JPS62291992A - Circuit transcription foil for injection molding and method of forming circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a circuit transfer foil for injection molding and a circuit transfer method, and more specifically, a circuit transfer foil for injection molding and a circuit transfer method, and more particularly, a circuit transfer foil that can transfer a circuit simultaneously with the molding of a transfer target by injection molding, and a contact portion of the circuit. The present invention relates to a circuit transfer foil for injection molding that allows connection by soldering, and a circuit forming method in which a circuit can be formed at the same time as a transfer target is molded using the circuit transfer foil.

[Technical background of the invention]

Conventionally, the method of transferring electrical circuits using conductive resin involves forming a conductive thin film over the entire surface of a support film, laminating it on the object to be transferred, and applying heat that can apply heat and pressure only to the circuit (transferred part). A method of forming a circuit by transferring only the circuit portion to the transfer target using a board (Japanese Patent Laid-Open No. 5
No. 5-141789) is known.

Also, screen printing conductive paint on the support film,
There are also known circuit transfer foils and circuit transfer methods that are capable of transferring a circuit with good conductivity by roughly printing a circuit pattern using gravure printing, offset printing, or Kumbo printing and transferring this circuit pattern to a transfer target. (Japanese Patent Application No. 117264/1984, etc.).

Generally, electrical circuits are often connected to other electrical circuits, electrical components, electrical equipment, etc. by soldering, but the electrical circuits transferred and formed using conductive resin as described above are The drawback was that it was impossible to connect electrical parts and equipment with solder. That is,
Conductive resins such as conductive paints and conductive thin films that serve as conducting paths in electric circuits as described above are generally made by adding an appropriate amount of conductive particles to the resin to impart conductivity to the resin. In a conductive resin to which such conductive particles have been added, when the amount of the conductive particles added is small, the conductivity tends to improve as the amount of the conductive particles added increases. It is known that when the amount of conductive particles added increases, the conductivity tends to decrease due to an increase in the contact resistance between the particles. Even in conductive resin, if a large amount of conductive metal particles is added, soldering becomes possible, but as mentioned above, if the amount of metal particles added is such that it can be soldered, the resistance of the electric circuit will increase. The disadvantage is that the value increases, the characteristics required for the circuit are not satisfied, and the amount of metal particles added increases, resulting in increased costs.

Furthermore, when the amount of metal particles added to the conductive coating film is increased, the adhesion strength of the conductive coating layer to the support is significantly reduced, resulting in the disadvantage that it cannot be put to practical use.

Furthermore, in the conventional circuit transfer method as described above,
There is also a drawback that two steps are required in order to transfer a circuit to a previously formed transfer object: a step of molding the transfer object and a circuit transfer step.

[Summary of the invention]

The present invention has been made in view of the above-mentioned points, and provides a circuit transfer foil that can form an electric circuit having contact portions that can be connected by soldering at the same time as forming a transfer target, and a circuit formation method using the circuit transfer foil. The purpose is to

Therefore, the circuit transfer foil for injection molding according to the present invention is basically made by adding 5 pO to 2,000 parts by weight of metal particles to 100 parts by weight of resin to make contacts using a conductive paint for soldering. 300 to 1000 parts by weight of conductive particles are added to 100 parts by weight of resin to make contact with the contact part at least in part. It is characterized by printing a circuit pattern that is easily peelable from the film immediately after heating and pressing.

Further, in the circuit forming method according to the present invention, on the support film,
A contact portion is provided on a predetermined portion of the support film using a conductive paint for soldering, which is basically made by adding 500 to 2000 parts by weight of metal particles to 100 parts by weight of resin, and at least a portion of the contact portion is contacted. The conductive paint for conductive paths is basically made by adding 300 to 1000 parts by weight of conductive particles to 100 parts by weight of resin, and the circuit exhibits easy peelability immediately after heating and pressurizing the supporting film. A circuit transfer foil with a pattern printed thereon is placed so that the support film is in contact with the inside of a mold for injection molding the object to be transferred, and molten resin is press-fitted into the mold to mold the object to be transferred. Then, by peeling off the support film, the transfer object is formed and the circuit is transferred at the same time.

