JP2883204B2 - Solder pre-coated wiring board and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solder precoated wiring board and a method of manufacturing the same, and more particularly, to a solder precoated wiring board capable of mounting components with a high degree of integration and having excellent productivity and a method of manufacturing the same. suggest.

2. Description of the Related Art In recent years, as electronic components such as ICs and LSIs have been reduced in size and density, wiring boards for mounting these components have been required to have a fine pattern. Accordingly, the connection of surface-mounted components to a wiring board also needs to be further refined.

Conventionally, as a technique for connecting such surface-mounted components to a wiring board, a method of soldering, particularly a method of high productivity such as reflow soldering, has been widely used.
This method uses a copper foil part (pad) on the surface of a printed wiring board.
Is a technique in which a paste-like solder is supplied in advance, the surface-mounted components are positioned and mounted, and then the substrate is put into a heating furnace (reflow furnace) to melt and connect the solder.

(A) In this technique, as a method of supplying solder for surface mounting onto a pad of a wiring board, a molten solder plating method, a solder paste printing method, an electrolytic solder plating method, an electroless solder plating method, or the like has been adopted.

However, these solder supply methods have the following problems for performing fine pitch surface mounting.

In the hot-dip solder plating method, it is difficult to control the plating thickness and a uniform film cannot be obtained.

In the solder paste printing method, the limit of the pitch width at which the solder can be supplied is 0.3 mm, and it cannot cope with the narrowing of the pitch.

The electrolytic solder plating method requires a lead for energization,
This complicates the process and lowers the pattern wiring density.

In the electroless solder plating method, the formation of a plating film is a substitution reaction with copper, and it is difficult to increase the film thickness.

Further, as another solder supply method, there is a method in which a Sn film and a Pb film formed on pads of a wiring board by plating are alloyed to supply solder for surface mounting (Japanese Patent Application Laid-Open Nos. 2-101190 and 4-1992). -21795). According to this method, the solder having a desired alloy ratio can be easily and reliably provided on the pads of the wiring board.

However, this solder supply method has the following problems in performing fine pitch surface mounting.

When the Sn film and the Pb film are formed by electrolytic plating, an energizing lead is required, which complicates the process and lowers the pattern wiring density.

When forming a Sn film by electroless plating, it is difficult to increase the thickness.

Since the Sn film and the Pb film are formed as independent layers, it is difficult to completely alloy them during reflow.

(B) On the other hand, recently, a super solder technique and a self-solder QFP technique have been proposed as solder techniques for surface mounting. That is, the super solder is a solder generation technique for selectively depositing an alloy obtained by a heating reaction between the organic acids Pb and Sn on the pads of the wiring board. On the other hand, the self-solder QFP is a technique in which an outer lead (pin) portion of a surface mount component is preliminarily subjected to high-speed electrolytic solder plating and then mounted on a wiring board. Indeed, according to these techniques, fine pitch surface mounting on a wiring board is possible.

However, each of these conventional techniques has a problem that productivity is poor. In other words, the super solder technology has a high manufacturing cost and contains a large amount of solder components in the reaction residue, so that impurities (organic acid P
Since (b, Sn) is present to deteriorate the insulating properties of the resist, there is a problem in that a solid recovery device is required as a washing machine for a production line. On the other hand, the self-solder QFP technology has a manufacturing problem in that it is necessary to apply plating to each mounted component.

As described above, the conventional technique for dealing with the fine pitch surface mounting accompanying the rapid progress of miniaturization of wiring boards, high-density wiring, and miniaturization of surface mounting components, etc., has an insufficient thickness of the solder layer. The reliability of the mounted wiring board is lacking because of sufficient or insufficient required electrical insulation.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a technique relating to a solder pre-coated wiring board that can be mounted at a fine pitch and has excellent productivity.

DISCLOSURE OF THE INVENTION The present inventors have intensively studied to achieve the above object. As a result, the disproportionation reaction of Sn under a high alkali without using a reducing agent (Surface Technology, 16 (1982) 265-27)
5, U.S. Pat. No. 4,269,625) and a substitution reaction between Cu and Sn, Sn and Pb utilizing ionization tendency, by electroless plating, a desired thickness and a desired Sn / P after melting.
The inventors have found that a metal layer for electronic component connection having a b ratio can be formed and completed the present invention.

That is, the present invention provides a solder pre-coated wiring board in which a solder layer required for mounting is provided in advance on a conductor for connecting electronic components of the wiring board, wherein the solder layer is formed of at least one of a Sn thin film layer and a Sn crystal particle. And a Pb-coated Sn layer containing particles coated with a Pb film.Preferably, a Sn thin-film layer and at least a part of Sn crystal particles are formed of Pb. A solder pre-coated wiring board, characterized in that the metal layer formed of a Pb-coated Sn layer containing particles coated with a film is melted by heating to form an alloy layer.

