GB2186436A

GB2186436A - Making printed circuits

Info

Publication number: GB2186436A
Application number: GB08700719A
Authority: GB
Inventors: Yamahiro Iwasa
Original assignee: Asahi Chemical Research Laboratory Co Ltd
Current assignee: Asahi Chemical Research Laboratory Co Ltd
Priority date: 1986-01-14
Filing date: 1987-01-13
Publication date: 1987-08-12
Anticipated expiration: 2007-01-13
Also published as: GB2186436B; GB8700719D0; JPS62163389A; JPH0237117B2

Abstract

A method of making printed circuits on a base board (10) comprises the steps of applying adhesive (20) to both sides of the board, providing a through-hole (40) in the board, selectively applying a plating resist (60) to both sides of the board, applying copper (80) by electroless deposition to the non-resist-covered regions of the board and the interior of the through-hole to provide circuits (C10) as required, applying a further layer (60) of plating resist onto the areas already covered with plating resist, coating electrically conductive copper paste (90) onto the plating resist, heating the board to harden the paste, and plating copper (100) onto the hardened copper paste to form a second circuit layer (C20). <IMAGE>

Description

SPECIFICATION A method for forming electric circuits on a base board The invention relates to a method for forming electrically conductive circuits on a base board, and more particularly relates to a method for forming at least four laminations of circuits on the base board.

It has been general practice to form a resistor circuit or an electricity storing circuit on a copper laminated base board by soldering a lead or a chipshaped resistor or a condenser onto the copper laminated base board. The finished product is there fore bulky in addition to requiring so many processing steps and the resultant high cost including the cost of the resistor or a condenser. In the conventional rriethod, the loading density of the printcircuit base board is lower, and the reduction of product weight and of production process is difficult.

Moreover, since solding is required,there is often a misarrangement of leads and a misinertion of the resistor or the condenser.

Further, when forming complex circuits on the copper laminated base board, it becomes necessary to electrically connect the circuits to each other. Conventionally, a through-hole is provided to electrically connect the circuits on both sides of the base board because it has been impossible to form the circuits of more than two laminations on one side of the base board. Even if the through-hole is provided, it has been impossible to form more than two laminations of circuits, that is, one located on one side of the base board and the other located on the otherthereof.

It has been proposed to form more than two laminations of circuits on one side of a ceramics base board. For example, in case of the hybrid OC, it is usual to employ a paste of precious metal such as platinum-palladium or silver-palladium to form the circuits and the terminals thereof, and to employ a paste of ruthenium oxide to form a resistor and then to burn the base board ata high temperature (700 C- 1 000 C). Further it has been proposed to form more than two laminations of circuits on one side of a base board by printing a tungsten (W paste) and an isolat ing paste alternatelyon an alumina green sheetand then by burning the alumina green sheetatatem perature of about 1600tC. However, since such method require a high temperature burning treatment,theingredientsofcircuitstructureto be used are limited and the equipment required is costly. The methods are therefore not suitableforproducing the print-circuit boards for general use in combination with electronic apparatus.

It is therefore desired to establish an industrial methodforforming more than two laminations of circuits on one side of a polymer base board which may be treated at a lower temperature. In this case, it becomes necessary to develop on electrically conductive copper paste which has a property of electrically high conductivity and is specifically adapted to a metal plating, especially to a copper plating and which may be obtained at a lower cost. It has however been difficu It in practice to use the electrically conductive paste, because the copper particles in the paste are readily oxidised when the paste is heated to be hardened at a temperature of approximately 1500, and the paste has a high electric resistance and reduce the soldering property.Generally, the conventional electrically conductive copper paste is easily oxidised with a heat for hardening the paste, in contract to the precious metal such as silver. The oxidisation of copper powder in the paste will increase the electrical resistance and decrease the soldering property. These defects have made the conventional electrically conductive paste practically useless.