According to the circuit transfer foil for injection molding according to the present invention, an advantage is that an electric circuit having an electrical contact portion that can be connected to another electric circuit by solder can be formed on the transfer target at the same time as the transfer target is injection molded. There is. Further, the circuit forming method according to the present invention has the advantage that when injection molding an electric circuit whose contact portions can be soldered, the circuit can be formed by transfer at the same time as the object to be transferred is molded.

[Detailed description of the invention]

As shown in FIG. 1, the circuit transfer foil according to the present invention is produced by printing a conductive paint for conductive paths in a desired circuit shape on a support film 1, which exhibits easy peelability immediately after heating and pressing the support film 1. The circuit pattern 3 is formed using the same steps. The circuit pattern 3 is shown in Figure 2, which is a sectional view taken along line B-B in Figure 1.
As shown in the cross section in b), they are stacked and provided so as to be in contact with the contact portion 2. As shown in FIG. 2 fa), which is a sectional view taken along line A-A in FIG. It is formed.

The support film 1 on which the circuit pattern 3 is formed by the conductive paint for conductive paths is not fundamentally limited in the present invention, and has good adhesion to the circuit pattern 3 and the contact portion 2 at room temperature, Immediately after heating and pressurizing, it is necessary that the circuit pattern 3 and the contact portion 2 are easily separated from each other. Furthermore, it is possible to effectively use a synthetic resin film that is heat resistant to the extent that it does not soften or deteriorate at the temperature during injection molding, and is not susceptible to the solvents contained in conductive paints. can. Specific examples of the support film 1 include:
For example, polyester film, polyimide film,
Examples include plastic films such as polypropylene films and aluminum foil.

The conductive paint for conductive paths for printing the desired circuit pattern 3 on the support film 1 described above is capable of printing a good and fine circuit pattern on the support film 1;
It is necessary that the transfer foil satisfies various conditions such as basic performance as a transfer foil, such as good peeling from the support film 1 immediately after heating and pressing. In addition, in the present invention, since the circuit pattern 3 is transferred at the same time as injection molding, the rigidity and circuit pattern on the support film 1 are made such that the pattern on the support film 1 does not collapse under the pressure and temperature conditions during injection molding. Adhesion strength between the pattern 3 and the support film 1 is required so that it does not flow, and furthermore, it is necessary that the support film 1 can be easily peeled off immediately after injection molding.

In order to satisfy these conditions, the support film, the resin liquid (solvent and solute) that is the base material of the conductive paint,
Furthermore, it is important to select the type of conductive particles to be added to this resin liquid, and it is also necessary to consider the amount and particle size of the conductive particles. The resin that serves as the base material for such a conductive paint for conductive paths must be able to adhere to the support film 1 at room temperature, form an easily peelable circuit pattern immediately after heating and pressurizing it, and be suitable for injection molding. MEK
, ? Ketone solvents such as IrBK and cyclohexanone,
Aromatic hydrocarbon solvents such as toluene and xylene, IP
A, alcohol solvents such as butanol, ether solvents, ester solvents, DMF as others,
It can be a resin solution dissolved in one or more solvents such as N-methyl biaridone.

The conductive particles added to the resin solution are not fundamentally limited in the present invention as long as they can be uniformly dispersed in the resin solution and impart good conductivity.

For example, gold, silver, platinum, copper, nickel, aluminum,
The material may be one or more types of particles such as tin, zinc, etc., composites and alloy powders having -1-tintings on the surface of the metals mentioned above, and carbon particles.

A circuit that maintains rigidity and adhesion strength such that the pattern on the support film 1 does not collapse or flow under the pressure and temperature conditions during injection molding, and that allows the support film 1 to be easily peeled off after injection molding. It has been found that forming Pattern 3 is largely dependent on the amount and particle size of the conductive particles.

