EP0694990A1 - Method for selective metallization of plastic connectors - Google Patents
Method for selective metallization of plastic connectors Download PDFInfo
- Publication number
- EP0694990A1 EP0694990A1 EP94202140A EP94202140A EP0694990A1 EP 0694990 A1 EP0694990 A1 EP 0694990A1 EP 94202140 A EP94202140 A EP 94202140A EP 94202140 A EP94202140 A EP 94202140A EP 0694990 A1 EP0694990 A1 EP 0694990A1
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- Prior art keywords
- metal layer
- connector
- cavity
- depositing
- thickness
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- 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
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/1601—Process or apparatus
- C23C18/1603—Process or apparatus coating on selected surface areas
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- 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
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/1601—Process or apparatus
- C23C18/1633—Process of electroless plating
- C23C18/1646—Characteristics of the product obtained
- C23C18/165—Multilayered product
- C23C18/1653—Two or more layers with at least one layer obtained by electroless plating and one layer obtained by electroplating
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- 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
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/1601—Process or apparatus
- C23C18/1633—Process of electroless plating
- C23C18/1689—After-treatment
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- 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
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
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- 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
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/38—Coating with copper
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/02—Electroplating of selected surface areas
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
- H01R13/00—Details of coupling devices of the kinds covered by groups H01R12/70 or H01R24/00 - H01R33/00
- H01R13/648—Protective earth or shield arrangements on coupling devices, e.g. anti-static shielding
- H01R13/658—High frequency shielding arrangements, e.g. against EMI [Electro-Magnetic Interference] or EMP [Electro-Magnetic Pulse]
- H01R13/6598—Shield material
- H01R13/6599—Dielectric material made conductive, e.g. plastic material coated with metal
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
- H01R43/00—Apparatus or processes specially adapted for manufacturing, assembling, maintaining, or repairing of line connectors or current collectors or for joining electric conductors
- H01R43/18—Apparatus or processes specially adapted for manufacturing, assembling, maintaining, or repairing of line connectors or current collectors or for joining electric conductors for manufacturing bases or cases for contact members
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
- H01R13/00—Details of coupling devices of the kinds covered by groups H01R12/70 or H01R24/00 - H01R33/00
- H01R13/648—Protective earth or shield arrangements on coupling devices, e.g. anti-static shielding
- H01R13/658—High frequency shielding arrangements, e.g. against EMI [Electro-Magnetic Interference] or EMP [Electro-Magnetic Pulse]
- H01R13/6581—Shield structure
Definitions
- the present invention relates to a method for selective metallization of plastic connectors.
- noise countermeasures have to be taken on different levels.
- connections have to be made between on-board grounding and frame-grounding points to provide overall good grounding.
- shielding will have to be provided on cabinets besides establishment of a proper connection between connector casings and cable's woven metal sheaths, in order to reduce interference noise emission.
- filter elements may be used in series with signal lines, in order to reduce line-carried noise interferences.
- special wiring techniques may be used in order to reduce cross-talk between adjacent signal lines within cables or within cabinets.
- Figure 1a to 1f show different connector configurations, known as such, each having its own range of application.
- Figure 1a represents a conventional lower frequency application in which a connector 1 comprises several, e.g. 7, adjacent signal contact members 2. There is mutual coupling between adjacent signal contact members 2 and signal integrity may not be a concern.
- connector 1 comprises six signal contact members 2 and one ground contact member 3 at an arbitrary location.
- ground contact member 3 mutual inductance and capacitance to ground may be varied. Locating, for instance, the ground contact member 3 in the middle of the connector 1 would reduce the electrical loop length and would somewhat improve the performance.
- connector 1 comprises several signal contact members 2 and several ground contact members 3.
- the signal contact members 2 and ground contact members 3 alternate.
- the loop length is significantly reduced.
- There is less coupling via mutual impedance, and noise suppression with improved signal transmission is established.
- Such a configuration is easily achieved with conventional connectors by appropriate rooting and pole assignments. This does, however, imply a reduction of the number of signal contact members 2 in the connector 1, which reduces I/O density.
- connector 1 comprises seven adjacent signal contact members 2 and a ground plane 4 at one of its side surfaces.
- the ground plane 4 may be a metal plate, whereby the loop length can be further reduced. This then, can be a means of achieving further electrical enhancement of the connector 1 for the digital transmission of signals with a larger number of signal pins.
- the ground plane 4 is a better barrier to suppress unwanted stray EMI noise emitted from components adjacent to the connector.
