JP2556971B2 - Solder transfer carrier. Film, solder transfer carrier, film recycling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is applicable to various electronic devices such as an electronic circuit element, an electronic circuit board, and an electronic display element only in a predetermined portion where a solder needs to be formed. Can supply solder,
It is intended to provide a new solder transfer carrier film and a method of transferring solder to a predetermined portion of a transfer target such as an electronic device using the solder transfer carrier film.

[Prior Art] Conventionally, for example, when an electronic circuit element is mounted on an electronic circuit board, preliminary solder is previously provided at a predetermined position of a conductor (and / or a conductor of the electronic circuit element) of the electronic circuit board, and A solder reflow method (reflow soldering method) in which a circuit element is placed on the electronic circuit board and the solder is heated and melted again for electrical connection is widely used.

Then, in order to supply the preliminary solder, as a (conventional example I), a method of screen-printing a solder paste containing a large number of solder powders and a solvent such as a flux on a predetermined conductor portion of the electronic circuit board, or ( As a conventional example II), there is a method of previously immersing the electronic circuit board in a molten solder bath to provide preliminary solder.

In any case, reflow the pre-solder (reheat and melt)
Until then, the electronic circuit element is temporarily fixed (temporarily fixed) on the electronic circuit board.

When the former solder paste is used, the adhesiveness of the paste is used, and when the latter solder dipping method is used, the flux is applied on the preliminary solder to utilize its adhesiveness, or the adhesive is used. The electronic circuit element is temporarily fixed to the electronic circuit board.

[Problems to be Solved by the Invention] However, in the former method (conventional example I) of printing a solder paste, (I.1) solder balls are likely to occur during reflow, which may cause a short circuit. (I.2)
It is difficult to print solder paste on a conductor pattern with a small area. (I.3) If the solder paste sticks out of the conductor when the space (pitch) between adjacent conductors is small, a short circuit occurs. (I.4) Solder amount to be printed is small when the conductor area where the solder is to be provided is small, resulting in a small solder thickness, (I.5) Solder to be supplied It is difficult to control the amount accurately. (I.6) Solder paste is basate (cream) containing volatile solvent, so it is usually several hours after printing solder paste, especially long time. Therefore, there is a drawback in that it is necessary to mount the element on the substrate within a short working time of at most several days.

Also, the latter (conventional example II) solder dipping method requires (II.1) special solder resist treatment in order to eliminate excess solder from adhering to unnecessary locations other than the prescribed locations where solder should be provided. There is (II.2) when dipping in the molten solder bath,
There is a defect that the substrate and the element may be damaged by thermal shock.

[Means for Solving the Invention] The main purpose of the present invention is to eliminate all of the above-mentioned drawbacks. A support film having solder heat resistance and a plurality of predetermined portions on the surface of the support film are provided. Using a solder transfer carrier film consisting of a plurality of solder layers selectively attached to, the solder transfer carrier film is placed on the transfer target such as an electronic circuit element or an electronic circuit board, and the solder layer is By heating and melting, the solder is transferred to a predetermined portion of the transferred body.

The examples of the solder transfer carrier film of the present invention are roughly classified into the following two types.

(A) A solder heat resistant metal layer is provided on a solder heat resistant organic resin film such as a polyimide resin or a polyester resin with or without a solder heat resistant adhesive, and the metal layer is formed. A product in which a plurality of solder layers having a predetermined pattern are provided on the top.

(B) A plurality of solder layers having a predetermined pattern provided on a metal film having solder heat resistance.

The solder transfer carrier film of the above A is a resin film having solder heat resistance, and a metal having heat resistance to solder is deposited on the resin film by vapor phase plating such as vapor deposition or sputtering, or electroless plating. To form a metal layer, or a metal film having solder heat resistance is adhered via an adhesive having heat resistance to solder, and then a well-known photoresist is formed except for a predetermined portion where the solder layer should be provided. Finally, it can be obtained by electrolytically plating a solder layer by a usual electric field plating method using the metal layer as an electrode. The preliminary solder layer obtained by this electrolytic plating has poor storage stability because the solder layer obtained by the dipping method contains impurities dissolved in the molten solder bath, and it is difficult to obtain uniform solder thickness. Since there is no solder contamination, the storage stability is good, high reliability and composition uniformity are obtained, and solder thickness uniformity is obtained.

