(19)
(11)EP 2 412 007 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
22.07.2020 Bulletin 2020/30

(21)Application number: 10756901.4

(22)Date of filing:  26.03.2010
(51)International Patent Classification (IPC): 
B22F 3/105(2006.01)
B23K 26/34(2014.01)
B23K 35/02(2006.01)
H01L 21/48(2006.01)
H01L 21/268(2006.01)
H01L 21/768(2006.01)
B23K 103/00(2006.01)
B22F 7/04(2006.01)
H01L 21/288(2006.01)
H05K 3/12(2006.01)
B23K 26/32(2014.01)
H05K 3/46(2006.01)
B23K 101/36(2006.01)
(86)International application number:
PCT/US2010/028811
(87)International publication number:
WO 2010/111581 (30.09.2010 Gazette  2010/39)

(54)

BUFFER LAYER TO ENHANCE PHOTO AND/OR LASER SINTERING

PUFFERSCHICHT FÜR VERBESSERTES LICHT- UND/ODER LASER-SINTERN

COUCHE TAMPON POUR AMÉLIORER LE FRITTAGE PHOTOGRAPHIQUE ET/OU LASER


(84)Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR

(30)Priority: 27.03.2009 US 163894 P
01.05.2009 US 174758 P

(43)Date of publication of application:
01.02.2012 Bulletin 2012/05

(73)Proprietor: Ishihara Chemical Co., Ltd.
Kobe 652-0806 (JP)

(72)Inventors:
  • YANIV, Zvi
    Austin TX 78746 (US)
  • YANG, Mohshi
    Austin Texas 78759 (US)
  • LAXTON, Peter B.
    Alameda CA 94501 (US)

(74)Representative: HGF 
1 City Walk
Leeds LS11 9DX
Leeds LS11 9DX (GB)


(56)References cited: : 
EP-A2- 1 758 166
US-A1- 2003 213 614
US-A1- 2006 116 000
US-A1- 2007 281 249
US-A- 5 724 727
US-A1- 2005 026 423
US-A1- 2006 163 744
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] This application claims priority to U.S. Provisional Patent Applications Serial Nos. 61/174,758 and 61/163,894.

    Background Information



    [0002] The microelectronics and semiconductor packaging industries have begun to shift to printable electronics. Electronics circuits comprise a variety of components that are electrically connected to each other. Such electrical connections between different components may be made of conductive metal traces that can be printed on substrates with conductive inks. The inks are processed and sintered after deposition on a substrate in order to become conductive. Thermal sintering uses a high temperature (e.g., ≥ 250°C) to fuse the nanoparticles in the inks. Photonic (photo) and laser sintering utilize a very high intensity lamp/laser to fuse the nanoparticles in a very short period of time (e.g., microseconds) with a low temperature and so as not to damage the underlying substrates. However, the photo/laser sintering process has limits that require low thermal conductivity material for substrates in order for the nanoparticles to effectively absorb energy and sinter before heat energy dissipates into the substrate. In other words, the substrates that can be used in these applications will be very limited for low thermal conductivity materials.

    [0003] On the other hand, low thermal conductive substrates can be used for flexible printable electronics. Low temperature melting point materials such as polyethylene (PE), polyester (PET), etc., will prevent the nanoparticle inks from proper sintering, and the substrates will be damaged, with the result that the resistivity will be very high.

    [0004] US 2006/116000 A1 discloses a manufacturing method of an insulating film having a plurality of pores and a manufacturing method of a semiconductor device.

    Brief Description of the Drawings



    [0005] 

    Fig. 1 is a digital photo showing copper inks photo sintered on four silicon wafers.

    Fig. 2 is a digital photo showing copper inks before being photo sintered.

    Fig. 3 is a digital photo showing copper inks after being photo sintered.

    Fig. 4 is a digital photo showing laser sintered lines on a Kapton substrate.

    Fig. 5 is an enlarged digital photo showing the laser sintered lines of Fig. 4.

    Fig. 6 illustrates a graph showing that copper ink resistivity sintered by a laser is not only inversely proportional to laser power, but also inversely proportional to buffer layer thickness made of polyimide.

    Fig. 7 illustrates a graph showing thicknesses of cured polyimide measured at various spin speeds.

    Fig. 8 illustrates a graph showing that resistivity of sintered copper film is inversely proportional to polyimide thickness.