That is, if the amount of conductive particles contained in the conductive paint for conductive paths is too large, the rigidity of the circuit pattern 3 formed on the support film 1 will be improved (if the amount is even larger, it will become brittle). (There is a risk of it flowing due to the pressure during injection molding)
On the other hand, if the amount is too small, the adhesion strength will improve, but there is a risk that the conductivity will be poor. For this reason, the conductive particles have a ratio of 30% to 100% resin.
Add 0 to 1000 parts by weight. If it is less than 300 parts by weight, the amount of conductive particles is too small, making it difficult to ensure sufficient conductivity for an electric circuit (surface resistance of 1 Ω/hole or less), and the adhesion strength to the support film 1 becomes too large. Therefore, it becomes difficult to peel off the support film 1 after transferring the circuit.

Moreover, if it exceeds 1000 parts by weight, the circuit pattern 3 becomes brittle, resulting in a skin that collapses or flows under the pressure during injection molding.

The particle size of the conductive particles is an important factor in the circuit transfer for injection molding according to the present invention, in which the circuit pattern 3 is transferred simultaneously with the molding of the object by injection molding as described above.

It has been found that a circuit with good conductivity can be transferred by mixing and adding conductive particles having a relatively large particle size and conductive particles having a smaller particle size than the conductive particles. The reason for this is not necessarily clear, but it is thought to be due to the following reasons. That is, due to the pressure of the molten resin during injection molding, the support film 1
The upper circuit pattern 3 is under pressure load, and the circuit pattern 3
The density per unit volume of the conductive particles contained in the interior increases, but in this case, according to the close-packed field theory, by combining particles of class 2FF or higher with a particle size within a certain range, the porosity can be increased. By further applying injection pressure, the filling rate per unit volume increases. therefore,
It is thought that the conductivity is improved because the number of contact points is increased (the circuit pattern 3 formed by the conductive paint of the same composition is transferred to a pre-formed object without injection molding). Approximately A of the circuit formed by
).

Therefore, it is preferable to add conductive particles of at least two different particle sizes to the conductive paint for conductive paths according to the present invention. In this case, the combination with the optimum particle size is determined by the relative size of two or more types of particles. The particle size of large-sized conductive particles is usually 10 to 2
It is preferable that it is in μm. If it exceeds 10 μm, it becomes difficult to form the circuit pattern 3 on the support film 1 by printing means such as screen printing, while if it is less than 2 μm, the effect of mixing with relatively small-sized conductive particles becomes difficult. becomes smaller.

The particle diameter of the conductive particles having smaller dimensions than the above-mentioned large conductive particles is preferably 4 μm or less. This is because if it exceeds 4 μm, there is no point in dividing the particle size of the conductive particles into two or more types, and no improvement in conductivity can be expected.

Further, the weight mixing ratio of such large-sized conductive particles and small-sized conductive particles is preferably from 9515 to 501.
50 is good. This is because if the mixing ratio deviates from this, there is a possibility that the meaning of mixing the two types will be lost.

Other additives such as antioxidants, dispersants, etc. can be optionally added to the conductive paint.

Further, the contact portion 2 provided so as to be in contact with the circuit pattern 3 is formed as a lower layer of the circuit pattern 3, and this is provided at 18 points when the circuit pattern 3 is transferred to the object to be transferred at the same time as molding. This is to ensure that portion 2 is exposed on the surface of the object to be transferred.

The contact portion 2 has a higher content of metal particles than the circuit pattern 3 portion. Since this contact part 2 is a part to be soldered, unlike the circuit pattern 3, conductivity is not so much of a problem, and good solderability (solderability) and a good relationship with the circuit pattern 3 are important. It is required to have adhesion strength and to be able to be easily peeled off from the support film 1 immediately after the transfer object is formed.

As the base material of the conductive paint for solder that satisfies such conditions, it is preferable to use a resin that is the same as or similar to the resin used for the circuit pattern 3 described above. For example, one or more of acrylic, polyamide, epoxy, polyether, polyester resins, cyclized rubber, chlorinated rubber, rosin, etc., for example, MEK,
Ketone solvents such as MIBK and cyclohexanone, aromatic hydrocarbon solvents such as toluene and xylene, IPA
, alcohol solvents such as butanol, ether solvents, ester solvents, and others such as DMF, N-
It can be a resin solution dissolved in seven or more solvents such as medylpyrrolidone.