Then, the method for manufacturing a solder precoated wiring board of the present invention, in which a solder layer required for mounting is provided in advance on a conductor for connecting electronic components of the wiring board, includes the steps of: (a) to (c): (A) a step of forming a Sn thin film layer on an electronic component connecting conductor of a wiring board on which a conductive circuit is formed; (b) Sn is selectively deposited on the Sn thin film layer by a Sn disproportionation reaction. (C) forming at least a portion of each Sn crystal particle in the Sn crystal layer by a Sn-Pb substitution reaction based on ionization tendency.
A step of forming a Pb-coated Sn layer by coating with a Pb film, and the following steps (a) to (d); and (a) a wiring board on which a conductor circuit is formed. Forming a Sn thin film layer on the electronic component connecting conductor of (b), forming a Sn crystal layer by selectively depositing Sn on the Sn thin film layer by a Sn disproportionation reaction; (C) At least a part of each Sn crystal particle in the Sn crystal layer is subjected to Sn-Pb substitution reaction based on ionization tendency.
A step of forming a Pb-coated Sn layer by coating with a Pb film, and (d) a Pb coating containing particles formed by coating the Sn thin film layer formed in the above step and at least a part of the Sn crystal particles with the Pb film.
And melting the Sn layer by heating, and then cooling it to form an alloy layer.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a manufacturing process diagram showing one embodiment of a printed wiring board used in the present invention, and FIG. 2 is a manufacturing process diagram showing one embodiment of a solder supply in the method of the present invention. is there. Here, reference numeral 1 in the drawing denotes a substrate, 2 denotes an adhesive layer (insulating layer), 3
Is a resist, 4 is a Cu pad, 5 is a Sn thin film layer, 6 is a Sn crystal layer, and 7 is a Pb film.

BEST MODE FOR CARRYING OUT THE INVENTION The solder pre-coated wiring board of the present invention will be described in detail.

The present invention is not a technique using a conventional electroless eutectic solder plating solution. This is a technique in which a metal layer that becomes a desired solder alloy layer when melted by previously using a Sn electroless plating solution and a Pb electroless plating solution separately is provided on a conductor for electronic component connection in advance. .

In particular, the present invention is a technology for electroless plating of Sn crystals.
It is characterized by using a Sn disproportionation reaction and forming the metal layer from a Sn thin film layer and a Pb-coated Sn layer containing particles in which at least a part of Sn crystal particles is coated with a Pb film. There is.

By adopting such a configuration, it is possible to eliminate the shortage of the deposited film thickness, which is a disadvantage of the substitution type electroless eutectic solder plating, and to use a simple two-layer Sn-Pb film, namely, The disadvantage of not being completely alloyed can be eliminated. As a result, not only mounting with a pitch width of 0.3 mm, which was considered difficult, but also mounting with a narrower pitch can be performed with high reliability.

Here, the metal layer for electronic component connection is composed of a Sn thin film layer and a Pb-coated Sn layer, and by melting, finally, the Sn / Pb ratio becomes 99.9 / 0.1 to 80.0 / 20.0. It is desirable to set the composition ratio. The reason is that the Sn content is 99.9%.
If the Pb content exceeds 20.0%, the melting temperature of the solder will be too high, and if the Pb content exceeds 20.0%, the solder after melting will have a very high temperature. This is because it is easily oxidized.

In the present invention, as a wiring board for supplying solder, a board such as a subtractive board or an additive board can be used, and even if any wiring board is used, fine pitch and high-density mounting can be performed as compared with the related art. Become.

Above all, the additive substrate has a unique permanent resist, and since the self-alignment effect of this permanent resist can be used, it is easy to align the surface mount components when assembling, and when reflow soldering after mounting components. This is advantageous because solder bridges can be prevented by the solder dam effect. Therefore, the solder pre-coated wiring board of the present invention using the additive board is suitable for mounting electronic components having a finer pitch.

Next, a method for manufacturing the solder precoated wiring board of the present invention will be described.

(1) In manufacturing the solder precoated wiring board of the present invention, first, a predetermined printed wiring board is obtained by a method such as an additive method or a subtractive method.

Examples of the substrate used for the wiring substrate include a plastic substrate, a ceramic substrate, a metal substrate, and a film substrate. For example, a glass epoxy substrate, a glass polyimide substrate, an alumina substrate, a low-temperature fired ceramic substrate, an aluminum nitride substrate, an aluminum substrate, an iron substrate, a polyimide film substrate, and the like. Then, using these substrates, a single-sided wiring board, a double-sided through-hole wiring board, and a multilayer wiring board such as a Cu / polyimide multilayer wiring board are manufactured.

