JPH0579196B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a substrate for a hybrid integrated circuit, and more particularly to a method for manufacturing a circuit board on which a circuit is formed by plating precious metals.

[Conventional technology]

Generally, hybrid integrated circuit boards are equipped with semiconductors,
Gold wire bonding is required, and precious metal plating is sometimes used to prevent rust and improve solderability of the conductor. In recent years, the use of metal-based substrates has rapidly increased due to the demand for high-density packaging. Due to the structure of a metal base board, the conventional method of mechanically removing plated lead conductors may cause cracks in the insulating layer, destroy the insulating layer, and cause defects in the insulation between the conductor and the base metal. Since it causes problems, it has been removed by etching methods.

[Problem that the invention seeks to solve]

On the other hand, as a method for removing by etching, for example, there is a method of applying a plating-resistant tape on the plating lead conductor (Japanese Patent Application Laid-Open No. 59-31097,
58-225697). In this method, after plating, the tape is removed and the plated lead conductor portion is removed by copper etching.

In such a method, there are lead lines between the circuit conductors, and if the distance between the circuit conductors is narrow, it is impossible to attach the scratch-resistant tape to the lead lines. Another option is to apply a plating-resistant resist using a photographic method, but since the lead lines between fine circuit conductors are masked with extremely fine widths, precious metals may peel off during plating or the plating solution may seep in. Therefore, there was a problem that the precious metal plated lead line could not be cut and removed by copper etching.

In the present invention, in order to completely prevent insulation defects due to insufficient removal of lead lines when performing such copper etching, and to smoothly form fine circuits, the plating lead line portions are also plated with precious metals, and then a photosensitive liquid etching resist is applied to the circuit board. After exposing the plated lead line part using the photographic method, etching the precious metal, etching the nickel and copper,
The present invention provides a method for manufacturing a circuit board in which plating is removed at the lead line portion.

[Means for solving problems]

That is, the present invention provides a method for manufacturing a precious metal-plated circuit board of a metal base substrate formed by laminating copper foil on a base metal plate with an insulating layer interposed therebetween, in which a removable protective layer is formed on the base metal surface, and A first step of providing an etching resist on the surface of the other copper foil, a second step of etching the copper foil and then removing the etching resist, a third step of electrolytic plating in which the surface of the copper foil is plated with nickel and then plated with a precious metal, a photographic method. a fourth step of providing an etching resist on a portion other than the plating lead and the plating electrode; a fifth step of etching the precious metal of the plating lead and the plating electrolytic portion, and further etching nickel and copper; and a fifth step of etching the etching resist. This method of manufacturing a precious metal plated circuit board is characterized by comprising a sixth step of removing.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a completed cross-sectional view of a hybrid integrated circuit board according to the present invention, in which a copper foil 3 is laminated on a base metal 1 via an insulating layer 2, and further, nickel 4 and a noble metal 5 are laminated in sequence on the copper foil 3.

In the manufacturing process of the circuit board of the present invention, first, a first step is performed, using a board in which a copper foil 3 is laminated on the entire surface of one side of a base metal 1 with an insulating layer 2 interposed therebetween. The parts necessary for the circuit, the plating electrodes and the plating leads are coated with a photosensitive liquid etching resist 6, and a protective film 7 is pasted on the other metal surface of the base metal 1 (see Fig. 2A,
B). Next, the exposed copper foil 3 is etched to form a circuit, and at the same time, a plating electrode 8 and a plating lead 9 necessary for electrolytic plating are formed, and the photosensitive liquid etching resist 6 is removed (first step). Figure 3 A, B). 4A and 4B shown as the third step, nickel 4 and precious metal 5 are sequentially plated and laminated on the circuit part, the plating electrode, and the plating lead by electrolytic plating.
Figures A and B show a state in which a photosensitive liquid etching resist 6 is coated on the portion that will become the circuit section in order to remove the plating electrode and the plating lead formed by the noble metal 5 as the uppermost layer (fourth step).