Further it has been required to activate the surface of the hardened electrically conductive copper paste by means of a catalyst so as to expose the copper powderfrom the resin paste so that the exposed copper paste may act as the binder, that is, so many neuclei for the subsequent metal plating. Thus the conventional electrically conductive paste requires many processing steps.

Japanese Utility Model application Serial No.5542460 discloses a specific method, in which a high dielectric resist of polybutadiene is used as the dielectric coat, an adhesive paste, for example, of 20% of phenol resin, 63% of copper powder and 17% of solvent is used to form designed cuircuits,the adhesive paste is thickened to 20 > by means of a non-electrolytic plate, and then the plated adhesive paste is coated with copper so as to form the electrically conductive circuits of more than two layers on one side of a base board. This method has never been industrially reduced to practice.

After many years of research, the applicants now able to produce electrically conductive copper pastes that avoid the defects associated with the prior art mentioned above The newly developed electrically conductive copper pastes includes the electrically conductive copper paste ACP-020, ACP-030 and ACP-007P of Asahi Chemical Research Laboratory Co. Ltd. The electrically conductive copper paste ACP-020 is substantially omposed of 80% by weight of copper powder and 20% by weight of synthetic resin, and is extremely excellent in the electric conductivity, but more of less deteriorated in the soldering property.The electrically conductive copper paste ACP-030 is substantially composed of 80% by weight of copper powder and 15% by weight of synthetic resin, and is slightly lowerthan the ACP-020 as to the electric conductivity, but excellent in the soldering property. In the last place, the electrically con- ductive copper paste ACP-007P is an improvement of the ACP-030 and may be subjected to a metal plating such as a copper chemical plating without using a catalyst. In other words, the copper paste has excellent metal plating properties.

One object of the present invention is to eliminate the defects and disadvantages ofthe prior art. This is achieved by the effective use of the newly developed electrically conductive copper paste having the specially excellent metal plating property to form electrically conductive circuits of more than two laminations on one side of a base board.

It is another object of the invention to provide the circuits of at least four laminations on both sides of the base board including a resistor circuit on each side thereof, wherein the resistor paste of a pred etermined value of electric resistance is coated on a plating-resistant resist on both sides of the base board, and is then heated to be hardened. An electrically conductive paste is then coated on both sides of the base board in a manner as to electrically con nectto the resistor paste at least two circuits offirst lamination located on both sides ofthe resistor paste or the circuit of second lamination on one side ofthe resistor paste. The electrically conductive paste is then heated to be hardened to therebyform a resistor circuit on each side of the base board.

It is another object of the invention to form the circuits of at leastfour laminations on both sides ofthe base board including an electricity storing circuit, wherein a dielectric paste having a property of storing electricity is coated on a part ofthe circuit offirst or second lamination on each side of the base board, and then is heated to be hardened. An electrically conductive paste is then coated on both sides ofthe base board in a manner as to electricallyconnectto the dielectric paste another circuit offirst or second lamination on each side of the base board. The elec tricallyconductive paste is then heated to be hardened to form thereat an electricity storing circuit on each side of the base board.

It is still another object of the invention to provide a reliable print circuit board having the circuits of at leastfour laminations formed on both sides thereof including a resistor circuit or an electricity storing circuit on each side thereof, the print circuit board having a high loading density with reduction of weight and being produced in an extremely reduced processes without possible misarrangement of leads of misinsertion of a resistor element or a condenser.

