JP5775684B2 - Conductive metal pattern forming method and electronic / electric element - Google Patents

Description

  The present invention relates to a method for directly forming a selective functional pattern on the surface of a substrate, which has been actively researched recently, and in particular, a mounting substrate formed by modification or plating with excellent design of a resin substrate. For electronic and electronic devices, chemical devices, and direct printing technology applied to the market, it provides new means for the formation of increasingly sophisticated and sophisticated functional patterns, and the manufacture of electronic and electrical devices, printed electronics, bio devices, etc. At the same time, the quality and reliability are improved and the cost is further reduced.

There are many products that form a function by plating a metal on a resin substrate, and various plating methods and ground treatment methods have been proposed and used. In particular, various plating techniques are used for a modified product and a mounting substrate of an electronic / electrical device that are excellent in design by forming a selective conductive metal pattern on the surface of a resin substrate. Common plating products are often plated in solution. Since plating cannot be performed directly on the resin substrate, first, the entire surface of the resin is lightly roughened by performing a surface treatment, and then a metal catalyst such as Pd is deposited on the rough surface, and then a metal such as copper is electrolessly plated. The metal is grown thinly by electroplating. The adhesion strength of the metal pattern is also improved by roughening the surface. It may be thickened with electroless plating. Next, pattern formation is performed. For advanced mounting boards, generally by vacuum deposition or bonding metal films, first a strong metal thin film is applied to the entire surface of the resin substrate, and then a pattern is formed using a photosensitive resist. The metal is eroded and removed to form a desired conductive metal pattern. In either case, the metal layer on the entire surface of the substrate is etched to form a pattern.
Hereinafter, the present invention will be described in detail using a leading mounting board as a representative example.

  In recent years, various new technologies have been reported for manufacturing mounting substrates and the like whose applications are expanding. For example, there are a horizontal processing method and a vertical processing method which are disclosed in Japanese Patent Laid-Open No. 2-18399 and dipped in an interfacial treatment liquid in a corrosion bath as cited in the publication. Moreover, various interface treatment liquids and treatment agents are widely used in general. As a new surface modifier, a proposal such as International Publication No. WO 2007/066460 utilizing a metal complex has been made. In both cases, the entire surface is plated and the pattern is formed by etching, so that under-etching occurs along the interface during metal corrosion, and serious problems such as reduced reliability have emerged along with miniaturization. In addition, it is a waste of energy and resources to remove most of the plated copper and other metals.

  Due to these problems, the direct writing technology has recently attracted attention, and after printing nano silver paste, the technology of baking and drawing conductive patterns, the technology of drawing and forming patterns directly with inkjet printers, etc. have been widely studied. Yes. However, the electrical resistance is high, and many problems remain in the adhesive strength and pattern shape, which is very expensive. I haven't left the R & D stage yet.

  Microprinting technology has been developed and studied extensively for biodevices following the report of A. Kumar et al. Various devices have been devised as described in JP2009-90673A and JP2009-28947A, but they are originally intended for thin films such as monomolecular films, and there are significant restrictions on application development. It is very expensive.

Japanese Patent Publication No. Hei 2-18399 International Publication Number WO 2007/066460 JP 2009-90673 A JP2009-28947

A. Kumar, G.M.Whiteside et al. Langmuir 10 (1994) 1498

  In forming a pattern on the surface of a resin substrate, as shown in the background art, after forming a metal layer on the entire surface, an opening created by a photolithography process or the like is corroded to obtain a desired pattern. At this time, it is known that the joint interface between the metal and the resin is eroded by the corrosive liquid. If the width of the pattern becomes as fine as several tens of microns, this sub- to several-micron interface erosion becomes a non-negligible size, leading to a decrease in bonding strength and causing peeling, as well as various defects. Cause. Furthermore, this eroded portion propagates and grows with use, and thus has a non-negligible effect on long-term reliability. In particular, electrical and electronic devices are aimed at line widths of 20-30 microns or less, and such initial deterioration, aging deterioration, and characteristic change due to such interface erosion are major issues. This is one of the major factors that have put emphasis on recent direct writing research and development.