In the fifth step, first, only the exposed precious metal 5 is removed using an etching agent (see Fig. 6A,
B) Furthermore, nickel 4 and copper foil 3 are removed using an etching agent that etches them at the same time (Fig. 7A,
B). The present invention further includes removing the etching resist 6 coated with the photosensitive liquid etching resist 6 as a final necessary part (FIG. 8A,
B), remove the protective film 7 of the base metal,
By cutting the outer periphery of the base metal 1 as necessary (FIGS. 9A and 9B), the circuit board shown in FIG. 1 can be manufactured.

The material used as the base metal 1 of the present invention is a metal plate such as aluminum, copper, aluminum alloy, copper alloy, or alumite, which has good thermal conductivity, and the material used as the insulating layer 2 is, for example, an inorganic powder with good thermal conductivity. For example, thermosetting resins such as epoxy resins, polyimide resins, and phenolic resins containing alumina powder, boron nitride powder, beryllia powder, magnesia powder, quartz powder, etc. have good thermal conductivity. It is preferable as a resin for insulation.

According to the present invention, only the resolution of the etching resist controls the cutting width of the plating lead (electrode for plating and lead for plating).
For example, by using a photosensitive liquid etching resist 7 or the like, even ultra-fine plating leads can be cut. Further, as the noble metal plating, pure gold or pure silver plating with good gold wire bonding properties is preferable, and any conventionally used plating may be used. Next, aqua regia can be used to etch the gold or silver plated on the top layer, but since there are handling problems, in the present invention, iodine and alkali metal iodides such as sodium iodide, lithium iodide, Potassium iodide or the like is preferable and etches gold and silver at high speed. The underlying nickel and copper are then etched well with a chloride solution.

〔Example〕

Examples of the present invention are shown below, but the present invention is not limited thereto.

Example A protective film was laminated on the base aluminum surface of an aluminum base copper-clad insulating substrate (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name: Denka HITT Plate), and a photosensitive liquid etching resist was coated on the copper foil surface. After drying, an image was formed using a photographic method, a circuit was formed by copper etching, the etching resist was removed, a protective tape was applied to the end face of the aluminum base, and electrolytic nickel with a thickness of 5 μm and electrolytic pure gold with a thickness of 0.5 μm was applied. I was disappointed. Next, a photosensitive liquid etching resist is coated, and after drying, the plating leads (electrodes for plating and leads for plating) are exposed using a photographic method, and treated with a composition solution of 50 g of iodine and 250 g and 700 g of potassium iodide to remove pure gold. Etched. Then, after washing with water, iron chloride (40° Baume)
Nickel and copper were etched with the solution. The photosensitive liquid etching resist is then removed and the areas between the conductors are
A fine circuit was formed by removing the plating lead from a pattern having a plating lead at 150 μm.

〔Effect of the invention〕

According to the present invention, a fine circuit metal base substrate with excellent gold wire bonding properties can be manufactured, and pattern shoot defects due to residual lead do not occur, and the present invention is extremely useful for manufacturing fine circuit boards for high-density packaging.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a noble metal plated microcircuit metal base substrate according to the present invention. 2A to 9A are cross-sectional views showing the steps of the present invention, and FIGS. 2B to 9A are cross-sectional views showing the steps of the present invention.
FIG. 9B is a plan view. DESCRIPTION OF SYMBOLS 1... Base metal plate, 2... Insulating layer, 3... Copper foil, 4... Nickel, 5... Precious metal, 6... Etching resist, 7... Protective film, 8... Electrode for plating, 9... Lead for Metsuki.

Claims (1)

[Claims] 1. A method for manufacturing a noble metal-plated circuit board of a metal base board formed by laminating copper foil on a base metal plate with an insulating layer interposed therebetween, in which a removable protective layer is formed on the base metal surface. , a first step of providing an etching resist on the surface of the other copper foil, a second step of etching the copper foil and then removing the etching resist, a third step of electrolytic plating in which the surface of the copper foil is plated with nickel and then with a precious metal. a fourth step of applying an etching resist to the parts other than the plating lead and the plating electrode using a photographic method; a fifth step of etching the precious metal of the plating lead and the plating electrode part, and further etching the nickel and copper; A method for manufacturing a noble metal plated circuit board, comprising a sixth step of removing etching resist. 2. The method for manufacturing a circuit board according to claim 1, wherein the precious metal is gold or silver.