WO2006070053A1 - Method for manufacturing an enclosure of electronic equipment and an enclosure of electronic equipment - Google Patents

Method for manufacturing an enclosure of electronic equipment and an enclosure of electronic equipment Download PDF

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Publication number
WO2006070053A1
WO2006070053A1 PCT/FI2005/000551 FI2005000551W WO2006070053A1 WO 2006070053 A1 WO2006070053 A1 WO 2006070053A1 FI 2005000551 W FI2005000551 W FI 2005000551W WO 2006070053 A1 WO2006070053 A1 WO 2006070053A1
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WO
WIPO (PCT)
Prior art keywords
enclosure
coating
coated
steel sheet
metallic alloy
Prior art date
Application number
PCT/FI2005/000551
Other languages
French (fr)
Inventor
Jussi Talonen
Original Assignee
Jussi Talonen
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Jussi Talonen filed Critical Jussi Talonen
Publication of WO2006070053A1 publication Critical patent/WO2006070053A1/en

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Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
    • G06F1/16—Constructional details or arrangements
    • G06F1/18—Packaging or power distribution
    • G06F1/181—Enclosures
    • G06F1/182—Enclosures with special features, e.g. for use in industrial environments; grounding or shielding against radio frequency interference [RFI] or electromagnetical interference [EMI]
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
    • C23C2/0224—Two or more thermal pretreatments
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/08—Tin or alloys based thereon
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
    • G06F1/16—Constructional details or arrangements
    • G06F1/18—Packaging or power distribution
    • G06F1/181—Enclosures