- Figure 1e shows connector 1 with seven adjacent signal contact members 2 and a further ground plane 5 at a side surface of connector 1 opposite to ground plane 4, thereby further improving the high speed electrical performance.
- the connector 1 can be entirely enclosed by a shielding 6 which is similar to a Faraday cage and shields the signal contact members 2 from any outside electromagnetic radiation.
- one or more of the signal contact members 2 may be substituted by a ground contact member 3 to reduce cross-talk between the signal contact members 2.
- Figure 2 shows a chart developed to compare multi-row connection structures in terms of anticipated high-speed performance, in the context of high I/O and miniaturization needs.
- the chart is based on conventional knowledge in the field.
- In the bottom row of the chart according to figure 2 several connector configurations are schematically depicted.
- In the three rows above the bottom row the performance of each of these connector configurations as regards cross-talk, impedance matching, and signal density mounting is indicated by symbols explained under the chart.
- coaxial connectors out-perform other configurations. However, they are expensive and in general they do not satisfy the drive towards miniaturization and the need for connector modularity and systems approach.
- Pseudo-coaxial and electrically enhanced ground-planes are effective means in most modern electronic circuitries.
- the first connector configuration shown relates to a 1:1 arrangement of alternating signal contact members and ground contact members.
- the arrangement may have another ratio, as shown in figure 3.
- the transmission performance will be reduced.
- US Patent 4,600,480 discloses a method to selectively plate a connector comprising the steps of providing an electroless metal layer over all of first selected surfaces, and electroplating the first selected surfaces twice. Second selected surfaces are not plated by the electroplating step.
- this known method will only work under various specific conditions. As long as the first and second selected surfaces are subjected to the same external conditions the known method is not able to distinguish the first from the second selected surfaces and, therefore, under those conditions no selective metallization will be established. Moreover, no sharp transitions between the first and second selected surfaces can be expected by this known method.
- Selective plating of connector elements may also be done by sputtering techniques, as e.g. disclosed by US Patent 4,932,888 or by the application of conductive ink, as disclosed in US Patent 4,846,724.
- sputtering techniques as e.g. disclosed by US Patent 4,932,888 or by the application of conductive ink, as disclosed in US Patent 4,846,724.
- neither of these latter techniques leads to very accurate transitions between those parts being plated and those parts being not plated.
- Japanese patent application 54.67690 discloses the use of light beams, laser beams or electron beams to separate an integrally made conductive metal layer on a substrate into several conductive metal lines.
- the object of the present invention is to provide a method for selective metallization of connectors by which a very accurate distinction between plated and not plated surface areas can be obtained.
- the method for selective metallization of a plastic connector comprises the steps of:
- the present invention is based on the insight that the use of means to ablate one or more very small traces of an integrally made metal layer on a connector, by which traces several metal layer areas on the connector surface are established which are no longer electrically interconnected may result in, very accurate transitions between plated and not plated surface areas on the connector.
- a high energy beam may be used which is selected to be one of the following particle beams: an electron beam or ion beam.
- an electron beam or ion beam may be used.
- a light beam or a laser beam may be used.
- the ablating step may be carried out by grinding, e.g. by any suitable, high precision abrasive stream of particles.
- Removal of the non-selected metal layer areas as defined in step d. above may be done by chemical etching or by grinding.
- the diameter of the high energy beam may be about 75 ⁇ m.
- the first metal layer may comprise electroless copper or nickel.
- the first thickness may be between 1 to 2 ⁇ m.
- the second metal layer preferably comprises galvanically deposited copper.
- the second thickness preferably is between 5 to 10 ⁇ m.
- Step a. defined above may be preceded by immersing the connector in an alkaline bath to roughen its surface in contact with said bath.
- step d. defined above may be followed by e. depositing a top coat finish layer on said second copper layer, selected to be one of the following group of metals: nickel, gold, or tin-lead.
- Said finish layer may have a thickness between 2 to 4 ⁇ m.
- the proposed method offers great flexibility since metallized and not metallized parts of the connector surface may be separated by ablating traces of a first, very thin metal layer on the connector surface and these traces may have any predetermined contour.
- FIGS 1a to 1f show various connector configurations known from the prior art, in which shielding and/or grounding enhances connector performance.
- Figure 2 shows a chart based on knowledge in the field and in which several connector configurations are compared as to several electrical characteristics.
- Figure 3 shows some more possible connector configurations besides the ones shown in figure 2.
- Figures 4a to 4f show selective plastic metallization process steps according to the invention.
- FIGS 5a to 5f show application of the process according to the invention to one specific connector.
