WO1997030571A1 - Application d'un revetement suivant un motif - Google Patents

Application d'un revetement suivant un motif Download PDF

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Publication number
WO1997030571A1
WO1997030571A1 PCT/GB1997/000412 GB9700412W WO9730571A1 WO 1997030571 A1 WO1997030571 A1 WO 1997030571A1 GB 9700412 W GB9700412 W GB 9700412W WO 9730571 A1 WO9730571 A1 WO 9730571A1
Authority
WO
WIPO (PCT)
Prior art keywords
photosensitive
resist
coating
pattern
resistor
Prior art date
Application number
PCT/GB1997/000412
Other languages
English (en)
Inventor
Christopher Ian Wall
Clive Landells
Original Assignee
Electra Technology Limited
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 Electra Technology Limited filed Critical Electra Technology Limited
Priority to AU18019/97A priority Critical patent/AU1801997A/en
Publication of WO1997030571A1 publication Critical patent/WO1997030571A1/fr

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004—Photosensitive materials
    • G03F7/09—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers
    • G03F7/094—Multilayer resist systems, e.g. planarising layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H01C17/06—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base
    • H01C17/065—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base by thick film techniques, e.g. serigraphy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H01C17/06—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base
    • H01C17/065—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base by thick film techniques, e.g. serigraphy
    • H01C17/06506—Precursor compositions therefor, e.g. pastes, inks, glass frits
    • H01C17/06573—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the permanent binder
    • H01C17/06586—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the permanent binder composed of organic material
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
    • H05K3/06—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed chemically or electrolytically, e.g. by photo-etch process
    • H05K3/061—Etching masks
    • H05K3/064—Photoresists
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/09—Use of materials for the conductive, e.g. metallic pattern
    • H05K1/092—Dispersed materials, e.g. conductive pastes or inks
    • H05K1/095—Dispersed materials, e.g. conductive pastes or inks for polymer thick films, i.e. having a permanent organic polymeric binder
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/14—Related to the order of processing steps
    • H05K2203/1476—Same or similar kind of process performed in phases, e.g. coarse patterning followed by fine patterning