Definitions

  • the invention relates to a method for manufacturing an enclosure of electronic equipment, in which method an enclosure or at least part of an enclosure the raw material being steel sheet is coated with metallic alloy coating which contains at least zinc and tin and in which method an enclosure or at least part of an enclosure is manufactured this way of coated steel sheet by using sheet metal working techniques.
  • the present invention relates also to an enclosure of electronic equipment, where an enclosure contains at least one part, which is made of steel plate coated with metal alloy containing at least zinc and tin and that the part is in contact to electronic equipment or to its component.
  • Sheet metals used as enclosures of electronic equipments have to fulfil numerous requirements like manufacturability, global availability, demand for recycling, low price, electric conductive material and long lifetime against corrosion and oxidation.
  • these requirements can mostly be met with aluminium and steel sheet products.
  • zinc coated steel or aluminium sheets have to be passivated to avoid corrosion and oxidation.
  • the most used passivation method is based on use of hexavalent Chromium (Cr 6+).
  • Hexavalent Chromium is a very reactive metallic ion and it has been found to cause cancer and allergies. Avoid use of poisonous and hazardous substances, European Union (EU) has given two directives: WEEE (Waste of Electrical and Electronic equipment) and RoHS (Restriction of Hazardous Substances).
  • the aim of the invention is to provide a method for manufacture an enclosure for electrical device, in which the problems among available modern materials of the enclosures as mentioned above can be avoided.
  • Especially purpose of the invention is to provide a method, which allows production of the enclosure where there is no need for passivation of materials with hexavalent chromium and in which method passivation can be done with allowed passivation chemicals so that materials of en- closures achieve very good and long lasting electric conductivity, which ensures working of EMC-protection so that the requirements of the EU-directive mentioned above can be fulfilled.
  • the purpose of the invention is to provide a enclosure of electrical device, which is manufactured of material about the same cost as traditional materials and which properties fulfil requirements of manufacturability and global availability of the electronics industry.
  • the object of the invention is accomplished by a method for manufacturing an enclosure of electronic equipment and an enclosure of electronic equipment, the characteristics of which are presented in the claims.
  • Characteristic to the method in accordance with the invention is that the steel sheet used for the manufacturing is coated before manufacturing of the parts of the enclosure in that kind of continuous hot-dip-galvanising line, where coating process takes place after a heat treatment when the temperature of the steel strip has decreased to the desired coating temperature and that in the coating process the metallic alloy coating in which aluminium has been added is used.
  • the metallic alloy coating does not need further passivation of coated surface with hexavalent chromium. Under the circumstances enclosures or parts of them, which are manufactured with the defined method, will fulfil the requirements like new EU- directives of poisonous and hazardous substances, which are valid after June, year 2006.
  • the electric conductivity between joints of enclosures, part of it and/or its components is very good. Alloying of tin to coating mostly causes this high electric conductivity and this is also a method to ensure functional EMC-pro- tection of the enclosure.
  • the alloy coating also contains aluminium. With this addition of Al it is possible to improve adhesion of coating to steel strip surface. Suitable amount of aluminium addition is normally below 0,2 w-% of the alloy used for coating. This addition has a minor influence to the cost of the alloy coating, compared to the advantages, which can be achieved.
  • this kind of coating method as defined makes it possible to produce high quantities of coated steel strip by existing continuous hot-dip-galvanising lines, which allows to produce material for the enclosures with the same production costs as conventional hot-dipped steel strips. This all assists to produce, with the method defined, cost effectively enclosures compared to enclosures manufactured of hot-dip-galvanised steel sheets.
  • raw material of the enclosures for electric and electronic equipments which is made of coated steel strips produced with the defined method, fulfils requirements of electronics industry as productiveness and material global availabil- ity.
  • the steel sheet is coated with a metallic alloy coating which contains at the most 50 w-% of tin.
  • Tin is more valuable metal than steel or zinc and thus it is an advantage to use tin content as low as possible.
  • two alloy phases are formed, one is zinc rich phase, where most of the alloy consists of zinc and the other is tin rich phase, where most of the alloy is tin.