- FIG. 4 shows the subsequent steps according to the present invention.
- step 1 (figures 4a and 4b) an electroless metal layer 11 of a first predetermined thickness is deposited on the surface of a connector 10.
- the electroless metal layer 11 is preferably of copper, whereas the thickness of electroless metal layer 11 is preferably between 1 to 2 ⁇ m.
- one or more predetermined traces 12 are ablated from the first metal layer 11 to produce at least two electrically separate metal layer areas 11a, 11b.
- the ablation of traces 12 from metal layer 11 may be done by an electron beam, an ion beam, a light beam, a laser beam, or any other high energy beam. It is envisaged that also grinding by sand-blasting or ice-blasting, or the like, may be applied to make the traces 12.
- These traces 12 surround the separate metal layer areas 11a, 11b, in a predetermined way in order to have isolated metal layer areas 11a, 11b.
- a second metal layer of a second predetermined thickness is galvanically deposited on selected metal layer area 11b and not on metal layer area 11a. This can be easily achieved by emersion of the intermediate product of figure 4c in an electrolyte and applying a negative voltage to selected area 11b and not to area 11a. Then additional copper 13 of, for instance 5 to 10 ⁇ m, may be deposited on selected metal layer 11b, whereas not selected metal layer area 11a remains unchanged in thickness to its initial thickness of 1 to 2 ⁇ m.
- the product obtained is subjected to selective removal of the unchanged metal layer areas 11a. This may be done by emersion of the product obtained after the preceding step in figure 4d in an etch bath, long enough to etch at least 2 ⁇ m of copper. After that step, in which also some of the galvanically deposited copper layer 13 on the selected metal layer area 11b will be etched, still enough of the galvanically deposited copper layer 13 remains.
- a finishing layer 14 to protect the galvanically deposited copper layer 13, may be applied to layer 13. Finishing layers of other suitable metals, like gold or tin-lead, may be applied alternatively. Preferably, the finishing layer 14 has a thickness of 2 to 4 ⁇ m.
- the removal of the metal layer area 11a may be done by any suitable method: instead of a chemical etching process indicated above also grinding may be used.
- the diameter of the cross-section of the traces 12 may be as small as 75 ⁇ m.
- the galvanically deposited metal layer 13 may be made of any suitable metal.
- the step of depositing electroless copper layer 11 may be preceded by immersing the connector 10 in an alkaline bath to roughen the connector's surface in contact with said bath. Thus, micropores may be obtained which enhance the contact strength between the electroless copper layer 11 and the connector 10.
- Figures 5a to 5f show the application of the method according to figures 4a to 4f to a connector body in order to yield a shielded connector body.
- Figure 5a shows the surface of connector 10 which may be chemically roughened in a first step. However, this step may be omitted.
- first metal layer area 11a and second metal layer area 11b are ablated from the electroless copper layer 11 to obtain first metal layer area 11a and second metal layer area 11b.
- the first metal layer area 11a covers the inside surfaces of all cavities 15 of connector 10, which cavities 15 are intended to accommodate suitable contact members (not shown) afterwards.
- the second metal layer area 11b covers roughly the outside surface of connector 10.
- First metal layer are 11a and second metal layer area 11b are electrically separated by traces 12.
- a galvanically deposited copper layer 13 is applied to the second metal layer area 11b according to the process step described above in accordance with figure 4d.
- the first metal layer are 11a remains unchanged.
- the first metal layer area 11a covering the inside surfaces of the cavities 15 is removed, e.g. by chemically etching. By that etching step the thickness of the galvanically deposited copper layer 13 is also somewhat reduced.
- a finishing layer 14 preferably made of nickel, is applied to the galvanically deposited copper layer 13.
- any other suitable metal layer may be used instead.
- the end product shown in figure 5f is a connector 10 having a body which is entirely shielded at its outside surface.
- the connector shown in figures 5a to 5f only relate to one example.
- the method according to the invention was tested for a connector made of a polymer resin for high temperatures, known as Vectra A130.
- the tests have shown that this material is appropriate to be selectively metallised by the proposed method.
- the tests have shown that the electrical performance of a connector selectively shielded by the proposed method is similar to the electrical performance of a connector having separate metal shieldings.
- Vectra A130 has shown good results, the method according to the invention is not restricted to the application of this polymer resin only. The use of any other suitable polymer resin falls within the scope of the present invention.
