JPH04249395A - Soldering connection of terminal part - Google Patents

Abstract

PURPOSE:To enable soldering of terminal parts of both circuit substrates mutually before a flexible substrate such as FPC burns by bending an end part of a first circuit substrate to expose a terminal part thereof, by mounting the end part on a terminal part of a second circuit substrate and by heating the exposed terminal part for soldering connection. CONSTITUTION:A terminal part 4 of an upper FPC (flexible printed circuit) 3 is bent to expose up and a bent base film 8 is bonded by thermosetting adhesive each other. The FPC 3 is mounted on a FPC 1 so that an end of the terminal part 2 of the lower FPC 1 exposes slightly. A heater head 6 of a pulse heat soldering device is brought into direct contact with the exposed terminal part 4 of the FPC 3 from above, heated to about 180 deg.C or above to melt solder and terminal parts 2, 4 are connected by soldering. Thereby, it is possible to connect terminal parts well, to improve yield and to improve reliability of a product.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal soldering connection method for soldering a circuit board made of a flexible material to another circuit board and electrically connecting the terminals of both circuit boards.

0002

[Prior Art] For example, in the mounting process of liquid crystal display element modules, etc., terminals of circuit boards made of flexible materials such as FPC (flexible printed circuit) and TAB (tape automated bonding) are connected to FPC, PCB ( printed circuit board),
Solder the terminals of another circuit board such as a glass board using a pulse heat soldering machine (hereinafter referred to as pulse heat soldering machine) or a soldering iron, and then connect the terminals of both circuit boards together. An electrical connection is made.

0003

[Problems to be Solved by the Invention] Conventionally, as mentioned above, for example, a pulse heat soldering machine was used to solder FPCs and FPCs.
When electrically connecting the terminals by soldering them together, place the terminals of the upper FPC on top of the terminals of the lower FPC so that they are facing each other and in contact with each other. Heat it by touching it with the heater head of a pulse heat soldering machine. That is, the heater head does not come into direct contact with the terminal section, but instead heats the terminal section via the base film and adhesive layer of the upper FPC. Therefore, a large amount of heat escapes to places other than the terminals, and the temperature of the terminals does not rise easily, so there is a problem that the upper FPC in the part that contacts the heater head gets burnt before the terminals are connected to each other. get up. In addition, when connecting FPCs, only the tips of the terminals of the lower FPC are exposed, so when the solder is heated and melted, a solder fillet is formed between the terminals. is difficult to do. Therefore, conventionally, the terminal section of the FPC was connected to another FPC or
It was difficult to make good connections to the terminals of the CB, resulting in poor yield and low reliability.

[0004] An object of the present invention is to provide a method in which the terminal portions of both circuit boards can be soldered together before a flexible circuit board such as an FPC burns, and the terminal portions can be easily soldered and connected to each other by easily forming a solder fillet. Our goal is to provide the following.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes soldering a terminal portion of a first circuit board made of a flexible material to a terminal portion of a second circuit board, In the terminal part soldering connection method for electrically connecting these terminal parts to each other, the end part of the first circuit board is bent so that the terminal part of the first circuit board is exposed, and the end part is connected to the terminal part of the first circuit board. It is characterized in that it is placed on the terminal portion of the second circuit board, and the exposed terminal portion is heated and soldered.

[0006]

[Operation] In the present invention, the end portion of the first circuit board is bent so that the terminal portion of the first circuit board is exposed, and this end portion is folded into the second circuit board.
Since it is placed on the terminal portion of the circuit board, the exposed terminal portion can be directly heated with a heater head or the like. Therefore, since heat is directly transmitted to the terminal portions, the temperature of the terminal portions can be easily raised, and the terminal portions can be properly soldered and connected to each other before the first circuit board is scorched.

Furthermore, since the end portion of the first circuit board is bent so that the terminal portion of the first circuit board is exposed, the exposed portion of the terminal portion is large. Therefore, when the solder is heated, solder fillets are easily formed, and the terminal portions can be soldered well.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1(a) and 1(b) are process diagrams for explaining an embodiment of the terminal portion soldering connection method of the present invention. In this embodiment, a case is shown in which the terminal portions of the FPC and the terminal portions of the FPC are connected by soldering. 1 is a lower FPC, 2 is a terminal part of the lower FPC 1 made of, for example, a copper foil layer and a solder plating layer, 3 is an upper FPC, 4 is a terminal part of the upper FPC 3, which is made of, for example, a copper foil layer and a solder plating layer, and 5 is a terminal part of the upper FPC 3 made of, for example, a copper foil layer and a solder plating layer. A bent portion where the end of the upper FPC 3 is bent so that the terminal portion 4 of the upper FPC 3 is exposed, 6 is a heater head of a pulse heat soldering machine, 24 is a base film of the lower FPC 1, 25
8 is a cover film of the lower FPC 1, 8 is a base film of the upper FPC 3, 26 is a cover film of the upper FPC 3, and in (b), 7 is a solder fillet formed after solder melting.

FIG. 2 shows the folded portion 5 shown in FIG. 1(a).
FIG. 4 is a terminal portion made of a copper foil layer and a solder plating layer, 8 is a base film made of a flexible material such as polyimide, and 9 is a thermosetting adhesive layer.

That is, the end of the upper FPC 3 (first circuit board) is extended a little more than the conventional one, and the end of the upper FPC 3 is shaped as shown in FIGS. 2 and 1 so that the terminal section 4 is exposed above the upper FPC 3. As shown in (a), the folded base films 8 are bonded together using a thermosetting adhesive.

The connection method according to the present invention will be explained below. In other words, the upper FPC 3 with the end bent in this way
As shown in FIG. 1(a), the terminal part 2 of the lower FPC 1
Place it on the lower FPC1 so that the tip is slightly exposed,
From the top, the heater head 6 of the pulse heat soldering machine
As shown in FIG. 1(b), the terminal portion 4 is brought into direct contact with the terminal portion 4 exposed on the upper side of the upper FPC 3, and heated to approximately 180° C. or higher to melt the solder and connect the terminal portion 2 and the terminal portion 4. Connect by soldering.

As described above, in this embodiment, the ends of the upper FPC 3 are bent and the heater head 6 is brought into direct contact with the terminal portions 4 exposed on the upper side to heat them, so that heat is directly transmitted to the terminal portions 4 and 2. , the soldering temperature of the terminal parts 4, 2 can be easily raised to about 180° C. or higher, and the terminal parts 2 and 4 can be soldered and connected well. That is, the upper FPC 3 will not burn before soldering is completed.

Furthermore, since the exposed portion of the terminal portion 4 is large due to the bending of the upper FPC 3, a solder fillet 7 is easily formed between the terminal portions 2 and 4, as shown in FIG. 1(b). The terminal parts 2 and 4 can be well connected by soldering. That is, defects such as solder open are less likely to occur. Furthermore, since the terminal section 4 of the upper FPC 3 is exposed,
The appearance of the connection between the terminal parts 2 and 4 and the formation of the solder fillet 7 can be easily inspected. As a result, according to this embodiment, the yield can be improved and the reliability of the product can be improved.

Note that a soldering iron may be used instead of a pulse heat soldering machine, but soldering with a soldering iron takes time and the soldering properties are not stable.
A pulse heat method using a pulse heat soldering machine is desirable because it shortens the working time and provides good soldering properties.

FIG. 3 is a plan view showing the inside of a liquid crystal display module to which the terminal soldering connection method of the present invention is applied. 10 is a liquid crystal display element (liquid crystal display panel), 11
, 12 and 13 are respectively FPCs, 14 is a TAB, 15 is a liquid crystal driving LSI chip mounted on the TAB 14, and 16
is a PCB, 17 is a chip component mounted on FPCs 11, 12, and 13, 18 is a connector part into which a connector is inserted,
19 is a power supply circuit mounted on the back side of the PCB 16, 20 is a data conversion circuit mounted on the back side of the PCB 16, 21 is a terminal connection section between the FPC 11 or FPC 13 and the FPC 12, and 22 is the FPC 11 or FPC 13 and the PCB 16.
23 is a shield case.

The liquid crystal display element module of this embodiment is covered with two thin rectangular upper and lower shield cases 23 made of metal, for example, an upper shield case (not shown) and a lower shield case 23, and the upper and lower shield cases are combined and soldered. It is fixed by attaching etc. A liquid crystal display element 10 is attached to a liquid crystal display window (not shown) provided in these shield cases. The liquid crystal display element 10 is configured such that liquid crystal is sealed between two lower transparent glass substrates stacked one above the other and sealed with a sealing material. Inside the lower shield case 23 are FPCs 11, 12, 13, and PCB 16.
, TAB14, driving LSI chip 15, power supply circuit 19
, a circuit board such as a data conversion circuit 20, peripheral circuits, etc. are built-in.

The FPCs 11, 12, and 13 are made of a flexible material such as polyimide, and are connected to and mounted with chip components 17 of passive elements such as capacitors and resistive elements, and a TAB 14 on which a driving LSI chip 15 is mounted. FPC11
, 13 are provided with a video signal drive circuit, and the FPC 12 is provided with a vertical scanning circuit. The TAB 14 on which the driving LSI chip 15 is mounted is also made of a flexible material such as polyimide, and a plurality of TABs 14 are arranged around the outer periphery of the three sides of the liquid crystal display element 10, and are connected to the liquid crystal display element 10 and the FPCs 11, 12, 1.
It is electrically connected to 3. FPC11, 12, 13
are respectively attached to the lower shield case 23 through small holes provided therein and pins provided integrally with the lower shield case 23. A PCB 16 is attached to the outer periphery of the remaining side of the liquid crystal display element 10. PCB
Reference numeral 16 is made of glass epoxy or the like, and includes a connector section 18, a power supply circuit 19, and a data conversion circuit 20 that converts CRT data sent from a personal computer or the like through the connector section 18 into data for a TFT liquid crystal display module. It is installed. The reason why the PCB 11 is used instead of the FPC for the circuit board on the outer periphery of one side of the liquid crystal display element 10 is because the circuit board installed on this side does not have the problem of lead wire breakage unlike the FPC installed on the third side. This is because there are many mounted components such as power supply circuits and conversion circuits that must be soldered.

Since the TAB 14 and chip components 17 are thin, they can be mounted on the FPC boards 11, 12, and 13, but the power supply circuit 19 and conversion circuit 20 are not chip-shaped but are sealed with plastic or ceramic. It is thick because it is composed of integrated circuits (ICs) with external leads, transistors, passive components, etc., and is installed on the back side of the PCB 16, so that the liquid crystal display surface (top surface) is as flat as possible. . The chip component 17 is a ripple removal bypass capacitor electrically connected to the DC potential wiring from the power supply circuit 19 described above,
In order to increase mounting efficiency, they are placed at the four corners of the module.

Since the FPCs 11, 12, and 13 are made of a flexible material such as polyimide, the liquid crystal display element 10 and the FPC
The stress generated in the long axis direction of the FPC due to the difference in expansion rate between the PCs 11, 12, and 13 is absorbed by the bending of the flexible PFC, and the input side outer lead (not shown) of the TAB 14, which has the weakest strength, Cutting can be prevented and the reliability of the liquid crystal display element module against heat can be improved. In addition, as liquid crystal display screens become larger, as the size of the liquid crystal display element module increases, the drive circuit section including the TAB14 becomes heavier, but since FPC is lighter than PCBs, etc., the drive circuit section can be made lighter, and the TAB14 becomes heavier. The load on the input-side outer lead can be reduced, and reliability against vibrations and shocks can be improved. Furthermore, the weight of the entire liquid crystal display element module can be reduced.

FIG. 4 is a detailed plan view of the FPC 11 shown in FIG. A terminal connection portion 21 between the FPC 11 and the FPC 12 (FIG. 3) and a terminal connection portion 22 between the FPC 11 and the PCB 16 are shown with diagonal lines (hatching).

In the liquid crystal display element module of this example,
Terminal connection section 21 between FPC11 and FPC12, terminal connection section 21 between FPC13 and FPC12, terminal connection section 22 between FPC11 and PCB 16 shown in FIGS. 3 and 4
, and the terminal connection section 22 between the FPC 13 and the PCB 16
was formed as shown in FIGS. 1(a) and 2. That is, the terminal connection parts 21 and 22 of the FPCs 11 and 13 on the upper side with respect to the FPC 12 and the PCB 16 are connected to the terminal parts (
2 and 1 (a
) FPCs 11 and 13 are bent and folded as shown in
The base films are bonded together using a thermosetting adhesive. Therefore, as shown in FIGS. 1(a) and 1(b), by directly contacting and heating the exposed terminal portions of the FPCs 11 and 13 with the heater head, the temperature of the terminal portions can be easily increased. , the terminal parts can be soldered well, and the FPCs 11 and 13 will not burn before soldering is completed. Further, since the exposed portions of the terminal portions of the upper FPCs 11 and 13 are large, solder fillets are easily formed, the terminal portions can be soldered well, and defects such as solder open do not occur. Furthermore, since the terminal portions of the FPCs 11 and 13 are exposed, it is easy to visually inspect the connection status of the terminal portions and the formation status of solder fillets.

