JP2749966B2 - Printed circuit board structure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a printed board structure for connecting at least two printed boards.

[Prior Art] FIGS. 3 to 6 show typical examples of conventional connection between substrates.
Shown in the figure. In the case where conventional substrates are electrically connected to each other by soldering, for example, when the substrate disposed on the upper side is a flexible printed circuit board, as shown in FIG. 6, a portion required for soldering, that is, an exposed portion 1f of the pattern Is known in which the outer shape is processed into a nail shape (the structure will be described later). However, while this structure has good solderability, the nail 1f is damaged by an external force of a soldering iron or the like, and breakage is caused by cutting or the like. The structure of the substrate shown in FIGS. 3 to 5 is known as a structure having a low risk of disconnection. The structure of the substrate shown in FIG. Reference numeral 1 denotes a flexible printed board (hereinafter referred to as FPC),
And soldered. In the FPC 1, a copper foil pattern 1b is arranged on a pace 1a made of a polyimide material, and the upper surface of the pattern is covered with an insulating material 1c such as a cover film or a resist ink, and a tip portion thereof is connected for connection. It is exposed. The tip of the exposed part of the copper foil pattern 1b has a semicircular opening so that the solder material can be easily placed on it.
Has 1h. Reference numeral 3 denotes a substrate disposed below the FPC 1. The substrate 3 has a base material 3a (made of a hard material such as glass epoxy or a flexible material such as a polyimide material) on a base material 3a, and a pattern 3b for connection by soldering and a pattern on the FPC1. 1b are arranged at the same pitch 4 and the upper surface of the pattern 3b is covered with an insulating material 3c, 3c 'such as a cover film or a resist ink, and a connection pattern 3b is provided between the gaps 3c and 3c'. It is exposed.

Therefore, when connecting soldering the FPC1 and substrate 3, the outer portion end of FPC1 are superimposed to match the position of the l ₁ indicated by the two-dot chain line in FIG.

Wherein the distal end portion of the insulating material 3c of the substrate 3 is outer end portion of the normal FPC1 are provided from the position l ₁ located on the substrate 3 at positions l ₂ which is recessed inward by a predetermined distance d. This causes a portion where the copper foil pattern is not connected between the copper foil pattern 1b and the pattern 3b in which l ₂ protrudes forward from l _{1 due} to displacement between the substrates, so that solderability is deteriorated. Because.

In the actual solder connection, as shown in FIG. 5, the solder material 4 is laid over the pattern exposed portion 1b and the pattern 3b, and the connection is completed.

[Problems to be Solved by the Invention] However, if the connection between the substrates increases with the increase in the electric circuit scale, a high-density connection is required in a limited area. In addition, connection of a large number of signal lines at a narrow pitch is required. In response to this demand, the narrower the connection pattern pitch, the more frequently patterns leak.

The mechanism of the leak is (1) in addition to a simple solder bridge that occurs due to the proximity of the patterns, (2) as shown in FIGS. 4 and 5, the base 3a of the substrate 3,
A minute space B is generated between the tip side surface 3e of the insulating material 3c and the base 1a of the FPC 1, and the melted solder reaches the adjacent pattern along the space B along the side surface 3e like a capillary phenomenon. It will be. That is, a leak is generated in this manner.

For (1), the bridge can be prevented relatively easily by controlling the amount of solder to be applied.
Regarding the phenomenon (2), the appearance cannot be checked.
In addition, since it does not always occur under the same conditions, it is difficult to take countermeasures at present.

Means for Solving the Problems According to the present invention, in a printed circuit board structure in which a plurality of connection patterns are exposed on one of two printed circuit boards to be connected, an insulating coating of an end portion of the plurality of connection patterns is provided. By forming the layer in a stepped shape and penetrating between the patterns, the minute spacing B causing a leak is eliminated, and the flow of an adhesive substance such as solder is prevented.

Embodiment FIG. 1 and FIG. 2 show an embodiment of the present invention.

In the figure, the structure of the FPC 1 is not different from that of the conventional embodiment (FIG. 3), and the description is omitted here.

Reference numeral 2 denotes a printed circuit board disposed below the FPC 1.

The printed circuit board 2 is formed on a base material 2a (the material may be any of a hard material such as glass epoxy or a flexible material such as a polyimide material).
They are arranged at the same pitch as the connection pattern 1b above, and the upper surface is covered with insulating materials 2c and 2c 'such as a cover film or resist ink, and the gap is an exposed portion of the connection pattern.

Here, the shape of the end of the insulating material 2c is a position where the outer end of the FPC ₁ is protruded by D from the position l1 where the outer end of the FPC ₁ is aligned with the printed circuit board 2 in the gap region between the adjacent connection patterns 2b.
l has been extended to ₂ . The connection in the region of the patterns 2b, and then to the position l ₁ than "d" is retracted only to the inside of the position l ₃ shape.

Therefore, the outer shape of the insulating material 2c of the printed circuit board 2 has a stepped shape of a waveform having the same pitch as the arrangement pitch of the connection patterns 1b and 2b.

Next, the printed circuit board 2 and the FPC 1 described above are superimposed to perform the solder connection. When the FPC 1 and the printed circuit board 2 are superimposed, the minute interval B does not occur. This is because the space B is filled with the insulating material of the printed circuit board 2. Therefore, the leak phenomenon that occurs when the solder material is transmitted through the gap B does not occur.

Also, the substrate 2 protruding by “D” from the tip of the FPC1
Since the upper insulating material 2c is interposed between adjacent connection patterns, solder bridges can be prevented at the same time.

[Effects of the Invention] Since the structure is such that a minute space B is not generated between each connection pattern when one printed circuit board and the other printed circuit board are superimposed, a leak phenomenon caused by the transmission of the solder material through the gap B is prevented. Does not happen. At the same time, since an insulating material is interposed between adjacent connection patterns and a simple solder bridge can be prevented, a large number of connections can be made at a narrow pitch.

[Brief description of the drawings]

FIG. 1 is a perspective view of two printed boards according to the present invention, FIG. 2 is a top view of FIG. 1, FIG. 3 is a perspective view of a printed board showing a conventional example, and FIG. Top view, FIG. 5 is a sectional view taken along line AA of FIG. 4, FIG. 6 is a perspective view of a printed circuit board showing another conventional example, 1... Flexible printed circuit board, 2. … Connection pattern, 2c ・ 2c ′ …… Insulation material.

Claims (3)

(57) [Claims] 1. A printed circuit board structure in which a plurality of connection patterns are exposed on one printed circuit board in order to connect a plurality of patterns on at least two printed circuit boards. A printed circuit board structure, wherein a layer is formed in a step shape, and the insulating coating layer is inserted between the plurality of connection patterns. 2. A method for connecting a plurality of patterns on at least two printed circuit boards, exposing a plurality of connection patterns on one printed circuit board, and connecting the plurality of connection patterns on the one printed circuit board to the other. In a printed circuit board structure in which connection patterns at ends of a printed circuit board are connected in an overlapping state, an insulating coating layer at an end of the plurality of connection patterns of the one printed circuit board is formed in a step shape, and the plurality of connection patterns are formed. The printed circuit board structure, wherein the insulating coating layer is inserted so as to protrude from an end position of the connection pattern of the other printed circuit board. 3. The printed circuit board structure according to claim 1, wherein said stepped portion of said insulating coating layer is corrugated.