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- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
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Abstract
Method for selective metallization of a plastic connector comprising the steps of:
- a. depositing a first, electroless metal layer of a first predetermined thickness on the surface of the connector;
- b. ablating predetermined parts of said first metal layer to produce at least two electrically separate metal layer areas;
- c. depositing a second, galvanic metal layer of a second predetermined thickness to at least one selected metal layer area;
- d. removing any non-selected metal layer area.
Description
- The present invention relates to a method for selective metallization of plastic connectors.
- In the past years connector manufacturers have become increasingly aware of customer demands for higher I/O requirements using SMT while signal clock speed has increased. Simultaneously the drive towards miniaturization in all electronic segments is forcing designs to focus on new techniques to resolve other issues related to signal integrity such as shielding, grounding, mutual coupling cross-talk and signal reflection parameters. Electronic devices are becoming portable and are subsequently exposed to varying environments, and issues of noise suppression due to electromagnetic interferences (EMI) and electrostatic discharged (ESD) are of major concern for designers and users of electronic devices. Connectors play a key role for connection within electronic devices, but also to couple one device to another. In addition to fast-paced advances in electronic technology, transitions are being noticed from analogue signals to faster speed digital technology; simultaneously the operating voltages are being lowered for increased power efficiency - a trend that makes it more difficult to institute measures to suppress interfering noise emissions including EMI and ESD. Digital equipment is intrinsically vulnerable to noise; it also is prone to emit noise.
- In order to maintain signal integrity in high-speed applications noise countermeasures have to be taken on different levels. First of all, connections have to be made between on-board grounding and frame-grounding points to provide overall good grounding. Secondly, shielding will have to be provided on cabinets besides establishment of a proper connection between connector casings and cable's woven metal sheaths, in order to reduce interference noise emission. Thirdly, filter elements may be used in series with signal lines, in order to reduce line-carried noise interferences. Fourthly, special wiring techniques may be used in order to reduce cross-talk between adjacent signal lines within cables or within cabinets.
- Commonly current connector designs need to be enhanced to fit their application in modern electronic circuitry. Shielding and grounding facilities are required and designs need adaption.
- Figure 1a to 1f show different connector configurations, known as such, each having its own range of application.
- Figure 1a represents a conventional lower frequency application in which a
connector 1 comprises several, e.g. 7, adjacentsignal contact members 2. There is mutual coupling between adjacentsignal contact members 2 and signal integrity may not be a concern. - As frequency increases, more grounding will be required as shown in figures 1b and 1c. In
figure 1b connector 1 comprises sixsignal contact members 2 and oneground contact member 3 at an arbitrary location. By varying the location of theground contact member 3 mutual inductance and capacitance to ground may be varied. Locating, for instance, theground contact member 3 in the middle of theconnector 1 would reduce the electrical loop length and would somewhat improve the performance. - In the embodiment of
figure 1c connector 1 comprises severalsignal contact members 2 and severalground contact members 3. The signal contactmembers 2 andground contact members 3 alternate. Thus, the loop length is significantly reduced. There is less coupling via mutual impedance, and noise suppression with improved signal transmission is established. Such a configuration is easily achieved with conventional connectors by appropriate rooting and pole assignments. This does, however, imply a reduction of the number of signal contactmembers 2 in theconnector 1, which reduces I/O density. - In
figure 1d connector 1 comprises seven adjacentsignal contact members 2 and aground plane 4 at one of its side surfaces. Theground plane 4 may be a metal plate, whereby the loop length can be further reduced. This then, can be a means of achieving further electrical enhancement of theconnector 1 for the digital transmission of signals with a larger number of signal pins. In addition, theground plane 4 is a better barrier to suppress unwanted stray EMI noise emitted from components adjacent to the connector. - Figure 1e shows
connector 1 with seven adjacentsignal contact members 2 and a further ground plane 5 at a side surface ofconnector 1 opposite toground plane 4, thereby further improving the high speed electrical performance. - As shown in figure 1f the
connector 1 can be entirely enclosed by a shielding 6 which is similar to a Faraday cage and shields the signal contactmembers 2 from any outside electromagnetic radiation. - It is noted that in the configurations of figures 1d to 1f one or more of the
signal contact members 2 may be substituted by aground contact member 3 to reduce cross-talk between thesignal contact members 2. However, this results in a lower I/O density. - Figure 2 shows a chart developed to compare multi-row connection structures in terms of anticipated high-speed performance, in the context of high I/O and miniaturization needs. The chart is based on conventional knowledge in the field. In the bottom row of the chart according to figure 2 several connector configurations are schematically depicted. In the three rows above the bottom row the performance of each of these connector configurations as regards cross-talk, impedance matching, and signal density mounting is indicated by symbols explained under the chart. Clearly, coaxial connectors out-perform other configurations. However, they are expensive and in general they do not satisfy the drive towards miniaturization and the need for connector modularity and systems approach. Pseudo-coaxial and electrically enhanced ground-planes are effective means in most modern electronic circuitries.