The solder transfer carrier film B is formed by forming a well-known photoresist on a metal film having solder heat resistance except a predetermined portion where a solder layer should be provided, and using the metal film as an electrode, solder is formed by electrolytic plating. It can be obtained by electrolytic plating.

The resin film, the adhesive layer, the metal layer, or the metal film needs to withstand the temperature at which the solder layer is transferred to the transfer target by heating at the melting temperature or higher.

Further, it is desirable that the solder layer adhered on the metal layer or the metal film be completely thermally transferred to the transfer target,
Therefore, as the metal layer or the metal film, at least the surface of the transferred metal layer of copper, tin or the like having a good solder wettability on the transferred object, nickel, kovar, stainless steel or the like having a poor solder wettability It is desirable to use the above metal.

[Embodiment] The solder transfer carrier of the present invention according to FIGS. 1 and 2.
An example of the film 10 (10a) will be described in detail.

1 is a plan view of the solder transfer carrier film 10a,
FIG. 2 is a sectional view taken along the line AA of FIG.

In FIG. 1 and FIG. 2, the solder transfer carrier film 10a is a large number of island-shaped solder layers having a predetermined pattern such as a rectangle or a circle at predetermined positions on the surface of a flexible film.
It has 20 and a sprocket hole 90 for carrying and positioning, and can be wound on a normal reel (not shown).

In the figure, the solder layer 20 has a plurality of solder layers 20n and 20 (n + 1) each of which has an island-shaped rectangular pattern of two rows and four columns.

The solder transfer carrier film 10a is formed, for example, on a heat resistant resin film 40 such as polyimide, polyether imide, fluororesin, polyester (polyethylene terephthalate) or the like via a heat resistant adhesive layer 60 such as epoxy resin, Metal layer 30a such as metal foil such as copper and aluminum
, A well-known photolithography method, a screen printing method, etc., about 1 to 100 microns of polyimide resin, photosensitive polyimide resin, cyclized polybutadiene leaving a predetermined pattern-shaped solder layer formation scheduled portion on the metal layer 30a. A heat resistant resist layer 50 such as resin is provided, and a photoresist layer
For example, the solder layer 20 having a thickness of about 5 to 500 μm is provided on the exposed surface of the metal layer 30a where the 50 is not formed.

The copper foil 30 is provided on the resin film 40 via the adhesive layer 60.
A commercially available flexible printed wiring board (FPC) can be used as a stack of a. For example, commercially available polyimide
The soldering heat resistance temperature of base and polyester base FPC is
320 degrees C, 30 seconds, 190 degrees C, 20 seconds or more, base thickness
12,25,50,75,100,125 micron, copper foil thickness 18,35 micron, adhesive layer thickness around 20 micron.

At least the exposed surface of the metal layer 30a is coated with a metal having poor solderability such as nickel, copearl, or stainless steel, which is easy to transfer the solder to the transfer target at the time of solder transfer by heating, which will be described later, by plating or the like. Is desirable. Metal layer
When electrolytic plating is performed with a metal having poor solderability using 30a as an electrode, a metal plating layer having poor solderability, that is, the solder layer 20 easily thermally transferred, is formed only on the exposed surface of the metal layer 30a.

The large number of solder layers 20 can be formed to have an arbitrary predetermined thickness of, for example, 5 to 500 microns by electrolytically plating the solder using the metal layer 30a as a common electrode.

It is also possible to form the solder layer 20 by putting the exposed surface side of the metal layer 30a in a molten solder bath or by printing a solder paste and then heating it to melt and cool the solder. However, in this case, at least the surface thereof needs to be a metal having a good solderability such as copper, which makes it difficult to completely transfer the solder layer 20 to the transfer target at the time of transfer.

Therefore, when the solder layer 20a is formed by the former electrolytic plating method on the metal layer 30a where at least the exposed surface is coated with a metal having poor solderability by plating or the like, complete transfer of the solder layer 20 at the time of solder transfer Is possible.