  • Tin rich phase has a tendency to enrich to the surfaces of the material. Under these circumstances, even if the tin content of the alloy is lower than the content of zinc, there is more tin rich phase on external surfaces of material, when alloy coating is produced with method defined above. This tin rich phase is very conductive material and consequently it is highly advantageous for the EMC-protection.
  • the steel sheet is coated so that the coating thickness of the finished metallic al-loy coating is at least 2 ⁇ m.
  • Sufficient corrosion protection and EMC-protection for an application can be achieved with this kind of coating thickness.
  • Coating thickness can be much thicker for demanding outdoor applications.
  • the coating thickness can be defined case by case so, that depending of the environmental conditions sufficient corrosion protection can be achieved, but costs of producing coating are still as low as possible.
  • corrosion protection of the alloy coating can be improved by passivating open alloy coated surfaces with passivation chemicals, which fulfils the EU direc- tives mentioned earlier. These passivation chemicals can be electric conductive organic layers.
  • Characteristic to the enclosure of electronic equipment is the enclosure or at least one part of the enclosure has been manufactured from metallic alloy coated steel sheet which has been coated in such type of continuous hot-dip-galvanising line where the coating process has taken place after a heat treatment, when the temperature of steel strip has decreased to the wanted coating temperature and that the metallic alloy coating, which has an addition of aluminium has been used as a coating of the steel strip.
  • This kind of enclosure or part of it has better corrosion protec- tion than an enclosure made of unpassivated, conventionally galvanised steel sheet. Under these circumstances enclosure made of this kind of material does not need surface protection of hexavalent chromium, which kind of passivation is forbidden at EU-region after July l ist 2006.
  • This alloy coating can let without any passivation treatment against corrosion for normal applications and for more demanding corro- sive environments it can be passivated with lighter, EU-directives fulfilling chemicals, which can not protect sufficiently conventional hot dip galvanised steel products like hexavalent chromium.
  • metallic alloy coating of the enclosure has a good adhesion to steel surface due to the aluminium addition.
  • the alloy coating has also high electric conductivity, which ensures also good electric con- ductivity between separate components and other parts of the enclosure. Electric conductivity of the alloy coating will not decrease unlike aluminium or conventional hot dip galvanised steel sheets because of corrosion or oxidation, because the metallic alloy coating has good electric conductivity even after oxidation or formation of patina.
  • enclosure made of alloy coated steel sheet as defined by the invention has low production costs and it fulfils requirements of electronic industry for global availability and manufacturability.
  • the figure 1 illustrates a enclosure of electronic equipment according to the invention
  • the figure 2 illustrates gross-section of the wall of the cover part of the enclosure according to figure 1.
  • the enclosure of figure 1 is an enclosure for computer central unit.
  • Main parts of the enclosure are cover 1, body structure 2 and front panel 3, where are necessary openings for disc drive, flash memory and for example CD/DVD-station.
  • Body structure of the enclosure is that component, where required electric devices and components of the central unit, like power supply, mother board and disc stations, are mounted.
  • Cover part 1 and body structure 2 are manufactured of coated steel sheets using currently known sheet metal working techniques (like for an example punching, cutting and bending).
  • Front surface of the cover is painted with commonly known paint system for computer enclosures.
  • the body structure holds commonly known structures for mounting the cover, power supply, hard disc, motherboard and other components of computer. This mounting to enclosure can be done with screws and/or other commonly known fastening methods.
  • Cover of the enclosure is box-like structure, which is open from the front and the back.
  • the cover is pushed over the body structure and it is attached with fastening screws to the body.
  • the cover has fastening projections at the edge of open back and front for attachment with the screws.
  • the front panel 3 is fastened to attaching structures at the front of body structure.
  • the front panel consists of a front board, which has openings for disc stations. These openings, if not used, are covered with lids, which can be unfastened if needed.
  • the front board has also other components, like buttons of switches etc., depending of construction and application of the computer. In general, these parts of the front panel are manufactured of plastics or of other suit- able material for application.
  • Steel sheet parts of the body structure 2 presented in figure I i and the cover part 1 are both manufactured of metallic alloy coated cold rolled steel strip.
  • cold rolled steel is coated using continuous hot dip galvanising line, where coiled steel strip is first decoiled, heat treated and cooled for suitable coating temperature before essential coating by hot dipping process.
