JPH0770805B2 - Printed circuit board - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board of an electronic device, and more particularly to a transfer transfer mounting system for a plurality of electric resistance elements.

Conventional technology Conventionally, paper phenol, paper epoxy, glass cloth epoxy,
A hybrid circuit board was manufactured by surface-mounting individual components on a printed wiring board based on alumina porcelain, alumina nitride, or the like.

Problem to be Solved by the Invention Among the individual components of this type, the number of resistor elements is the largest, and the time and cost required to mount these are becoming enormous.

The present invention aims to provide a new mounting means with the goal of reducing the time and cost, and provides an economical and reasonably reliable means.

Means for Solving the Problems The present invention provides, as a specific means, a provisional substrate on which a plurality of resistors are formed by printing. By utilizing the fact that the printing position and shape of the resistor can be controlled by a printing mask, printing is performed at the resistor mounting position on the true substrate, relative to the transferable position. In this way, a component that can be transferred and placed is formed.

For the transfer, cutting preparation work is performed on the temporary substrate in the form of V-cut, half-cut, perforation, laser processing, punching processing, etc., and each element is selectively pressed against the true substrate at most. By doing so, transfer placement becomes possible. After cutting and transferring, the bonding to the true substrate may be performed by soldering afterwards, but for the one formed by printing or applying solder paste or adhesive (conductive and non-conductive) on the true substrate in advance, The transfer mounting component is soldered or heat-bonded to the true substrate.

When soldering to the electrode of the resistor element is difficult (when solderability or solder heat resistance is insufficient), a copper foil or a copper plating electrode is used as a necessary auxiliary electrode. It goes without saying that the printing direction, thickness, electrode material, shape and size of electrodes and resistors, wattage, resistivity, number of printing layers, printing sequence, number of printings, etc. of the resistor element can be applied by existing technology. Nor. However, since the expansion and contraction value of the true substrate material and the expansion and contraction value of the temporary substrate material do not always match, when the surface mount component including the resistance element is bonded between the bonding electrodes, the differential stress generated between the fixed spans , The joint life of the joint is shortened.

Action According to the present invention, with respect to the temporary substrate for printing the circuit element, at least to the lower portion between the electrode fixing span,
Since the resin layer or the rubber layer having a large Young's modulus is arranged as the cushion layer, the mounting cost of the circuit element and the reliability after bonding can be improved and improved.

EXAMPLE An example of the present invention will be described with reference to the sectional views in order of steps of FIG.

In FIG. 1a, one or both of a flexible epoxy resin and a nitrile rubber are mixed or layered on the temporary substrate 1 of the present invention to form a cushion layer 7.
These cushion layers are printed or applied and thermoset at 120-220 ° C. for 5-120 minutes prior to the formation of the resistor and its electrodes. Resistor 3 containing an inorganic powder such as carbon is printed on the thus-prepared temporary substrate 1 and baked at 120 to 220 ° C., preferably 150 to 180 ° C. to adjust to a predetermined resistance value. The electrode of the temporary substrate 1 is the electrode of the above-mentioned resistor, which is formed by printing before or after printing the resistor and by baking before or simultaneously with baking of the resistor. The V-shaped groove 6 for cutting is formed on the temporary substrate 1 from one side or both sides. The used portion of the temporary substrate 1 becomes the used piece 4, and the unused portion of the temporary substrate 1 becomes the unused piece 5.

In FIG. 1b, the true substrate 11 has an electrode 12 as a temporary substrate. In FIG. 1c, the temporary substrate 1 of the present invention is turned downward. In FIG. 1d, the temporary substrate 1 of the present invention is divided into a used piece 4 and an unused piece 5. Then, the electrode 12 of the true substrate 11 and the electrode portion 2 of the used piece 4 of the temporary substrate 1 are brought into contact with each other and joined with a tin-lead eutectic solder. At this time, the solder may be supplied as a paste. It is desirable that the temporary substrate 1 and the true substrate 11 have the same coefficient of expansion within the range of −55 to 150 ° C., which is the quality use temperature. However, in reality, since the temperatures of the temporary substrate 1 and the true substrate 11 are not the same, the expansion / contraction values are not always equal. Therefore, in the present invention, when the temperature difference (between the temporary substrate 1 and the true substrate 11) is up to about 100 ° C., the stress generated in the fixed span of the resistance element electrode is 250 mm or 400
The Young's modulus of the cushion layer 7 of the temporary substrate 1 was adjusted so as to correspond to mm.

EFFECTS OF THE INVENTION According to the present invention, it is possible to collectively carry out surface mounting of a large number of individual components, improve connection reliability after joining, and use an economical material structure.

[Brief description of drawings]

1 (a) to 1 (d) are cross-sectional views in order of each step in the process of forming a printed circuit board according to an embodiment of the present invention. 1 ... Temporary substrate, 2 ... Temporary substrate electrode, 3 ... Inorganic powder-based resistor, 4 ... Used piece, 5 ... Unused piece, 6 ... V-shaped groove, 7 ... Cushion resin Layer, 11 ... True substrate, 12 ... True substrate electrode.

Claims (1)

[Claims] 1. A cushion layer formed by printing with a resin layer having a high Young's modulus, an electric resistance layer containing carbon powder formed by printing on the cushion layer, and an electric resistance layer formed by printing on the electric resistance layer. An organic first substrate having an electrode layer, and a second substrate that is a printed circuit board having an electrode layer made of copper. A printed circuit board, wherein an electrode layer on the electric resistor layer of the first substrate is opposed to and bonded to the electrode layer.