JPH03165090A - Printed circuit board - Google Patents

Abstract

PURPOSE:To achieve economy and moderate reliability by preparing a circuit board which is obtained by printing and forming a plurality of resistors on a temporary board and further, performing printing a position where the resistors are mounted on a real board in such a way that the above position faces a position to which the resistors can be transferred and then, forming component parts. CONSTITUTION:A cushion layer 7 is formed by mixing or laminating, for example, either or both of a flexible epoxy resin or nitrile rubber and the like in/on a temporary board 1 and resistors 3 containing an inorganic powder like carbon are printed and baked and then, are regulated at a prescribed value of resistance. Then, V-shaped grooves 6 for cutting out are processed into the temporary board 1 from one side or both sides. The temporary board 1 is directed to the lower side and it is divided into working pieces 4 and unworkable pieces 5 and further, electrodes 12 of a real board 1 abut upon electrode parts 2 of the working pieces 4 on the temporary board 1 and bonding of these electrodes is performed by eutectic soldering of copper - lead. Since a resin layer holding a large Young's modulus or a rubber layer is disposed as the cushion layer to the above mentioned temporary board for printing circuit elements, at least, to a lower part between electrode fixed spans, mounting cost of the circuit elements and reliability obtained after bonding are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a circuit board for electronic equipment, and more particularly to a transfer mounting system for a plurality of electrical resistance elements.

Conventional technology Conventional, paper phenol, paper epoxy, glass cloth epoxy,
Hybrid circuit boards were manufactured by surface mounting individual components on printed wiring boards made of alumina porcelain, alumina nitride, etc. as base materials.

Problems to be Solved by the Invention Among these types of individual components, the number of resistor elements is the largest (and the time and cost required to mount them are becoming enormous).

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

Means for Solving the Problems In the present invention, as a specific means, a temporary substrate is prepared with a plurality of resistors printed thereon.

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 real substrate, relative to the transferable position. In this way, a part that can be transferred and placed is formed.

Transferring involves preparatory work for cutting on the temporary substrate, ■Cut, half cut, perforation, and laser processing.

This is done in the form of a punching process, etc., and by selectively pressing each element onto the real substrate, transfer mounting is possible. After cutting out and transferring, it may be joined to the true board by soldering later, but it is not possible to connect it to the true board by printing or applying solder paste or adhesive (conductive or non-conductive) to the true board in advance. The above-mentioned transfer mounting component is soldered or heat-bonded to the true substrate.

If the solder connection to the electrode of the resistor element is difficult (if the solderability or solder heat resistance is insufficient), a copper foil or copper-plated electrode is used as a necessary auxiliary electrode. It goes without saying that existing technology can be used to determine the printing direction, thickness, electrode material, shape and size of electrodes and resistors, wattage, resistivity, number of printed layers, printing order, number of printings, etc. of the element. However, since the expansion and contraction values of the real substrate material and the expansion and contraction values of the temporary substrate material do not necessarily match,
When a surface mount component including the resistance element is bonded between bonding electrodes, the bonding life of the bonded portion is shortened due to differential stress generated between the fixed spans.

According to the present invention, a resin layer or a rubber layer having a large Young's modulus is disposed as a cushion layer at least in the lower part between the electrode fixing spans of the temporary substrate for printing circuit elements, so that the circuit elements can be printed on the temporary substrate. It is possible to improve the installation cost and the reliability after bonding.

Embodiment An embodiment of the present invention will be described with reference to the sequential sectional views of each step in FIG.

In FIG. 1a, a cushion layer 7 is formed on the temporary substrate 1 of the present invention by mixing or layering one or both of flexible epoxy resin and nitrile rubber, for example. These cushion layers are printed or coated before the formation of the resistor and its electrodes, and heated for 5 to 12 hours at 120 to 220°C.
Heat cure for 0 minutes. A resistor 3 containing an inorganic powder such as carbon is printed on the temporary substrate 1 thus created.
Baking is performed at 0 to 220°C, preferably 150 to 180°C, and the resistance is adjusted to a predetermined value. The electrodes of the temporary substrate 1 are the electrodes of the resistor, and are formed by printing before or after printing the resistor and baking before or at the same time as baking the resistor. A V-shaped groove 6 for cutting out is formed on one or both sides of the temporary substrate 1. The utilized portion of the substrate 1 becomes the used piece 4, and the unused portion of the substrate 1 becomes the unused piece 5.

In Figure 1, the real substrate 1 is the electrode 12 as a temporary substrate.
have. In FIG. 1C, the temporary substrate 1 of the present invention is oriented downward. In FIG. 1d, the temporary substrate 1 of the present invention is divided into used pieces 4 and unused pieces 5. Then, the electrode 12 of the real substrate 1 and the electrode portion 2 of the used piece 4 of the temporary substrate are brought into contact and joined with tin-lead eutectic solder. At this time, the solder may be supplied as a paste. It is desirable that the expansion/relaxation coefficients of the substrate 1 and the substrate 2 are the same within the range of -55 to 150[deg.] C., which is the temperature at which they are used. However, in reality,
Since the temperatures of substrate 1 and substrate 2 are not the same, the expansion and contraction values are not necessarily the same. Therefore, in the present invention, when the temperature difference (between substrate 1 and substrate 2) is up to about 100°C, the cushion layer 7 of temporary substrate 1 Adjusted to increase Young's modulus.

Effects of the Invention According to the present invention, a large number of individual components can be surface-mounted all at once, connection reliability after bonding can be improved, and an economical material composition can be used.

[Brief explanation of the drawing]

FIGS. 1A to 1C are cross-sectional views 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 resistor, 4...Used pieces, 5...Unused pieces, 6...V-shaped groove, 7... ...Cushion resin layer, 11...
True substrate, 12... Electrode of true substrate.

Claims (1)

[Claims] A resin layer with a high Young's modulus as an intermediate layer between the resistor and the substrate as a sheet used when printing and baking a plurality of electrical resistors containing inorganic powder such as carbon or organic resin on an organic paper-based substrate. A printed circuit board that is formed by being transferred to a separately prepared printed wiring board-like structure such as copper-clad or copper-plated.