    Fig. 9 illustrates a graph showing that adhesion of copper ink film to polyimide is proportional to polyimide thickness.

    Fig. 10 illustrates a graph showing that laser writing line width is proportional to the laser power density.

    Figs. 11A - 11F illustrate a process in accordance with embodiments of the present invention.


    Detailed Description



    [0006] The invention is set out in the independent claims. Preferred embodiments are defined by the dependent claims.

    [0007] Embodiments of the present invention disclose a photo sintering process to effectively sinter metallic nanoparticles on a polyimide substrate, thus causing the film to be very conductive near the bulk material. On the other hand, the photo sintering process does not perform well on nanoparticle inks coated on substrates possessing a high thermal conductivity, such as ceramics and silicon wafer. Table 1 shows the thermal conductivity for a variety of materials.
    Table 1
    item #materialdensity (g/cm3)heat capacity (J/g.K)heat conductivity (W/m.K)thermal effusivitymelting point, C degrees
    1 air 0.0013 1 0.025 0.00 NA
    2 paper 0.33 0.73 0.030 0.01 NA
    3 Polyimide (kapton) 1.42 1.09 0.120 0.19 NA
    4 PMMA (resist) 1.19 1.46 0.160 0.28 180
    5 PET (Mylar) 1.23 1.13 0.176 0.24 150
    6 LCP (liquid crystal polymer) 1.4 1.6 0.500 1.12 300
    7 PE (polyethylene, high density) 0.95 2.3 0.500 1.09 125
    8 water 1 4.2 0.600 2.52 0
    9 glass 2.3 0.753 1.330 2.30 950
    10 SiO2 2.2 0.75 1.380 2.28 1600
    11 MgO 3.2 0.84 5.900 15.86 2852
    12 carbon-amorphous 1.51 0.707 6.280 6.70 3600
    13 Si3N4 2.8 0.69 7.950 15.36 1900
    14 TiO2 4.25 0.69 9.000 26.39 1843
    15 CuO/Cu2O 6.5 0.536 18.000 62.71 1235
    16 Ti 4.5 0.523 21.000 49.42 1668
    17 Al2O3 (ceramics) 2.5 0.81 30.000 60.75 2054
    18 solder (60/40 Sn/Pb) 8.5 0.197 50.210 84.08 185
    19 Ni 8.9 0.444 88.000 347.74 1455
    20 Mo 10.2 0.25 134.000 341.70 2623
    21 Si 2.33 0.7 148.000 241.39 1414
    22 carbon-graphite 2.25 0.707 167.360 266.23 3600
    23 Al 2.7 0.88 209.000 496.58 660
    24 Au 19.3 0.13 318.000 797.86 1086
    25 Cu 8.9 0.385 398.000 1363.75 1064
    26 carbAL 2.3 0.75 425.000 733.13 3600
    27 Ag 10.5 0.24 427.000 1076.04 962
    28 carbon -diamond 3.51 0.506 543.920 966.03 3800
    29 carbon nanotubes     6000.000    


    [0008] Low conductivity materials, such as polyimide, can be used as a coating material onto other high thermal conductivity substrates, such as ceramics and silicon wafer, in order to isolate heat energy dissipation from nanoparticles during a photo sintering process so that the nanoparticles are fused more effectively. How quickly heat dissipates depends on the thickness of the low thermal conductivity material (e.g., polyimide film).

    [0009] The following experiment was conducted for showing how the present invention operates. Three wafers were spin coated with 1, 1.5, and 2.3 microns thick DuPont PI-2610 polyimide, respectively, and thermal cured at 350°C for 30 minutes. One bare silicon wafer was used for a reference (wafer #1). All four wafers were coated with copper ink using a drawdown process. After a 60 minute drying process at 100°C, each wafer was divided into three zones that were individually sintered with three different energy levels. The resistance for each zone and each wafer was measured with a voltmeter, with the results shown in Table 2, which shows the electrical resistances of a copper film after photo sintering with various coating thicknesses of polyimide on silicon wafers.
    Table 2
    wafer #polyimide thickness (µm)copper ink (µm)Zone 1: resistance with energy 1Zone 2: resistance with energy 2Zone 3: resistance with energy 3
    1 0 3.2 >20 MΩ >20 MΩ >20 MΩ
    2 1 3.2 >20 MΩ >20 MΩ >20 MΩ
    3 1.5 3.2 >20 MΩ >20 MΩ >20 MΩ
    4 2.3 3.2 >20 MΩ >20 MΩ 20 Q
    where energy 1 = 3 sinter shots with 850/1050 V, 1000 µsec
    energy 2 = 4 sinter shots with 850/1150 V, 1000 µsec
    energy 3 = 5 sinter shots with 850/1250 V, 2000 µsec