As the material of the solder layer 20, tin 63-lead 37% eutectic alloy (melting point: 183 ° C, soldering temperature: usually 200 to 300 ° C)
Most common tin-lead type solders such as, for example, well-known low melting point solders (melting point 70 to 170 ° C.) in which low melting point metals such as Bi, In and Cd are added to the above Sn and Pb in order to lower the melting point. ) Etc. are used.

The solder heat resistant temperature of the resin film 40 is, for example, 320 ° C. for polyimide resin, 30 seconds or more, and 190 ° C. for polyester resin.
C, 20 seconds or more, and since the fluororesin and the polyether-imide resin are located between polyimide and polyester, the solder material is selected and used in consideration of the solder heat resistance temperature of the resin. That is, for example, in the case of polyimide, it is preferable to use the eutectic alloy having a melting point of 183 degrees, and in the case of polyester, it is preferable to use the low melting point solder having a lower melting point.

It is desirable to apply a soldering flux on the solder layer 20 of the solder transfer carrier film 10a in advance.

An embodiment of a method for transferring a solder layer onto any transfer target 70 using the above-mentioned solder transfer carrier film 10a will be described with reference to FIGS. 3 and 4.

In FIGS. 3 and 4, 10a is a resin film 40 provided with a metal layer 30a via an adhesive layer 60, and solder is applied to the exposed surface (opening) of the metal layer 30a where the resist layer 50 is not formed. layer
Solder transfer carrier film with 20 formed (B in Fig. 1)
-Cross section along line B), 70 is copper, tin-plated copper, silver, silver-
A transfer-receiving body provided with a transfer-receiving portion 70a made of a metal having good solderability such as a palladium, and 80 is a heating tool (heating plate) that also serves as a pressure.

Here, the transferred body 70 means a printed circuit board (that is, a printed circuit or a printed circuit board or a wiring board) such as a resin base or a ceramic base provided with a transferred portion 70a such as a conductor land or a conductor lead. It also includes a flat panel display device such as a liquid crystal display device having a transferred portion 70a in which a metal film having a good solderability is formed in advance on a metal oxide lead electrode.

The solder transfer carrier film 10a having the solder layer 20 formed thereon corresponding to the pattern of the transferred portion 70a of the transferred body 70 is positioned and mounted on the transferred body 70, and a plurality of transferred portions 70a are formed. The plurality of solder layers 20 are brought into contact with each other in a one-to-one correspondence, the heating tool 80 is pressed from above the solder transfer carrier film 10a, and the solder layers 20 are melted at or above their melting temperature, for example, about
When heated to 190 to 300 ° C., the plurality of solder layers 20 on the solder transfer carrier film 10a are melted and collectively transferred onto the plurality of transferred portions 70a on the transferred body 70. After about 3 to 20 seconds, the solder transfer carrier from the transferred object 70
When the film 10a and the heating tool 80 are removed, a plurality of transfer solder layers 20a are formed on the transferred portion 70a on the transferred body 70.

In order to shorten the solder transfer time and transfer the solder completely, it is desirable to heat the transfer target 70 from below to the solder melting temperature or below by a hot plate, infrared rays, or the like.

In order to prevent occurrence of a ridge-like protrusion on the surface of the solder layer 20a and a bridge that short-circuits a plurality of different transfer solder layers 20a adjacent to each other, the thermal transfer operation of the solder described above is performed using a non-heated nitrogen or the like. It is desirable to perform in an active gas atmosphere.

The used solder transfer carrier film 10a shown in FIG. 4 in which the solder has been transferred and almost disappeared is the metal layer 30a.
It is economical because it can be reused a plurality of times by electrolytically plating the solder again with the electrodes as electrodes.

FIG. 5 shows another embodiment of the solder transfer carrier film of the present invention, which is different from the above embodiment in that the resin film 40 is mainly deleted.

In the cross-sectional view of the solder transfer carrier film 10b shown in FIG. 5, 40a is a metal film such as copper or aluminum, 50 is a photoresist layer formed on the upper surface of the metal film 40a, leaving a solder adhesion planned portion, 20 Is a solder layer formed by an electrolytic plating method or the like on the exposed portion (opening) of one surface of the metal film 40a where the photoresist layer 50 is not formed.

