JPH0135492Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a hybrid integrated circuit, and particularly to a hybrid integrated circuit having external terminals with good solderability.

(Prior Art) Small electronic components such as multilayer chip capacitors and multilayer chip coils are known. This type of laminated electronic component has a thin film-like external terminal on the side, and these components are directly mounted on a printed circuit board and solder is applied between the external terminal and the wiring on the printed circuit board. Allows for direct attachment.
However, the types of metal materials for external terminals are limited because external terminals may peel off due to heat and mechanical force during soldering, and there are problems with solder affinity and other problems.

Silver and silver alloys are commonly used for this type of external terminal because they have good adhesion to the base and good conductivity, but there is a problem that when immersed in the solder bath, silver etc. dissolves into the solder bath. . In order to prevent this, attempts have been made to form a layer of tin or the like on the surface of a base layer of silver or the like, but a fully satisfactory result has not yet been obtained.

(Purpose of the invention) An object of the invention is to provide a hybrid integrated circuit having external terminals with good solderability. This device has good conductivity, good adhesion to the base, no problems of elution into the solder bath, no problems of oxidation due to outside air, and has external terminals with high mechanical strength (hard to peel). The purpose of this research is to provide a multilayer capacitor network with high performance.

(Summary of the invention) As mentioned above, although silver is an excellent external terminal, it easily dissolves in solder, so the inventor of the present invention decided to cover the silver and silver alloy layer with a nickel layer by electroplating. I tried. Although this solved the problem of thinning of the solder, the surface of the nickel layer became more susceptible to oxidation, causing problems in terms of solder coverage and resistance. Then, by forming a tin layer on the outer surface, it was found that this problem was solved. However, due to the increased number of layers, a peeling phenomenon was observed in the external terminal itself. Therefore, this problem could be solved by further interposing a copper layer between the silver or silver alloy layer and the nickel layer. Furthermore, although the silver or silver alloy layer was formed by low-temperature baking, when the other layers were formed by electroplating, an excellent external terminal without the above-mentioned problems was obtained. Moreover, according to the electroplating method, each layer of the external terminal is completely covered by the upper layer, and a laminated layer with just the right amount and deficiency can be obtained at the periphery, so that the characteristics are improved. Therefore, the portion of the external terminal of the present invention other than the silver or silver alloy layer is limited to the electroplated layer.

(Structure of the invention) The invention will be described in detail below with reference to the drawings.
1-2 illustrate hybrid integrated circuits. A hybrid integrated circuit is one in which passive elements such as L, C, R, etc. and active elements such as transistors and diodes are assembled in high density inside or on the outside of a substrate, and is known per se. Since the present invention relates to an external terminal for a lead-out end drawn out to the periphery of a hybrid integrated circuit, the circuit portion is only schematically illustrated. For example, a capacitor section 13 made of a dielectric material 16 containing a conductive metal layer 15 so as to form a plurality of capacitors.
The substrate is a laminate (for example, a sintered body) including an inductor portion 19 made of an insulating magnetic layer 18 containing a conductor 17 so as to form a plurality of coils, and printed wiring 20 and a capacitor 2 are arranged on the surface of the laminate (for example, a sintered body).
1, 22 (forms a capacitance with the internal electrode),
Equipped with resistor film R, transistor TR, etc. All external terminals for leading out internal and external functional components to each other or to an external circuit are formed in a membrane shape on the outer periphery of the hybrid integrated circuit. These external terminals have a special configuration of the present invention. Since all the external terminals have the same structure, only the external terminal 2 will be described below with reference to FIG.

If necessary, the end face 23 of the hybrid integrated circuit is polished by a method such as barrel polishing to properly expose the lead-out ends of wiring, electrodes, inductors, etc. on the end face 23, and silver or silver alloy (Ag-Pd, etc.) powder is pasted. The base silver or alloy layer 24 is formed by applying the conductive paint and baking it.
(hereinafter simply referred to as a silver layer). A copper layer 25 is formed on the silver layer by electroplating. There are various methods for electroplating a small component partially having a conductive layer, and any method may be used to electroplate the small component. Copper layer 25 is silver layer 2
4 and the next formed nickel layer 26 to strongly adhere these two layers. Next, a nickel layer 26 is formed by the same electroplating method. The nickel layer 26 acts as a protective coating for the silver and copper layers and can suppress the problem of solder thinning on the external terminals. The nickel layer also adheres well to and is chemically stable with the copper layer and the subsequently formed tin layer. Finally, nickel layer 2
A tin layer 27 is formed on the surface of 6 by electroplating. The tin layer prevents oxidation of the nickel layer 26. tin layer 2
7 is easily melted in the solder bath, but the nickel layer 2
The presence of the copper layer 25 can prevent the silver and copper layers from melting, and the presence of the copper layer 25 can improve the peeling resistance of the external terminal.

As described above, the present invention was able to provide an excellent sintered laminated inductor.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a hybrid integrated circuit according to an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is an enlarged partial sectional view thereof. 1, 2, 3,...12: External terminal, 13: Capacitor section, 19: Inductor section, 23: End surface, 2
4: Silver or silver alloy layer, 25: Copper layer, 26: Plating layer, 27: Tin layer.

Claims (1)

[Scope of utility model registration request] Passive elements such as capacitors, inductors, and resistors, and active elements such as transistors and diodes,
It consists of a hybrid integrated circuit board built-in and/or mounted with wiring patterns for these, and a plurality of external terminals provided on the outer periphery of the circuit board. or a hybrid integrated structure comprising a silver alloy layer and an electroplating layer formed on this layer, wherein the plating layer is comprised of a copper layer, a nickel layer, and a tin layer in order from the bottom. circuit.