    [0010] Except for zone 3 of wafer 4, all zones from the four wafers did not experience a change in resistance after photo sintering. Zone 3 of wafer 4 experienced a change in its metallic color at the highest energy level, as shown in Fig. 1. The area had a severe blow off. The surrounding area had copper debris left that was conductive. This is clear evidence that the polyimide material may be used as a thermal insulator. The thickness of polyimide may be more than 3 microns. The thermal conductivity is 0.12 and 148 W/m.K for polyimide and silicon, respectively. The heat dissipated into the silicon substrate (wafer #1) too quickly to sinter the copper nanoparticles since there was no polyimide material.

    [0011] Wafers 1, 2, and 3 all had high resistance (greater than 20 mega ohms). Wafer 4 at the center zone with 20 ohms resistance as shown in Fig. 1 appeared that the copper nanoparticles film started to be fused, sintered, and turned into a copper color. The thicker low thermal conductivity material can thus be used as a good thermal insulator.

    [0012] In addition to the liquid polyimide disclosed above, a dry polyimide film was also utilized. The copper ink was coated on a 50 micron polyimide film (Kapton). The sample was placed on a silicon wafer and a carbAL high thermal conductive heat sink, as shown in Fig. 2. Silicon grease was coated in between the Kapton and the silicon wafer and carbAL to ensure good thermal contact. The sample was photo sintered simultaneously in a single shot. The copper was sintered very well and turned a shiny copper color, as shown in Fig. 3. It did not matter what materials the Kapton was residing on. At least a 50 micron thick polyimide is sufficiently thick to isolate and prevent heat energy dissipation for photo sintering processes, though a thickness of less than 50 microns may be utilized for embodiments where less conductivity is desired of the conductive traces.

    [0013] In addition, laser sintering was utilized on silicon wafers with the same setup as described above. The laser was a solid state diode with an 830 nm wavelength and an 800 mW power. The focus beam size was 15 microns in diameter and controlled by a collimator and an objective lens, as shown in Figs. 4 and 5.

    [0014] This laser had sufficient power to sinter and fuse the nanoparticles and turn the copper ink conductive. There were four silicon wafers coated with various polyimide thicknesses of 1, 1.5, 2, and 3 microns, respectively, along with a bare silicon wafer as a reference. The resistivity of each wafer is plotted with laser power in Fig. 6, which indicates that the copper film conductivity is proportional to the polyimide thickness, and the heat generated by the laser is transferred to the substrate less with polyimide present than the bare silicon wafer without polyimide. This is clear evidence that any material having a low thermal conductivity, such as polyimide material, may be used as a thermal insulator and enhance the photo and laser sintering processes.

    [0015] Furthermore, a variety of polyimide thicknesses were coated on silicon wafers and cured at 350°C for one hour. Then the standard copper ink was coated by drawdown, dried in an oven, and photo/laser sintered. Electrical measurements were performed and characterized the copper ink samples.

    [0016] Three types of polyimide material made by DuPont were used to spin coat on silicon wafer at 1000, 2000, 3000, 4000 and 5000 rpm. Fig. 7 illustrates a graph showing thicknesses of cured polyimide measured at various spin speeds. The range was from 1 to 20 microns on each wafer, respectively.