Furthermore, it is clear that metal particles with good solderability are preferable as the metal particles added to this resin solution.

Such metal particles are generally metal particles that have a smaller ionization tendency than hydrogen. Examples of such metal particles include gold, silver, platinum, copper, nickel, tin,
It can be one or more of metal particles such as, or composites and alloy powders whose surfaces are coated with the metals described above.

Furthermore, the amount of metal particles added to the contact portion 2 is 10% of the resin.
The amount is 500 to 2000 parts by weight relative to 0 parts by weight.

If it is less than 500 parts by weight, the content of metal particles is too small and soldering becomes difficult, while if it exceeds 2000 parts by weight, the adhesion strength with the circuit pattern 3 or the support film 1 will be poor, It becomes brittle and cannot be put to practical use. Furthermore, it also has the disadvantage of high cost.

Further, the particle size of the metal particles varies depending on the method of forming the contact portion 2, but in the case of a printing method (also varies depending on the method), it is generally preferably 10 μm.
It is preferable that it is less than m. If it exceeds 10 μm, for example, coating streaks will occur in gravure printing, and clogging will occur in screen printing, resulting in the possibility that fine contact portions cannot be formed.

When manufacturing the circuit transfer foil for injection molding as described above, first, the contact portions 2 are coated on the support film 1 with the conductive paint for soldering as described above by a printing technique such as screen printing, gravure printing, or pad printing. Form.

The thickness of this contact part 2 basically needs to be thick enough for soldering, but on the other hand, it must not be so thick as to significantly impair the conductivity of the injection molding or circuit. . Therefore, the thickness of this contact portion 2 is preferably 1 to 1
The thickness is preferably 5 μm.

Furthermore, since this conductive paint for solder contains a large amount of metal particles, it tends to have a high viscosity.

For this reason, it may be difficult to form by the above-mentioned printing means. In such cases,
The contact portion 2 can also be formed by methods other than printing means.

In the case of forming by printing, the conductive paint for solder generally preferably has a viscosity of 10 to 1000 voids, although this varies depending on the printing method. 10
If it is less than 1 poise, printing will easily sag, and 1
This is because if it exceeds 000 poise, printing becomes difficult.

The viscosity of such a conductive paint can be adjusted by the amount of solvent, the type of resin used as the base material, the amount of metal particles added, or the addition of various reagents to the conductive paint.

After forming the contact portion 2 in this manner, a circuit pattern 3 is further printed on the support film 2 using a conductive paint for conductive paths. The printing method for printing this circuit pattern 3 is not determined by the present invention. For example, it can be effectively printed using well-known printing methods such as screen printing and gushivia printing.

This conductive paint for conductive paths is preferably printed on the support film 1 to a thickness of 15 to 30 μm. If the thickness of the conductive paint is less than 15 μm, the conductivity 1 described above
In order to obtain a resistance of Ω/mouth or less, a large amount of conductive particles must be filled, while if it exceeds 30 μm, printing of a circuit pattern by screen printing or the like may become difficult.

It goes without saying that the line width of the circuit pattern 3 or the distance between lines is preferably smaller. In the circuit transfer foil used in the present invention, in order to make it possible to form a circuit with the above-mentioned line width or line distance of 1 mm or less, the viscosity of the conductive paint to be printed is set to 10 to 1000 voids, most preferably 10 to 40 voids.
It is preferable to adjust to 0 poise. If the viscosity of the conductive paint is less than 10 poise, there is a risk that the wires will be distorted and the circuit will be short-circuited, while if it exceeds 1000 poise, it will be difficult to print the circuit board on the support film 1. be.