- In figure 2 the first connector configuration shown relates to a 1:1 arrangement of alternating signal contact members and ground contact members. Of course, the arrangement may have another ratio, as shown in figure 3. However, by increasing the ratio of signal contact members to ground contact members the transmission performance will be reduced.
- As shown by figures 1d to 1f the electrical performance of connectors for higher frequencies is enhanced by shielding at least selected parts of the connectors.
- In order to shield (selected parts of) connectors several methods have already been proposed.
- US Patent 4,600,480 discloses a method to selectively plate a connector comprising the steps of providing an electroless metal layer over all of first selected surfaces, and electroplating the first selected surfaces twice. Second selected surfaces are not plated by the electroplating step. However, this known method will only work under various specific conditions. As long as the first and second selected surfaces are subjected to the same external conditions the known method is not able to distinguish the first from the second selected surfaces and, therefore, under those conditions no selective metallization will be established. Moreover, no sharp transitions between the first and second selected surfaces can be expected by this known method.
- Another method of selectively plating connectors is known from US Patent 5,141,454. In this known method first selected surface areas are chemically roughened, creating micropores which function as anchor sides for plating. Those parts of the surface of the connector not being chemically roughened will not be suitable for plating in the next step in which electroless plating is used to build conductive layers on the chemically roughened surface areas of the connector. Typically copper is applied to render a conductive base surface. Said base surface may be further metallized by electroless, electrolytic or emersion plating techniques. Applicable metals include nickel, tin, silver, palladium and gold. However, since the distinction between those surface areas which are plated and those which are not is made by a chemically roughening process the accuracy of the transition between the plated and unplated surface area on the connector is limited.
- Selective metallization of plastic elements is also known from the leaflets: "Mitsui-Pathtek Process Type" (6/90) from Mitsui-Pathtek Corporation and: "Elite; Molded Circuit Interconnects" from Du Pont. However, the processes to separate plated parts from not plated parts as described in these leaflets are based on chemical etching which my not always result in as sharp transitions as required.
- Selective plating of connector elements may also be done by sputtering techniques, as e.g. disclosed by US Patent 4,932,888 or by the application of conductive ink, as disclosed in US Patent 4,846,724. However, neither of these latter techniques leads to very accurate transitions between those parts being plated and those parts being not plated.
- Since more accuracy between separating plated parts and not plated parts of connectors is an essential element for further miniaturization of connectors, very accurate separating techniques are needed.
- A very accurate separation between different metal surface areas on a printed circuit board is disclosed by Japanese patent application 54.67690, which discloses the use of light beams, laser beams or electron beams to separate an integrally made conductive metal layer on a substrate into several conductive metal lines.
- G.K.H. Schammler, and others, "Comparison of the metallization of chemically and laser-etched structures in BPDA-PDA polyimide", IEEE Transactions on components, hybrids, and manufacturing technology, Vol. 16, Nr. 7, November 1993, pages 720-723, shows that the use of laser ablation may lead to very steep side walls of vias, which are filled with electroless copper.
- Neither Japanese patent application 54.67690 nor G.K.H. Schammler suggest how to use high energy beams or the like to manufacture selectively metallized plastic connectors.
- The object of the present invention is to provide a method for selective metallization of connectors by which a very accurate distinction between plated and not plated surface areas can be obtained.
- Therefore, the method for selective metallization of a plastic connector according to the invention comprises the steps of:
- a. depositing a first, electroless metal layer of a first predetermined thickness on the surface of the connector;
- b. ablating predetermined parts of said first metal layer to produce at least two electrically separate metal layer areas;
- c. depositing a second, galvanic metal layer of a second predetermined thickness to at least one selected metal layer area;
- d. removing any non-selected metal layer area.
- The present invention is based on the insight that the use of means to ablate one or more very small traces of an integrally made metal layer on a connector, by which traces several metal layer areas on the connector surface are established which are no longer electrically interconnected may result in, very accurate transitions between plated and not plated surface areas on the connector.
- In order to ablate said traces from said metal layer on the connector a high energy beam may be used which is selected to be one of the following particle beams: an electron beam or ion beam. However, alternatively, also a light beam or a laser beam may be used. As a further alternative, the ablating step may be carried out by grinding, e.g. by any suitable, high precision abrasive stream of particles.