  • the enclosure described in figure 1 is manufactured using steel strip coated with metallic alloy, which content is 30 w-% Sn, 69,85 %-w Zn and 0,15 % Al.
  • the final outcome of the coating process done with hot dip galvanising line is steel strip with coating, where zinc and tin have formed zinc rich phase and tin rich phase.
  • the zinc rich phase has typically about 98 % of zinc and 2 % of tin.
  • the tin rich phase has typically about 90 % of tin and 10 % of zinc.
  • Composition and deviation of the phases can be effected by alloying elements and/or by changing processing parameters of hot dip galvanising process.
  • Coating on the continuous hot dip galvanising line is done following way: steel strip for coating is guided with rolls to pot, which is filled with molten metallic alloy coating, which temperature is somewhat over the liquidus temperature (in this case about 400 - 420 0 C). In this case time for dipping the strip to the pot is about 3 seconds.
  • part of molten metallic alloy on the surface of strip is blown back to the pot by air-knives, which are directed to strip surface at an angle.
  • the air-knives are controlled so, that in this case there will be about 10 mm coating thickness of metallic alloy coating on the both sides of strip.
  • Next step is to cool down the strip (cooling rate is typically about 20-40 ° C/s).
  • the strip is recoiled and packed. After this procedure strip coil is transported to place where it is decoiled, straightened out and cut on sheets of suitable size. These sheets are used to manufacturing of cover and body structure of the enclosure.
  • Body structure part and cover part of the enclosure are manufactured of metallic alloy coated steel sheet, which production was defined above. This manufacturing is done by sheet metal working techniques with sheet metal working centres, which can cut, punch and bend sheet metals. Components for body structure are in most cases completed, but front surface of the cover part 1 is commonly painted with suitable surface paint to fill up requirements of computer manufacturer.
  • FIG 2 is presented material structure of the cover part. Steel sheet 4 has on both sides metallic alloy coat 5 and the front surface has also layer of paint 6 on the top of the coating. Unpainted, pure metallic alloy coating on the backside of the cover part ensures, that inner surfaces of enclosure have good elec- trie conductivity for proper EMC-protection.
  • Front panel 3 and other plastic parts of enclosure are manufactured of several plastic qualities using for example extrusion or other production methods. Finally the front panel, the cover part and other components of body structures are installed to the body structure, now enclosure is prepared for installation of computer electronics. Enclosure components composition or one part of it can alternately be done later, when electronic equipments and components of central unit are first installed to body structure of enclosure.
  • the method defined by the invention can be carried out by several ways, which can greatly differ from the example application.
  • the enclosure of computer central unit, presented above, is only one example application of the method defined by the in- vention.
  • the essential fact of the method defined by the invention is, that enclosure or at least one part of it is manufactured of continuous hot dip coated steel sheet, where metallic alloy coating consist of at least of zinc and tin. Under these circumstances the method can be applied to all that kind of electrical devices, where good electric conductivity is needed for joint surfaces and other structures.
  • the most cost effective solution of hot dip coating is the continuous hot dipping process, but of course coating can also be done by method where uncoated steel sheet parts of en- closure are dipped to molten metallic alloy as completed sheet components after they have had a certain preheat treatment.
  • composition of metallic alloy, pot temperature, thickness of the coating and for example post treatments of the coating can be carried out by several ways with the method defined by the inven- tion, instead of method presented for an example above.
  • Zinc-tin-coating research work has shown, that too low tin content can lead to poor coating adhesion to steel substrate.
  • tin has a relatively high price for an alloying element, thus increasing the total cost of the coatings with higher tin content.
  • the coating experiments showed, that controlling of the furnace atmosphere during the heat treat- ment of the steel and with suitable alloying elements and/or additives it is possible to increase tin enrichment to surfaces of the coating and it is very likely to ensure good electric conductivity with quite low tin contents.
  • the coating can contain also other metals or other substances as alloying elements.
  • copper addition can change phase structure of the coating, which has certain effects on electric conductivity of this metallic alloy coating and thus the effect on EMC-protection of the enclosure manufactured of the material.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Human Computer Interaction (AREA)
  • Computer Hardware Design (AREA)
  • Power Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Electromagnetism (AREA)
  • Coating With Molten Metal (AREA)
  • Casings For Electric Apparatus (AREA)