    [0017] After samples were prepared, both photo and laser sintering were performed on the copper inks. Different types of sintering were compared versus resistivity and adhesion, as well as line width for laser sintering. Table 3 shows samples photo sintered at the same energy level with various thicknesses of polyimide. Table 4 shows samples laser sintered at a fixed power level with various thicknesses of polyimide.
    Table 3
    sample #polyimide thickness (µm)Cu ink thickness (µm)resistivity (ohm-cm)adhesion (1-10)
    1 0 3 3.00E+01 1
    2 5 2 1.30E-04 2
    3 6.5 2 4.00E-05 4
    4 8.7 2 1.60E-05 7
    5 12.5 2 1.52E-05 7
    6 10 1.5 1.50E-05 8
    7 14 1.5 1.40E-05 8
    8 20 1.5 1.14E-05 8
    Table 4
    sample #polyimide thickness (µm)resistivity (ohm-cm) at 840 mWadhesion (1-10)line width (µm) at 840 mWline width (µm) at 409 mW
    11 0 1.60E-04 1 70 35
    12 1 1.26E-05 5 74 38
    13 1.5 1.36E-05 5 77 39
    14 2 9.33E-06 3 83 40
    15 3 6.00E-06 1 88 42
    16 5 4.75E-06 8 92 65
    17 7 4.82E-06 8 103 75
    18 12 3.61E-06 8 150 88
    19 20 5.47E-06 8 180 120


    [0018] Fig. 8 illustrates a graph showing that resistivity of sintered copper film is inversely proportional to polyimide thickness. The saturated points for resistivity are approximately at 10 microns for photo sintering and approximately at 5 microns for laser sintering. Power density of photo sintering is much lower than that of laser sintering, providing a reason why its resistivity is higher.

    [0019] Fig. 9 illustrates a graph showing that adhesion of copper ink film to polyimide is proportional to polyimide thickness. There are some noise points, but the trend is clear from the graph. The thicker the polyimide is, the better the adhesion is. Again, critical points of polyimide thickness for the good adhesion are approximately at 10 microns for photo sintering and approximately at 5 microns for laser sintering.

    [0020] Fig. 10 illustrates a graph showing that laser writing line width is proportional to the laser power density. With given laser power, the laser writing line width is also proportional to the polyimide film thickness, providing more evidence that polyimide is a good thermal insulator for these processes. The laser energy and heat deposited on the copper ink surface could not spread any deeper vertically but laterally while the polyimide thickness increased.

    [0021] Referring to Figs. 11A - 11F, a process for performing embodiments of the present invention is illustrated. A substrate 1101 is provided on which electronic circuitry is to be mounted. In Fig. 11B, traces of a metal material 1102 are deposited in a desired pattern on the substrate 1101, using a well-known manufacturing process. In Fig. 11C, a layer of low thermal conductivity material 1103, such as polyimide, is coated over the metal traces 1102 and substrate 1101. To create further patterns for the conductive traces to be deposited, vias 1104 are formed through the material 1103, exposing portions of the metal traces 1102. In Fig. 11E, an ink jet apparatus 1106 deposits a conductive ink 1105, such as copper nanoparticles, over the material 1103 and the metal traces 1102 exposed by the vias 1104. In Fig. 11F a photo or laser sintering process is performed on the deposited conductive ink nanoparticles 1105 to sinter them into conductive traces 1107, as described herein. Depositing of the conductive inks and the sintering processes are described in U.S. Patent Publication No. 2008/0286488 A1.

    Summary



    [0022] 
    1. 1. The effectiveness of a photo sintering process depends on not only metallic nanoparticle size, but also the type of substances.
    2. 2. Effective photo sintering is achieved with nanoparticles below 300 nm.
    3. 3. The thermal conductivity of substrates will affect metallic ink photo sintering. The lower the thermal conductivity of the substrate, the better the electrical conductivity of the nanoparticle film.
    4. 4. High thermal conductive substrates can be tailored and isolated by coating low thermal conductivity material, such as polyimide or polymer, for an effective photo sintering process.
    5. 5. The thickness of coating of polyimide required to isolate thermal heat dissipation is approximately 1 - 50 microns.
    6. 6. The copper ink becoming a conductive film has been demonstrated on high thermal conductive material such as silicon wafer with both laser and photo sintering.
    7. 7. Heat dissipation on high thermal conductive silicon wafers has been shown with a variety of polyimide thicknesses coated on a wafer. A low thermal conductive material can be used as a buffer layer to slow down heat dissipation and enhance the photo or laser sintering.
    8. 8. Copper ink may be sintered well with polyimide coated on a silicon wafer with resistivity at 1x10-5 ohm-cm by photo sintering and 4x10-6 ohm-cm by laser sintering.
    9. 9. The polyimide material may be not only utilized as a heat insulator on high thermal conductive substrates and enhance copper ink photo and laser sintering effectiveness, but also applied to low melting temperature substrates as a heat insulator to protect from heat damage during a sintering process.
    10. 10. Polyimide layer and metal trace layer can be repeated several times as multilayer circuits.
    11. 11. Polyimide layer can be used as a dielectric material and incorporated as capacitors.
    12. 12. Nano-copper ink can be used at top layer conductor as a contact metal in two-dimensional and three-dimensional chip packaging applications.