- Removal of the non-selected metal layer areas as defined in step d. above may be done by chemical etching or by grinding.
- When a light beam or a laser beam is used the diameter of the high energy beam may be about 75 µm.
- The first metal layer may comprise electroless copper or nickel. The first thickness may be between 1 to 2 µm.
- The second metal layer preferably comprises galvanically deposited copper.
- The second thickness preferably is between 5 to 10 µm.
- Step a. defined above may be preceded by immersing the connector in an alkaline bath to roughen its surface in contact with said bath.
- If desired, step d. defined above, may be followed by e. depositing a top coat finish layer on said second copper layer, selected to be one of the following group of metals: nickel, gold, or tin-lead.
- Said finish layer may have a thickness between 2 to 4 µm.
- In one embodiment of the method according to the invention
- said connector comprises at least one cavity extending from a first side to a second side;
- step b. comprises the step of ablating predetermined parts of said first metal layer on contours around the cavities on said first side and in further contours around the cavities on said second side in order to produce metal layer areas within each cavity, which are electrically separated from at least one metal layer area outside each cavity;
- step c comprises depositing a second, galvanic metal layer of said second predetermined thickness to the at least one metal layer area outside each cavity, and
- step d. comprises the step of removing the metal layer areas within each cavity.
- By this latter method a selectively metallized connector is obtained wherein all signal contact members are shielded against external electromagnetic radiation.
- The proposed method offers great flexibility since metallized and not metallized parts of the connector surface may be separated by ablating traces of a first, very thin metal layer on the connector surface and these traces may have any predetermined contour.
- The invention will now be explained in greater detail by reference to some drawings, in which the method according to the invention is explained in general and in one specific embodiment. This specific embodiment is just meant to show one way of using the method according to the invention and is not meant to restrict the shapes of metallized and not metallized surface areas on a connector.
- Figures 1a to 1f show various connector configurations known from the prior art, in which shielding and/or grounding enhances connector performance.
- Figure 2 shows a chart based on knowledge in the field and in which several connector configurations are compared as to several electrical characteristics.
- Figure 3 shows some more possible connector configurations besides the ones shown in figure 2.
- Figures 4a to 4f show selective plastic metallization process steps according to the invention.
- Figures 5a to 5f show application of the process according to the invention to one specific connector.
- Figure 4 shows the subsequent steps according to the present invention. In step 1 (figures 4a and 4b) an
electroless metal layer 11 of a first predetermined thickness is deposited on the surface of aconnector 10. Theelectroless metal layer 11 is preferably of copper, whereas the thickness ofelectroless metal layer 11 is preferably between 1 to 2 µm. - In
step 2 one or morepredetermined traces 12 are ablated from thefirst metal layer 11 to produce at least two electrically separatemetal layer areas traces 12 frommetal layer 11 may be done by an electron beam, an ion beam, a light beam, a laser beam, or any other high energy beam. It is envisaged that also grinding by sand-blasting or ice-blasting, or the like, may be applied to make thetraces 12. These traces 12 surround the separatemetal layer areas metal layer areas - In the third step (figure 4d) a second metal layer of a second predetermined thickness is galvanically deposited on selected
metal layer area 11b and not onmetal layer area 11a. This can be easily achieved by emersion of the intermediate product of figure 4c in an electrolyte and applying a negative voltage to selectedarea 11b and not toarea 11a. Thenadditional copper 13 of, for instance 5 to 10 µm, may be deposited on selectedmetal layer 11b, whereas not selectedmetal layer area 11a remains unchanged in thickness to its initial thickness of 1 to 2 µm. - In the next step (figure 4e) the product obtained is subjected to selective removal of the unchanged
metal layer areas 11a. This may be done by emersion of the product obtained after the preceding step in figure 4d in an etch bath, long enough to etch at least 2 µm of copper. After that step, in which also some of the galvanically depositedcopper layer 13 on the selectedmetal layer area 11b will be etched, still enough of the galvanically depositedcopper layer 13 remains. - If required, as shown in figure 4f, a
finishing layer 14 to protect the galvanically depositedcopper layer 13, may be applied tolayer 13. Finishing layers of other suitable metals, like gold or tin-lead, may be applied alternatively. Preferably, thefinishing layer 14 has a thickness of 2 to 4 µm. - The removal of the