As a method of forming a conductive circuit on the wiring board, for example, electroless and electrolytic plating of copper, nickel, gold, silver, etc., sputtering of chromium, molybdenum, etc., and paste printing of copper, silver, palladium, tungsten, etc. can be applied. However, it is particularly preferable to use electroless and electrolytic copper plating.

In the manufacturing method of the present invention, after forming the conductor circuit by the above-described various methods, it is also possible to supply different types of metal layers by further various methods.

Further, in the method of the present invention, the above-described conductor circuit is formed by using various methods implemented on a known printed wiring board. For example, there are a method of etching a circuit after applying electroless plating to a substrate and a method of forming a circuit directly when applying electroless plating.

(2) Next, preferably, thiourea is formed on the electronic component connecting conductor of the wiring board on which the conductive circuit is formed as described above.
A Sn thin film layer is formed by a Cu-Sn substitution reaction based on Cu complex formation. This step is necessary before the step of Sn disproportionation plating, since the Sn disproportionation reaction described below does not occur on the Cu surface but only on Sn.

The thickness of this thin film is 0.1 to 2 μm, preferably 0.3 to 0.
It is desirable to set it to 5 μm. The reason for this is that when the thickness is less than 0.1 μm, the Sn disproportionation reaction does not occur, while it is difficult to form a film exceeding 2 μm.

The reason for adding thiourea in this step is, for example,
In the case of the Cu pad, if thiourea is not present, the standard electrode potential of Cu is more noble than the standard electrode potential of Sn, so that substitutional precipitation of Sn does not occur on the Cu pad. In the presence of SN (NH ₂ ) ₂ ), Cu forms a thio complex, so that the standard electrode potential shifts in a more negative direction than that of Sn, whereby substitutional precipitation of Sn can be performed.

The metal forming the conductor is not limited to Cu, but may be Ni, Au, Ag, Cr, W, Mo, or the like.
In this case, the standard electrode potential of the conductor circuit metal needs to be lower than that of Sn.

(3) Next, an Sn crystal layer is formed on the Sn thin film layer formed on the electronic component connection conductor of the wiring board by electroless plating by a disproportionation reaction of Sn based on selective deposition on Sn. I do.

The electroless plating by disproportionation reaction of Sn, from alkaline solution free of reducing agents, disproportionation Asuzusan ^{_{ion, 2Sn (OH) 3 - →}} Sn + Sn (OH) 6 2- by place, It refers to self-catalytic electroless plating.

The Sn crystal layer obtained in this manner is in a state in which crystal grains are aggregated because the precipitated crystals are coarse, and therefore, becomes porous. Pb coating obtained when substituting at least a part of each Sn crystal particle of such a porous crystal layer with Pb
The Sn layer is easier to form a complete alloy layer at a lower temperature than the simple Sn-Pb two-layer structure according to the prior art.

This Sn crystal particle, in order to respond to fine patterning, to reduce its average particle diameter, 1 ~ 100μm,
Preferably, the thickness is about 50 μm. The reason for this is that if the average particle size of the Sn crystal particles is less than 1 μm, it is necessary to slow down the precipitation rate of the Sn crystals, so that in order to obtain a Sn layer of a desired thickness, the plating time becomes longer, and the plating resist becomes longer. This is because it cannot withstand a high-temperature, highly alkaline plating bath. On the other hand, when the average particle diameter of the Sn crystal particles exceeds 100 μm, the surface area of the Sn crystal particles for substituting Pb decreases.

The precipitation rate of the Sn crystal particles is, in terms of thickness after melting,
It is desirable to set it to 1 to 50 μm / hr. The reason for this is that if the deposition rate is less than 1 μm / hr, the plating resist cannot withstand a high-temperature, highly alkaline plating bath, while if the deposition rate exceeds 50 μm / hr, the average particle size of the Sn crystal particles Is increased, and the surface area for replacing Pb is reduced.

Here, the source of Sn may be a Sn (II) metal salt, preferably chloride (SnCl ₂ .2H ₂ O), acetate (Sn (CH ₃ COO) ₂ ), borofluoride (Sn (B
F ₄ ) ₂ ) and sulfate (SnSO ₄ ) are preferred.

In the prior art, it was difficult to obtain a Sn film having a thickness of 20 μm or more by electroless plating. In this regard, in the electroless plating using the disproportionation reaction, a Sn film having a thickness of 20 μm or more can be easily obtained.