    Claims

    1. A method for depositing conductive lines (1107) on a substrate (1101) comprising:

    coating a layer (1103) of material having a low thermal conductivity over the substrate depositing a film (1105) of conductive ink over the layer of material having the low thermal conductivity; and

    sintering the film of conductive ink,

    characterised in that the layer of material having a low thermal conductivity has a thickness of at least 2.3 µm.


     
    2. The method as recited in claim 1, further comprising depositing a metal layer (1102) in a pattern on the substrate and coating the layer of material having a low thermal conductivity over the patterned metal layer and the substrate.
     
    3. The method as recited in claim 2, further comprising:
    forming a via (1104) through the layer of material having the low thermal conductivity thereby exposing a portion of the patterned metal layer, wherein the depositing of the film of conductive ink includes depositing the film of conductive ink into the via to thereby coat the portion of the patterned metal layer with the film of conductive ink, wherein the film of conductive ink coating the portion of the patterned metal layer is also sintered.
     
    4. The method of claim 1, wherein a resistivity of the sintered film deposited over the layer of material having the low thermal conductivity has a lower resistivity than the sintered film not deposited over the layer of material having the low thermal conductivity.
     
    5. The method of claim 1 wherein an adhesion of the sintered film to the layer of material having the low thermal conductivity is better than an adhesion of the sintered film not deposited over the layer of material having the low thermal conductivity.
     
    6. The method as recited in any preceding claim, wherein the layer of material having the low thermal conductivity comprises a polymer, such as polyimide.
     
    7. The method as recited in any preceding claim, wherein the sintering is performed with a photo sintering apparatus or wherein the sintering is performed with a laser sintering apparatus.
     
    8. The method as recited in claim 7, wherein the sintering is performed with a laser sintering apparatus comprising a solid state diode with an 830 nm wavelength and 800 mW power, optionally wherein the solid state diode has a focus beam size of 15 microns in diameter.
     
    9. The method as recited in any preceding claim, wherein the substrate is silicon or ceramic.
     
    10. The method as recited in claim 1, wherein the substrate has a thermal conductivity greater than the layer of material having the low thermal conductivity.
     
    11. The method as recited in any preceding claim, wherein the film of conductive ink comprises copper nanoparticles.
     
    12. The method as recited in claim 1, wherein the layer of material having the low thermal conductivity has a thickness of at least 5 µm, when the sintering is performed with a laser sintering apparatus.
     
    13. The method as recited in claim 1, wherein the layer of material having the low thermal conductivity has a thickness of at least 10 µm, when the sintering is performed with a photo sintering apparatus.
     
    14. Electronic circuitry comprising:

    a substrate (1101);

    a pattern of metal traces (1102) deposited on the substrate;

    a layer (1103) of low thermal conductive material coated over the substrate and the pattern of metal traces deposited on the substrate, wherein vias (1104) are formed through the layer of low thermal conductive material over portions of the pattern of metal traces; and

    a film (1105, 1107) of sintered conductive ink coated over the layer of low thermal conductive material coated over the substrate, wherein the film of sintered conductive ink is coated over the portions of the pattern of metal traces within the vias formed through the layer of low thermal conductive material,

    characterised in that the layer of low thermal conductive material has a thickness of at least 2.3 µm.


     
    15. The electronic circuitry as recited in claim 14, wherein the substrate has a thermal conductivity greater than the layer of low thermal conductive material.
     
    16. The electronic circuitry as recited in claim 14 or claim 15, wherein the layer of low thermal conductive material is polyimide.
     
    17. The electronic circuitry as recited in claim 15, wherein the layer of low thermal conductive material comprises polyimide and the sintered conductive ink comprises sintered copper nanoparticles having the characteristics of copper nanoparticles sintered with an apparatus selected from: a photo sintering apparatus; and a laser sintering apparatus.
     