According to the circuit forming method of the present invention, the circuit transfer foil 4 described above is placed in one of the molds 5a of the injection mold 5 for producing the transferred object.
Then, the support film 1 is scattered so as to come into contact with the inner wall of the mold 5a, the mold 5b is covered with the mold 5a, and the molten resin 7 is injected from the resin injection port 6 to cover the transfer target. This allows the circuit to be transferred at the same time as manufacturing. and,
By peeling off the support film 1 of the circuit transfer foil 4, it is possible to form a circuit buried in the transfer object at the same time as molding the transfer object.

In the method of forming a circuit simultaneously with injection molding as described above, the pressure and temperature within the injection mold 5 are especially important. That is, if the pressure inside the mold is small, the circuit pattern 3 of the circuit transfer foil 4 may not be transferred well, and a portion of the circuit pattern 3 may remain on the support film 1 when the support film 1 is peeled off. Furthermore, when the pressure inside the mold is high, there is a risk that the drawn circuit will not collapse.

Furthermore, if the temperature of the injected resin is too high, there is a risk of damaging the conductive paint portion or the support film portion.

Among the above-mentioned injection conditions, the pressure within the mold is particularly important.

It has been found that a good pressure in the mold as mentioned above is preferably between 200 and 1000 Kg/cod, taking into account the above. The pressure inside the mold is as follows: mold 4
It can be controlled by the viscosity of the molten resin injected into the molten resin and the injection pressure.

If the viscosity of the molten resin is too high, uneven pressure will be applied to the circuit transfer foil 4, which may cause parts with a small pressure load to remain on the support film 1, and the injection pressure will also increase.
There is also a risk of damage to the circuit.

If the viscosity is too low, the applied pressure will be relatively small, making it difficult to transfer the circuit on the circuit transfer foil 3.

Taking this into consideration, the viscosity of the resin used to manufacture the transfer object when injected into the injection mold 5 is preferably 103 to 105 voids. The above viscosity is 1
If it is less than 0.03 poise, the pressure load on the circuit transfer foil 4 will be small, and there is a risk that good transfer will not be performed.On the other hand, if it exceeds 105 poise, the pressure load will become uneven,
There are areas where the transfer is good and areas where the transfer is poor.

The viscosity of the resin as described above changes depending on the temperature of the molten resin, but this temperature must not be such as to damage the conductive paint portion or the support film portion as described above. Therefore, it is desirable that the temperature at the time of injection of the resin having the above viscosity range is 400° C. or lower.

In addition, the injection pressure of the above molten resin is 400 to 2300 kg.
/cnl is better. The injection pressure of resin in the above viscosity range is 2300Kg/ca! If the
This is because if it is lower than 400 Kg/-, there is a risk that the circuit will not be transferred well.

Examples of resins that satisfy these conditions include A[
lS, polyacecool, polysulfan, PP01 modified ppo, polycarbonate, polycarbonate, l
Examples include ll5P, PP, P and HA.

4 and 5 show a circuit formed by the circuit forming method according to the present invention, and as is clear from these figures, the circuit pattern 3 is transferred into the transfer target 8, and The contact portion 2 has a structure exposed on the surface of the transfer target 8. For this reason, the contact portion 2
By soldering, it becomes possible to connect other electrical circuits, electrical equipment, electrical components, etc.

EXAMPLE A connection portion having a diameter of 1.5 mm and a thickness of 5 μm was formed on a polyester film by screen printing using a conductive paint for soldering having the composition shown below (viscosity: 70 poise).

Composition 1 Acrylic resin 100 parts by weight Methylisobutylketone 150 parts by weight particles
800 parts by weight Next, using a conductive paint for conductive paths (viscosity: 70 voices) having the following composition, a circuit pattern was printed by screen printing with a line width of 0.8 mm, a distance between lines of 0.8 mm, and a thickness of 25 μm. did.

