JPS6049698A - Connecting structure of printed board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a connection structure for printed circuit boards used in various electronic devices, and particularly relates to a connection structure for printed circuit boards used in various electronic devices. This ensures reliable electrical connection.

<Background Art and its Problems> 1- Generally, various electronic devices are equipped with printed circuit boards on which various circuit components are mounted for circuit configuration. As the notebook printed circuit board, a rigid printed circuit board using a hard material and a flexible printed circuit board having flexibility are known.

Furthermore, as electronic equipment bodies become more complex in shape or smaller, rigid printed circuit boards and flexible printed circuit boards, or flexible printed circuit boards and flexible printed circuit boards may be connected to form a so-called connected printed circuit board.

In other words, this type of connected printed circuit board can be used to effectively utilize the space within the electronic device body by bending the flexible printed circuit board section, or to easily form a multilayer structure into a printed circuit board without the need for wiring with lead wires. Because it is extremely useful for downsizing electronic devices and simplifying internal structures, such as improving wiring density, it is particularly used in ultra-small electronic devices and electronic devices with complicated shapes.

By the way, conventionally, in order to connect printed circuit boards to printed circuit boards, for example, a connector is used to connect the two printed circuit boards, and then the printed circuit boards are stacked with their connection lands facing each other, and then thermocompression bonding is performed. A method was adopted to do so. However, with the above-mentioned method, it is possible when the connection lands are arranged locally on the printed circuit board, but it is not possible when the connection lands are distributed over the entire surface of the printed circuit board. In particular, when using the above-mentioned connector, there is a drawback that it is not suitable for downsizing the main body of an electronic device.

Therefore, as shown in FIGS. 1 and 2, for example, connection holes 5 are formed in the centers of the connection lands 2 formed on one printed circuit board 1 and the connection lands 4 formed on the other printed circuit board 3. .
4 to electrically connect the side substrates 1 and 3.

However, in such a connection method, a difference in level occurs between each connection land 2 and 4 due to the thickness of the printed circuit board 3, and due to the surface tension of the solder and the property that it is extremely easy to adhere to metal, it is difficult to use the method shown in FIG. Solder is deposited on each connection land 2 and 4, and each connection land 2
, 4 cannot be connected effectively.

Therefore, as shown in Fig. 3, a method has been considered in which the lead member 7 is inserted into the connection hole 5°6 and soldered is dipped, but this requires an independent process for inserting the lead member 7. At the same time, the number of parts also increases, making it unsuitable.

In addition, as shown in FIG. 4, a flexible printed circuit board 8
A method of applying copper plating 10 to the connection hole 9 has been considered. However, plating the connection holes 9 of the flexible printed circuit board 8 is technically difficult and undesirable.

<Object of the invention> The present invention was made in view of the above-mentioned circumstances, and when connecting the connecting lands of printed circuit boards,
It is an object of the present invention to enable each connection land to be reliably connected without contact failure.

<Summary of the Invention> In order to achieve the above object, the present invention connects one printed circuit board having a connection land and the other printed circuit board having a connection land on the periphery of the through hole, and connects the connection land of the one printed circuit board with the connection land of the other printed circuit board. A feature is that the through holes of the printed circuit board are laminated in correspondence with each other, the through holes are covered with solder cream, and the solder cream is melted into the through holes by reflow to connect each of the connection lands. shall be. Connection structure of printed circuit board.

<Example> Hereinafter, an example according to the present invention will be described in detail using FIGS. 5 to 10.

In the embodiment shown below, the present invention is applied to the case where a rigid printed circuit board 20 and a flexible printed circuit board 21 whose base material is a synthetic resin film such as polyimide resin are to be bonded.

Various electrical elements such as transistors and resistors are mounted on one side 20A of the rigid printed circuit board 20, and these electric elements are mounted on one side 20A1 and the other side 20B of the printed circuit board 20. They are electrically connected to each other through the arranged wiring patterns 22 and 23 to form a predetermined electric circuit.

