JPH02151389A - Solder material - Google Patents

Abstract

PURPOSE:To produce the solder material which well joins conductive junctures spaced to face each other by incorporating fine conductive materials having the m.p. higher than the m.p. of solder at a specific ratio into the solder. CONSTITUTION:The fine conductive materials 53 which are in granular, fibrous or other forms and have the m.p. higher than the m.p. of the solder 52 (cream solder) and solder wettability are mixed at 10 to 100 pts.wt. with 100 pts.wt. solder to constitute the solder material 54. Pt, Au, carbon, Al, Ni, Cr, Zn, Fe, Cu, etc., are usable as the fine conductive materials 53 and the grain size thereof is preferably about 5 to 75mum. The fine conductive materials 53 act as a binder when terminals 63, 64 spaced to face each other are soldered by using such solder material 54. The solder material 54 well joins the two terminals 63, 64.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solder material, and particularly to a solder material suitable for use in soldering between spaced apart and opposing conductive connections.

[Summary of the invention]

The present invention provides a solder material that electrically connects conductive connections by mixing a specific amount of a fine conductive substance with a melting point higher than that of the solder, thereby making it possible to connect terminals that are spaced apart from each other. It also allows soldering.

[Conventional technology]

Conventionally, a conductive pattern (42
) When a chip component (50) such as a flat coil is mounted on a circuit board (41) on which a conductive pattern (42) is formed, the connection portion (42a) between the terminal (49) of the chip component (50) and the conductive pattern (42) The electrical connection between them is made by solder, for example cream solder (61). (43) is an adhesive for temporarily fixing the chip component (50).

Also, as shown in Figure 12, when connecting terminals (63) and (64) on the board (62) that are too far apart from each other, simply use ordinary cream solder (61). If you just solder the cream solder (61), it will aggregate and separate (see A in the same figure).
) and (64) after passing the lead wire (65) between them.
Cream solder (61) is applied to include the lead wire (65) and soldered (see B in the same figure).

For this type of ream solder (61), an alloy mainly composed of tin and lead is usually used.

[Problem to be solved by the invention]

However, when mounting the above-mentioned chip component (50) on the circuit board (41), for example, as shown in FIG. (49) and the connection part (42a) of the conductive pattern (42)
The part that protrudes from between the
) may occur. At this time, normal cream solder (
61), cream solder (61) is applied as shown in Figure 11.
1) is separated from the terminal (49) of the chip component (50) and the connecting portion (42a) of the conductive pattern (42), resulting in a gap in which no electrical connection is made.

Also, as shown in Figure 12, the terminals (63) and (64) formed at intervals on the board (62) must be connected by soldering via lead wires (65). Instead, a lead wire (65) is required, and the process of arranging the lead wire (65) increases, making the connection work complicated.

In view of this point, the present invention provides a solder material (so-called solder paste) that enables soldering between conductive connection parts that are spaced apart from each other.

[Means for Solving the Problems] The solder material (54) of the present invention uses a fine conductive material (53) (containing conductive particles, conductive fibers, etc.) having a higher melting point than the solder (52) in the solder material (54). (52) 10 to 100 parts by weight are mixed to 100 parts by weight.

If the amount of the fine conductive material (53) is less than 10 parts, the fluidity as a solder material will increase, it will aggregate and easily cause solder breakage, and the effect of containing the fine conductive material (53) will not be obtained. . Moreover, if the amount exceeds 100 parts by weight, the fluidity as a solder material will be insufficient and the adhesiveness to terminals, conductive patterns, etc. will be weakened. Also, when screen printing solder material, solder material (
(solder paste) will not easily fall through the screen plate, making it difficult to print.

[Effect]

When the above-mentioned solder material is attached to conductive connections spaced apart from each other and heated, the fine conductive substance (53) with solder wettability mixed in the solder (52) acts as a binder. The solder material (54) provides a good connection between both terminals without separating them.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

Solder material according to the present invention (so-called cream solder) (54)
As shown in Fig. 1, the solder has solder wettability in the cream solder (52) mainly consisting of tin-lead, and is made of conductive particles or conductive fibers, etc., which have a higher melting point than the cream solder (52). It is constituted by mixing a fine conductive material (53). The fine conductive substance (53) is made of a material that has some degree of solder wettability, has a low solid solution rate in molten solder, and can maintain its shape, for example, granular or fibrous, even when the solder (52) is melted. Preferably, noble metals such as Pt and Au, carbon, A 1 , Ni, Cr, Zn,
Fe, Cu, etc. can be used. Further, it is preferable that the fine conductive substance (53) is mixed in an amount of 10 parts by weight to 100 parts by weight with respect to the cream solder (52). Fine conductive material (
The particle size and shape of 53) are selected as appropriate depending on the application, and are small enough not to clog the printing screen or dispenser when supplying cream solder, and large enough not to cause mounds of supplied solder to collapse even when melted. It is preferable to choose something.

Therefore, the particle size of the fine conductive material (53) is 5 μm.
It is possible to set the thickness to about 75 μm.

Next, a case will be described in which this solder material (54) is applied to mounting a flant coil on a circuit board.

First, the flat coil (1) will be described.・As shown in Figure 5, this flat coil (1) is made of a copper foil (2) that is wound and laminated to a thickness that provides the desired characteristics, and has a terminal (2) made of a solder layer at the beginning and end of the winding. 3) 5(4) is integrally provided over the entire width of the coil in the direction of the coil width.

Copper foil (2) forming the coil part of the flat coil (1)
As shown in Figure 6, an adhesive layer (1
2), (13) are laminated. In this embodiment, two adhesive layers (12) and (13) are coated with a polymer film (11) such as a polyimide film sandwiched therebetween in order to ensure the insulation layer. Here, the thickness of the copper foil (2) is 35 μm, and the thickness of each of the adhesive layers (12) and (13) is 6 μm.
Moreover, a polyimide film with a thickness of 13 μm is used as the polymer film (11). In addition, polymer film (
11) is not necessarily required; for example, it is sufficient to simply coat both sides of the copper foil (2) with adhesive layers (12) and (13), although not shown.

In this example, each terminal (3), (4) attached to the winding start position (i.e., the inner circumferential surface of the coil) and the winding end position (i.e., the outer circumferential surface of the coil) of the copper foil (2) has a thickness of Q,
It is formed as a solder layer with a thickness of 2 mm or less, for example, a thickness Q of 1 mm. In this way, in this example, the terminal (3) is formed as a solder layer with a thickness of 0.1 mm, so even if it is manufactured through the process of wrapping it around the core material (7) several times, which will be described later, the copper foil It is possible to obtain a highly reliable flat coil (1) that does not have torn pieces as shown in (2).

The process of creating such a flat coil (1) will be explained. First, a polymer film (11) or an adhesive (12), (13
) is laminated using a device as shown in FIG. That is, the polymer film (11) supplied from the unwinding roll (21) is guided to the adhesive applicator (22), and both surfaces of the polymer film (11) are coated with adhesive. Next, dryer (2
3) through which the adhesive is inserted (in a semi-softened state), and then laminated (24) to an unwinding roll (25).
Copper foil (2) supplied from
26). Through the above steps, a raw roll of the laminate (6) consisting of the copper foil (2), the polymer film (11), and the adhesive layers (12) and (13) is obtained.

Then, the raw fabric roll of the laminate (6) is cut into a predetermined width using a cutting machine, and one end of the laminate (6) that has been made into the raw fabric roll (the starting position of the coil) is coated with, for example, bar-shaped solder or cream solder. It is melted to form a solder layer (31) that will become the terminal (3) as shown in FIG. The width of the solder layer (31) is set to 2 mm in this example, and the solder layer (31) is formed using rod-shaped solder or cream solder having a melting temperature of about 180°C.

For example, when using rod-shaped solder, the proportion of solder is 60% tin and 40% lead, and the melting temperature is 183°C.
Using a soldering robot, the coating width was 0.5
mm ~10mm S coating thickness 0.005mm ~0.
Apply to a thickness of 2mm. Note that the thickness of the solder layer is 0.
If it is less than 0.005 mm, it will not be possible to apply it uniformly to the surface of the laminate (6), so the lower limit of this thickness is 0.005 mm.
In. The upper limit depends on the problem when winding the laminate (6) as described above. Also, in the case of cream solder,
Cream solder containing 60% tin and 40% lead is printed on the copper foil (2) using silk or a punched board. In this case, the printing width is 0.5m+n~lQmm, and the printing thickness is 0.5m+n~lQmm.
Adjust from 02mm to Q, 2mm. Note that printing is difficult if the thickness of the cream solder is less than 0.0 mm, so the lower limit of this thickness is set to 0.02 mm. Then, a temperature of 300° C. is applied to the printed portion to melt it.