Definitions

  • This invention is concerned with the formation of a non-photosensitive coating in a pattern of defined character. More specifically it is concerned with the formation of so called “Polymer Thick Film” (PTF) resistors and conductor patterns on insulating substrates to form circuit boards and other similar products during the course of their manufacture .
  • PTF Polymer Thick Film
  • Printed circuit boards have resistors and conductive patterns applied to them by a number of techniques.
  • thin films are formed by for example sputtering and other atomic deposition methods where thicknesses of the order of nanometers or Angstroms are required.
  • resistors and conductor patterns may be applied by hybrid or thick film technology.
  • application takes place in a thickness of the order of 10 to 15 ⁇ m by screenprinting of resistors and conductor patterns on to a ceramic substrate.
  • the conductors are noble metals such as silver, gold, palladium and platinum and the resistors may be for example, of ruthenium oxide.
  • the conductive and resistive materials are employed in the form of powders dispersed in a glass frit held in a resinous binder. When a thick film has been deposited, the coatings are fired at temperatures generally in the range of 800 to 1200°C whereby polymer and resin material present is vapourised and the glass melts. The metal present then sinters into the substrate in the desired pattern.
  • the PCB industry requires the printing of conductive and resistive elements on to synthetic resin substrates which are generally flat and are to have other elements mounted on the top surface thereof. This allows a variety of compact formats to be devised.
  • the substrates will not however withstand the higher temperatures mentioned in connection with the projection of conventional hybrid or thick film technology.
  • PTF resistors and conductors typically consist of a mixture of conductive particles, usually powdered or flaked, of materials such as carbon, graphite, silver, nickel or silver-coated nickel dispersed in a non-conductive polymer binder system. It has thus been possible for the use of noble metals, with the exception of silver, to be dispensed with.
  • PTFs applied to resinous substrates differ from the CERMET resistors used in the manufacture of hybrid circuits in that the binder system, being polymer based, requires a relatively low curing temperature compared to the high temperatures required for the firing of the CERMET resistors.
  • resistor patterns have been created directly on a substrate by screenprinting resistor paste in the pattern required through a stainless steel or polyester mesh equipped with an emulsion or stencil. This process is followed by a relatively low temperature curing operation to evaporate the solvent and crosslink the polymer binder in order to achieve a stable resistance value for the resistor pattern. If multiple patterns of different resistor pastes are required, then the printing step can be followed by a drying stage to evaporate the solvent and permit printing of the subsequent resistor paste. When all the required printed operations have been completed, the dried resistor pastes can all be cured together, thus saving time and energy. The value of the resistor produced is affected by a number of factors e.g.
  • the resistance can be represented by the formula below: -
  • the resistor value obtained is independent of the actual dimensions of the resistor.
  • the resistor value is independent of the actual dimensions.
  • the dimensions of the resistor pattern are determined primarily by the heat dissipation required for the resistor, with large heat dissipation requirements generally requiring larger resistors.
  • the maximum heat dissipation is influenced mainly by the thermal characteristics of the substrate . For substrates of high thermal conductivity or where heat dissipation requirements are low, resistors can be much smaller, thus making more space available on the substrate for circuit traces and/or components.
  • This invention relates to method for the formation of a non-photosensitive polymer thick film pattern of defined character on a substrate, which comprises the following steps.
  • d exposing the photosensitive resist imagewise in a pattern required to be present in the non-photosensitive first coating
  • steps a and b may be carried out more than once to build up the non-photosensitive second coating which is preferably a resistor paste coating.
  • the photosensitive resist also termed herein photoresist, may undergo drying before it is subjected to imagewise exposure. Washing off of photoresist which is not wanted (usually unexposed photoresist) and excess non-photosensitive coating may be carried out simultaneously or in successive steps.
  • g removing remaining photosensitive resist with a resist stripper material and h: curing the residual non-photosensitive first coating material.
  • a temperature as low as 120°C may be used for this purpose although temperatures in the range 100-200°C can be used to achieve cure.
  • the first step of the process involves the application of the first resistor pattern. This is done to produce a pattern with dimensions larger than those eventually required and may be achieved by:-
  • the resistor paste can be applied as a complete film covering all or part of the substrate.
  • the application methods used can be, but are not limited to one or more of the following: - screenprinting, curtain coating, electrostatic spray, air spray, airless spray, roller coating, dip coating, spin coating, doctor blade coating.
  • the resistor paste used is one which is chosen to give the resistance value required after final curing. It is also chosen to be compatible with the substrate used. The resistor application step is carried out carefully to ensure, so far as is possible, an even and equal thickness for each resistor pattern.
  • Step 2 Following the printing step, the resistor paste is dried carefully to evaporate the solvent content, without initiating any thermal polymerization.
  • the drying system used can be typically, but is not limited to, one or a combination of one or more of the following systems convection air assisted box oven, convection air assisted tunnel oven, infra red (IR) radiation heated tunnel oven, combination air and IR heated tunnel oven or any other system which is capable of providing a closely controlled source of heat and sufficient exhaust ventilation to remove solvent vapour without causing premature polymerization of the resistor paste.
  • IR infra red
  • the initial and intermediate drying profiles used may need to be shorter than that used when only one printing operation is used in order to ensure that premature polymerization of the resistor paste does not occur.
  • the final drying step can then be longer to ensure that all the solvent has been removed from the different resistors prior to application of the photoresist.
  • the photoresist can be applied by any of the methods common for this purpose. Such methods include but are not limited to screenprinting, curtain coating, electrostatic spray, air spray, airless spray, roller coating, dip coating, spin coating, doctor blade coating, in the case of liquid resists, and roll lamination, in the case of dry film resists.