  In physical plating methods such as vacuum deposition and sputtering, the adhesion strength to the substrate is considered to be very strong, but the above-mentioned interface erosion is also a problem as the line width becomes narrower. Pattern deposition on the order of several hundred microns is possible, but fine patterns and fine lines cannot be expected at all.

  On the other hand, in the copper plating method in a liquid that is inexpensive and suitable for mass production, the adhesion strength varies greatly depending on the method of plating plating. In general, the interface is roughened by surface corrosion treatment or the like to increase the adhesion strength, but generally the strength is insufficient. In addition, there is another problem that the entire surface of the substrate becomes rough, and the deterioration of the interface occurs greatly due to the corrosion at the time of pattern formation. Has been a major obstacle to miniaturization. Further, in pattern formation, interfacial erosion occurs as described above, which causes a decrease in initial peel strength and further deterioration in long-term reliability.

In addition, in the actual process, there is a risk that the surface of the erosion interface deteriorates every time the treatment process is performed, and the surface may be soiled or damaged each time the treatment process is performed, thereby preventing a decrease in yield and reliability. Therefore, maintenance and adjustment costs such as very precise maintenance and management of various facilities and devices are increasing. For this reason, there is a strong demand for simplification and shortening of the process.
In any of the above-described methods, the entire area of the remaining pattern portion, circuit pattern, etc. is small, and in reality, most of the plated metal is removed. Furthermore, it is a major issue from the viewpoint of environmental costs associated with the treatment of waste liquids such as a large amount of corrosive liquid, and resource saving and energy saving.

  In direct writing technology, which has been actively researched and developed recently, environmental problems such as the above-mentioned interfacial erosion problems and waste liquid treatment have been reduced. The cost is high, and many problems remain in the adhesive strength and pattern shape. In addition, microprinting technology for bio-elements and the like is originally intended for thin films such as monomolecular films, and there are significant restrictions on application development involving thick films. Furthermore, fine and delicate adjustments are necessary and lack of stability, resulting in very high costs.

The present invention relates to a method for forming a conductive metal pattern suitable for mass production and an electronic / electrical element.
The gist thereof includes a plating base preparation step, a pattern formation step, and an electroless plating step in this order, and in the method of forming a selective conductive metal pattern on the surface of the insulating resin substrate, the pattern formation step comprises: . B. a printing process in which a high-viscosity corrosive liquid having a viscosity of 1000 cps or more having the insulating resin corrosivity is formed on the surface of the insulating resin substrate in the conductive metal pattern ; Conductive metal pattern characterized by including a process of holding the insulating resin substrate for a certain period of time through a corrosive process of slightly corroding the surface of the insulating resin substrate to the conductive metal pattern, and then removing the highly viscous corrosive liquid. It is a forming method. Hereinafter, a specific description will be given by taking a well-known mounting board widely used in electronic devices as an example. Bio-elements and chemical sensors also have similar processes, although it seems complicated at first glance.

The gist of the present invention is that the conductive metal pattern is temporarily printed on the conductive metal pattern once formed by the electroless plating step in the conductive metal pattern forming method. The conductive metal pattern is formed by selectively removing a portion of the conductive metal pattern on the surface of the insulating resin substrate by corrosion. And it is the electronic electrical element manufactured using these conductive metal pattern formation methods.

  Based on FIG. 1, the gist of the present invention will be described. As shown in FIG. 1A, when the aqueous solution 2 is dripped onto the clean resin substrate 1, a contact angle 3 is generated to form a polka dot 4, or the end is shaped like a seaweed, so that it can be accurately and accurately obtained. It is generally known that a pattern cannot be drawn. For this reason, a ground treatment for roughening the substrate is essential. On the other hand, it is generally known that when the surface is roughened, the solution 2 spreads quickly and a fine pattern cannot be formed. For this purpose, it is a conventional method to roughen the entire surface and form a pattern with photolithography after plating. However, the present inventor has found that when a corrosive solution that reacts with the substrate is imprinted, it is not repelled at all, but a fine pattern can be directly and simply formed by reversing ease of repelling and difficulty of bleeding. The present invention of the metal pattern formation method that breaks the conventional limit has been reached.