According to the invention, we propose a method forforming electrically conductive circuits on a base board, comprising the steps of: a) applying and adhesive on both sides of the base board to provide an adhesive-applied base board; b) processing the adhesive-applied base board to provide a through-hole extending all through the thickness of the base board; c) performing a catalysttreatment ofthe base board; d) coating a plating-resistant on predetermined portions on both sides ofthe base board; e) heating the base board to harden the platingresistant resist;; f) performing a non-electrolytic copper plating on the portions having no plating-resistant resist is coated thereon on both sides of the base board, and on the inner periphery ofthethroughhole, to thereby provide thereat a copper plating layer in formation of a pluralityofcircuitsoffirstlaminationwhich are electrically connected to each other on both sides of the base board; g) coating the plating-resistant resist on the portions having the plating-resistant resist has been coated thereon and/or the parts of the circuits offirst lamination on both sides ofthe base board; h) heating the base board to harden the platingresistant resist; i) coating an electricallyconductive copper paste on the portions having the plating-resistant resist re peatedlycoated thereon;; j) heating the base board to harden the electrically conductive copper paste; k) performing a pre-plating treatment of the base board; and I) performing a chemical copper plating on the surface ofthe electrically conductive copper paste to provide thereat a plurality of circuits of second lamination on both sides of the base board.

In one embodiment for producing circuit laminations including a resistive circuit, the method comprises: m) coating a resistor paste having a predetermined value of electric resistance on at least one ofthe portions having the plating-resistant resist coated thereon on each side of the base board; n) heating the bas board to harden the resistor paste; o) coating an electrically conductive paste on both sides of the base board in a manner as to electrically connect to the resistor paste the circuits offirstor second lamination located on both sides ofthe resistor paste on each side of the base board; and p) heating the base board to harden the electrically conductive paste to form a resistor circuit on each side of the base board.

In another embodiment for producing circuit laminations including an electricity storage circuit, the method comprises: q) coating a dielectric paste having a property of storing electricity on a part of one ofthe circuits of first or second lamination on each side of the base board; r) heating the base boardto hardenthedielectric paste; s) coating an electrically conductive paste on both sides of the base board in a manner asto electrically connect to the dielectric past at least one ofthe circuits of first or second lamination located adjacentto the dielectric paste; and t) heating the base board to harden the electrically conductive paste to form thereat an electricity storing circuit on each side of the base board.

The finished circuit board can be made much thinner than conventional boards and at almost half the cost.

Otherfeatures and advantages will be apparent from the following description by way of example, of embodiments of the invention with reference to the attached drawings in which: Figures 1 to 9show a first embodiment ofthe invention, in which: Figure 1 is an adhesive-applied base board shown in vertical section; Figure 2 is the adhesive-applied base board shown in vertical section and having a through-hole provided therein; Figure 3 is the adhesive-applied base board shown in vertical section and having a catalyst treatment applied thereto; Figure 4 is the adhesive-applied base board shown in vertical section and having a plating-resistant resistcoatedthereon; ; Figure5isthe adhesive-applied base board shown in vertical section and having a non-electrolytic copper plating applied thereon to providethereatthe circuits offirst lamination; Figure 6 is the adhesive-applied base board shown in vertical section and having a plating-resistant resist coated thereon; Figure 7isthe adhesive-applied base board shown in vertical section and having an electricallyconductive copper paste coated thereon; Figure 8is the adhesive-applied base board shown in vertical section and having a chemical copper plating applied thereon; Figure 9 is the adhesive-applied base board shown in vertical section and having an overcoat coated thereon; Figures 10through 12 show a second embodiment of the invention, of which:: Figure 10 is the adhesive-applied base board as shown in Figure 8, but having a resistor paste coated thereon; Figure 11 is the adhesive-applied base board shown in vertical section and having an electrically conductive paste coated thereon; Figure 12 is the adhesive applied base board shown in vertical section and having an overcoat coated thereon; Figures 13to 75shOw a third embodiment of the invention of which: Figure 13 is the adhesive applied base board as shown in Figure 8 but having a dielectric paste coated thereon; Figure 14is the adhesive applied base board shown in vertical section and having an electrically conductive paste coated thereon; and Figure 15 is the adhesive applied base board shown in vertical section and having an overcoat coated thereon.