Abstract

The invention relates to a method for manufacturing an enclosure of electronic equipment, in which method an enclosure or at least part of an enclosure (1, 2) the raw material being steel sheet (4) is coated with metallic alloy coating (5) which contains at least zinc and tin and in which method an enclosure or at least part (1, 2) of an enclosure is manufactured this way of coated steel sheet (4, 5) by using sheet metal working techniques. Characteristic to the method according to the invention is that the steel sheet (4) used for the manufacturing is coated before manufacturing of the parts of the enclosure (1, 2) in that kind of continuous hot-dip-galvanising line where coating process takes place after a heat treatment when the temperature of the steel strip has decreased to the desired coating temperature and that in the coating process the metallic alloy coating (5) where aluminium has been added is used. The invention relates also to an enclosure of electronic equipment manufactured in accordance with the method according to the invention.

Description

METHOD FOR MANUFACTURING AN ENCLOSURE OF ELECTRONIC EQUIPMENTANDANENCLOSUREOFELECTRONICEQUIPMENT
The invention relates to a method for manufacturing an enclosure of electronic equipment, in which method an enclosure or at least part of an enclosure the raw material being steel sheet is coated with metallic alloy coating which contains at least zinc and tin and in which method an enclosure or at least part of an enclosure is manufactured this way of coated steel sheet by using sheet metal working techniques. The present invention relates also to an enclosure of electronic equipment, where an enclosure contains at least one part, which is made of steel plate coated with metal alloy containing at least zinc and tin and that the part is in contact to electronic equipment or to its component.
Nowadays, industrial applications for enclosures and frame structures of electrical and electronic equipments are mostly based on use of sheet metal. These plates are typically steel coated or treated by various methods or aluminium or stainless steel. Coated steel strips are typically electro galvanised (ZE) or hot dip galvanised (HDG) steels, whose surface is protected with chromate passivation or with other pre-treatment intending to protect sheet metal against corrosion of parts, which should have metallic appearance for EMC-properties. Recently has been developed electro galvanised (electroplated) coatings of steel plates for electronic enclosures, where the coating properties are improved by alloying Zinc with Tin and/or Copper or where enclosures made of coated steel are treated with electro conductive organic coatings.
Sheet metals used as enclosures of electronic equipments have to fulfil numerous requirements like manufacturability, global availability, demand for recycling, low price, electric conductive material and long lifetime against corrosion and oxidation. Currently these requirements can mostly be met with aluminium and steel sheet products. However, zinc coated steel or aluminium sheets have to be passivated to avoid corrosion and oxidation. The most used passivation method is based on use of hexavalent Chromium (Cr 6+). Hexavalent Chromium is a very reactive metallic ion and it has been found to cause cancer and allergies. Avoid use of poisonous and hazardous substances, European Union (EU) has given two directives: WEEE (Waste of Electrical and Electronic equipment) and RoHS (Restriction of Hazardous Substances). These directives prohibit use of hexavalent chromium at the EU region, starting from date July list 2006. If traditional coated steel (HDG, ZE) or aluminium is not further passivated, materials of enclosures are more obviously affected by corrosion and oxidation. Even thin layers of oxides or corrosion products can cause significant changes of electric conductivity of materials, consequently leading to poor EMC-properties (= protection against electric and electromagnetic waves) of enclosures. For a reliable and interference-free working of electric device, basic demand is working EMC-protection. Because of this fact EU has its own di- rective so called "EMC-directive" (89/336/EEC). This directive defines the following: electrical and electronic equipments on the markets have to fulfil certain requirements for EMC-protection. Device, which does not fulfil these requirements, is ordered to be removed from the markets.
The aim of the invention is to provide a method for manufacture an enclosure for electrical device, in which the problems among available modern materials of the enclosures as mentioned above can be avoided. Especially purpose of the invention is to provide a method, which allows production of the enclosure where there is no need for passivation of materials with hexavalent chromium and in which method passivation can be done with allowed passivation chemicals so that materials of en- closures achieve very good and long lasting electric conductivity, which ensures working of EMC-protection so that the requirements of the EU-directive mentioned above can be fulfilled. Also the purpose of the invention is to provide a enclosure of electrical device, which is manufactured of material about the same cost as traditional materials and which properties fulfil requirements of manufacturability and global availability of the electronics industry.
The object of the invention is accomplished by a method for manufacturing an enclosure of electronic equipment and an enclosure of electronic equipment, the characteristics of which are presented in the claims.
Characteristic to the method in accordance with the invention is that the steel sheet used for the manufacturing is coated before manufacturing of the parts of the enclosure in that kind of continuous hot-dip-galvanising line, where coating process takes place after a heat treatment when the temperature of the steel strip has decreased to the desired coating temperature and that in the coating process the metallic alloy coating in which aluminium has been added is used. When enclosure for electrical device or part of it is manufactured of steel sheet coated as mentioned above, the metallic alloy coating does not need further passivation of coated surface with hexavalent chromium. Under the circumstances enclosures or parts of them, which are manufactured with the defined method, will fulfil the requirements like new EU- directives of poisonous and hazardous substances, which are valid after June, year 2006. In addition, the electric conductivity between joints of enclosures, part of it and/or its components is very good. Alloying of tin to coating mostly causes this high electric conductivity and this is also a method to ensure functional