  After analyzing this interface phenomenon, the following findings were obtained. The shape of the solution on the substrate is determined by the chemical physical bonding force and the surface tension. This is why water polo can be formed on Teflon (registered trademark). However, this phenomenon is a story in an unreacted equilibrium state. The solution temporarily sticks to the surface and then rises (i.e., repels) to reach an equilibrium state so as to be in an equilibrium state. On the other hand, in the case of a reactive solution, the surface state of the substrate changes due to the reaction at the non-equilibrium interface where the solution is temporarily adhered, and the binding force increases and does not repel. The reaction then proceeds further and a new stable equilibrium is reached.

FIG. 1B shows an example of the basic concept of the present invention based on this observed phenomenon and consideration. When the reaction liquid 2 that corrodes the base resin is imprinted on the resin base 1, it tends to become round due to surface tension because the bonding strength with the base is weak, but the printing shape is temporarily maintained. During this time, the corrosive agent contained in the reaction liquid 2 infiltrates the base, starts to modify the surface and starts to form an activated layer, and the binding force gradually increases to maintain the shape. After a certain period of time, the corrosive agent diffuses to the interface to form a sufficient corroded surface, and a stable pattern 6 is formed to keep the shape of the printing plate stable. Therefore, the printed reaction liquid 2 is hardly repelled on the surface of the substrate 1, and a pattern 6 that maintains the shape of the printing plate can be formed.
In principle, the shape of a printed pattern solution and its change are mainly determined by surface tension, affinity, viscosity and time. Immediately after printing, the surface affinity is low to prevent the spreading of the pattern solution, and at the next moment, corrosion starts and the interface affinity is increased to prevent repellency, keeping the shape of the printed pattern 6 and further preventing corrosion. By proceeding, an appropriate surface activation layer 5 is formed.

  It should be noted that some repelling may be observed when printing such an ultra fine pattern. At this time, it has also been found that light surface treatment of the substrate and thickening of the corrosion solution are effective in accordance with the above principle. Needless to say, as in a general process, a clean resin substrate surface is obtained in advance by cleaning the surface of the substrate, plasma treatment, ozone treatment, or the like.

As a printing method, general methods such as silk screen printing, gravure printing, ink jet printing, and direct drawing can be used.

Next, after washing and removing the reaction solution, catalyst particles such as Pd are deposited on the roughened roughened surface in accordance with an ordinary plating method, and a conductive metal layer is formed and thickened by electroless treatment. If necessary, it can be formed thicker by electrolytic plating. As a result, a metal plating that accurately reflects the printed pattern was realized. In addition, when it roughened a little in advance as mentioned above, it was recognized that Pd etc. slightly precipitated in addition to a desired pattern very rarely, and a metal spot grew. At this time, the above minute metal spot-like precipitates could be easily removed by lightly etching back.
Alternatively, a catalytic metal salt such as a Pd compound may be added to the reaction solution in advance and deposited on the activated layer, and electroless plating may be performed immediately after washing.

  In addition, when performing electrolytic plating, the pattern must be connected. If there is a part that is not continuous and becomes floating islands, even if electroless plating is possible, electrolytic plating cannot be performed. In such a case, create a continuous dummy pattern once, complete the temporary pattern with electrolytic plating, and then selectively print the corrosive high-viscosity liquid on the unnecessary pattern part. By removing the film, a desired pattern can be finally formed, and an electronic / electrical element having a desired thick film can be obtained.