With reference to Figures 1 to 9, a first embodi- mentofthe invention will be described. A polymer base board 10 has an adhesive 20 applied on both sides thereof, and thus an adhesive applied base board 30 is provided as shown in Figure 1. The adhesive applied base board 30 is processed to have a through-hole 40 having an inner peri phery 40a extending all through the thickness thereof as shown in Figure 2. The adhesive applied base board 30 is then subjected to a catalyst treatment, and then metal particles 50 are attached on both sides of the base board and on the inner periphery 40a ofthethrough-hole 40 as shown in Figure 3.The metal particles 50 may be palladium (Pd) byway of example to be utilised as so many nucleusesforthe subsequent nonelectrolytic copper plating.

The catalyst treatment of the adhesive applied base board 30 is made with a catalyst of palladium oxide (Pdc12) and tin chloride (Sncl2) or an alkali cata lystsolution of palladium only, andthen metal particles 50 of palladium are attached on the surfaces of the adhesive applied base board 30. The metal particles 50 are used as the nuclei to expose the copper therearound in the subsequent non-electrolytic copper plating.Since both palladium and copper are a metal and little energy is required to provide a sur- face between the two substances and have the atomic arrangement of a substantially same period (both are oftheface-centered cubic lattice and the lattice constants are approximating such as 3.8898A and 3.61 soA respectively), the copper is progressively exposed on the colloid palladium in the non-electrolytic copper plating and thus the copper plating may be applied on the metal particles 50.

Afterthe catalyst treatment is finished, a platingresistant resist 60 such as the resist CR-2001 developed by Asahi Chemical Research Laboratory Co.

is coated on both sides ofthe adhesive-applied base board 30 on the portions 30a where there are no circuits formed as shown in Figure 4. The platingresistant resist 60 is then heated at about 1 50"C for about 30 minutes to be hardened. A non-electrolytic copper plating is performed on both sides of the adhesive-applied base board except the portions having the plating-resistant resist 60 is coated thereon, and on the inner peri p hery 40a of the through-hole 40 as shown in Figure 5.With the nonelectrolytic copper plating, a copper plating layer having the thickness of 1.0 > m-3.0,am in an hour in a copper plating bath of a temperature of about 70"C, pHl2thoughthe mentioned values may be more or less varied in dependence upon the composition of the copper plating bath. The copper plating layer is practically required to have the minimum thickness of 5ssm, and the plating timewill be 1.7-5 hours. Thus a copper plating layer 80 is provided in formation of the circuits Clo of first lamination on both sides of the adhesive-applied base board 30.The circuits C10 of the first lamination are electrically connected to each other on both sides of the base board 30 through the copper plating layer80 ofthe inner periphery 40a of thethrough-hole40.

The plating-resistant resist 60 is again coated on both sides of the adhesive-applied base board 30 on the portions where the plating-resistant resist 60 was precededly coated or on parts of the circuits Aloof first lamination which will not be electrically connected to the circuits of second lamination which will be mentioned herein as shown in Figure 6, and the resist 60 is heated to be hardened.

Subsequently as shown in Figure 7, an electrically conductive copper paste 90 such as the paste ACP007P developed by Asahi Chemical Research Laboratory Co., Ltd. which is specifically adapted to a copper plating, is coated by way of screen printing on the portions having the plating-resistant resist 60 is repeatedly coated thereon on both sides of the adhesive-applied base board, and then is heated at the temperature of about 1 50"C for 30-60 minutes to be hardened.

The adhesive-applied base board 30 is then processed with a pre-plating treatment. Namely the base board 30 is washed for several minutes with a water solution of 4-5% by weight of causic soda (NaOH) by way of example, and then is applied with a su rfacetreatmentfor several minutes by means of a water solution of 5-10% by weight of hydrochloric acid (HCl. With this surface treatment, many copper particles are exposed on the surface of the electrically conductive copper paste 90 from among the binder-thereof, which may be used as the neuclei in the subsequent process of copper plating. In this case, it is notedthatthecatalysttreatmentisnotneeded which may otherwise be needed in the normal nonelectrolytic copper plating.