EMC-pro- tection of the enclosure. The alloy coating also contains aluminium. With this addition of Al it is possible to improve adhesion of coating to steel strip surface. Suitable amount of aluminium addition is normally below 0,2 w-% of the alloy used for coating. This addition has a minor influence to the cost of the alloy coating, compared to the advantages, which can be achieved. Furthermore, this kind of coating method as defined makes it possible to produce high quantities of coated steel strip by existing continuous hot-dip-galvanising lines, which allows to produce material for the enclosures with the same production costs as conventional hot-dipped steel strips. This all assists to produce, with the method defined, cost effectively enclosures compared to enclosures manufactured of hot-dip-galvanised steel sheets. In addition raw material of the enclosures for electric and electronic equipments, which is made of coated steel strips produced with the defined method, fulfils requirements of electronics industry as productiveness and material global availabil- ity.
In an advantageous application of the method the steel sheet is coated with a metallic alloy coating which contains at the most 50 w-% of tin. Tin is more valuable metal than steel or zinc and thus it is an advantage to use tin content as low as possible. When coating is done by hot-dipping process with zinc-tin-alloy, two alloy phases are formed, one is zinc rich phase, where most of the alloy consists of zinc and the other is tin rich phase, where most of the alloy is tin. Tin rich phase has a tendency to enrich to the surfaces of the material. Under these circumstances, even if the tin content of the alloy is lower than the content of zinc, there is more tin rich phase on external surfaces of material, when alloy coating is produced with method defined above. This tin rich phase is very conductive material and consequently it is highly advantageous for the EMC-protection.
In the second advantageous application of the method the steel sheet is coated so that the coating thickness of the finished metallic al-loy coating is at least 2 μm. Sufficient corrosion protection and EMC-protection for an application can be achieved with this kind of coating thickness. Coating thickness can be much thicker for demanding outdoor applications. The coating thickness can be defined case by case so, that depending of the environmental conditions sufficient corrosion protection can be achieved, but costs of producing coating are still as low as possible. Furthermore, corrosion protection of the alloy coating can be improved by passivating open alloy coated surfaces with passivation chemicals, which fulfils the EU direc- tives mentioned earlier. These passivation chemicals can be electric conductive organic layers.
Characteristic to the enclosure of electronic equipment is the enclosure or at least one part of the enclosure has been manufactured from metallic alloy coated steel sheet which has been coated in such type of continuous hot-dip-galvanising line where the coating process has taken place after a heat treatment, when the temperature of steel strip has decreased to the wanted coating temperature and that the metallic alloy coating, which has an addition of aluminium has been used as a coating of the steel strip. This kind of enclosure or part of it has better corrosion protec- tion than an enclosure made of unpassivated, conventionally galvanised steel sheet. Under these circumstances enclosure made of this kind of material does not need surface protection of hexavalent chromium, which kind of passivation is forbidden at EU-region after July l ist 2006. This alloy coating can let without any passivation treatment against corrosion for normal applications and for more demanding corro- sive environments it can be passivated with lighter, EU-directives fulfilling chemicals, which can not protect sufficiently conventional hot dip galvanised steel products like hexavalent chromium. In addition metallic alloy coating of the enclosure has a good adhesion to steel surface due to the aluminium addition. The alloy coating has also high electric conductivity, which ensures also good electric con- ductivity between separate components and other parts of the enclosure. Electric conductivity of the alloy coating will not decrease unlike aluminium or conventional hot dip galvanised steel sheets because of corrosion or oxidation, because the metallic alloy coating has good electric conductivity even after oxidation or formation of patina. Under these circumstances metallic alloy coating of the enclosure en- sures working earth connections and EMC-protection for a long product lifetime. Furthermore, enclosure made of alloy coated steel sheet as defined by the invention has low production costs and it fulfils requirements of electronic industry for global availability and manufacturability.
Next, the invention will be explained in more detail with reference to the accompa- nying drawings, in which,
The figure 1 illustrates a enclosure of electronic equipment according to the invention, and
The figure 2 illustrates gross-section of the wall of the cover part of the enclosure according to figure 1.
The enclosure of figure 1 is an enclosure for computer central unit. Main parts of the enclosure are cover 1, body structure 2 and front panel 3, where are necessary openings for disc drive, flash memory and for example CD/DVD-station. Body structure of the enclosure is that component, where required electric devices and components of the central unit, like power supply, mother board and disc stations, are mounted. Cover part 1 and body structure 2 are manufactured of coated steel sheets using currently known sheet metal working techniques (like for an example punching, cutting and bending). Front surface of the cover is painted with commonly known paint system for computer enclosures. The body structure holds commonly known structures for mounting the cover, power supply, hard disc, motherboard and other components of computer. This mounting to enclosure can be done with screws and/or other commonly known fastening methods. Cover of the enclosure is box-like structure, which is open from the front and the back. The cover is pushed over the body structure and it is attached with fastening screws to the body. The cover has fastening projections at the edge of open back and front for attachment with the screws. The front panel 3 is fastened to attaching structures at the front of body structure. The front panel consists of a front board, which has openings for disc stations. These openings, if not used, are covered with lids, which can be unfastened if needed. The front board has also other components, like buttons of switches etc., depending of construction and application of the computer. In general, these parts of the front panel are manufactured of plastics or of other suit- able material for application.