  According to the present invention, a functional product having a fine pattern and an electronic / electric element having a fine circuit pattern can be provided by a low-cost printing method suitable for mass production. Further, in a fine circuit pattern used for an electronic / electrical element, an undercut as shown in FIG. 2 is generated for forming a fine line even if a conventional process for giving excellent adhesive strength by a sputtering method or the like is used. 7 and the deterioration of the interface caused problems such as a decrease in peel strength and a decrease in reliability. However, the present invention eliminates such a problem.

In addition, the conventional process goes through many processing steps, which increases the maintenance and adjustment costs of various facilities and various equipment, and also has the disadvantages of soiling and scratching the surface each time the processing process is performed, as well as yield and reliability degradation. However, in the present invention, since all the processes are greatly simplified, these problems are solved at once. Furthermore, not only the process operation rate was improved, but also secondary effects such as a significant improvement in productivity such as an increase in yield were recognized.
Furthermore, in the present invention, resources are saved because the plating is applied only to the pattern portion such as a circuit pattern having a very small area, and an extra corrosive solution for removing the metal plated on the entire surface is not required. It is energy saving. The cost reduction effect by these is also great.
Needless to say, the same technique can be applied to bio-elements and chemical sensors, and the same excellent features as described above can be obtained.

Principle diagram Interface undercut Effect of reaction liquid corrosion agent concentration

The basic interface processing method of the present invention will be described in detail below using a leading mounting board as a typical application example. It goes without saying that various applications can be developed with various combinations of substrates and reaction solutions.
Using a 38-micron polyimide film as the insulating resin substrate, the surface was first degreased and cleaned in the base preparation step. Next, a desired pattern was printed by gravure printing with an alkaline corrosion solution that hydrolyzes and corrodes the polyimide film surface. A latent pattern was transferred onto the polyimide film surface through a pattern formation process consisting of a surface activation process in which the surface of the polyimide film was moderately roughened by leaving it for several seconds to several tens of seconds, and then the corrosion solution was removed and washed.

  Further, the surface having a latent pattern activated by the corrosion solution is subjected to a general palladium application treatment, followed by treatment with a general electroless nickel plating solution or an electroless copper plating solution. The metal pattern was revealed. As a result, an electroless copper pattern almost identical to the printed pattern was obtained. A thick electroless copper plating was applied as it was, and after washing with pure water, an electrolytic copper plating was applied if necessary to form a thick highly conductive copper pattern, which was then washed to obtain a finished product.

  When the concentration of the corrosive solution is low, the pattern repels faster and the pattern becomes thinner. At this time, the pattern shape can be maintained by lowering the repelling speed by increasing the viscosity of the corrosive liquid. Conversely, when the density was high, the pattern tended to thicken (see Fig. 3). In this case, the size of the pattern could be maintained by expediting the removal of the corrosion solution.

  Further, when a thin electroless conductive metal pattern was made apparent, catalyst Pd adhered to a portion other than a predetermined portion, and a minute metal deposit formed by using this as a nucleus sometimes occurred. Such deposits did not grow by electrolytic plating and could be effectively removed by light etch back.

  In order to thicken the discontinuous floating island pattern with electrolytic plating, apply a continuous pattern with a dummy pattern, apply electrolytic plating, and then print or stamp an adhesive corrosion solution that corrodes the plated metal. The dummy part was removed by corrosion. As a result, various independent patterns were formed consistently by the printing method.

  As a substrate, a polyimide film having a width of 50 cm and a thickness of 38 microns was cut into an appropriate size, and the surface was degreased. As the degreasing solution, an aqueous solution containing 44% of standard mono-ethanolamine and 1.7% of polyoxyethylene alkyl ether and some chelating agents was used. Furthermore, after washing with distilled water, a KOH 4 mol / L solution that hydrolyzes and corrodes the polyimide surface is added with a surfactant, a thickener, and a thixotropic agent. A linear pattern, a 100 micron square checkerboard pattern, and a 10 mm × 30 mm rectangle were printed.

