JPS6370495A - Electrostatic-proof shelf for electronic circuit board - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to anti-static supports for electronic circuit boards, and more particularly to anti-static shelves for electronic circuit boards that are adjustably mounted in storage cabinets or containers.

BACKGROUND OF THE INVENTION Circuit boards used by the telecommunications and electronics industries contain solid-state microelectronic components that are expensive and highly sensitive to static electricity. often,
The circuit boards, which cost $1,000 or $10,000, can sometimes be destroyed under low-fi conditions by momentary static electricity, such as falling from a person's hand onto a metal railing. Ru. After removing a circuit board from active service in a computer, switching system, etc., the circuit board is also destroyed by free and rapid discharge of the components. Therefore, it is necessary to protect circuit boards from surrounding static electricity charges.

Traditional solutions to static electricity and discharge problems have centered on containers for circuit boards, such as plastic bags or paper boxes, which are made conductive with a suitable anti-static agent. Chemical agents that provide antistatic properties are described, for example, in US Pat. No. 3,405,001. Also, examples of known antistatic containers for electronic components are U.S. Pat.
No. 901 is listed in each specification. U.S. Patent No. 4
．． No. 293,070 describes a container made of paperboard coated on the inside surface of the container with conductive carbon black particles to prevent static electricity on the outside of the container from passing through the container.

In the above-mentioned US Pat. No. 4,231,901, conductive urethane foam is used for packaging electronic devices to protect them from static electricity.

The urethane foam contains a binder and is usually uniformly impregnated with a large amount of conductive material, such as carbon black, silver, aluminum or metal salts. And, U.S. Pat. No. 4,223,368 describes an electrostatic discharge protection device adapted to surround edge connectors of circuit cards. The package ξ includes a shunt for electrically connecting the card's edge connector.

When removing a circuit board from an electronic circuit device main body, it is inconvenient to repackage the circuit board into an individual storage container such as the above-mentioned paper box or bag. However, future fl.
For general use, it is necessary to house such circuit boards in a way that protects them against damage from electrostatic discharge. Therefore, the circuit board can be placed for convenient modification when needed, and is easily stored in a cabinet or other container that protects the circuit board and the components on the circuit board from damage caused by electrostatic discharge. Providing quality is a benefit. Such a cabinet is
It is necessary to provide flexibility with respect to the type and size of circuit boards accommodated.

The present invention relates to an adjustable anti-static fence for a storage cabinet or similar container.

Known U.S. Pat. No. 4,563,722 (issued January 7, 1986) describes an anti-static shelf for adjustable support of electronic circuitry in a storage cabinet. and is cited herein.

The shelf includes a base member having parallel planar top and bottom surfaces. A plurality of parallel pairs of rails (hereinafter referred to as rail pairs) extend outward from the top surface of the base member. The rails in each rail pair are spaced apart by a first spacing, and adjacent rail pairs are separated from each other by a second spacing. A plurality of rail pairs extend in line with a rail pair extending outwardly from the top surface of the base member. Molded ear means forming the corner elements of the shelf base members are described in U.S. Pat. No. 4,555,744 (issue date = 198
5, Nov. 26, 2003) for adjustably mounting the base member to a storage cabinet such as that shown in the following. The shelf should be formed as a unitary piece from conductive plastic to conduct any charge that would otherwise be exerted through the atmosphere through the cabinet to the ground rather than to the circuit boards housed therein. The friction caused by sliding the circuit board into its storage position on the shelf can be dissipated in a similar manner. Plus deck railings also provide high resistance to prevent triboelectric build-up.

During use, several shelves are arranged in a stacked device storage cabinet. The space between successive shelves is determined by the height of the circuit boards stored between these shelves. The circuit boards to be stored are slid into grooves formed in the top surface of the lower shelf and into corresponding grooves in the bottom surface of the higher shelf mounted directly above the lower shelf. Circuit boards of different heights are easily accommodated by adjusting the space between the lower and higher shelves. The space of the shelf is adjustable; slide the ear on the shelf into the longitudinal track of the cabinet, insert the fastener through the ear behind the track, and unfasten the fastener when the adjusted height is reached. Do it with caution. Circuit boards of different widths are accommodated by grooves of various widths on the shelves. For example, if the rails of each rail pair forming a groove are closer together than the rails of an adjacent rail pair, a thin circuit board will be supported between the rails of the rail pair, while a relatively thick circuit board will be supported between the rails of the rail pair. The circuit board is supported between the rails of adjacent rail pairs.