Composition 2 Thermoplastic polyester resin 100 parts by weight Aromatic solvent 120 parts by weight Silver-coated copper particles (average particle size 8 μm) 480 parts by weight Silver-coated copper particles (average particle size 2 μm) 320 parts by weight This circuit transfer foil was supported as described above. While the film was placed in contact with the injection mold for molding the transfer object, ABS resin (viscosity 4 x 10
Injection conditions: Injection temperature 220-24
0℃, injection pressure (gauge pressure) 800g/crl,
Back pressure 5Kg/cnl, Screw J knee rotation speed 50r, p,
m, ), the object to be transferred was molded.

Next, by Mll gtt the support film, a line width of 0.8 mm and a line distance of 0 are formed on the ABS resin molded product.
．． A good 8 mm circuit could be formed with high precision. The electrical conductivity of this circuit was 0.3 Ω/port or less, and the adhesive strength was also good.

In the circuit obtained by transferring the circuit pattern at the same time as molding as in this example, the surface of the molded product and the surface of the circuit are on the same level (only the circuit part does not become convex), so care must be taken when handling. Another advantage is that it is possible to prevent circuit defects due to

In addition, using the same circuit transfer foil, we applied 8Kg/CIl+ to a rough-molded ABS resin transfer target at 190℃.
Transfer was performed under these conditions to form a circuit. The surface resistance of the circuit at this time was 1.0 Ω/port, which was about 1/4 of the surface resistance of the circuit manufactured in the above example.

Furthermore, the contact portions could be successfully connected to other electrical components using solder.

〔Effect of the invention〕

As explained above, according to the circuit transfer foil for injection molding and the circuit forming method of the present invention, a circuit transfer foil on which a circuit pattern of conductive paint is printed by a printing method such as screen printing or gravure printing is used. Because the circuit is formed by transferring to the transfer target at the same time as the transfer body is formed, there is no need for expensive or special equipment, and there is no waste of conductive material, resulting in even better conductivity. There is an advantage that a circuit having the following characteristics can be formed in one step.

Furthermore, the contact portion has the advantage that other electrical circuits, electrical components, electrical equipment, etc. can be connected by soldering.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a specific example of the circuit transfer foil used in the present invention, FIG. 2 is a sectional view of the circuit transfer foil, and FIG. FIG. 4 is a schematic view of the process of molding, FIG. 4 is a front view of the circuit transferred to the object to be transferred, and FIG. 5 is a sectional view of the object to be transferred.

DESCRIPTION OF SYMBOLS 1...Support film, 2...Contact part, 3.04 circuit pattern, 4...Circuit transfer foil, 5...Injection mold.

Applicant's agent Tadashi Ame Miya Box 1 diagram LA L.

Figure 3 Figure 4 Procedural amendment (voluntary) July 29, 1985

Claims (4)

[Claims] (1) Metal particles are placed on a predetermined portion of the support film using resin 1.
00 parts by weight and add 500 to 2000 parts by weight of the resin 100 parts by weight to provide a contact part with a basic conductive paint for soldering.
300 to 1000 parts by weight of conductive particles are added to the basic conductive paint for conductive paths, and a circuit pattern that is easily peeled off the support film immediately after heating and pressing is printed. Features of circuit transfer foil for injection molding. (2) The circuit transfer foil according to claim 1, wherein the conductive particles added to the conductive paint for conductive paths are conductive particles of at least two different particle sizes. (3) Metal particles are placed on a predetermined portion of the support film using resin 1.
00 parts by weight and add 500 to 2000 parts by weight of the resin 100 parts by weight to provide a contact part with a basic conductive paint for soldering.
A conductive paint for conductive paths that is basically made by adding 300 to 1000 parts by weight of conductive particles to the part by weight, and a circuit transfer printed with a circuit pattern that shows easy peelability immediately after heating and pressurizing the support film. Laying the foil so that the support film is in contact with the inner wall of a mold for injection molding the transfer target,
A method for forming a circuit, characterized in that the object to be transferred is molded by press-fitting a molten resin into the mold, and then the support film is peeled off to mold the object to be transferred and simultaneously transfer the circuit. (4) The circuit forming method according to claim 3, wherein the conductive particles added to the conductive paint for conductive paths are conductive particles of at least two different particle sizes.