In the next place as shown in Figure 8, the adhesive-applied base board 30 is immersed in a chemical copper placing bath to perform a chemical copper plating on the surface of the electrically conductive paste 90. As the result, copper plating layers 100 are provided in formation of the circuits C20 of second lamination on both sides ofthe adhesive-applied base board. Thus the circuits C20 of second lamination are electrically connected to the adjacent circuits C10 of first lamination. This chemical copper plating bath is pH 11-13 and is of the temperature 65 C-75 C, and the thickness of the copper plating layer 100 is more than 5##m with a plating speed being 1.5,am 3##m per hour.

In this way, the circuits C20 of second lamination may be formed with the copper plating layer 100 and the electrically conductive copper paste 90 on both sides of the adhesive-applied base board 30, and accordinglythe circuits Clo, C20 of at least four laminations may be formed on both sides of the base board 30.

Finally as shown in Figure 9, an overcoat 110 such as the plating-resistant resist CR-2001 developed by Asahi Chemical Research Laboratory Co., Ltd. is coated on both sides ofthe adhesive-applied base board 30, and thus a print-circuit base board 120 is finished up.

According to the embodiment, the circuits C10, C20 of at least four laminations may be formed on a single base board 30 byway ofthe additive method only.

Now in reference to Figure 8 and Figures 10 through 12, a second embodiment of the invention will be explained. Since the embodiment is processed in the same mannerwith the first embodiment until the step of Figure 8 is reached, this intermediate explanation is omitted herein, and only the steps from Figure 9to Figure 12will be explained with the same reference numerals used as to the parts which are common to both embodiments.

In reference to Figure 10, a resistor paste 140 of a predetermined value of electric resistance is coated on the portions of plating-resistant resist 60 having no electrically conductive copper paste 90 coated thereon on both sides ofthe adhesive-applied base board 30, and the resistor paste 140 is then heated to be hardened. An electrically conductive paste 150 such as a silver paste is then coated on both sides of the base board 30 in a manner as to electrically con nect to the resistor paste 140 at least two circuits C1 of first lamination located on both sides of the resistor paste 140, and the electrically conductive paste 150 is then heated to be hardened as shown in Figure 11.

Thus a resistor circuit 130 is formed on each side of theadhesive-applied base board 30 in additiontothe circuits C10, C20 of first and second laminations formed at least in four laminations. Then the overcoat 110 is coated on both sides ofthe adhesiveapplied base board 30. Thus a print-circuit board 220 is finished up as shown in Figure 12 bytheadditive method only.

Now in reference to Figure 8 and Figures 13 through 15, a third embodiment of the invention will be explained. Since the embodiment is processed in the same mannerwiththesecondembodimentuntil the step of Figure 8 is reached, this intermediate explanation is omitted herein, and only the steps from Figure 13 to Figure 15 will be explained with the same reference numerals used as to the parts which are common to both embodiments.

In reference to Figure 13, a dielectric paste 180 having a property of storing electricity is coated on a part of one of the circuits Clo, C20 offirstand second laminations on both sides ofthe adhesive-applied base board 30, and then is heated to be hardened. An electrically conductive paste 180 such as a silver paste is coated on both sides of the adhesive-applied base board 30 in a manner asto electrically connect to the dielectric paste 180 another circuit C10 of first lamination on each side of the base board 30, and the electrically conductive paste 190 is then heated to be hardened.In this way, an electrically storing circuit 160 is formed on each side ofthe adhesive-applied base board 30 in addition to the circuits Clo, C20 of at least four laminations on both sides of the adhesiveapplied base board 30.

In this embodiment, the electrically conductive paste 190 is used to electrically connect to the dielectric paste 180 the circuits C,O, C20 offirstand second laminations located on the right side of the plating-resistant resist 60. It is however needless to say that one of the circuits Clo, C20 ofthe first and second lamination may be connected to the dielectric paste 180.

Finally as shown in Figure 15, an overcoat 110 is coated on both sides of the adhesive-applied base board 30 and is then heated to be hardened. Thus a print-circuitboard320isfinished up.