It turns out that the completely integrated ff1lli has some drawbacks. If the conductive plastic material is not properly formulated or if the mold does not operate correctly, it may become voided or vulnerable to distraction. That is, if a significant load is applied, the integrally formed ears will crack or collapse. It has been found that the risk of failure is increased due to the integral nature of the shelf, where the ears are unable to flex relative to the base member of the shelf under load loading.

Accordingly, the base member is adapted to receive a conductive metal ear at the mating portion that slides into the respective end of each track used to adjustably mount the base member and shelf to the longitudinal tracks of the storage cabinet. It is useful to vary the design by providing three tracks around the perimeter. The metal ears, for example made from aluminum, function to conduct static electricity that impinges on the shelf or to discharge static charges from the circuit board through the cabinet to ground. .

The base member may be movable under load with respect to the wearing ear to prevent collapsing or clubking of the base member under load. Ears made of metal are stronger than those made of plastic. The metal ears can be easily machined to form elongated openings for receiving mounting fasteners that can be adjusted relative to the longitudinal tracks of the storage cabinet to secure the shelves together. It can be placed in an appropriate position or away from the room.

The shelf of the present invention is disclosed in U.S. Pat.
, 55u, No. 744 (patent issue date: November 26, 1985, title of the invention: NIB PLUG-IN TYPE CIRCUIT BOARD STORAGE CABINET). The contents of that US patent are incorporated herein by reference.

(Examples) Hereinafter, the present invention will be described with reference to the accompanying drawings showing examples.

In FIG. 1, a shelf 10 is shown for storing circuit boards and dissipating static charge to the ground. The shelf 10 includes a base member 11 having a parallel planar top 12 and bottom 13. A plurality of parallel rail pairs 14 extend outwardly from the top surface 12 of the base member 11. Each pair of rails is spaced apart by a first spacing 50, and adjacent rail pairs are spaced apart by a second spacing 52 (see FIG. 4).

The matching groove thus formed can accommodate circuit boards of various thicknesses. Most circuit boards are 50mm wide
(hereinafter referred to as groove 50).

However, in special cases, i.e. when the edges of the known circuit board are fitted with connectors and gate elements, a larger width is required to provide sufficient space for the insertion of the circuit board into the shelf IO. 52 grooves (hereinafter referred to as grooves 52) are required.

A plurality of complementary rail pairs 15 extend outwardly from the bottom portion 13 of the base member 11. Each rail pair 15 is aligned with a complementary rail pair 14 extending from the upper surface 12 of the base member 11. In this way, the 'ri'f 50 having a relatively narrow width and the groove 52 having a relatively wide width are arranged in a straight line on both sides of the top surface 12 and the bottom surface 13 of the base member 11, respectively.

Shelf 10 is adjustably mounted to a storage cabinet using ears or tabs 26, 28, 30 and 32 integrally formed with the base member at each corner. Ears or tabs 30 and 32 are provided adjacent the front end 16 of the base member 11. These ears or tabs 30 and 32 are referred to as front tabs. Front tabs 30 and 32 are attached to the base member 1 along the front end 16 to maximize the use of the shelf 10.
1 and extending from side ends 24 and 22 of 1 .

The rear tabs 26 and 28 are located at the rear end 2 of the base member 11.
0 and is generally a flat plate substantially perpendicular to the front tab. The rim 18 extends from the rear end 20 and extends upwardly beyond the upper surface 12 of the base member 11. Lip 18 prevents circuit boards supported on shelf 10 from being pushed past rear end 20 of base member 11. Since the shelf 10 is accessed (used) by sliding the circuit board from the front end, there is no problem even if the rear tabs 26 and 28 extend from the rear end 20. Conversely, from the front end 16 of the base member 11 to the front tab 30
and 32 are extended, access to shelf 10 is restricted. Thus, it is preferred that the front tabs 30 and 32 extend from the side ends 24 and 22 as shown.

The shelves IO are preferably injection molded from structural polyethylene or polypropylene that has been treated to be electrically conductive. One material that can be used for this purpose is Laneyon (A
``Rho Ohmic'' conductive plastic sold by Co., Ltd., Inc. (Oklahoma City, Oklahoma) or NOW Plastics Corporation.
One example is the plastic sold under the registered trademark ``Unifuse'' by the United Nations University of New York (N.Y.). In selecting a suitable conductive plastic for shelf 10, two electrical properties are relevant. First, the material can safely dissipate static electricity on printed circuit boards. If the shelf material is highly conductive, electrostatic discharge will occur through the shelf due to the rapid discharge of the printed circuit foil board. A sheet resistance of 105-1013 ohms/portion (ohms/C) plus 6 resistors was found to be sufficient to safely discharge charged equipment.