Steel sheet parts of the body structure 2 presented in figure I i and the cover part 1 are both manufactured of metallic alloy coated cold rolled steel strip. When this kind of steel strip is produced, cold rolled steel is coated using continuous hot dip galvanising line, where coiled steel strip is first decoiled, heat treated and cooled for suitable coating temperature before essential coating by hot dipping process. The enclosure described in figure 1 is manufactured using steel strip coated with metallic alloy, which content is 30 w-% Sn, 69,85 %-w Zn and 0,15 % Al. The final outcome of the coating process done with hot dip galvanising line is steel strip with coating, where zinc and tin have formed zinc rich phase and tin rich phase. The zinc rich phase has typically about 98 % of zinc and 2 % of tin. The tin rich phase has typically about 90 % of tin and 10 % of zinc. Composition and deviation of the phases can be effected by alloying elements and/or by changing processing parameters of hot dip galvanising process.
Coating on the continuous hot dip galvanising line is done following way: steel strip for coating is guided with rolls to pot, which is filled with molten metallic alloy coating, which temperature is somewhat over the liquidus temperature (in this case about 400 - 420 0C). In this case time for dipping the strip to the pot is about 3 seconds. When the strip arises from the pot, part of molten metallic alloy on the surface of strip is blown back to the pot by air-knives, which are directed to strip surface at an angle. The air-knives are controlled so, that in this case there will be about 10 mm coating thickness of metallic alloy coating on the both sides of strip. Next step is to cool down the strip (cooling rate is typically about 20-40 ° C/s). Next the strip is recoiled and packed. After this procedure strip coil is transported to place where it is decoiled, straightened out and cut on sheets of suitable size. These sheets are used to manufacturing of cover and body structure of the enclosure.
Body structure part and cover part of the enclosure, as defined in figure 1, are manufactured of metallic alloy coated steel sheet, which production was defined above. This manufacturing is done by sheet metal working techniques with sheet metal working centres, which can cut, punch and bend sheet metals. Components for body structure are in most cases completed, but front surface of the cover part 1 is commonly painted with suitable surface paint to fill up requirements of computer manufacturer. In figure 2 is presented material structure of the cover part. Steel sheet 4 has on both sides metallic alloy coat 5 and the front surface has also layer of paint 6 on the top of the coating. Unpainted, pure metallic alloy coating on the backside of the cover part ensures, that inner surfaces of enclosure have good elec- trie conductivity for proper EMC-protection. Front panel 3 and other plastic parts of enclosure are manufactured of several plastic qualities using for example extrusion or other production methods. Finally the front panel, the cover part and other components of body structures are installed to the body structure, now enclosure is prepared for installation of computer electronics. Enclosure components composition or one part of it can alternately be done later, when electronic equipments and components of central unit are first installed to body structure of enclosure.
The method defined by the invention can be carried out by several ways, which can greatly differ from the example application. The enclosure of computer central unit, presented above, is only one example application of the method defined by the in- vention. The essential fact of the method defined by the invention is, that enclosure or at least one part of it is manufactured of continuous hot dip coated steel sheet, where metallic alloy coating consist of at least of zinc and tin. Under these circumstances the method can be applied to all that kind of electrical devices, where good electric conductivity is needed for joint surfaces and other structures. The most cost effective solution of hot dip coating is the continuous hot dipping process, but of course coating can also be done by method where uncoated steel sheet parts of en- closure are dipped to molten metallic alloy as completed sheet components after they have had a certain preheat treatment. In addition composition of metallic alloy, pot temperature, thickness of the coating and for example post treatments of the coating can be carried out by several ways with the method defined by the inven- tion, instead of method presented for an example above. Zinc-tin-coating research work has shown, that too low tin content can lead to poor coating adhesion to steel substrate. On the other hand, tin has a relatively high price for an alloying element, thus increasing the total cost of the coatings with higher tin content. The coating experiments showed, that controlling of the furnace atmosphere during the heat treat- ment of the steel and with suitable alloying elements and/or additives it is possible to increase tin enrichment to surfaces of the coating and it is very likely to ensure good electric conductivity with quite low tin contents.
In addition, during the research work it was found out, that pure zinc-tin-alloy coating does not give proper protection against corrosion for enclosures, which are used at very severe conditions. If necessary, metallic alloy coatings containing zinc and tin can have treatments to improve protection against oxidation and formation of patina. These treatments can be chemical passivation or coating with thin organic electrically conductive layers, which will fulfil new EU-directives getting their legal force in the near years. This kind of post treatment makes enclosures made of zinc- tin-coated steel sheet more protective against corrosive environments than enclosures made of conventional hot-dip-galvanised steel will make after the same treatments. Furthermore, to improve different wanted properties for metallic alloy coating of enclosures defined by the invention, the coating can contain also other metals or other substances as alloying elements. For example, copper addition can change phase structure of the coating, which has certain effects on electric conductivity of this metallic alloy coating and thus the effect on EMC-protection of the enclosure manufactured of the material.
The invention is not limited to the presented advantageous application but it can vary within the frames of the idea of the invention formed in the claims.