In the embodiment, the circuits Clo, C20 are formed in two laminations on each side of the adhesiveapplied base board 30. It is however needless to say that the same processes maybe repeated onthe overcoat 1 to further increasethe laminations of circuits, for example, into more than six laminations of circuits in all.

Further it would be necessary to briefly explain the electrically conductive copper paste, the electrically resistant paste, the plating resistant paste and the dielectric paste which are used in this invention.

AstothepasteACP-Oo7Pdeveloped byAsahi Chemical Research Laboratory Co., Ltd. by way of ex ampleforan electrically conductive copper paste which is specifically adapted to a copper plating, it is generally known that copper is easily oxidized, and more especially copper in the condition of powder particles may be more easily oxidised because the exposed outer surface is enlarged. In contrast to the non-oxidizable paste of precious metals, it becomes necessary to provide a paste of such ingredients as to removetheoxidizedfilm of the copper powder particles and also to prevent the reoxidization ofthe copper particles. In order to provide an electrically conductive copper paste which may be easily used and easily secured to a base material, it is important to properly select and properly mix the ingredients such as copper powder, binder, special additive (for example, anthracene, anthracene carboxylic acid, anthradine, anthranilic acid), dispersant and solvent.

The copper particles are different in the configuration thereof depending upon the production method thereof. In the electrolytic method, the copper particles are deposited in high purity and also in branched shapes. In the reduction method wherein the oxides are reduced by a reducing gas, the copper particles are provided in spongy and porous shapes.

The electrically conductive copper paste to be used in connection with this invention is required to havethefollowing properties: 1. To be easily coated by way of screen printing in formation offine patterns.

2. Fixed secu rely to the base board.

3. To be resistant against a high temperature alkali bath of copper chemical plating.

4. Fixedly secured to the copper plating.

5. Having a invariable viscosity in the elapse of time to maintain a stabilized printability.

In order to satisfy the above mentioned requirements the electrically conductive copper paste is required to contain the copper particles of high purity in the branch shapes as deposited by the electrolysis and/or the copper particles of porous spongy shapes as reduced from the metal oxides. The copper particles may be processed into flakes.

Further in order to highten the content rate of the copper particles in the paste, it is required to fill the copper particles of different sizes and shapesto a maximum density.

As to the binder of the electrically conductive copper paste, the binder is required to act as a veh icleforso much copper particles and as an effective adhesive to the base board. Furtherthe binder must resist against the alkali bath of a copper chemical plating.

It was found that the electrically conductive copper paste was best when the copper paste contained the epoxy resin which has a larger content rate of copper particles and hightensthe deposition rate of the plating, and further increases the adhesive property of the plating film.

With respect to the property ofthe copper plating deposited on the electrically conductive copper paste ACP-007P, the copper plating is reddish brown and paste like and has a viscosity of 300-500ps atthe temperature of 25 C. The adhesive property to a copper laminated base board and to a resin base board has been confirmed by a taping test. Further the adhesive propertytothe electrically conductive paste has been confirmed by the taping test. The sol- dering property is more than 96% as to the extension rate and is more than 3.0 kg as to thetensileforce (3 x 3mm2).

The components of the electrically conductive copper paste and the conductivitythereofare mentioned in detail in the same applicant's Japanese Patent applications 55-6609 (laid open: 56-103260) (corresponding U.S. patent No.4353816) and 60216041 (corresponding to U.S. patent application of serial No.06/895716), and therefore the description thereof is omitted herein.

With respect to the electrically resistant paste, the paste contains a refined powder of carbon or graphite or the like of high purity as an electrically conductive element and a heat hardened resin such as epoxy resin, phenol resin, melamine resin, acrylic resin orthe like as a binder, and further contains, as a viscosity modifier, a solvent which is evaporated slowlyata high temperature.