    18. The electronic circuitry as recited in any of claims 14 to 17, wherein the substrate is silicon or ceramic.
     
    19. The method of claim 6 or the electronic circuitry of claim 15, wherein the layer of low thermal conductive material comprises polyimide and the polyimide has a thickness of at least 5 µm, optionally wherein the polyimide has a thickness of at least 50 µm.
     
    20. The method or electronic circuitry of any preceding claim, wherein the layer of low thermal conductive material slows down heat dissipation to thereby enhance the photo or laser sintering.
     


    Ansprüche

    1. Verfahren zum Abscheiden von Leiterbahnen (1107) auf einem Substrat (1101), umfassend:

    Beschichten einer Schicht (1103) aus Material, das eine niedrige Wärmeleitfähigkeit über dem Substrat aufweist,

    Abscheiden eines Films (1105) aus leitfähiger Tinte über der Schicht aus Material, das die niedrige Wärmeleitfähigkeit aufweist; und

    Sintern des Films aus leitfähiger Tinte, dadurch gekennzeichnet, dass die Schicht aus Material, das eine niedrige Wärmeleitfähigkeit aufweist, eine Stärke von mindestens 2,3 µm aufweist.


     
    2. Verfahren nach Anspruch 1, ferner umfassend ein Abscheiden einer Metallschicht (1102) in einem Muster auf dem Substrat und Beschichten der Schicht aus Material, das eine niedrige Wärmeleitfähigkeit aufweist, über der gemusterten Metallschicht und dem Substrat.
     
    3. Verfahren nach Anspruch 2, ferner umfassend:
    Bilden eines Durchgangs (1104) durch die Schicht aus Material, das die niedrige Wärmeleitfähigkeit aufweist, wodurch ein Abschnitt der gemusterten Metallschicht freigelegt wird, wobei das Abscheiden des Films aus leitfähiger Tinte ein Abscheiden des Films aus leitfähiger Tinte in den Durchgang beinhaltet, um dadurch den Abschnitt der gemusterten Metallschicht mit dem Film aus leitfähiger Tinte zu beschichten, wobei der Film aus leitfähiger Tinte, der den Abschnitt der gemusterten Metallschicht beschichtet, auch gesintert wird.
     
    4. Verfahren nach Anspruch 1, wobei ein Widerstand des gesinterten Films, der über der Schicht des Materials abgeschieden ist, das die niedrige Wärmeleitfähigkeit aufweist, einen geringeren Widerstand aufweist als der gesinterte Film, der nicht über der Schicht des Materials abgeschieden ist, das die niedrige Wärmeleitfähigkeit aufweist.
     
    5. Verfahren nach Anspruch 1, wobei eine Adhäsion des gesinterten Films an der Schicht des Materials, das eine niedrige Wärmeleitfähigkeit aufweist, besser ist als eine Adhäsion des gesinterten Films, die nicht über der Schicht des Materials abgeschieden ist, das Material, das die niedrige Wärmeleitfähigkeit aufweist.
     
    6. Verfahren nach einem der vorherigen Ansprüche, wobei die Schicht aus Material, das die niedrige Wärmeleitfähigkeit aufweist, ein Polymer umfasst, wie z. B. Polyimid.
     
    7. Verfahren nach einem der vorherigen Ansprüche, wobei das Sintern mit einer Lichtsintervorrichtung ausgeführt oder wobei das Sintern mit einer Lasersintervorrichtung ausgeführt wird.
     
    8. Verfahren nach Anspruch 7, wobei das Sintern mit einer Lasersintervorrichtung ausgeführt wird, die eine Festkörperdiode mit einer Wellenlänge von 830 nm und einer Leistung von 800 mW umfasst, optional wobei die Festkörperdiode eine Fokussierstrahlgröße von 15 Mikrometern im Durchmesser aufweist.
     
    9. Verfahren nach einem der vorherigen Ansprüche, wobei das Substrat Silicium oder Keramik ist.
     
    10. Verfahren nach Anspruch 1, wobei das Substrat eine Wärmeleitfähigkeit aufweist, die größer ist als die Schicht des Materials, das die niedrige Wärmeleitfähigkeit aufweist.
     
    11. Verfahren nach einem der vorherigen Ansprüche, wobei der Film aus leitfähiger Tinte Kupfernanopartikel umfasst.
     
    12. Verfahren nach Anspruch 1, wobei die Schicht des Materials, das die niedrige Wärmeleitfähigkeit aufweist, eine Stärke von mindestens 5 µm aufweist, wenn das Sintern mit einer Lasersintervorrichtung ausgeführt wird.
     