In this embodiment as well, similarly to the above embodiment, it is desirable to electrolytically plate the exposed surface of the metal film 40a with a metal having poor solderability. By doing so, it is possible to completely transfer the solder layer 20 on the solder transfer carrier film 10b to the transfer target 70 during solder transfer.

The solder transfer carrier film 10b of this embodiment is similar to the above-described embodiment shown in FIG. 3 and FIG. It is possible to melt and transfer to the transferred portion 70a.

Further, as a conventional technique, Japanese Patent Laid-Open No. 51-50466 is known, which is a method in which a solder paste is printed on the surface of a non-solderable object (indirect body) such as ceramics, rangen, or paper which cannot be soldered. An object is prepared, the surface of the indirect body to which the solder paste is attached is brought into close contact with the wiring board, and heat treatment is performed in this state to transfer the solder onto the wiring board.

Then, a solder paste made by mixing powdered solder and flux is printed on the surface of the indirect member by screen printing.

However, in this conventional technique, the solder paste is volatile and paste-like (cream-like) as in the case where the solder paste is directly printed on the substrate provided with the conductive pattern and the components are mounted and then the reflow soldering is performed. In addition, there is a constraint that the solder should be heated and transferred onto the substrate provided with the conductive pattern within a short working time of usually several hours after the solder paste is printed on the indirect body. Handling of the printed indirect body was troublesome.

Further, in this conventional technique, as in the case where solder paste is printed directly on a substrate provided with a conductive pattern and reflow soldering is performed after components are mounted, solder balls are likely to be generated during reflow, and a pattern with a small area is formed. There are drawbacks such as difficulty in forming a solder layer and difficulty in obtaining uniform transferred solder thickness.

On the other hand, in the present invention, since the solidified solder layer is provided on the surface of the support film to form the solder transfer carrier film, all the above-mentioned drawbacks of the prior art are eliminated, and there is no restriction on the pot life. The advantages are that solder balls are less likely to occur, it is easy to form a solder layer having a pattern of a small area, and the transferred solder thickness is uniform.

[Effects of the Invention] As described above, the present invention provides a solder transfer carrier film having a solder layer attached to a plurality of predetermined locations on the surface of a heat-resistant support film, and a solder transfer method using the same. The solder layer on the above-mentioned solder transfer carrier film is provided in a dry manner by a very simple thermal transfer method.
It is possible to transfer to a predetermined position on a transfer target such as an electronic circuit element or an electronic circuit board, and to provide a solder layer on the transfer target with a good yield.

Further, in the present invention, as compared with the conventional example I in which the solder paste is printed on a predetermined conductor such as an electronic circuit board or an element, a solder transfer carrier film provided with a solid solder layer in advance is used. Defects (I.1) to (I.6) can be eliminated.

Furthermore, in the present invention, compared with the conventional example II in which the electronic circuit board, the element, etc. are immersed in the molten solder bath, since the solder transfer carrier film in which the solder layer is formed in advance only at a predetermined location is used, The drawbacks (II.1) to (II.2) of can be eliminated.

Further, in the present invention, since the solder layer on the solder transfer carrier film is formed by the electrolytic plating method, a solder layer having a uniform thickness and good storage stability can be obtained as compared with the conventional examples I and II. Therefore, the solder thickness is uniform on the transferred object,
A solder layer having good storage stability can be obtained.

Further, as in the embodiment of the present invention, when the metal layer on the solder transfer carrier film or at least the exposed surface of the film is a metal having poor solderability, and the solder layer is electrolytically plated thereon, the solder The solder layer on the transfer carrier film can be completely thermally transferred onto the transfer target, and no solder layer remains on the solder transfer carrier film after the thermal transfer.

Furthermore, the solder transfer carrier film 10 for an electronic circuit board of the present invention is made of a heat-resistant resin film provided with a heat-resistant metal layer or a heat-resistant metal film, and has a long sprocket hole. Have a good support film.

