JPS606555B2 - Resistor structure of hybrid integrated circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resistor structure for a hybrid integrated circuit, and more particularly to one in which the resistor is formed by nickel plating.

Generally, in a hybrid integrated circuit, conductive paths are formed on a substrate, semiconductor elements and the like are fixed thereto, and a resistor is formed by printing a paste mixed with carbon particles between the conductive paths.

Further, hybrid integrated circuits have been put into practical use in which heat dissipation efficiency is increased by using a metal with good thermal conductivity for the hybrid integrated circuit board. 1st
The figure is a cross-sectional view of a hybrid integrated circuit using a metal substrate. The substrate 1 is made of aluminum, and an insulating thin layer 2 of aluminum oxide is formed by anodizing the surface of the aluminum. It has a structure in which a copper foil is bonded onto a layer 2 with a resin layer 3 which also serves as an insulator, and a conductive path 4 is formed in a desired pattern, and a semiconductor element (not shown) or the like is fixed onto the conductive path 4. Furthermore, a resistor is formed between predetermined conductive paths, but if the resistor is formed using carbon particles, the technical limit is to create a layer resistance RS of at least 100, which is not practical. Generally speaking, the lowest resistance is about 1000, and it has been difficult to create a low resistance of several ohms or less in a hybrid integrated circuit.

Therefore, a method of forming low resistance using nickel plating was developed. This involves relatively thick nickel plating between predetermined conductive paths. However, when forming a low resistance element with nickel plating, there is no problem because the layer becomes thick, but when forming a general resistor or a high resistance element, a problem arises because the layer becomes thin.

As shown in FIG. 1, when a relatively thin nickel plating layer 5 is formed between the conductive paths 4, a crack occurs at the boundary 6 between the nickel plating layer 5 and the conductive path 4, causing a defect in which the nickel plating layer 5 is disconnected. there were. Experimental research has shown that when the thickness of the nickel plating layer 5 is 1 mm or more, there is almost no disconnection.
If it is less than 1 μm, the number of disconnections increases rapidly, making it impossible to put it into practical use. The present invention has been made in view of the above points,
The present invention provides a hybrid integrated circuit that eliminates disconnections in the nickel plating layer and enables high resistance.

The present invention will be described in detail below with reference to the drawings. Figure 2A
, B, and C are process-by-step cross-sectional views showing examples of the present invention;
7 is a substrate, which is made of aluminum with good thermal conductivity.

In FIG. 2A, the surface of the substrate 7 is first anodized to form an insulating thin layer 8 of aluminum oxide, and an insulating adhesive resin layer 9 is provided over the entire surface of the insulating thin layer 8. The copper foil is bonded using this adhesive resin layer 9. The copper foil is etched into a predetermined pattern using an etching solution such as ferric chloride to form a conductive path 10. This conductive path 10 is electrically insulated from the substrate 7 by the insulating thin layer 8 and the adhesive resin layer 9. Next, a resist 11 is applied on all the conductive paths 10 and the adhesive resin layer 9 except for the part where the resistor is to be formed, that is, a part of a predetermined conductive path 10 and the adhesive resin layer 9 exposed between the conductive paths 10. A mask is formed by coating by screen printing or the like. Further, by plating, an activator is applied to the portion where the resistor will be formed, and activated so that nickel adheres only to that portion. The substrate 7 formed in this manner is subjected to a plating process. The plating process is carried out by immersing the substrate 7 in an electroless coating solution made of nickel sulfide, sodium hypophosphite, etc.
Then, nickel is deposited on the adhesive resin layer 9, and the first nickel plating layer 12 is obtained. First nickel plating layer 1
The thickness of plate 2 can be controlled by appropriately setting the temperature and concentration of the electroless plating solution and determining the length of time that the substrate 7 is immersed in the plating solution. , a resist 13 is applied on the first nickel plating layer 12.

A resist 13 is formed between the first nickel plating layer 12 and the conductive path 1.
It is applied to the central part of the first nickel plating layer 12, excluding the vicinity of the stepped part that occurs at the boundary part 14 with 0 and the part where the first nickel plating layer 2 and the conductive path 10 overlap. The substrate 7 coated with the resist 13 is immersed in the above-mentioned electroless glazing solution, and the second nickel plating layer 15 is formed on the boundary 14.
It is deposited nearby and is formed thicker than the first nickel plating layer 12 and at least one layer thicker. The resist 11 formed in FIG. 2A and the resist 13 formed in FIG. 2B are dissolved and removed by a solvent such as trichlene.

Along with the removal of the resists 11 and 13, the nickel spread on the resists 11 and 13 is also removed, and the surfaces are further brushed to remove burrs, and as shown in FIG. The first nickel plating layer 12 and the second nickel plating layer 15 remain on the roller. The structure of the resistor formed in this manner is shown in FIG. 2C.

The first nickel plating layer 12 is firmly adhered to the adhesive resin layer 9, and furthermore, since the conductive path 10 is made of copper which has good adhesion to nickel, it can be said that there is no contact resistance at the part that overlaps with the conductive path 10. Therefore, the influence on the resistor can be ignored and variations can be reduced. Furthermore, since the second nickel plating layer 15 is thickly formed in close contact with the first nickel plating layer 12 on the boundary portion 14 where disconnection is likely to occur, disconnection cannot occur. Therefore, high resistance and low resistance due to nickel plating can be simultaneously formed in the same hybrid integrated circuit. The resistance value as a resistor is determined by the first nickel plating layer i2, that is, the distance between the ends of the 22nd nickel plating layer 15 to the width and thickness of the first nickel plating layer 12. The first nickel plating layer 12 is formed on one side or less, and has a layer resistance RS of 5.
A relatively high resistance of about 00 to 1000 can be obtained.

Furthermore, the first nickel plating layer 12 can be trimmed in the same way as a conventional carbon resistor, and adjustments can be made while the circuit is in operation after all the elements are fixed. In addition, the first nickel plated metal layer 2 has an adhesive resin layer 9.
Since it is closely attached to the substrate 7 via the thin insulating layer 8, even if a large amount of heat is generated when a large current is passed through the resistor, the heat is transferred to the substrate 7 and is efficiently dissipated, resulting in a large power capacity. This is advantageous for circuit configuration. As mentioned above, by forming the second nickel plating layer on the boundary between the first nickel plating layer and the conductive path, "disconnection is completely prevented" and high resistance due to nickel plating can be achieved, making it possible to achieve the same It is possible to simultaneously form high resistance and low resistance in a hybrid integrated circuit using nickel plating, and it is possible to efficiently manufacture a hybrid integrated circuit without using a secondary carbon resistor. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a conventional example, and FIGS. 2A, B, and C are process sectional views showing an embodiment of the present invention.

7...' Substrate, 8... Insulating thin layer, 9...
... Adhesive resin layer, 10... Conductive path, 11... Resist, 12... First nickel plating layer, 13...
...Resist, 14...Boundary portion, 15...Second nickel plating layer.

Figure 1 Figure 2

Claims (1)

[Claims] 1 conductive paths formed on a hybrid integrated circuit board, a first nickel plating layer formed by exposing any of the conductive paths, applying a resist, and plating the exposed portions; A resistor structure of a hybrid integrated circuit comprising: a second nickel-plated layer formed thicker than the first nickel-plated layer by plating near the boundary where the first nickel-plated layer and the conductive path overlap.