The electrical connection between the wiring pattern 22 arranged on one side 20A of the printed circuit board 20 and the wiring pattern 23 arranged on the other side 20B is made in the through hole 24 as shown in FIG. This is done in the plating section 25. That is, the wiring pattern 22 on the side surface 20A
A connection land 26 is provided at a predetermined position, and a connection land 27 is similarly provided at a position corresponding to the predetermined position of the wiring pattern 23 on the other side surface 20B.

A through hole 24 is formed in the center of each of the connecting lands 26 and 27, and the through hole 24 is plated with so-called through hole plating using, for example, copper. Therefore, the connection lands 26 and 27 provided on both side surfaces 20A and 20B are electrically connected by the plated portion 25 formed by through-hole plating.

On the other hand, the flexible printed circuit board 21 is made of a base film 3 made of polyimide resin material, as shown in FIG.
0, a wiring pattern 31 made of copper foil or the like and a coverlay film 32 are laminated and pasted, and connection lands 33 are provided at predetermined positions. Note that the cover lay film 3 at a position corresponding to this connection land 33
2 is cut out so that the connection land 33 can be exposed to the outside.

A hole 34 for degassing during soldering is bored in the center of the twisted connection land 33.

The above-mentioned rigid printed circuit board 20 and flexible printed circuit board 21 have respective connection lands 26 as shown in FIG.
, 27 and 33 correspond to each other, and the coverlay film 32 and the other side surface 20B of the rigid printed circuit board 20 are bonded together with a thermosetting adhesive such as an epoxy resin adhesive, for example. Ru.

As a result, the connection lands 27. of each of the boards 20.21.
Only 33 corresponds to the thickness of the coverlay film 32.
They face each other with a gap 35 at a predetermined interval, and the other portions are insulated by the coverlay film 32.

In order to connect the connection lands 26, 27 of the rigid printed circuit board 20 and the connection lands 33 of the flexible printed circuit board 21 with solder as described above, a solder cream printing process necessary for reflowing various electrical elements is required. At this time, solder cream 40 is also printed on the connection land 26 arranged on one side 20A of the hard printed circuit board 20. As a result, the connection land 26 and the through hole 24 for connecting the connection land 26 and the connection land 27 on the other side surface 20B are covered with the solder cream 40.

Then, with the various electrical elements placed on the hard printed circuit board 20 on which solder cream 40 is printed in two rows, the printed circuit board 20, 21 is placed in a reflow oven. As a result, each of the electrical elements is connected to the hard printed circuit board 20.
The solder cream 40 melts and flows into the through hole 24 .

Then, the melted solder cream 40 gets entangled with the plated part 25 formed in the through hole 24 of the hard printed circuit board 20 due to its affinity with the plated part 25, reaches the connecting land 33 of the flexible printed circuit board 21 from the bottom, and reaches the connecting land 33 of the flexible printed circuit board 21.
3 and the plated portion 25 are electrically connected. At the same time, the solder cream 40 permeates into the gap 35 formed between the connection land 27 on the other side 20B side of the rigid printed circuit board 20 and the connection land 33 of the flexible printed circuit board 21 due to capillary action, and connects the connection land 27. Establish continuity between the two.

Therefore, as shown in FIG. 7, melted solder cream 40
The plated part 25 and the flexible printed circuit board 2 are
1 connection land 33 can be reliably connected.

At this time, as mentioned above, the melted solder cream 40 is attached to the substrate 20 (hard pudding) and the flexible printed circuit board 21.
Since it also penetrates into the gap 35 created between the connecting lands 33 of the two, the connection can be made even more securely.

Note that the gas generated when melting the solder cream 40 described in Section 2 in the reflow unit is exhausted to the outside through the gas venting hole 34, and the solder cream 40 obediently flows through the through hole 24 as shown in FIG. Flow inside. Therefore, by adjusting the amount of the solder cream 40 to an appropriate amount, the solder cream 40 or the outside of the printed circuit board 20, 21,
In particular, the flexible printed circuit board 21 can be prevented from protruding to the outside, and the printed circuit board 20 as described above.
21 can be installed in a smaller space.

Therefore, it is also possible to downsize the main body of the electronic device.

According to this embodiment, in order to connect the rigid printed circuit board 20 and the flexible printed circuit board 21, both sides of the rigid printed circuit board 20 can be connected without providing a special wiring pattern or connection land for so-called routing. Since the through hole 24 used for the connection of the connection pattern 26.2γ arranged in the second embodiment can be used, the process can be omitted.