    13. Verfahren nach Anspruch 1, wobei die Schicht des Materials, das die niedrige Wärmeleitfähigkeit aufweist, eine Stärke von mindestens 10 µm aufweist, wenn das Sintern mit einer Lichtsintervorrichtung ausgeführt wird.
     
    14. Elektronische Schaltung, umfassend:

    ein Substrat (1101);

    ein Muster von Metallspuren (1102), die auf das Substrat aufgebracht sind;

    eine Schicht (1103) aus niedrig wärmeleitendem Material, die über das Substrat und das Muster aus Metallspuren, die auf das Substrat abgeschieden sind, beschichtet ist, wobei Durchgänge (1104) durch die Schicht aus niedrig wärmeleitendem Material über Abschnitten des Musters aus Metallspuren gebildet sind; und

    einen Film (1105, 1107) aus gesinterter leitfähiger Tinte, der über die Schicht aus niedrig wärmeleitendem Material beschichtet ist, die über das Substrat beschichtet ist, wobei der Film aus gesinterter leitfähiger Tinte über die Abschnitte des Musters aus Metallspuren innerhalb der Durchgänge beschichtet ist, die durch die Schicht aus niedrig wärmeleitendem Material gebildet sind,

    dadurch gekennzeichnet, dass die Schicht aus niedrig wärmeleitendem Material eine Stärke von mindestens 2,3 µm aufweist.


     
    15. Elektronische Schaltung nach Anspruch 14, wobei das Substrat eine höhere Wärmeleitfähigkeit aufweist als die Schicht aus niedrig wärmeleitendem Material.
     
    16. Elektronische Schaltung nach Anspruch 14 oder 15, wobei die Schicht aus niedrig wärmeleitendem Material Polyimid ist.
     
    17. Elektronische Schaltung nach Anspruch 15, wobei die Schicht aus niedrig wärmeleitendem Material Polyimid umfasst und die gesinterte leitfähige Tinte gesinterte Kupfernanopartikel umfasst, die die Eigenschaften von Kupfernanopartikeln aufweisen, die mit einer Vorrichtung gesintert werden, die ausgewählt ist aus: einer Lichtsintervorrichtung; und einer Lasersintervorrichtung.
     
    18. Elektronische Schaltung nach einem der Ansprüche 14 bis 17, wobei das Substrat Silicium oder Keramik ist.
     
    19. Verfahren nach Anspruch 6 oder die elektronische Schaltung nach Anspruch 15, wobei die Schicht aus niedrig wärmeleitendem Material Polyimid umfasst und das Polyimid eine Stärke von mindestens 5 µm aufweist, optional wobei das Polyimid eine Stärke von mindestens 50 µm aufweist.
     
    20. Verfahren oder elektronische Schaltung nach einem der vorherigen Ansprüche, wobei die Schicht aus niedrig wärmeleitendem Material eine Wärmeableitung verlangsamt, um dadurch das Licht- oder Lasersintern zu verbessern.
     


    Revendications

    1. Procédé de dépôt de lignes conductrices (1107) sur un substrat (1101) comprenant :
    l'application d'une couche (1103) de matériau ayant une faible conductivité thermique sur le substrat ; le dépôt d'un film (1105) d'encre conductrice sur la couche de matériau ayant la faible conductivité thermique ; et le frittage du film d'encre conductrice, caractérisé en ce que la couche de matériau ayant une faible conductivité thermique a une épaisseur d'au moins 2,3 µm.
     
    2. Procédé selon la revendication 1, comprenant en outre le dépôt d'une couche métallique (1102) dans un motif sur le substrat et le revêtement de la couche de matériau ayant une faible conductivité thermique sur la couche métallique en motif et le substrat.
     
    3. Procédé selon la revendication 2, comprenant en outre : la formation d'un via (1104) à travers la couche de matériau ayant la faible conductivité thermique exposant ainsi une partie de la couche métallique en motif, dans lequel le dépôt du film d'encre conductrice comprend le dépôt du film d'encre conductrice dans le via pour ainsi revêtir la partie de la couche métallique en motif avec le film d'encre conductrice, le film d'encre conductrice revêtant la partie de la couche métallique en motif étant également fritté.
     