A second important electrical factor in the materials described above is the ability to dissipate the charge that occurs due to triboelectric factors. That is, as you pull the material across the board or floor, the material may rub against a dissimilar benchtop or floor, creating static electricity, or the material may rub against a dissimilar benchtop or floor, or may slide around when inserting a circuit board. Static electricity is generated by electrostatic discharge.The ability of a material to dissipate static electricity can be measured by the rate at which the static electricity dissipates.Suitable materials have a dissipation rate of 0.5 when charged to 3,000-5,000 volts. 5 to 2 seconds or less. Because the shelves are made of conductive material, the conduction speed is relatively high (
It may be adjusted from a conductive state) to a slow bleed state (or static dissipative state) or to a slow bleed state (or antistatic state), or any combination as desired to suit a particular application. For example, when in a conductive state, it conducts static charge from the electronic circuit board through the conductive layer of the shelf and the conductive frame of the cabinet to ground. When in a static dissipative state, it helps prevent static electricity from building up around the circuit board and acts as a slow-bleed conductor, preventing any discharge of static electricity from the circuit board itself and the air through shelves and cabinets to earth. encourage When in the antistatic state, as in the case described above, it prevents static electricity build-up caused by inserting a circuit board into the shelf, and slowly conducts the charge to the ground.

2 to 4 show how the shelf 10 is installed in the storage cabinet. The storage cabinet includes a track 46 having an opening 48. A fastener or screw 42 is inserted through the opening 40 in the tab 28 and screwed into the auxiliary plate 44. Auxiliary plate 44 is then inserted into groove 48 and fastener 42 is tightened to tighten tab 28.
The edge of the track 46 is fixed between and the auxiliary plate 44.

Other tabs 26, 30 and 32 on shelf IO securely secure the track to the storage cabinet in a similar manner. Opening 38.3 in each tab 26.30 and 32
4 and 36 are provided to receive the fastener 42.

As shown in FIG. 5, the circuit board 58 is stored between the shelves 10a and 1Qb that are sequentially installed in the storage cabinet. The circuit board 58 is connected to the shelves tab and 10a.
It can be removed from the storage cabinet by simply pulling in the forward direction of the groove formed by each upper rail pair 14 and 15.

FIG. 5 also shows the insertion of the circuit board 54. The top end 55 of circuit board 54 is positioned within the groove formed by rail pair 15 of shelf 10a. At the same time, the lower end 53 of the circuit board 54 is attached to the rail pair I4 of the shelf 10b.
It is inserted into the groove formed by the groove.

FIG. 6 is a front view of a storage cabinet with three shelves mounted on its tracks. As shown in Figure 6, shelf 1
0a, 10b and lOc are adjusted to be perpendicular to the storage cabinet. The rear tabs 26 and 23 of shelves 1°a SlOb and IOc are connected to the rear track 45
Be installed on. Front tabs 30 and 32 of shelf 10a, lob and IOc are attached to front track 56. Circuit boards 54 and 58 are mounted between shelf 10a and IOb. 1lOc stores the circuit board 62 at the position shown in the figure, and stores the short circuit board 60 at the position shown by the imaginary line. By loosening the threaded fasteners 42 on each tab 26.28.3o and 32, the shelf 1
0c is now moved from the position of 22g to a lower position. Next, slide the shelf downward as shown, and attach the shelf to the lower position using the fasteners 47f;-i,
Direction (1,000 dimensions 1η direction 12 tracks from conductive material
and 56 and a storage cabinet (not shown), the charge dissipated by the six shelves 10 is conducted through the track and the storage cabinet. In use, storage cabinets are typically grounded to provide the safest possible protection for the circuit boards contained within the cabinet.

However, it has been found that fully integrally molded shelves IO have drawbacks. If the conductive plastic material is not properly formulated or if the mold is not operated correctly, it may become voided or vulnerable to distraction. That is, if the shelf is subjected to a significant load, the integrally formed ears or tabs 26, 28, 30 and 32 will crack or collapse. It has been found that the risk of failure is increased due to the integral nature of the shelf where the tabs are not able to flex relative to the base member 12 of the shelf under load loading.

Therefore, as shown in FIGS. 7 and 8, the periphery of the base member 11 on the shelf 60, especially the sides'! ! It has been found that the design is modified to include three elongated slots or tracks 62, 64 and 66 in the g sections 22 and 24 and the upper and lower edges of the trailing end 20. At opposite ends of track 66 and at the forward ends of tracks 62 and 64 adjacent the forward wall of base member 11, C
Conductive metal ears 68 having channel members 70 having a cross-sectional shape and flanges are slidingly engaged to engage these slots or tracks 62 .
64 and 66.

Tracks 62 and 64 are tightly seated on rear end 20 and track 66 extends to opposite ends 22 and 24. As shown in FIG. 5, ears or tabs 68 are used to adjustably attach base member 11 and shelf 60 to longitudinal slots or tracks of a storage cabinet. The metal ears 63 are formed, for example, from aluminum, and the shelf 60 is designed to prevent static charges or charges discharged from the circuit board from impacting thereon by grounding them through the cabinet and the cabinet, and to attach them when loaded. It functions to flex the base member 12 relative to the ears 63.

In this way, it is possible to prevent the base from collapsing or clubbing under load. Ear 68 made of metal
is stronger than plastic molded products. Additionally, the metal ears can be easily beveled to form elongated openings 72 for receiving mounting fasteners 12, which are adjusted relative to the longitudinal slots or tracks 46 of the storage cabinet. The columns can be spaced apart from each other or placed in appropriate positions.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an anti-static fence used to dissipate static electricity from installed circuit boards, and FIG. 2 is a perspective view of an anti-static fence used to dissipate static electricity from mounted circuit boards.
Figure 3 is a detailed view of a part of the corner of the shelf in Figure 3. Figure 3 is a partial side view of a corner of the shelf in Figure 1 after the storage cabinet tracks have been installed. A partial front view of a corner of the shelf in Figure 1, and Figure 5 is a perspective view of the two shelves in Figure 1 attached to the tracks of the storage cabinet to illustrate the storage and arrangement of circuit boards. , FIG. 6 shows a plurality of FIG. FIG. 7 is a front view of the shelf, FIG. 7 is a perspective view of a shelf as a modification of the present invention, and FIG. 8 is a sectional view taken along line 8-8 in FIG. 10, 10a, fob, ioc and 60... shelf,
ll...Base member, 12...Top part of base member, 13...Bottom part of base member, 14 and 15...
Rail pair, 16...Front end of base member, 18.
... Edge, 20 ... Rear end of base member, 22 and 2
4... Side end of base member, 26.23.30 and 3
2... Mimata: Matabu, 3.1.36.33 and 40.
...Opening, 42...Zipper or 12, 44.
... Auxiliary plates, 46 and 56 ... Slots or tracks, 43 ... Openings or grooves, 50 and 52 ... 71"
rF, 53...lower end of circuit board, 54.58.60
and 62... circuit board, 55... upper end of circuit board, 62.64 and 66... slot or track, 6
8...Ear or tab, 70...Staggered nonel member, 72
···Aperture. Appearing person: Plug-in Storage System Incorporated Company F' Agent: Patent attorney Haka Aoyama 1 person Written amendment (voluntary) 1. Display of the case Patent Application No. 215600 of 1985 2, Name of the invention Electrostatic prevention shelf for electronic circuit board 3, Person making the amendment Relationship to the case Patent applicant address United States 06460 Funechant,
592 Point Avenue, Mill 7 Ord, Bonn Name: Plug-In Storage Systems, Inc. 4, Agent 5, Amendment Order Date: Voluntary (Submitted at the same time as the request for examination of the application)

