 and 6 are structure diagrams of a shoe and a boot with a conductive attachment 1 in its bottom sole according to an embodiment of the present invention. Figure 7 is a structure diagram of a shoe with a conductive attachment 1 in its heel strap according to an embodiment of the present invention. Refering to Figure 5, 6, and 7, the metallic thread can be sewn in a single or any pattern of lines onto the strip in shoes or boots as long as the exposed thread facing the ESD floor. Optionally, a conductive wire may be used to incorporate into the static dissipative strip so that part of the wire is touching the bottom sole and part of the wire is touching the floor. Figure 8 is another structure diagram of the wire attachment 1 which can be of any shape or configuration preferably with round contour design (without sharp ends for safety reason) formed into a clip-like structure that can be clip-on into the static dissipative strip easily.

Figure 9 is a structure diagram of a grounding roller with a conductive attachment 1 according to an embodiment of the present invention. Refering to Figure 8, the conductive attachment 1 such as metallic thread or conductive wire may be sewn into the static dissipative lining layer of the grounding roller.

In summary, the invention achieves a simple and cost-effective static charge reduction technique which the prior arts failed to address, which can be used to improve or modify ESD products like static dissipative straps, shoe grounders, static dissipative loops, heel straps or grounding rollers to achieve a simple and effective static charge reduction solution.

The invention is unique as all prior arts cited in the background of the invention are more sophisticated than the current invention leading to higher cost of manufacturing and other limitations in commercial attractiveness in numerous applications. When implementing present method and structure for reducing body static voltage, following advantageous effects will be obtained: improved body static voltage is achieved simply by adding a conductive attachment, without the need of doing any additional design or additional work. Accordingly, the invention is operable to effectively drain static charge from body to ground readily and safely, so as to reduce body static voltage in a simple and cheap way to ensure human safety in an ESD environment.

The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.

The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to activate others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.

Claims

1. A method for reducing body static voltage, which comprises sewing a highly conductive attachment partially, selectively or full length into a chosen section(s) of a static dissipative strip with its exposed portion facing the ESD floor.

2. The method for reducing body static voltage of claim 1, wherein the method further comprises sewing the conductive attachment at a designated location that does not come into direct contact with the human body.

3. The method for reducing body static voltage of claim 1, wherein the electrical property of the conductive attachment is less than l*10e5 ohm.

4. The method for reducing body static voltage of claim 3, wherein the electrical property of the conductive attachment is less than l*10e3 ohm.

5. The method for reducing body static voltage of claim 4, wherein the electrical property of the conductive attachment is less than l*10el ohm.

6. The method for reducing body static voltage of claim 5, wherein the conductive attachment is made of metal.

7. A structure for reducing body static voltage, which comprises a static dissipative strip and a highly conductive attachment partially, selectively or full length sewn into a chosen section(s) of the static dissipative strip with its exposed portion facing the ESD floor.

8. The structure for reducing body static voltage of claim 1, wherein the highly conductive attachment is at a designated location that does not come into direct contact with the human body.

9. The structure for reducing body static voltage of claim 1, wherein the conductive attachment is metallic thread or conductive wire.

10. The structure for reducing body static voltage of claim 1, wherein the static dissipative strip is a shoe grounder.