As already mentioned, the sprocket holes provided in this long support film have the advantage that they can be used for transportation and / or positioning. Further, as a result, the normal solder transfer carrier film 10 can be wound up on a normal reel, and the solder transfer carrier film 10 for an electronic circuit board of the present invention can be supplied in a compact reel state. You can

Further, the solder transfer carrier film 10 (10a, 10b) for an electronic circuit board of the present invention is a solder transfer carrier film.
The solid solder layer 20 on the transfer target part 70 of the transfer target body 70 made of an electronic circuit board is composed of conductor lands, conductor leads, etc.
The solid solder is melt-transferred onto the 70a by heating to become the transfer solder 20a.

The used solder transfer carrier film for the electronic circuit board is again electrolytically plated with solder using the metal layer 30a or the metal film 40a as an electrode, and the heat resistant resist layer of the metal layer 30a or the metal film 40a. Solder transfer carrier film for electronic circuit board by attaching the solder layer 20 again to the exposed surface not provided with
10 (10a, 10b) can be reused multiple times.

Therefore, the solder transfer carrier film 10 for an electronic circuit board of the present invention can be recycled and used a plurality of times, so that the present invention is economical and almost eliminates the need for waste materials and disposal. It is an environmentally friendly thing that can.

Further, for the electronic circuit board of the present invention, the solder transfer carrier film 10 can be supplied in the state of the compact reel described above, that is, the solder transfer carrier film 10.
Solder transfer carrier film 10 that has been used in a compact state by sequentially winding it on another normal reel
Can be recovered, and the solder transfer carrier film 10 can be regenerated by electrolytically plating the solder again, and can be reused.

[Brief description of drawings]

The drawings are for explaining the solder transfer carrier film and the solder transfer method of the present invention. FIG. 1 is a plan view showing an embodiment of the solder transfer carrier film of the present invention, and FIG. 2 is a sectional view taken along the line AA of FIG. 3 and 4 are cross-sectional views showing a solder transfer method of the present invention using a solder transfer carrier film (FIG. 3 shows before transfer and FIG. 4 shows after transfer). FIG. 5 is a sectional view showing another embodiment of the solder transfer carrier film of the present invention. (Explanation of symbols) 10,10a, 10b …… Solder transfer carrier film, 20,20a, 2
0n, 20 (n + 1) …… Solder layer, 30a …… Metal layer, 40a ……
Metal film, 50 ... resist layer, 60 ... adhesive layer, 70
... Transfer target (electronic circuit board, electronic circuit element, etc.), 70a
...... Transfer area, 90 sprocket hole.

Claims (2)

(57) [Claims] 1. A solder transfer carrier film capable of transferring a solder layer by heating at a plurality of predetermined positions of an object to be transferred composed of an electronic circuit board. A heat resistant resin film provided with a heat resistant metal layer. Alternatively, a long support film made of a heat-resistant metal film having a plurality of sprocket holes, and solder is attached on the support film so as to expose the metal layer or the metal film at the predetermined position. And a heat-resistant resist layer provided except for a plurality of predetermined locations, at least the exposed surface of the metal layer or the metal film is a metal surface having poor solderability, the exposed surface is a plurality provided by electrolytic plating method. Solder transfer carrier for electrical circuit board transfer, characterized by having a solder layer of
the film. 2. A solder transfer carrier film capable of transferring a solder layer by heating at a plurality of predetermined positions of an object to be transferred composed of an electronic circuit board. A heat resistant resin film provided with a heat resistant metal layer. Alternatively, a long support film made of a heat-resistant metal film having a plurality of sprocket holes, and solder is attached on the support film so as to expose the metal layer or the metal film at the predetermined position. And a heat-resistant resist layer provided except for a plurality of predetermined locations, at least the exposed surface of the metal layer or the metal film is a metal surface having poor solderability, the exposed surface is a plurality provided by electrolytic plating method. And a solder transfer carrier film for electronic circuit board transfer, the solder layer on the solder transfer carrier film being transferred to After transferring to the body, a solder layer is formed again by electrolytic plating on the exposed surface of the metal layer or the metal film on which the heat resistant resist layer is not provided, using the metal layer or the metal film as an electrode. A method for recycling a solder transfer carrier film, which is characterized by: