JPS5874272A - Soldering method of high density wiring - Google Patents

Abstract

PURPOSE:To execute soldering with high accuracy, pressing a connecting part uniformly, by making an electrode terminal and a lead wire contact through solder, pinch-holding them by a strong magnet and a flexible metallic plate attracted by the magnet, and irradiating infrared rays. CONSTITUTION:On a strong magnet, desirably a permanent magnet 16, which has been embedded in a part of a rack 15 in advance, a connecting part of plural electrode terminals whose wiring has been executed with high density, of a warped ceramic substrate 9, and plural lead wires of a flexible printed cable 6 is made to contact through solder, on which plural hole 17 parts which have been etching-worked, of a flexible metallic plate 18 of 0.02-0.3mm. in thickness, attracted by a magnet of a stainless steel plate, etc. are placed, and as necessary the lead wire is corrected by a precise pincette through said hole 17. To the connecting part which has been press-fixed by the metallic plate 18 attracted by said magnet 16, heat energy such as infrared rays, etc. is irradiated, by which soldering is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for connecting a flexible printed cable (hereinafter abbreviated as FPC) to a large number of electrode terminals on a circuit board formed by vapor deposition or printing.

In recent years, the development of information terminal equipment has been active, and as a result, electrode interconnection technology has naturally become important, and high-density and lightweight interconnects using PPC are rapidly becoming widespread. An example of a conventional connection method using this FPC will be explained with reference to a perspective view in FIG. 1 and a sectional view in FIG. 2.

Figure 1 shows a selected solder wire 3 on a large number of electrode terminals 2 formed on the edge of a glass substrate 1 by a method such as vapor deposition.
After cross-loading and fixing with 7 lux, an F'PC consisting of a flexible transparent resin film 4 and a lead wire 5 (hereinafter abbreviated as "lead") etched with copper foil is placed on top of it.
A large number of leads 5 of No. 6 are aligned in upper and lower positions with each electrode terminal 2.

Next, as shown in FIG. 2, the transparent quartz plate 7 is fixed while being pressurized all at once with arbitrary force, and the solder wire 3 is sandwiched to connect the solder wire 3 to heat energy that is focused by infrared rays 8 from above. By irradiating the area, the solder 3 melts and spreads to each terminal 2 and each lead 5, which are easy to wet, and the solder located outside each connection area spreads to each connection area. Surface tension of solder 1 Capillary phenomenon The body is drawn closer and constricted.

Finally, they are separated, and a large number of connected parts, whose top and bottom positions are aligned, are simultaneously connected together with a single solder wire.

In this method, lead 5 of ll'Pc is pre-plated with solder)
The inventors of the present invention have already filed a development application (Japanese Unexamined Patent Application Publication No. 51-27461) after discovering that higher density can be achieved at lower cost than the method of connecting after bonding.

But no - above? In the bonding method, if the 0 surface of the connection part is not uniformly flat, solder #! 3 is not applied uniformly to each connection part, and a uniform amount of □ solder is not distributed to each connection part, making it impossible to connect many pieces at once as desired. . . . Engineering□3. ．． )ゎ4jllEJVCypfL, yo, in 2018, ceramic substrates 9 that can form multilayer circuits at low cost rapidly appeared,
Since the ceramic itself is a powder sintered body, the electrode terminals 10 formed on this substrate warp (undulate) during the manufacturing process and lose flatness, so many terminals are connected at once. had a big problem. By the way, it is said that the warpage of a ceramic plate is 100μm/25I1m. One attempt to solve this problem is to apply heat transfer energy to the connection part by applying a flexible resistance heating element to the top surface of the aligned FPC, but it is difficult to apply pressure uniformly due to the bending condition of the board. There are also drawbacks such as the inability to observe the connection part inside the solder material.

Further, a method of uniformly applying pressure to the connecting portion will be explained with reference to the cross-sectional view of FIG. 4.

, 1□' In the same figure, the FPC lead 5 is applied to the electrode terminal 10 on the curved substrate 9, the flexible pressure film 11 is applied from above, and the N2 gas 12 is applied to the lead 5 of the FPC.
A large number of boards are simultaneously and uniformly pressed 13 with a pressure film on the connection part while applying heat energy such as infrared rays 8 to the back surface 14 of the connection part of the board.

This connection method is used when the connection pitch is as rough as 1 wire/m, when the alignment accuracy is low, when there is a low risk of short circuits (bridging) due to lead contact due to misalignment between adjacent terminals after setting, or This is effective when connection can be made without the need for position correction.

However, since thermal energy is applied directly to the substrate 9, the substrate is likely to be thermally damaged, and therefore, step heating or the like is required for a long period of time. Furthermore, in high-density wiring that requires 5 wires/wa with a connection pitch of about 115, vertical positional deviations before and after pressurization tend to occur frequently during setting, and it is impossible to correct the position from the back side of the board. It has the following disadvantages.

SUMMARY OF THE INVENTION An object of the present invention is to provide a connection method that eliminates the above-mentioned drawbacks and allows for easy position adjustment while applying pressure uniformly to a large number of connection parts.

