JPH0461193A - Manufacture of metal based wiring board - Google Patents

Abstract

PURPOSE:To improve the heat conductivity of an insulating layer by increasing bonding strength between an electroplating layer and the insulating layer by forming the insulating layer by applying an epoxy resin material containing a high heat conduction inorganic filler on a surface of a metal base, and forming an electroless plating layer by roughening the surface and forming thereon the electroplating layer. CONSTITUTION:An insulating material containing epoxy resin as a chief ingredient is applied on a surface of a metal base 2 to form an insulating layer 3. To the epoxy resin an aluminum oxide and an aluminum nitride both being a high heat conduction inorganic filler added by 30% by weight or more and 80% by weight or less. Then, after roughening the surface of the insulating layer 3 an electroless plating layer 4 is deposited. Thereafter, a resist film 5 having an opening 6 of the same pattern as a circuit pattern is formed on the electroless plating layer 4, to which copper electroplating is applied to separate the resist film 5. Further, the electroless plating layer 4 exposed from the electroplating layer 7 is removed by etching to yield a predetermined pattern conductor circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a metal-based wiring board. Specifically, the present invention relates to a method of manufacturing a metal-based wiring board using a semi-additive method.

[] Background technology and its problems] In recent years, electronic equipment has become lighter, thinner, and more dense, and this
With the increasing density of the top parts used in

The amount of heat generated per unit area has increased significantly.

Therefore, the wiring boards on which these electronic components are mounted are also required to have excellent heat resistance and heat dissipation. Recently, printed wiring boards based on metal plates having high thermal conductivity such as iron, copper, and aluminum have been used to meet these demands.

A common method for manufacturing conventional metal-based wiring boards is the so-called Zabutrakiving method, in which the copper foil bonded to the surface of the metal base is selectively left in the necessary parts, and other parts are dissolved and removed by etching. Met. According to the Sub-Y-Lakdave method, the copper foil is bonded to the surface of the metal base using an adhesive, so the peel strength of the copper foil is strong, but since side etching of the copper foil occurs during etching, it is difficult to use on a mass production basis. It was difficult to produce high-density pattern circuits. Furthermore, according to the Zabtractive method, the eradication solution also requires a large amount of washing water, which poses a problem in wastewater treatment.

Therefore, an additive method for creating conductor circuits by selectively depositing metal in necessary areas has come to be used as a method for creating high-density circuit boards. This additive method includes a fully additive method in which a conductor circuit is formed only by electroless plating on an insulating layer formed on the surface of a metal base, and a fully additive method in which a conductive circuit is formed on an insulating layer formed on the surface of a metal base. There is a semi-additive method in which electrolytic plating is applied and further electrolytic plating is applied to obtain the thickness of the conductor circuit. For the insulating layer described in L, either thermosetting resin or thermoplastic resin can be used in any of the abu-bubu methods, but from a thermal perspective, it is easy to apply, versatile, and heat resistant. A certain epoxy resin is used.

[]Problems to be solved and attempted by the invention] The above additive method has excellent mass productivity, is capable of fine wiring, and is capable of producing metal wiring boards for high-density packaging. 6. However, since the conductor [llj] path is fixed to the surface of the insulating layer by electroless plating, its peel strength is strongly influenced by the quality of the insulating layer. Before (・) The adhesion state of the electroless plating layer changes dramatically depending on the surface roughness of the insulating layer that has been subjected to roughening treatment. In the case of a layer, there is no @ solution on the surface of the insulating term.
This method has the drawback that the peel strength of the conductor circuit is weaker than the Zabu-Rakdaib method.

In addition, resin tar materials have lower thermal conductivity than metal materials, so if epoxy resin is used as an insulating layer, the heat dissipation of metal-based wiring boards will decrease, making it impossible to take advantage of the benefits of using metal-based materials. was there.

The present invention has been made in view of the drawbacks of the conventional example described in Section 4, and its purpose is to improve the electroless plating layer and the insulating layer in a method of manufacturing a metal-based wiring board by a semi-additive method. The objective is to increase the bonding strength with the insulating layer and to improve the thermal conductivity of the insulating layer.

[Means for solving the problem] Therefore, the method for manufacturing a metal-based wiring board of the present invention includes the following steps:
A method for manufacturing a metal-based wiring board in which an insulating layer is formed on the surface of a metal base, and a conductive layer is formed on the surface of this insulating layer, the method comprising a thermally conductive inorganic filler such as aluminum oxide or aluminum nitride. After forming an insulating layer by applying an epoxy resin material containing 30% by weight or more to 80% by weight or less, the surface of the insulating layer is roughened, and then this The method is characterized in that the conductor layer is provided by forming an electroless plating layer on the surface of the insulating layer and forming an electrolytic plating layer on the electroless plating layer.

[Function] In the present invention, a thermally conductive inorganic filler is dispersed in an insulating layer made of an epoxy resin material, so if the surface of the insulating layer is roughened using a strong acid, etc. The thermally conductive inorganic filler in the layer dissolves, creating pores in the insulating layer, or the thermally conductive inorganic filler precipitates on the surface of the insulating layer, roughening the surface of the insulating layer. As a result, when electroless plating is applied on the insulating layer, the electroless plating layer becomes stronger than the surface of the insulating layer due to the anchoring effect of the thermally conductive inorganic filler or pores. Even when an epoxy resin is used for the insulating layer, it is possible to obtain a conductive layer that is difficult to physically peel off, and it is possible to obtain a large peel strength.

In addition, since the thermally conductive inorganic filler is dispersed in the insulating layer made of epoxy resin material, the thermally conductive inorganic filler is heat-resistant.・It becomes a bridge, and the thermal conductivity of the insulating layer increases in the direction of F−.
do.

Note that the amount of the thermally conductive inorganic filler added is 30% by weight.
If the amount is less than 80% by weight, the improvement in the thermal conductivity effect by the thermally conductive inorganic filler will be weak, and if it exceeds 80% by weight, it will be difficult to apply the epoxy resin material containing the thermally conductive inorganic filler to the insulating layer. Therefore, the amount added is preferably 30% by weight or more and 80% by weight or less.

In the present invention, the semi-additive method (・
Thus, manufacturing a metal-based wiring board 1. Therefore, the thickness of the conductor layer can be obtained by electrolytic plating.Compared to the straight plate method, which obtains the thickness of the conductor layer only by electroless plating, it is possible to obtain the thickness of the conductor layer by electrolytic plating. ml, and the production time of the metal-based wiring board can be shortened.

``Embodiment'' Hereinafter, examples of the present invention will be described in detail.

The small items shown in FIGS. 12(a) to 12(f) are steps for manufacturing a metal base wiring board 1 by a semi-additive method.

In this process, as shown in FIG. Here, the material of the metal base 2 is not particularly limited and may be iron, copper, etc., but aluminum is preferable because it has a strength of 11 mm and is easy to use.The type of epoxy resin is Although not particularly limited, for example, bisphenol A-type glycidyl needles, cresol novolaks, and phenol novolaks are preferable.Although there are no particular restrictions on the type of curing agent for epoxy resins, for example, amine-based, Acid anhydrides, latent hardening agents, etc. can be used.

Epoxy resins are usually used to make the application process easier.
This epoxy resin is used after being diluted with an organic solvent such as chlorine, aromatic hydrocarbons, etc., and this epoxy resin is filled with an inorganic filler that has good thermal conductivity and has insulation properties. As this insulating and thermally conductive inorganic filler, aluminum ingot (A!220.
) or aluminum nitride (AQN) is preferable (7).For thermally conductive inorganic fillers and 1., objects with a center particle size of 20.11 or less and a purity of 99.8% or more are desirable; If it becomes too large than 20ufT'l, the thermally conductive inorganic filler tends to settle before the epoxy resin hardens, and the peel strength of the conductor circuit 8 decreases. If the amount added is less than 30% by weight, the improvement of the heat conduction effect in the insulating layer will be weak, and if it is more than 75% by weight, the viscosity will become high and it will be difficult to apply the epoxy resin. If it becomes ., coating becomes difficult.Therefore, it is preferable that the addition of the thermally conductive inorganic filler (i) and 17 is from 1.'30% by weight to 180% by weight.

Next, the insulating layer 3 formed on the surface of the metal base 2 is swollen with an organic solvent or steam, and the surface of the insulating layer 3 is roughened using a strong oxidizing agent such as chromic acid. , the thermally conductive inorganic filler dispersed in the epoxy resin may precipitate or dissolve on the surface of the insulating layer 3 and generate pores in the insulating layer 3, causing roughening treatment. After roughening the surface of the insulating layer 3, the surface of the insulating layer 3 is activated with a Pd-3n activator, as shown in FIG. 1(b). As shown in the figure, an electroless plating layer 4 is deposited on the electroless copper plating or electroless nickel plating to a thickness of J, gn or less.

After this, in order to selectively deposit electrolytic plating, as shown in FIG.
A resist film 5 having a thickness of approximately 35 mm is formed. The resist material size 2 is not particularly limited, but is suitable for use in microfabricated photosensitive resist materials, and can be in liquid form, film form, negative type, or positive type.

Next, as shown in FIG. 1(d), electrolytic copper plating is applied to deposit a copper electrolytic plating layer 7 on the surface of the electroless plating layer 4 exposed from the resist film 5. After obtaining the thickness, as shown in FIG. 1(e), the resist film 5 is
of! The electroless plating layer 4 exposed from the electrolytic plating layer 7 is removed by etching 12.
), a conductor circuit 8 having a predetermined pattern consisting of two layers, an electroless plating layer 4 and an electrolytic plating layer 7, is obtained on -1 of the insulation N3.

In this way, if a metal-based wiring board is manufactured using the semi-additive method, the thickness of the conductor circuit can be obtained mainly through electrolytic plating, so the production time will be reduced compared to the full-alive method using only electroless plating. It can be shortened (to a few minutes).

In addition, as mentioned above, if a thermally conductive inorganic filler such as M2O3 or AQN is dispersed in the insulating layer, the surface of the insulating layer will be easily roughened, so the surface of the insulating layer will be electroless. When a plating layer is formed, the anchor effect between the electroless plating layer and the insulating layer becomes stronger, and the peel strength of the conductor circuit can be increased. Furthermore, the thermal conductivity of the insulating layer can be increased by these thermally conductive inorganic fillers without impairing the insulating properties of the insulating layer, and as a result, the metal-based wiring board has good heat dissipation. For example, aluminum force (AQ2
The thermal conductivity of 03) is 20 W/m'', the thermal conductivity of SiO□ is 3.3 W/m・X, and the thermal conductivity of aluminum nitride CAQN) is 100 W/m-''K. By filling the insulating layer with a material such as alumina or aluminum nitride, the thermal conductivity of the insulating layer can be significantly improved. In particular, if aluminum is used, it is possible to obtain an insulating layer that is inexpensive and has high thermal conductivity. Furthermore, the thermally conductive inorganic filler improves the heat resistance and thermal shock resistance of the metal-based wiring board.

In the above embodiment, the conductor circuit is formed only on the 191 side of the metal base wiring board, but it goes without saying that the conductor circuit may be formed on both sides of the metal base wiring board.

. Hereinafter, more specific embodiments of the present invention will be explained by comparing them with the conventional examples 2-9.

(Example) Keisa], mm aluminum substrate 1\lik1iiU
After resinizing with 111 ethane, an epoxy resin composition having the composition shown in Table 1 was applied to the surface of the real aluminum substrate by a doctor blade method, and after curing at room temperature, further [BO'C] was applied. It was heated and cured for 5 hours to form an insulating layer.

(Begins ']・Margins) Table 1 Next, the aluminum substrate on which the insulating layer was formed was immersed in a chromium-sulfuric acid solution heated to 45°C for 5 minutes to roughen the surface, and then washed with water. After that, I soaked it in diluted salt alcohol. Then, activation treatment (1) and activation treatment (2) were performed at li% l under the conditions shown in Table 2.

Table 2 (blank below) (blank below) Further (・5゛8, under the conditions shown in Table 3, electroless square copper plating was performed to determine the thickness of the insulating layer, t, mO, A thin copper film (electroless plating layer) was obtained. 6. Table 3 After this, a solvent-removable dozyin 1" lume was applied to the 10th layer of the button 1 thin film. Irradiate the area with ultraviolet light [After baking the pattern in step 2,
A resist film with a desired pattern was formed using l.lichloroethane and ↓ film development 12. Next, electroplating was performed on the copper thin film using electrolytic copper plating strip Inno 4 as shown in Table 4 to obtain a conductor circuit with the required film thickness.
The L/cyst film was peeled off using 11 methane.

Table 4 (blank below) Finally, the conductive circuit was obtained by immersing it in an ammonium persulfate solution with a concentration of 20 g/Q for several minutes to peel off the electroless copper plating from the exposed portion of the electrolytic copper plating.

(Conventional example 1) Thickness: 1. An adhesive having the composition shown in Table 5 was applied to an aluminum substrate of 1.0 mm in diameter using a doctor blade method [1
1. After evaporating the solvent to dryness, 2.
It was cured by heating for a period of time to form an insulating layer.

Then, a conductor circuit with a desired pattern was obtained by the semi-abbreviation method similar to that in the example.

Table 5 After applying an adhesive having the composition shown in Table 5 using a doctor blade method and drying the solvent to form an insulating layer,
Layer 35mm thick copper foil on insulation layer, 5kgf/am
A copper-clad metal base wiring board was obtained by heat-pressing at 180° C. for 12 hours at a pressure of 2. Thereafter, the same foil was etched by iron chloride etching, and a conductor circuit with a desired pattern was obtained by a subtractive method.

(Comparison of Example, Conventional Example 1 and Conventional Example 2) After obtaining the metal base wiring boards of Example, Conventional Example 1 and Conventional Example 2 as described above, for each metal base wiring board,
Measure the peel strength of the conductor circuit, half-day heat resistance, thermal conductivity in the thickness direction of the wiring board, and minimum wiring width of the conductor circuit.
compared.