Note that similar results can be obtained by setting the composition and melting temperature of the rod-shaped solder and cream solder to the values shown in the table below, for example. In addition, in this table, the proportion of each component of the solder is shown in weight %.

(2) In the case of bar-shaped solder (2) In the case of cream solder Next, the laminate (6) is wrapped around a core material (shirt) (7) as shown in FIG. 8, using, for example, a water-soluble adhesive. The cross-sectional shape of the core material (7) may match the shape of the desired coil, and may have various shapes such as triangular, circular, elliptical, and polygonal.

Next, after wrapping the laminate (6) around the core material (7) many times to a thickness that provides the desired characteristics, as shown in FIG. A solder layer (32) that will become a terminal (4) is formed. The width of the solder layer (32) is the same as that formed at the winding start position of the coil.
It should be approximately 2 mm. In this example, when winding the core material (7), it is crimped from three sides using an air cylinder (not shown) to adjust the winding state of the coil block (9), which will be described later.

In addition, in this example, the thickness of the solder color (31) is approximately 0.1 mm, so even if it is wrapped around the core material (7) many times as described above, the solder layer (31) will not thicken. Since the copper foil (2) does not bulge out greatly in any part, the copper foil (2) will not be torn to pieces.

The whole obtained in the above steps is called a coil block (9). This coil block (9) is cut into coils (1) having a predetermined width t as shown in FIG. This is a flat coil (1) in appearance.

The entire surface (top, bottom, and circumferential surfaces) except for terminals (3) and (4) is coated with insulation. Various cutting methods can be used, such as mechanical cutting using a wire saw, electric discharge machining, and laser cutting. After cutting, the core material (7) is separated by placing it in water, completing the flat coil (1). The flat coil (1) manufactured in this way is made of copper foil (
2), the adhesive layer (12>, (13)), and the polymer film (11) are densely laminated, and the copper foil (2)
This results in a highly reliable flat coil (1) that will not separate from the terminals (3) and (4). In this flat coil (1), terminals (3) and (4) made of a thin solder layer extending in the width direction of the coil are formed on the inner and outer circumferential surfaces of the coil. There is no danger of the laminate (6) made of copper foil (2) etc. being torn or cut during winding. Even in such a case, dimensional defects caused by distortions, wrinkles, etc. of the copper foil (2) can be prevented. In addition, since the terminals (3) and (4) are made of a solder layer, they are not located in the portions that are not soldered to the laminate (6), thereby preventing poor conduction at the cut portion.

Furthermore, since the terminals (3) and (4) are made of a solder layer with a thickness of 0.2 mm or less, they can be easily wrapped around the core material (7) many times after being attached to the original fabric of the laminate (6). Even if there is, only the terminal portion will not bulge out to a large extent, and the copper foil (2) will be prevented from being torn and disconnected.

The flat coil (1) configured as described above is then mounted on the circuit board (41) as shown in FIGS. 2 and 3. That is, first, as shown in FIG. 2A, a circuit board (41) having a conductive pattern (42) formed on the surface of an insulating board (43) is temporarily fixed to the part where the flat coil (1) is to be placed. Apply adhesive (44) by printing. In addition, the terminal (3) of the flat coil (1),
(4) is a conductive pattern and turn (4) to be electrically connected.
The fine conductive material according to the present invention is applied to the surface of the connection part (42a) of 2)! A cream solder (54) containing (53) is attached, for example, by printing. Note that although only the terminal (3) side is shown in the figure, the same applies to the terminal (4) side (also below).

The thickness d of this cream solder (54) is the flat coil (
The width (that is, the height) t of the terminals (3) and (4) of 1) can be made smaller than the width (i.e., the height) t of the terminals (3) and (4).Next, as shown in FIG. ), (4) are placed on the circuit board (41) so that they are close to the connection part (42a) to which the cream solder (54) is attached and are perpendicular to the surface of the connection part (42a). At this time, when the flat coil (1) is temporarily fixed with the adhesive (44), the terminals (3), (4) and the conductive pattern (
The adhesive (44) may protrude between the connecting portions (42a) of 42).