metal layer area 11a (figure 4e) may be done by any suitable method: instead of a chemical etching process indicated above also grinding may be used. - When a laser beam or a light beam as a high energy beam is used, the diameter of the cross-section of the
traces 12 may be as small as 75 µm. - It is not necessary to start with electroless copper as a first layer; instead, electroless nickel may be used as well. The galvanically deposited
metal layer 13 may be made of any suitable metal. - The step of depositing electroless copper layer 11 (figure 4b) may be preceded by immersing the
connector 10 in an alkaline bath to roughen the connector's surface in contact with said bath. Thus, micropores may be obtained which enhance the contact strength between theelectroless copper layer 11 and theconnector 10. - Figures 5a to 5f show the application of the method according to figures 4a to 4f to a connector body in order to yield a shielded connector body. Figure 5a shows the surface of
connector 10 which may be chemically roughened in a first step. However, this step may be omitted. - In the second step (figure 5b) the
electroless copper layer 11 is deposited on the surface ofconnector 10. - In the second step traces 12 are ablated from the
electroless copper layer 11 to obtain firstmetal layer area 11a and secondmetal layer area 11b. The firstmetal layer area 11a covers the inside surfaces of allcavities 15 ofconnector 10, which cavities 15 are intended to accommodate suitable contact members (not shown) afterwards. The secondmetal layer area 11b covers roughly the outside surface ofconnector 10. First metal layer are 11a and secondmetal layer area 11b are electrically separated bytraces 12. - In the next step (figure 5d) a galvanically deposited
copper layer 13 is applied to the secondmetal layer area 11b according to the process step described above in accordance with figure 4d. The first metal layer are 11a remains unchanged. In the process step according to figure 5e the firstmetal layer area 11a covering the inside surfaces of thecavities 15 is removed, e.g. by chemically etching. By that etching step the thickness of the galvanically depositedcopper layer 13 is also somewhat reduced. - In the process step according to figure 5f a
finishing layer 14, preferably made of nickel, is applied to the galvanically depositedcopper layer 13. However, as indicated above, any other suitable metal layer may be used instead. The end product shown in figure 5f is aconnector 10 having a body which is entirely shielded at its outside surface. Of course, the connector shown in figures 5a to 5f only relate to one example. By varying thetraces 12 selectively metallized areas of any shape may be obtained. - The method according to the invention was tested for a connector made of a polymer resin for high temperatures, known as Vectra A130. The tests have shown that this material is appropriate to be selectively metallised by the proposed method. Moreover, the tests have shown that the electrical performance of a connector selectively shielded by the proposed method is similar to the electrical performance of a connector having separate metal shieldings. Although the use of Vectra A130 has shown good results, the method according to the invention is not restricted to the application of this polymer resin only. The use of any other suitable polymer resin falls within the scope of the present invention.
Claims (14)
- Method for selective metallization of a plastic connector comprising the steps of:a. depositing a first, electroless metal layer of a first predetermined thickness on the surface of the connector;b. ablating predetermined parts of said first metal layer to produce at least two electrically separate metal layer areas;c. depositing a second, galvanic metal layer of a second predetermined thickness to at least one selected metal layer area;d. removing any non-selected metal layer area.
- Method according to claim 1 wherein in step b. a high energy beam is used and is selected to be one of the following particle beams: an electron beam or ion beam.
- Method according to claim 1 wherein in step b. a high energy beam is used and is selected to be one of the following radiation beams: a light beam or a laser beam.
- Method according to claim 1 wherein in step b. said ablation is carried out by grinding.
- Method according to claim 1 wherein step d. is selected to be one of the following removing steps: removing by chemical etching or removing by grinding.
- Method according to claim 3 wherein the diameter of the high energy beam is about 75 µm.
- Method according to claim 1 wherein the first metal layer is selected to be one of the elements of: electroless copper or nickel.
- Method according to claim 1 wherein the first thickness is between 1 to 2 µm.
- Method according to claim 1 wherein the second metal layer comprises galvanically deposited copper.
- Method according to claim 1 wherein the second thickness is between 5 to 10 µm.
- Method according to claim 1 wherein step a. is preceded by immersing the connector in an alkaline bath to roughen its surface in contact with said bath.
- Method according to claim 9 wherein step d. is followed bye. depositing a top coat finish layer on said second copper layer, selected to be one of the following group of metals: nickel, gold, or tin-lead.
- Method according to claim 12 wherein said finish layer has a thickness between 2 to 4 µm.