  35 seconds after printing, and immediately washed with pure water to remove the infiltrating liquid, the active interface obtained by applying palladium as a catalyst was applied. Palladium was imparted to the polyimide interface by a conventional method using a commercially available drug. Traces of a linear pattern having a width of 55 to 105 microns and a length of 3 mm and a checkered pattern of 105 microns square were observed with a microscope. As a whole, a pattern with a width of about 5-10% thick was formed.

At this point, a sample was cut from the polyimide film subjected to a series of treatments, and the distribution of palladium was measured by ESCA. As a result, a linear pattern and a checkered pattern having a predetermined width of 55 to 105 microns were confirmed. In addition, no trace of peculiar palladium was observed in the other portions. Subsequent electroless copper plating treatment revealed a pattern of approximately the same size with a thickness of about 1 micron.
The formed copper pattern was observed to be a linear pattern having a width of 55-110 microns and a length of 3 mm and a checkered pattern having a 110-micron square. As a whole, a pattern with a width of about 5 to 10% thick was formed, but it was confirmed that the pattern had almost the same size.

  Next, a predetermined size was cut out from a rectangular pattern of 10 mm × 30 mm and heat-treated at 150 ° C., and then a peel strength test (JIS C 6471 8.1) between the metal layer and the polyimide film was performed. Using a tensile strength tester (TEST STAND MODEL-1310DW and FORCE ANALYZER EXPLORER2), the peel strength of the metal layer was measured at a tensile speed of 50 mm / min and a tensile angle of 90 °. The peel strength after the heat treatment was about 0.4 N / mm, which was a considerably high value as a direct plating film.

As in Example 1, as the degreasing solution, an aqueous solution containing 44% of standard mono-ethanolamine and 1.7% of polyoxyethylene alkyl ether and some chelating agents was used. Furthermore, after washing with distilled water, a KOH 4 mol / L solution that hydrolyzes and infiltrates the polyimide surface is mixed with an aqueous solution containing 1% gum arabic, 3% PVA, 3% sodium alginate, and a syrupy high-viscosity infiltrating solution is screened. A linear pattern with a width of 50 to 100 microns and a length of 3 mm and a checkered pattern with a 100 micron square were printed, and a 10 mm × 30 mm rectangle was printed. When the treatment was carried out in the same manner as in Example 1, a linear pattern with a thickness of 3 microns, an electroless copper plating thickness of 3 microns, a length of 55 to 105 microns, and a length of 3 mm and a checkered pattern of 105 microns square were observed with a microscope. As a whole, a pattern with a width of about 3 to 10% thicker was formed.
The peel strength was about 0.45 N / mm, which was a practical value.

Viscosity is increased from 1 cps like water to tens of thousands cps like clay by changing the amount and type of thickener and thixotropic agent that hydrolyzes the polyimide surface, and the standing time after printing is 5 seconds. Changed to 50 seconds. It was as short as 5 seconds for the low viscosity corrosive liquid and as long as 50 seconds for the high corrosive liquid. The other conditions were the same as in Example 1. Table 1 shows the results obtained by measuring a linear width of 50 mm to 100 microns and a length of 3 mm. Note that hard clay is excluded because it could not be printed in reality.
The peel strength of the non-defective pattern was not changed from about 0.4 to 0.45 N / mm as in the case of Example 1.

In Example 2, the polyimide surface of the substrate was lightly plasma treated to change it to hydrophilic. Other conditions are exactly the same as in Example 2. The results are shown in Table 2. As can be seen from the table, the hydrophilization process moistened the corrosion solution and preferentially advanced the corrosion reaction. As a result, it was shown that the pattern became thicker in the low-viscosity range, and the favorable range expanded. Was recognized.
The peel strength of the non-defective product was slightly improved to about 0.4 to 0.5 N / mm.