The components of the electrically resistant paste are each required to have a specific property. Forexample, as the functional powder, the particles must befineand uniform and further of high purity as well as high quality. Furtherthe particles must be of little difference in the electric resistance value and must be familiar with the resin to be mixed therewith.

As to the property of polymer, it is preferable that the paste is easily dissolved with the particles and will not be filmy if placed for a long time in a normal temperature. The paste further is required to be not hardened at a normal temperature and to be quickly hardened when heated. The hardened paste must not be vary in volume and must be slightlyflexible and further easily adhesive to the base board.

Furtherthe paste must be resistant against heat and humidity, and also must be easilyadhesivetotheun- dercoat as will as to the overcoat.

As to the property of solvent, the paste is required to be stabilized in the successive printing operations, that is, not to fill the prints and not be deteriorate the emulsion film. The paste is further required to be slow in the evaporation speed at a normal temperature and reluctant to absorb water, notto abruptly change the viscosity thereof at the temperature + 10 C and to have no poison and/or irritating smell at a normal temperature and in the vapor at the time of heating.

The electrically resistant paste such as the paste TU-1 K has been developed by Asahi Chemical Research Laboratory Co., Ltd. so as to fully satisfythe requirements as mentioned above. The electrically resistant paste maintains very stabilized resistance, that is, the resistance variation rate is only about 0.5% atthe soldering temperatures at240'C. Further the paste will not abruptly absorb the heat andwill not respond to the heat until the soldering temperature is reached as actually indicated by a heat difference analysis curve, and therefore the volume variation of the resistor is extremely small.

With respecttothe plating resistant resist such as the resist CR-2001 developed by Asahi Chemical Research Laboratory Co., Ltd. so as to be used in the present invention, this resist is coated on a first circuitwhich is not electrically connected to a second circuit which is to be formed on the first circuit.

Therefore the resist is required to have an isolating property and atthe same time an alkali resistant property. Actually the resist has been developed to maintain the acidity more than 4 hours in the alkali bath of 700C and of pH12 just like the copperchemical plating bath.

Similar to the electrically conductive copper paste ACP-007P, the resist contains as a main component an epoxy resin and is printed through a 180-mesh polyester screen and then is heated for 30 minutes at the temperature 1 500C so as to be hardened. The printing film is preferably 1 5-30#m so as to resist chemicals and voltages. The main features are asfoI- lows: The resist is easily adhered to the base on which the resist is coated, and to a copper lamination and further is not deteriorated is immersed in the alkali bath of pH12 for a long time. The resist is quite safeinthe practical use becausethe hardenerto be used is alkali having little poison.The resist is coated bywayofscreen printing and hasa hardener 1 Og mixed with the principal component 1009 thereof, and is hardened in a set time 15-30 minutes atthe temperature 1 50-2000C.

The plating resistant resist is green in the condition of ink and has an adhesion (cross-cut) 100/100 on a copper lamination, a surface hardness of more than 8H when measured by a pencil, a solvent resistant property (in trichloroethylene) by more than 15 sec., a soldering heat (260 C) resistant property of more than 5 cycles, a surface isolation resistance value of more than 5 x 1013Q, a volume resistance value of 1 x 1 014#-cm, a voltage (15cm) resistant propertyof more than 3.5kV and a dielectrictangent (1 MHz) of less than 0.03.

The dielectric paste to be used in the invention has been developed as corresponding to the types 1 and 2 of the chip condenser standards, and the electrostatic capacity is 100pF-1000pF. The dielectric paste is produced from the barium titanate (BaTO3) which is burned into flakes or into a plate and is ground into particles of 2 > m-10 > m which arethen mixed with a binder with more than 50% byweight of the particles, which are further mixed with an organic solvent and is kneaded into a paste. For a binder, a resin such as phenol resin, epoxy resin, melamine resin, et., may be used. Fora solvent, butyl carbithol may be used as a main elementtogetherwith carbithol or butyl cellsole.