Furthermore, each board 20, 210 can be connected by reflowing, which is performed to connect various electric elements to the printed circuit board 20, and in this respect, steps such as soldering can be omitted.

In the above embodiment, the solder cleaner 40 was melted and connected by reflow, but as shown in FIG. The connecting land 51 of the flexible printed circuit board 50 is formed by providing an open portion 54 with a large diameter and performing solder dipping.
Each board 50 .
520 connections can be made.

By the way, in the above embodiment, the wiring patterns 22 and 23 are provided on both sides 20A and 20B of the rigid printed circuit board 20.
The present invention was applied to a connection between a so-called double-sided board and a flexible printed circuit board 21 on which a wiring pattern is arranged, but it is also applicable to a connection between a so-called single-sided board and a flexible printed circuit board 21 on which a wiring pattern is arranged only on one side of a rigid printed board. The present invention may also be applied.

In this case, as shown in FIG. 9, an opening (through hole) 61 is formed at a predetermined position on the flexible printed circuit board 600, and a connection land 62 is provided around the periphery of this opening 61. Then, the flexible printed circuit board 60 and the single-sided substrate 63 are laminated and bonded by matching the opening 61 with the connection land 64 of the single-sided substrate 63.

Then, solder cream 40 is printed on the connection land 62 of the flexible printed circuit board 60, and this solder cream 40 is melted into the opening 61 by reflow.

As a result, as shown in FIG. 10, the melted solder cream 40 flows into the opening 61 due to its own weight, reaches the connection land 64 of the single-sided board 63, and also becomes entangled with the connection land 62 of the flexible printed circuit board 60.

Therefore, by printing a sufficient amount of solder cream 60, the connection lands 64 of the single-sided board 63 and the connection lands 62 of the flexible printed circuit board 60 are bonded with the solder cream 40.
connection can be made securely.

<Effects of the Invention> As is clear from the above description, according to the present invention, solder cream is melted into the through holes of the printed circuit board by reflow, and the connection lands of each printed circuit board are connected with this solder cream. By doing so, each connection land can be reliably connected.

In addition, since the connection of each connection land can be performed simultaneously with the connection of various electric elements using adhesive flow, an independent connection process for connecting each printed circuit board to each other can be omitted.

Furthermore, in particular, as in the present invention, by connecting each printed circuit board using through holes, connection can be made at any position on each laminated board, which is extremely advantageous in designing the wiring pattern.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a conventional printed circuit board connection structure. FIG. 2 is an enlarged sectional view, and FIGS. 3 and 4 are plan views showing other connection structures. FIG. 5 is a perspective view showing a printed circuit board connection structure according to the present invention. 6 and 7 are enlarged sectional views of the main parts, and FIG. 6 shows the before beam flow, and FIG. 7 shows after the beam flow, respectively. FIG. 8 is a sectional view showing another printed circuit board connection structure according to the present invention. 9 and 10 are cross-sectional views showing other printed circuit board connection structures according to the present invention, with FIG. 9 showing the beam before flow and FIG. 10 showing the beam after flow, respectively. 20.52...... Rigid printed circuit board 21.50.60... Flexible printed circuit board 25...・・・・・・
...Plated part 24.54.61...Through hole 26.27, 33, 51.55.62.64...
・・・・・・・・・・・・・・・Connection land 40・
・・・・・・・・・・・・・・・・・・・・・Solder cream 57・・・・・・・・・・・・・・・・・・・・・
Half Il'r163・・・・・・・・・・・・・・・
...Single-sided circuit board patent applicant Sony Corporation representative Patent attorney Kodo Koike 1) Sakae Mura - 15- Figure 1 Figure 5

Claims (1)

[Claims] One printed circuit board having a connection land and the other printed circuit board having a connection land around the through hole,
Laminate the connection lands of one printed circuit board and the through holes of the other printed circuit board in correspondence, cover the through holes with solder cream, melt this solder cream into the through holes by reflow, and then A printed circuit board connection structure formed by connecting connection lands.