- Method according to claim 1 wherein- said connector comprises at least one cavity (15) extending from a first side to a second side;- step b. comprises the step of ablating predetermined parts (12) of said first metal layer on contours around the cavities on said first side and in further contours around the cavities on said second side in order to produce metal layer areas (11a) within each cavity, which are electrically separated from at least one metal layer area (11b) outside each cavity;- step c. comprises depositing a second, galvanic metal layer of said second predetermined thickness to the at least one metal layer area (11b) outside each cavity;- step d. comprises the step of removing the metal layer areas (11a) within each cavity.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP94202140A EP0694990A1 (en) | 1994-07-22 | 1994-07-22 | Method for selective metallization of plastic connectors |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP94202140A EP0694990A1 (en) | 1994-07-22 | 1994-07-22 | Method for selective metallization of plastic connectors |
Publications (1)
Publication Number | Publication Date |
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EP0694990A1 true EP0694990A1 (en) | 1996-01-31 |
Family
ID=8217057
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP94202140A Withdrawn EP0694990A1 (en) | 1994-07-22 | 1994-07-22 | Method for selective metallization of plastic connectors |
Country Status (1)
Country | Link |
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EP (1) | EP0694990A1 (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0807963A2 (en) * | 1996-05-10 | 1997-11-19 | Itt Manufacturing Enterprises, Inc. | Method for processing lateral faces of electronic components |
WO1999016147A1 (en) * | 1997-09-23 | 1999-04-01 | Ericsson, Inc. | Switchable matching circuits using three-dimensional circuit carriers |
FR2780560A1 (en) * | 1998-06-30 | 1999-12-31 | Framatome Connectors Int | CONNECTOR FOR HIGH FREQUENCY SIGNALS |
WO2003004261A1 (en) * | 2001-07-03 | 2003-01-16 | N.V. Bekaert S.A. | Layered structure providing shielding characteristics |
EP1317027A1 (en) * | 2001-11-30 | 2003-06-04 | DDK Ltd. | Electrical connector |
EP1755200A3 (en) * | 2005-08-18 | 2008-08-06 | IMS Connector Systems GmbH | Housing for electrical plug and socket connections |
FR2917541A1 (en) * | 2007-06-15 | 2008-12-19 | Souriau Soc Par Actions Simpli | Shielded sub miniature connection assembly for cable connector, has molded thermoplastic receptacle shell comprising flange provided with oblong apertures into which projecting dimples of back plate are locked |
US7670180B2 (en) | 2007-06-15 | 2010-03-02 | Souriau | Shielded subminiature connection assembly and process of forming such an assembly |
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Cited By (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0807963A2 (en) * | 1996-05-10 | 1997-11-19 | Itt Manufacturing Enterprises, Inc. | Method for processing lateral faces of electronic components |
EP0807963A3 (en) * | 1996-05-10 | 1999-01-07 | General Semiconductor Ireland | Method for processing lateral faces of electronic components |
WO1999016147A1 (en) * | 1997-09-23 | 1999-04-01 | Ericsson, Inc. | Switchable matching circuits using three-dimensional circuit carriers |
US5986607A (en) * | 1997-09-23 | 1999-11-16 | Ericsson, Inc. | Switchable matching circuits using three dimensional circuit carriers |
FR2780560A1 (en) * | 1998-06-30 | 1999-12-31 | Framatome Connectors Int | CONNECTOR FOR HIGH FREQUENCY SIGNALS |
EP0969571A1 (en) * | 1998-06-30 | 2000-01-05 | Framatome Connectors International | Connector |
WO2003004261A1 (en) * | 2001-07-03 | 2003-01-16 | N.V. Bekaert S.A. | Layered structure providing shielding characteristics |
US7026060B2 (en) | 2001-07-03 | 2006-04-11 | N.V. Bekaert S.A. | Layered structure providing shielding characteristics |
CN100375675C (en) * | 2001-07-03 | 2008-03-19 | 贝卡尔特股份有限公司 | Layered structure providing shielding characteristics |
EP1317027A1 (en) * | 2001-11-30 | 2003-06-04 | DDK Ltd. | Electrical connector |
EP1755200A3 (en) * | 2005-08-18 | 2008-08-06 | IMS Connector Systems GmbH | Housing for electrical plug and socket connections |
FR2917541A1 (en) * | 2007-06-15 | 2008-12-19 | Souriau Soc Par Actions Simpli | Shielded sub miniature connection assembly for cable connector, has molded thermoplastic receptacle shell comprising flange provided with oblong apertures into which projecting dimples of back plate are locked |
US7670180B2 (en) | 2007-06-15 | 2010-03-02 | Souriau | Shielded subminiature connection assembly and process of forming such an assembly |
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