Next, as shown in Fig. 2C, the flat coil (1) is temporarily fixed and placed in a heating furnace to melt the cream solder (54), which corresponds to the terminals (3), (4), etc. The connecting portion (42a) of the conductive pattern (42) is soldered.

At this time, even if there is a non-solderable part (51) between the coil terminals (3), (4) and the connection part (42a) of the conductive pattern due to the adhesive (44) protruding, the solder (52) Since the fine conductive material (53) is contained therein, the cream solder (54) does not separate but connects the terminals (3), (4) and the connection part (4).
2a) It is possible to solder between them. In addition, since the terminals (3) and (4) of the flat coil (1) are composed of a solder layer, the molten cream solder (45) blends well with the terminals (3) and (4) and rises up. In this way, the terminals (3) and (4) are welded over their entire width (that is, their entire height), resulting in good soldering.

Cream solder (5) containing the above-mentioned fine conductive substance (53)
According to the mounting of the flat coil using 4), paste the cream solder (45) by printing and attach the flat coil (1).
By passing it through a heating furnace in a temporarily fixed state, it is possible to easily and reliably solder the coil, thereby simplifying the mounting of this type of flat coil. Also, since the terminals (3), , and (4) of the flat coil (1) are formed with a solder layer,
Good compatibility with cream solder (45), terminal (3),
Cream solder (4) with a thickness d thinner than the height t of (4)
5) will be reliably soldered even if it is attached.

In the examples shown in FIGS. 2 and 3, the cream solder (54) according to the present invention is applied to the mounting of the flat coil (1), but it is of course applicable to the mounting of chip components other than flat coils. .

The cream solder (54) according to the present invention can also be applied to the case where the terminals (63> and (64)) which are separated from each other on a circuit board etc. are connected by soldering as shown in FIG. At this time, the conductive substance (53) in the solder (52) fills the gap between the terminals (63) and (64), acts as a binder, and acts like a lead wire, so the lead wire (65) is Connect the terminal (63) without using it.
) and (64) can be connected only by soldering. Therefore, soldering can sometimes reduce the process of attaching lead wires and lead wires.

〔Effect of the invention〕

According to the solder material of the present invention, 10 to 1 part of a fine conductive substance having a melting point higher than that of ordinary solder is added to 100 parts by weight of the solder.
00 weight m is mixed, even when soldering between conductive connections that are separated by sandwiching non-solder wettable parts, the solder material does not aggregate and separate on both terminals, allowing for good soldering. can do. Therefore, it is suitable for use, for example, in mounting chip components, connecting conductive connections separated on a substrate, and the like.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of the solder material according to the present invention, FIG. 2 is a process diagram in which the solder material according to the present invention is applied to the mounting of a flat coil, and FIG. 3 is a plan view of the mounted state of the flat coil. FIG. 4 is a plan view of another usage example of the solder material according to the present invention;
Fig. 5 is an external perspective view of the flat coil of the present invention, Fig. 6 is an enlarged sectional view of the main part of the original coil, and Figs. 7 to 10 show an example of the manufacturing process of the flat coil according to the process order. , FIG. 7 is a schematic diagram showing the step of forming an insulating layer on the copper foil, and FIG. 8 is a perspective view showing the step of winding the copper foil around the core material.
Fig. 9 is a perspective view of the coil block, Fig. 1O is an external perspective view showing the coil block after cutting, Fig. 11 is a sectional view showing conventional mounting of chip components, and Fig. 12 and B are explanations of the present invention. 13th process diagram showing the state of soldering subjected to
Prisoner and B are plan views showing other examples of soldering conditions for explaining the present invention. (1) is a flat coil, (3), (4) are terminals, (
41) is a circuit board, (42) is a conductive pattern, (61)
(52) is solder, (53) is a fine conductive material, and (54) is a solder material according to the present invention. Agent Paige Ito
Hidemori Matsukuma Figure 4 Figure 2 - Flat coil J, 4... Naruko 41... 1 Raku ni group 42... -41 LJV turn Figure U Figure 13 Figure 11 Figure 12 Procedure Amendment February 17, 1999

Claims (1)

[Claims] A solder material made by mixing 10 to 100 parts by weight of a fine conductive substance with a melting point higher than that of the solder to 100 parts by weight of the solder.