The present invention is characterized in that a plurality of electrode terminals wired at high density on a substrate and a plurality of lead wires are soldered together. Contact the connection part with the lead wire through solder,
The connecting portion is held between a stand provided with a strong magnet and a flexible metal plate that is attracted by the strong magnet, and the connecting portion is soldered by applying arbitrary thermal energy.

Hereinafter, specific examples will be described with reference to the cross-sectional view of FIG. 5 and the top view of FIG. 6.

FIG. 5 shows an FPC 6 placed on a ceramic substrate 9 with a warp on a strong magnet 16 embedded and fixed in advance in a part of a pedestal 15, and a 0.1 m thick ferrite plate, for example, a stainless steel plate, attracted by the magnet. Series 5U8405 (or SU
A holding mask 18, which is a flexible metal plate with holes 17 etched to allow infrared irradiation energy to be applied to the connection part, is loaded, and the flexible FPC 6 is fixed under pressure. do. In addition.

The magnet used may be a permanent magnet or an electromagnetic magnet, and in consideration of workability, equipment, etc., permanent magnets are more desirable. Next, check that the terminals and leads on the warped board 9 are aligned at the top and bottom, and if they are misaligned, use a tool with a fine tip, such as precision tweezers, to hold down the FPC 6 from Kure 17 on square 8. move. In the case of 'Mo, the FPC6 is firmly fixed with the valve mask 18, and the FPC6 is
When it is difficult to move the FPC 6, moving the mount 15 itself away from the magnet 16 using an arbitrary method weakens the suction force of the holding mask 18, making it easier to correct the movement of the FPC 6.

The shape of the holding mask 18 was machined as shown in Fig. 5, and the shape of the hole 17 was such that sufficient irradiation energy could pass through the connection part, and the hole 17 could be used to correct the movement of the FPC with a tool. A wide variety of hole shapes are possible.

In this embodiment, the leads of the FPC are uniformly pressed and fixed over each electrode terminal, thereby reducing short-circuit (bridging) defects. Furthermore, since there is a hole in the presser mask,
Infrared irradiation thermal energy is directly transmitted to the FPC through the hole in the mask.
is applied to the solder wire through the heat exchanger, improving thermal efficiency. Further, the connection portion can be observed during heating through the hole in the presser mask, and the position of the connection portion can be corrected through the hole in the presser mask, so that short-circuit defects can be further reduced.

Figure 7 shows that the inventors measured 300 electrode terminals on the ceramic substrate shown in Figure 3 using a roughness meter (5 terminals/1 MIL, and the overall width was approximately 60 mm).
The flatness of the presser mask (mm) in Figure 7 (a) and the flatness of the presser mask in the state shown in Figure 5 using the presser mask in Figure 6 were measured in Figure 7 (b). This shows the results. In this way, if the holding mask has a thickness of about 0.1 mm, the holding mask will bend along the edge of the substrate, and the V
C. We were able to demonstrate that it was tracking well.・：″
,.

When a holding mask with a thickness of 0.3 m+ or more was used, the FPC partially lifted in connection experiments, resulting in as many as 30 connection failures. If a thin presser mask with a thickness of 0.02 mm or less is bent too much during handling, bending marks will remain.
It was also found that they must be handled with care, as they cannot be reused.

Therefore, it can be seen that selecting the thickness of the presser mask in accordance with the warpage of the substrate is a condition for creating a defect-free connection.

Although the present embodiment has been described using a ceramic substrate as an example, the present invention can also be applied to general substrates having warpage, such as glass substrates and printed circuit boards.

Further, the lead wire to be connected is not limited to FPC, but may be a general lead wire such as a multi-core lead wire.

As described above, according to the present invention, since a flexible holding plate is used, the lead wire can be uniformly pressurized and fixed over each electrode terminal, thereby reducing defects such as short circuits.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a conventional method explaining the present invention in detail;
3 is a perspective view of the substrate used in the present invention; FIG. 4 is a sectional view of a conventional method explaining the specific embodiment shown in FIG. 3; FIG. 5 is a sectional view explaining a specific embodiment of the present invention, FIG. 6 is a plan view explaining in detail the present invention used in FIG. 5, and FIG. i//3 +MltI7/1

Claims (1)

[Claims] i. A plurality of electrode terminals wired at high density on a substrate;
In the case where a plurality of lead wires are soldered, the connection portion between the electrode terminal and the lead wire is brought into contact with each other via solder, and a mount provided with a strong magnet is attracted to the strong magnet, and A method for soldering high-density wiring, characterized in that the connecting portion is held between flexible metal plates and the connecting portion is soldered by applying a desired amount of thermal energy. 2. A method for soldering high-density wiring according to claim 1, characterized in that at least one hole is provided in the metal plate. 3. In claim 1 or 2. A method for soldering high-density wiring, characterized in that the thickness of the metal plate is 0.02 wg to 0.3 wg. 4. In claims 1 to 3. A high-density wiring soldering method characterized in that the strong magnet is a permanent magnet.