【Attachment】

2. Claims (1) A base member made of a conductive plastic material having parallel planar top and bottom parts, a plurality of parallel grooves arranged on the top part, and valley grooves in the top part. a complementary parallel groove disposed in the bottom portion extending in the same direction and aligned with the groove, and means for adjustably mounting the base member to a storage cabinet; A storage cabinet or a storage cabinet similar thereto, characterized in that the adjustment and mounting means is bent with respect to the base member so that the base portion can withstand repeated loading of electronic circuit boards without damage. An anti-static shelf for electronic circuits that adjustably supports electronic circuit boards. 2. A shelf as claimed in claim 1, wherein the adjustment attachment means are formed from a movable tab mounted on each corner of the base member and a locking means for attaching the tab to a corresponding track within the storage cabinet. (3) The base member is substantially square and includes tracks on the top and bottom sides of at least three edges thereof, and a tab is inserted into each of the tracks at a corner of the base member. Shelf mentioned in section. (4) The shelf of claim 2, wherein each tab is formed from a conductive metal. (5) The shelf according to claim 4, wherein the conductive metal is aluminum. (6) Each tab forms a flange in a channel portion having a C-shaped cross section to be received in a track.
Shelf mentioned in section. (7) Each tab has an opening, while each fastening means has a threaded fastener inserted through the opening of each tab and screwed onto the auxiliary plate for insertion into the opening of the corresponding track. Claim 2, wherein the tab and the auxiliary plate form a clamping member, and when the threaded fastener is tightened, the tab and the auxiliary plate are tightened to the corresponding tracks to attach the shelf to the tracks of the storage cabinet. shelf. (8) A shelf according to claim 7, wherein each opening extends across a wide width. (9) The base part 4 is located at the front end, the rear end, and the front +'2
:; having opposite side end parts perpendicular to the rear end part and extending upwardly from the rear end part beyond the upper surface part;
Claim 2, wherein the circuit gf supported on the base member is prevented from being pushed out beyond the rear end.
Shelf mentioned in section. (10) Do the tabs at the rear corners of the base member extend from the rear end of the base member, and are each tab orthogonal to each front tab? ,? Scope of Claims No. 3
Shelf mentioned in section. (11) Conductive plastic material or polyethylene or polypropylene for injection molding (1 item divided by 7) as set forth in claim 1. (12) Grooves of 1 size in the top and bottom parts. n has a relatively narrow width, while the second group of grooves has a relatively wide width, and relatively narrow grooves and relatively wide grooves are alternately arranged in the top surface part and the bottom part. Shelf according to claim 1 placed on the bottom. Procedural amendment (method) % formula % 1, Case description 2, Title of invention Electrostatic viewing prevention for electronic circuit board I Mei 3 Make amendments h Relationship to the case Patent applicant address United States 06 = 160 Bond Point A\New 5, Milford, Connecticut
No. 92 Name Plug-in Storage Nostems
Inkohoraichi 4, agent

Claims (12)

[Claims] (1) A base member made of a conductive plastic material having parallel planar top and bottom parts, a plurality of parallel grooves disposed on the top part, each of which extends in the same direction as each groove in the top part; a plurality of complementary parallel grooves disposed on the bottom portion in line with the grooves;
and means for adjustably mounting the base member on the storage cabinet, the adjustment mounting means being deflected relative to the base member so that the base member can withstand repeated loading of electronic circuit boards without damage. An anti-static shelf for electronic circuit boards adjustably supporting electronic circuit boards in a storage cabinet or the like, characterized in that: 2. A shelf according to claim 1, wherein the adjustment attachment means are formed from movable tabs mounted on each corner of the base member and mechanical fastening means for attaching the tabs to corresponding tracks within the storage cabinet. (3) The base member is substantially square and includes tracks on the top and bottom sides of at least three edges thereof, and a tab is inserted into each of the tracks at a corner of the base member. Shelf mentioned in section. (4) The shelf of claim 2, wherein each tab is formed from a conductive metal. (5) The shelf according to claim 4, wherein the conductive metal is aluminum. (6) Each tab forms a flange in a channel portion having a C-shaped cross section to be received in a track.
Shelf mentioned in section. (7) Each tab has an opening, while each fastening means has a threaded fastener inserted through the opening of each tab and screwed onto the auxiliary plate for insertion into the opening of the corresponding track. Claim 2, wherein the tab and the auxiliary plate form a clamping member, and when the threaded fastener is tightened, the tab and the auxiliary plate are tightened to the corresponding tracks to attach the shelf to the tracks of the storage cabinet. shelf. (8) The shelf according to claim 7, wherein each opening extends with a wide width. (9) The base member has a front end portion, a rear end portion, and opposite side end portions perpendicular to the front end portion and the rear end portion, and has an edge extending upwardly from the rear end portion beyond the upper surface portion; 3. The shelf of claim 2, wherein a circuit board supported on the base member is prevented from being pushed beyond the rear end. 10. The shelf of claim 3, wherein each tab at a rear corner of the base member extends from the rear end of the base member and is orthogonal to each front tab. (11) The shelf according to claim 1, wherein the conductive plastic material is polyethylene or polypropylene, which is a structural material for injection molding. (12) The first groove group on the top surface part and the bottom surface part has a relatively narrow width, while the second groove group has a relatively wide width, and the relatively narrow grooves on the top surface part and the bottom surface part have a relatively narrow width. 2. A shelf according to claim 1, wherein the shelves and relatively wide grooves are arranged alternately on the top and bottom sides.