Although not shown, reinforcing plates are laminated and provided at predetermined portions of the FPCs 11, 12, and 13, that is, the connection portion of the TAB 14 and the mounting portion of the chip component 17.
Reinforces the PC from the back. This makes it possible to stably and easily connect the TAB 14 and mount the chip component 17, resulting in good workability. Furthermore, this reinforcing plate is FPC1
1, 12, and 13 in the long axis direction, and the flexible F
As the PCs 11, 12, and 13 bend, stress is effectively absorbed. In addition, FPC11,
When using PCBs instead of 12 and 13, connecting parts such as a connecting FPC are required to connect the divided PCBs, but here FPCs 11, 12, 13
Since these connecting parts are used, these connecting parts can be omitted, and the number of connecting steps can be reduced by half. In addition, the terminal connection portions 21 and 2
Unlike other multilayers, FPC 11, 1 is composed of only two folded layers and is highly flexible.
2.13 It is easy to connect with comrades and it is possible to absorb stress. Further, by providing dummy terminals on both the left and right sides of the terminal portions of the terminal portion connecting portions 21 and 22, the number of terminals to be soldered at the connecting portions between FPCs can be increased, so that the connection strength can be increased. Furthermore, connecting this dummy terminal to a DC power supply wiring (AC grounding point) such as a ground wiring is effective as a countermeasure against noise.

Although the present invention has been specifically explained above based on the above embodiments, the present invention is not limited to the above embodiments, and it goes without saying that various modifications can be made without departing from the gist thereof. be. For example, in the above example,
Although FPCs are connected to each other, it goes without saying that the lower substrate is not limited to FPC, but may also be a PCB, a glass substrate, or the like. Furthermore, the upper substrate is not limited to FPC, but can also be applied to TAB and the like. Further, in the above embodiment, an example was shown in which the present invention was applied to a liquid crystal display element module, but it goes without saying that the present invention can be applied to other devices, modules, and the like.

[0024]

[Effects of the Invention] As explained above, in the terminal soldering connection method of the present invention, the temperature of the terminal can be raised quickly, so it is possible to prevent the circuit board from burning before soldering is completed, and to prevent solder fillets from forming. Since it is easy to connect, the terminal parts can be connected well. As a result, yield can be improved and product reliability can be improved.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are process diagrams for explaining one embodiment of the terminal portion soldering connection method of the present invention.

FIG. 2 is an enlarged detailed view of the folded portion shown in FIG. 1(a).

FIG. 3 is a plan view showing the inside of a liquid crystal display module to which the terminal soldering connection method of the present invention is applied.

FIG. 4 is a detailed plan view of one FPC shown in FIG. 3;

[Explanation of symbols]

1...Lower FPC, 2...Terminal section of lower FPC, 3...Upper FPC
PC, 4... Terminal part of upper FPC, 5... Bent part of upper FPC, 6... Heater head, 7... Solder fillet, 8...
Base film, 9...Thermosetting adhesive layer, 10...Liquid crystal display element, 11, 12, 13...FPC, 14...TAB, 1
5...Drive LSI chip, 16...PCB, 17...Chip components, 18...Connector section, 19...Power supply circuit, 20...Data conversion circuit, 21...FPC11 or FPC13 and FP
Terminal connection part with C12, 22...FPC11 or FP
Terminal connection portion between C13 and PCB 16, 23... Shield case, 24... Base film, 25, 26... Cover film.

Claims (1)

[Claims] [Claim 1] A terminal part soldering connection in which a terminal part of a first circuit board made of a flexible material and a terminal part of a second circuit board are soldered and these terminal parts are electrically connected to each other. In the method, an end portion of the first circuit board is bent so that a terminal portion of the first circuit board is exposed, and the end portion is placed on the terminal portion of the second circuit board; A terminal part soldering connection method characterized by heating the exposed terminal part and making a soldering connection.