  • the photosensitive resist material may be applied by screenprinting a pattern material to a previously produced pattern of non-photosensitive material applied in accordance with the procedure of Step 1 (i) .
  • the photoresist is dried after application, by evaporating the solvent in a similar fashion to the resistor paste.
  • the drying system used can be typically, but is not limited to, one or a combination of one or more of the following systems convection air assisted box oven, convection air assisted tunnel oven, infra red (IR) radiation heated tunnel oven, combination air and IR heated tunnel oven or any other system which is capable of providing a closely controlled source of heat and sufficient exhaust ventilation to remove solvent vapour without causing premature thermal polymerization of the photoresist.
  • the drying stage is not applicable.
  • the photoresist After application and, where appropriate, drying, the photoresist is exposed imagewise, through a photographic master of the pattern required, to radiation of an appropriate frequency and intensity to suit the particular photoresist being used .
  • the photoresist may be exposed directly using a laser to produce the image required.
  • the exposure step may cause light hardening or light softening of the photoresist.
  • the exposure step causes light hardening through radiation induced polymerization and causes the exposed areas of photoresist to become insoluble in the developing medium.
  • the photoresist is exposed in such a manner that the areas required to remain after developing, such as those over the previously printed resistor patterns, receive radiation and the areas required to be removed in the developer do not.
  • the exposure step causes light softening and the exposed areas of photoresist become soluble in the developing solution.
  • the photoresist is exposed in such a- manner that the areas required to remain after developing, such as those over the previously printed resistor patterns, do not receive radiation and the areas required to be removed in the developer do.
  • the developing medium may typically be an aqueous solution of an organic or inorganic acid or alkali, or may be an organic solvent.
  • the resistor material is soluble in the same developing medium as the photoresist, the exposed areas of resistor material will be removed, whereas the resistor material remaining under the photoresist will be protected from the developing medium by the photoresist and will not. Therefore by ensuring, that the photoresist image is of the exact size dimensions required for the resistor, the developer will remove only the excess resistor material from the oversized resistor patterns produced in steps 1 - 3, leaving the resistor pattern in the exact size required.
  • the developing medium used is one which will effectively remove the excess resistor material exposed by the previous developing step for the photoresist, without removing, attacking or otherwise damaging the photoresist remaining on the board.
  • the photoresist may optionally be removed. Removal may be effected by the use of an appropriate photoresist stripper.
  • the photoresist stripper must be selected to be one which will not detrimentally affect, in terms of resistance value, hardness or other necessary physical characteristic, the, as yet, uncured resistor patterns in a permanent way.
  • a photoresist stripper may be selected whose effect on the resistor value is predictable and consistent so that it can be compensated for by choosing an appropriately higher or lower value resistor paste.
  • the photoresist can be allowed to remain on the circuit board or other substrate and not be removed.
  • the photoresist must be selected such that by remaining on the board and hence over the resistor patterns, it does not detrimentally affect, in terms of resistance value, hardness or other necessary physical characteristic, the resistor patterns in a permanent way, either before or after the final cure stage or.
  • the effect of the photoresist on the resistor value may be predictable and consistent so that it can be compensated for by choosing an appropriately higher or lower value resistor paste.
  • Step 9 it may be necessary to final cure the resistor patterns and/or the photoresist where this is remaining on the board.
  • the final cure may be carried out by the application of heat or radiation or a combination of both.
  • the curing operation can typically be carried out by, but is not limited to, the use of one, or a combination of two or more, of the following systems convection air assisted box oven, convection air assisted tunnel oven, infra red (IR) radiation heated tunnel oven, combination air and IR heated tunnel oven, ultra violet (UV) radiation, electron beam radiation, vapour phase curing system, microwave radiation, or any other system which is capable of providing a closely controlled source of heat and/or energy.
  • convection air assisted box oven convection air assisted tunnel oven, infra red (IR) radiation heated tunnel oven, combination air and IR heated tunnel oven, ultra violet (UV) radiation, electron beam radiation, vapour phase curing system, microwave radiation, or any other system which is capable of providing a closely controlled source of heat and/or energy.
  • IR infra red
  • UV ultra violet
  • a printed circuit board comprising a pattern of etched copper track 1 and resistor termination pads 2 ( Figure 1) was provided with PTF resistor patterns thereon by the following method: - a) A PTF carbon resistor paste, reference ED6000, manufactured by Electra Polymers & Chemicals, was screenprinted through a stainless steel screen of 200 mesh onto the etched copper circuit board of Figure 1 which had been produced with suitable resistor termination pads 2 ( Figure 1) .
  • the stencil image used to produce the resistor pattern produced resistor images 3 which were larger than the required size ( Figure 2) .
  • a printed circuit board comprising a pattern of etched copper track and resistor termination pads with PTF resistor patterns thereon, was produced by a method which was essentially that of Example 1 with the exception that Step d) was omitted and the non light hardened photoresist and the excess resistor material were washed off in one step using the organic solvent as in step e) .
  • the resistor patterns had substantially the same resistance value as those of Example 1.
  • a printed circuit board comprising a pattern of etched copper track and resistor termination pads with PTF resistor patterns thereon was produced by a variant of the method of Example 1 in which by way of a difference in procedure the photoresist was removed with a 5% solution of sodium hydroxide after Step e) and before Step f) .
  • the resistor patterns had a somewhat lower value than in Examples 1 and 2 being about 120 Ohms/square.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Architecture (AREA)
  • Structural Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Parts Printed On Printed Circuit Boards (AREA)
  • Manufacturing Of Printed Circuit Boards (AREA)