In Example 1 described above, first, electroless plating is performed with a nickel electroless plating having a thickness of 0.1 micron with a commercially available electroless nickel solution made of nickel sulfate, nickel chloride, hypophosphite, etc. And washed with pure water. Thereafter, electroless copper plating was performed in the same manner as in Example 1. As a result, a linear pattern having a width of 55 to 110 microns and a length of 3 mm and a checkered pattern of 105 microns square were observed with a microscope. As a whole, a pattern with a width of about 5-10% thick was formed.
At the same time, when the peel strength was measured after heat-treating the pattern at 150 degrees, it showed a very high value of about 0.6 to 0.8 N / mm. It was found that the peel strength by the sputtering method generally reported is not inferior and is very high. This is presumed to be due to the high adhesion strength of nickel at the interface.
Nickel has oxidation resistance and an effective barrier against oxygen and moisture, so that the stability of the copper interface is increased and long-term reliability is improved. Even after high temperature treatment at 150 ° C. for 200 hours, a high value of 0.55 N / m or more was maintained, and long-term reliability was confirmed.
(Comparative Example 1)

A conventional copper plating treatment was performed in the same manner as in Example 1. At this time, the viscosity of the corrosive liquid was approximately 1 CP like water, and the surface treatment was performed by immersing the entire surface in the corrosive liquid instead of printing. Thereafter, an electroless plating was formed to a thickness of 1 micron. Thereafter, normal photolithography and etching were performed to produce a linear pattern having a width of 50 to 100 microns and a length of 3 mm, similar to Example 1.
When a cross section of a 50 micron linear sample plated with copper was observed with a TEM, due to side etching, corrosion of the polyimide interface between the copper and the substrate was observed, and under-etching was generally observed. I could see it inside. When strong etching was performed after photolithography, biting of several microns was observed (FIG. 2).
On the other hand, in the sample of Example 1, it was found that the interface between the substrate and the polyimide was aligned from end to end without any abnormality. Naturally considering the manufacturing process.
If the line becomes even thinner, it is likely that the line floats up and peels off in the comparative sample.
Also in Example 2-3, TEM observation was performed in the same manner. As a result, it was found that the interface consistency was good. This is also a natural result from the manufacturing process.

  In the same manner as in Example 3, using various concentrations of caustic potash solution, the Pd adhesion amount was examined. As shown in FIG. 3, the caustic potash solution of about 0.5 N progressed to some extent with the roughening of the polyimide film, Pd adhesion started to be noticeable, and sufficient Pd precipitation was observed at about 1 N or more. As the concentration increased, stable pattern formation was observed.

  The present invention relates to a method for directly forming a selective functional pattern on the surface of a substrate, which has been actively researched recently, and in particular, a mounting substrate formed by modification or plating with excellent design of a resin substrate. It provides new means for the formation of functional patterns that are becoming increasingly refined and sophisticated, and the manufacture of electronic and electrical elements and bio-elements. In addition to greatly improving the reliability, further resource saving and energy saving will be realized.

DESCRIPTION OF SYMBOLS 1 Base body 2 Reaction liquid 3 Contact angle 4 Polka dot 5 The activation layer 6 which the interface layer modified | denatured 6 Pattern 7 Undercut 8 Wiring

Claims (3)

In the method of forming a selective conductive metal pattern on the surface of the insulating resin substrate , including a plating base preparation step, a pattern formation step, and an electroless plating step in this order, the pattern formation step comprises : Printing process viscosity with the insulating resin corrosive to the insulating resin substrate surface to form a more highly viscous etching solution 1000cps to the conductive metal A pattern shape, B. Fixed time held via the corrosion process of corrosion of the insulating resin substrate surface slightly the conductive metal A pattern shape, then the highly viscous etching solution conductive metal A pattern was characterized in that it comprises a step of removing the Forming method Wherein on the conductive metal A pattern once formed by an electroless plating process in the conductive metal A pattern forming method according to claim 1, part by printing the etching solution to corrode the conductive metal selective A pattern A method of forming a conductive metal pattern , comprising selectively removing a conductive metal pattern on the surface of the insulating resin substrate by removing the conductive metal by corrosion.   An electronic / electrical element manufactured using the conductive metal pattern forming method according to claim 1.

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