    4. Procédé selon la revendication 1, dans lequel une résistivité du film fritté déposé sur la couche de matériau ayant la faible conductivité thermique a une résistivité inférieure à celle du film fritté non déposé sur la couche de matériau ayant la faible conductivité thermique.
     
    5. Procédé selon la revendication 1, dans lequel une adhérence du film fritté à la couche de matériau ayant la faible conductivité thermique est meilleure qu'une adhérence du film fritté non déposé sur la couche de matériau ayant la faible conductivité thermique.
     
    6. Procédé selon l'une quelconque des revendications précédentes, dans lequel la couche de matériau ayant la faible conductivité thermique comprend un polymère, tel qu'un polyimide.
     
    7. Procédé selon l'une quelconque des revendications précédentes, dans lequel le frittage est effectué avec un appareil de photo-frittage ou dans lequel le frittage est effectué avec un appareil de frittage laser.
     
    8. Procédé selon la revendication 7, dans lequel le frittage est effectué avec un appareil de frittage laser comprenant une diode à l'état solide avec une longueur d'onde de 830 nm et une puissance de 800 mW, facultativement dans lequel la diode à l'état solide a une taille de faisceau de focalisation de 15 microns de diamètre.
     
    9. Procédé selon l'une quelconque des revendications précédentes, dans lequel le substrat est du silicium ou de la céramique.
     
    10. Procédé selon la revendication 1, dans lequel le substrat a une conductivité thermique supérieure à la couche de matériau ayant la faible conductivité thermique.
     
    11. Procédé selon l'une quelconque des revendications précédentes, dans lequel le film d'encre conductrice comprend des nanoparticules de cuivre.
     
    12. Procédé selon la revendication 1, dans lequel la couche de matériau ayant la faible conductivité thermique a une épaisseur d'au moins 5 µm, lorsque le frittage est effectué avec un appareil de frittage laser.
     
    13. Procédé selon la revendication 1, dans lequel la couche de matériau ayant la faible conductivité thermique a une épaisseur d'au moins 10 µm, lorsque le frittage est effectué avec un appareil de photo-frittage.
     
    14. Circuit électronique comprenant :

    un substrat (1101) ;

    un motif de traces métalliques (1102) déposées sur le substrat ;

    une couche (1103) de matériau à faible conductivité thermique revêtue sur le substrat et le motif de traces métalliques déposées sur le substrat, dans lequel des vias (1104) sont formées à travers la couche de matériau à faible conductivité thermique sur des parties du motif de traces métalliques ; et un film (1105, 1107) d'encre conductrice frittée revêtu sur la couche de matériau à faible conductivité thermique revêtu sur le substrat, dans lequel le film d'encre conductrice frittée est revêtu sur les parties du motif de traces métalliques à l'intérieur des vias formées à travers la couche de matériau à faible conductivité thermique, caractérisé en ce que la couche de matériau à faible conductivité thermique a une épaisseur d'au moins 2,3 µm.


     
    15. Circuit électronique selon la revendication 14, dans lequel le substrat a une conductivité thermique supérieure à la couche de matériau à faible conductivité thermique.
     
    16. Circuit électronique selon la revendication 14 ou la revendication 15, dans lequel la couche de matériau à faible conductivité thermique est en polyimide.
     
    17. Circuit électronique selon la revendication 15, dans lequel la couche de matériau à faible conductivité thermique comprend du polyimide et l'encre conductrice frittée comprend des nanoparticules de cuivre fritté ayant les caractéristiques de nanoparticules de cuivre frittées avec un appareil choisi parmi : un appareil de photo-frittage ; et un appareil de frittage laser.
     
    18. Circuit électronique selon l'une quelconque des revendications 14 à 17, dans lequel le substrat est en silicium ou en céramique.
     
    19. Procédé selon la revendication 6 ou circuit électronique selon la revendication 15, dans lequel la couche de matériau à faible conductivité thermique comprend du polyimide et le polyimide a une épaisseur d'au moins 5 µm, facultativement dans lequel le polyimide a une épaisseur d'au moins 50 µm.
     
    20. Procédé ou circuit électronique selon l'une quelconque des revendications précédentes, dans lequel la couche de matériau à faible conductivité thermique ralentit la dissipation thermique pour ainsi améliorer le photo-frittage ou frittage laser.
     




    Drawing



































    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description