Example 1 The electrically conductive copper paste ACP-007P was directly printed on a paper phenol base board and heated atthetemperatureof 1 500C for a predetermined time so as to be hardened. Then the alkali and acid treatment was performed to the base board and subsequentlythe chemical copper plating was performed to provide a chemical copper plating layer of Siim thickness. A lead (tin coated lead 0.5mum+) was soldered (within 3 seconds) to the measuring terminal. In this case, itwasfoundthat the solder tensile strength (kg/3 x 3 mm2) was 5.1 kg when the paste was hardened in 30 minutes, and 5.9 kg when the paste was hardened in 60 minutes.

In case a glass epoxy resin base board was emplyed on the same condition, it was found thatthe tensile strength was 5.9 kg when the paste was hardened in 30 minutes, and 6.2 kg when the paste was hardened in 60 minutes.

Example2 The plating-resistant resist CR-2001 was printed on a phenol resin base board and was heated atthe tem perature of 1 50"C for 30 minutes so as to be hard- ened. Subsequently the electrically conductive copper paste ACP-007P was printed and heated at thetemperature of 1 for a predetermined time so asto be hardened. Then the alkali and acid treatment was performed, and then the chemical copper plating was performed to provide a copper plating layer of 6#m thickness. A lead (tin coated lead 0.5mum+) was soldered (within 3 seconds) to the measuring terminal. In this case, it was found that the solderten- sile strength (kg/3 x 3mm2) was 5.9 kg when the paste was hardened in 30 minutes, and 6.1 kg when the paste was hardened in 60 minutes.

In case a glass epoxy resin board was employed on the same condition, it was found that the soldertensile strength was 6.1 kg when the paste was hardened in 30 minutes, and 6.9 keg when the paste was hardened in 60 minutes.

Claims

1. A method for forming electrically conductive circuits on a base board comprising the steps of: a) applying an adhesive on both sides of the base board to provide an adhesive applied base board; b) processing the adhesive applied base board to provide a through-hole extending all through the thickness ofthe base board; c) performing a catalyst treatment of the base board; d) coating a plating-resistant resist on predetermined portions on both sides of the base board; e) heating the base board to harden the plating resistant resist;; f) performing a non-electrolytic copper plating on the portions having no plating-resistant resist is coated thereon on both sides of the base board, and on the inner periphery of the th rou g h hole, to thereby provide thereat a copper plating layer in formation of a plurality of circuits of first lamination which are electrically connected to each other on both sides of the base board; g) coating the plating-resistant resist on the portions having the plating-resistant resist has been coated thereon and/or the parts of the circuits of first lamination on both sides of the base board; h) heating the base board to harden the platingresistant resist; i) coating an electrically conductive copper paste on the portions having the plating-resistant resist re peatedly coated thereon;; j) heating the base board to harden the electrically conductive copper paste; k) performing a pre-plating treatment of the base board; and I) performing a chemical copper plating on the surface of the electrically conductive copper paste to providethereata plurality of circuits of second lamination on both sides of the base board.

2. A method according to claim 1 and comprising m) coating a resistor paste having a predetermined value of electric resistance on at least one of the portions having the plating resistant resist coated thereon on each side ofthe base board; n) heating the base board to harden the resistor paste; o) coating an electrically conductive paste on both sides of the base board in a manner asto electrically connect to the resistor paste the circuits of first or second lamination located on both sides of the resistor paste on each sude of the base board; and p) heating the base board to harden the electrically conductive paste to form a resistor circuit on each side of the base board.

3. A method according to claim 1 comprising q) coating a dielectric paste having a property of storing electricity on a part of one of the circuits of first or second lamination on each side of the base board; r) heating the base board to harden the dielectric paste; s) coating an electrically conductive paste on both sides of the base board in a manner as to electrically connect to the dielectric paste at least one of the circuits of first or second lamination located adjacentto the dielectric paste; and t) heating the base board to harden the electrically conductive paste to form thereat an electricity storing circuit on each side of the base board.