The results are shown in Table 6 below.

(Margin below) (Conventional example 2) Thickness 1. Table 6 is the same as in Conventional Example 1 on an aluminum substrate of mm.
Followed Section 15□7. That is, after forming a conductor layer on the surface of an aluminum substrate via an insulating layer, the conductor is removed by knife cutting or etching on both sides of the aluminum substrate, and as shown in FIG. length L=1.Ot)+nm, width W≧25+n
Prepare a sample 23 by leaving a conductor 22 with a width W=101TllI+ in the center of the
2 was peeled off in a direction perpendicular to the aluminum substrate 21, and the minimum load F per unit width was measured. In addition, the solder heat resistance is determined by the melting temperature in the solder bath (in this case, 260°C).
When a metal-based wiring board is placed in a solder solution, the time required for separation of the aluminum board and the insulating layer or cracks to occur in the epoxy resin of the edge layer of the onion fh is determined. Furthermore, the thermal conductivity of the wiring board in the direction of the I-plane was measured as shown in Figure 3 (-, τ not shown). A sample metal base wiring board 33 is placed on one of the heat dissipation blocks 32.
Place the transistor that becomes the heat source 35 through the copper plate 34! ! The heat source 3
The heat dissipation block 3 is
This is done by measuring the temperature difference between 2 and the heat generation tf, 35.
Thermal conductivity was determined from the ratio of 1° temperature rise (m''K) to power consumption (Vv').

As can be seen from Table 6 above, the Toda heat resistance of the examples is as follows:
Similarly to Conventional Example 1, also made by the semi-additive method, it has a heat resistance time that is twice or more than twice that of Conventional Example 2, which is made by the subtractive method. Furthermore, the minimum wiring width is also the same as that of the embodiment using the semi-additive method and the conventional example 1.
When compared with conventional example 2 using the subtractive method,
An extremely fine minimum wiring width has been achieved.

Moreover, the conductor peel strength is the highest in Conventional Example 2 obtained by the subtractive method. However, when comparing Example 1, which was also made using the semi-additive method, the peel strength of Example 1 was four times that of Conventional Example 1, indicating that the effect of mixing alumina powder into the insulating layer was It is noticeable. Furthermore, the thermal conductivity of the metal-based wiring board of the example is four times the thermal conductivity of each of conventional examples 1 and 2, and by dispersing the thermally conductive inorganic filler, A high thermal conductivity was obtained.

Therefore, by dispersing the thermally conductive inorganic filler in the insulating layer, it was possible to obtain a metal-based wiring board with excellent characteristics.

[Effects of the Invention] According to the present invention, when the surface of the insulating layer is roughened, the surface of the insulating layer is easily roughened due to the thermally conductive inorganic filler precipitated or dissolved on the surface of the insulating layer. During electroless plating, the bond between the electroless plating layer and the insulating layer becomes stronger, and the peel strength of the conductor circuit increases. You can make it higher. In addition, due to the thermally conductive inorganic filler in the insulating layer, the thermal conductivity of the insulating layer is 11, and the thermal conductivity of the entire metal-based wiring board is good, which improves the heat dissipation properties of the metal-based 1-wire board.・The layer becomes better. Furthermore, since we manufacture metal-based wiring boards using a semi-additive method, we are able to manufacture high-density wiring boards without the risk of night edging, and we can also create conductive layers of the required thickness in a relatively short time. You can increase your productivity by increasing your productivity.

[Brief explanation of drawings]

Figure 1 (a) (b) (c) (d) (e) (f
) is a schematic sectional view showing the manufacturing process of an embodiment of the present invention,
FIG. 2 is a perspective view for explaining a method for measuring peel strength of a conductor circuit, and FIG. 3 is a front view showing an apparatus for measuring thermal conductivity of a metal base wiring board. 2...Metal base 3...Insulating layer 4...Electroless plating layer 7...Electrolytic plating layer 8...Conductor circuit diagram

Claims (1)

[Claims] (1) A method for manufacturing a metal-based wiring board in which an insulating layer is formed on the surface of a metal base and a conductive layer is formed on the insulating layer, the method comprising using a material with good thermal conductivity such as aluminum oxide or aluminum nitride. After forming an insulating layer by applying an epoxy resin material containing an inorganic filler at a ratio of 30% to 80% by weight to the surface of the metal base, the surface of the insulating layer is roughened, and then, An electroless plating layer is formed on the surface of this insulating layer,
A method for manufacturing a metal-based wiring board, characterized in that a conductor layer is provided by forming an electrolytic plating layer on an electroless plating layer.