Claims

1. A method for manufacturing enclosure of electronic equipment, in which method the enclosure or at least part of the enclosure (1, 2) the raw material being steel sheet (4) is coated with metallic alloy coating (5) which contains at least zinc and tin and in which method the enclosure or at least part (1, 2) of the enclosure is manufactured this way of coated steel sheet (4, 5) by using sheet metal working techniques, c h a r a c t e ri z e d in that the steel sheet (4) used for the manufacturing is coated before manufacturing of the parts of the enclosure (1,2) in that kind of continuous hot-dip-galvanising line where coating process takes place after a heat treatment when the temperature of the steel strip has decreased to the desired coating temperature and that in the coating process the metallic alloy coating (5) where aluminium has been added is used.
2. A method in accordance with claim 1, c h ar a c t eri z e d in that the the steel sheet (4) is coated with a metallic alloy coating which contains at the most 50 w-% of tin.
3. A method in accordance with claim 1 or 2, c h ar a c t e r i z e d in that the steel sheet (4) is coated so that the coating thickness of the finished metallic alloy coating is at least 2 μm.
4. An enclosure of electronic equipment, which enclosure includes at least one part (1, 2) which has been made of steel sheet coated with metallic alloy (4, 5) contain- ing at least tin and zinc, where the electronic equipment or part of it has been attached, ch ar a c t e ri z e d in that the enclosure or at least one part (1,2) of the enclosure has been manufactured from metallic alloy coated steel sheet (4, 5), which has been coated in that kind of continuous hot-dip-galvanising line where the coating process has taken place after a heat treatment, when the temperature of steel strip has decreased to the wanted coating temperature and that the metallic alloy coating (5), which has an addition of aluminium has been used as a coating of the steel strip.
5. An enclosure of electronic equipment in accordance with claim 6, c h a r - a c t e r i z e d in that the metallic alloy coating (5) of the steel sheet (4) contains at most 50 w-% of tin.
6. An enclosure of electronic equipment in accordance with claim 4 or 5, c har acte riz e d in that the thickness of the metallic alloy coating (5) of the steel sheet (4) is at least 2 μm.
PCT/FI2005/000551 2004-12-27 2005-12-27 Method for manufacturing an enclosure of electronic equipment and an enclosure of electronic equipment WO2006070053A1 (en)

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FI20041671A FI20041671A (en) 2004-12-27 2004-12-27 A method of manufacturing an electronic device enclosure and an electronic device enclosure
FI20041671 2004-12-27

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110964998A (en) * 2018-09-29 2020-04-07 上海梅山钢铁股份有限公司 Hot galvanizing production process

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3962501A (en) * 1972-12-15 1976-06-08 Nippon Steel Corporation Method for coating of corrosion-resistant molten alloy
US4123292A (en) * 1976-12-23 1978-10-31 Armco Steel Corporation Method of treating steel strip and sheet surfaces for metallic coating
JP2000119833A (en) * 1998-10-09 2000-04-25 Nippon Steel Corp HOT DIP Sn-Zn PLATED STEEL SHEET FOR ELECTRICAL MEMBER
US6194653B1 (en) * 1998-03-24 2001-02-27 General Instrument Corporation Enclosure design having an integrated system of retention, electromagnetic interference containment and structural load distribution

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3962501A (en) * 1972-12-15 1976-06-08 Nippon Steel Corporation Method for coating of corrosion-resistant molten alloy
US4123292A (en) * 1976-12-23 1978-10-31 Armco Steel Corporation Method of treating steel strip and sheet surfaces for metallic coating
US6194653B1 (en) * 1998-03-24 2001-02-27 General Instrument Corporation Enclosure design having an integrated system of retention, electromagnetic interference containment and structural load distribution
JP2000119833A (en) * 1998-10-09 2000-04-25 Nippon Steel Corp HOT DIP Sn-Zn PLATED STEEL SHEET FOR ELECTRICAL MEMBER

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110964998A (en) * 2018-09-29 2020-04-07 上海梅山钢铁股份有限公司 Hot galvanizing production process
CN110964998B (en) * 2018-09-29 2021-11-16 上海梅山钢铁股份有限公司 Hot galvanizing production process

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FI20041671A0 (en) 2004-12-27

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