Abstract

L'application, sur un substrat, d'un premier revêtement non photosensible suivant un motif ayant un caractère défini, fait appel à l'utilisation d'un second revêtement photosensible pour définir l'image ou le motif. Le procédé est utilisable, plus particulièrement, pour la production de revêtements épais en polymère agissatn comme conducteurs et comme résistances, pour obtenir des éléments bien définis.
PCT/GB1997/000412 1996-02-13 1997-02-13 Application d'un revetement suivant un motif WO1997030571A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU18019/97A AU1801997A (en) 1996-02-13 1997-02-13 Coating pattern formation

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9603050.7A GB9603050D0 (en) 1996-02-13 1996-02-13 Coating pattern formation
GB9603050.7 1996-02-13

Publications (1)

Publication Number Publication Date
WO1997030571A1 true WO1997030571A1 (fr) 1997-08-21

Family

ID=10788708

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1997/000412 WO1997030571A1 (fr) 1996-02-13 1997-02-13 Application d'un revetement suivant un motif

Country Status (5)

Country Link
AU (1) AU1801997A (fr)
GB (2) GB9603050D0 (fr)
ID (1) ID19890A (fr)
TW (1) TW348368B (fr)
WO (1) WO1997030571A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0964410A2 (fr) * 1998-05-15 1999-12-15 BSH Bosch und Siemens Hausgeräte GmbH Substance à couche épaisse et procédé pour la fabrication d'une structure à couche épaisse
EP1629509A2 (fr) * 2003-05-30 2006-03-01 Motorola, Inc. Resistance polymere a couche epaisse, topologie de surface, et procede

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4119480A (en) * 1976-05-13 1978-10-10 Tokyo Shibaura Electric Co., Ltd. Method of manufacturing thick-film circuit devices
FR2574570A1 (fr) * 1984-12-07 1986-06-13 Thomson Csf Procede de photolithographie d'une couche epaisse de pate deposee sur un substrat
FR2602912A1 (fr) * 1986-08-14 1988-02-19 Thomson Csf Procede de realisation de circuits microelectriques

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4119480A (en) * 1976-05-13 1978-10-10 Tokyo Shibaura Electric Co., Ltd. Method of manufacturing thick-film circuit devices
FR2574570A1 (fr) * 1984-12-07 1986-06-13 Thomson Csf Procede de photolithographie d'une couche epaisse de pate deposee sur un substrat
FR2602912A1 (fr) * 1986-08-14 1988-02-19 Thomson Csf Procede de realisation de circuits microelectriques

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
A.K. COUSENS AND J.S. WHITAKER: "Polymer thick film systems and surface mount techniques", MICROELECTRONICS JOURNAL, vol. 18, no. 3, May 1987 (1987-05-01) - June 1987 (1987-06-01), LUTON GB, pages 22 - 40, XP002007316 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0964410A2 (fr) * 1998-05-15 1999-12-15 BSH Bosch und Siemens Hausgeräte GmbH Substance à couche épaisse et procédé pour la fabrication d'une structure à couche épaisse
EP0964410A3 (fr) * 1998-05-15 2000-09-20 BSH Bosch und Siemens Hausgeräte GmbH Substance à couche épaisse et procédé pour la fabrication d'une structure à couche épaisse
EP1629509A2 (fr) * 2003-05-30 2006-03-01 Motorola, Inc. Resistance polymere a couche epaisse, topologie de surface, et procede
EP1629509A4 (fr) * 2003-05-30 2009-10-21 Motorola Inc Resistance polymere a couche epaisse, topologie de surface, et procede

Also Published As

Publication number Publication date
ID19890A (id) 1998-08-20
AU1801997A (en) 1997-09-02
TW348368B (en) 1998-12-21
GB9603662D0 (en) 1996-04-17
GB9603050D0 (en) 1996-04-10

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