(4) The Sn formed by the disproportionation reaction of Sn
At least a portion of the Sn crystal grains in the crystal layer are replaced with Pb by a Sn-Pb substitution reaction based on ionization tendency, and Pb
A solder pre-coated wiring board having a film formed and a metal layer for forming a solder layer formed on a conductor for connecting electronic components is manufactured.

Pb coating in which Sn crystal layer is partially substituted with Pb by disproportionation reaction
Since the layer structure of the Sn crystal layer is an aggregate of Sn crystal particles, the Sn layer has a structure in which the surface of the Sn crystal particles is covered with a Pb film.

The Sn-Pb substitution reaction based on this ionization tendency is performed at room temperature to
It is desirable to carry out at 90 ° C., preferably at about 50 ° C. The reason is that when the temperature is lower than room temperature, the reaction rate becomes slow, and when it exceeds 90 ° C., the reaction rate becomes too fast, and it becomes difficult to control the composition of Sn / Pb.

The Pb film obtained by substituting at least a part of the Sn crystal grains by the Sn—Pb substitution reaction based on the ionization tendency has a thickness of 0.1 to 5 μm, preferably 0.3 to 3 μm. The reason for this is that if the thickness of the Pb film is less than 0.1 μm, a solder alloy layer cannot be formed between the Sn thin film layer and the Pb-coated Sn layer, while the Pb film has a thickness of 5 μm. If it exceeds, the Pb surface is oxidized.

Here, the source of Pb may be a Pb (II) metal salt, but is preferably a chloride (PbCl ₂ ) or an acetate (Pb
_{(CH 3 COO) 2 · 2H} 2 O), fluoroborate compound (Pb (B
F ₄ ) ₂ ) and nitrate (Pb (NO ₃ ) ₂ ) are preferred.

(5) More desirably, the solder pre-coated wiring board of the present invention thus manufactured is put into a heating furnace (reflow furnace) and heated, thereby melting the metal layer and alloying (soldering). Solder pre-coated wiring board.

According to the solder pre-coated wiring board of the present invention thus manufactured, the solder is melted and re-solidified by, for example, thermocompression bonding the connection part of the electronic component to the obtained solder layer.
Electronic components can be mounted on a substrate with high reliability.

In mounting such an electronic component, the electronic component is mounted on this alloy layer in advance without alloying the metal layer in a heating furnace (reflow furnace), and then in a heating furnace (reflow furnace). This may be performed by melting and alloying the metal layer.

Example 1 (1) Preparation of additive type printed wiring board (a) A mixture of 1275 parts by weight of melamine resin, 1366 parts by weight of 37% formalin, and 730 parts by weight of water was mixed with 10% sodium carbonate.
After adjusting to H = 9.0 and maintaining at 90 ° C. for 60 minutes, 109 parts by weight of methanol was added to obtain a resin solution.

(B) The resin liquid was dried by a spray drying method to obtain a powdery resin.

(C) The resin powder obtained in (b), the release agent, and the curing catalyst were pulverized and mixed by a ball mill to obtain a mixed powder.

(D) placing the mixed powder in a mold heated to 150 ° C.,
The molded product was held at a pressure of 50 kg / cm ² for 60 minutes. In this molding, the mold was opened and degassing was performed.

(E) The molded product obtained in (d) was pulverized and pulverized with a ball mill to obtain powders having particle diameters of 0.5 μm and 5.5 μm.

(F) Dissolve 60 parts by weight of phenol novolak type epoxy resin (manufactured by Yuka Shell), 40 parts by weight of bisphenol A type epoxy resin (manufactured by Yuka Shell) and 5 parts by weight of imidazole-based curing agent (manufactured by Shikoku Kasei) in butyl cellosolve acetate Then, with respect to 100 parts by weight of the solid content of this composition, the fine powder prepared in the above (5) was used in a ratio of 15 parts by weight having a particle size of 0.5 μm and 30 parts by weight having a particle size of 5.5 μm. Mix,
Thereafter, the mixture was kneaded with three rolls, and butyl cellosolve acetate was further added to prepare an adhesive solution having a solid content of 75%. The viscosity of this solution was measured according to JIS-K7117 using a digital viscometer manufactured by Tokyo Keiki Co., Ltd. at 20 ° C. for 60 seconds, and it was 5.2 Pa · s at 6 rpm and 2.6 Pa · s at 60 rpm. The value (thixotropic property) was 2.0.

(G) The glass epoxy substrate 1 (see FIG. 1 (a)) is roughened by polishing to form a JIS-B0601R _max = 2 to 3 μm roughened surface, and then the bonding made in (f) above is performed on the substrate. The agent solution was applied using a roll coater (see FIG. 1 (b)). The application method at this time is a coating roll,
The gap between the coating roller and the doctor bar was 0.4 mm, the gap between the coating roller and the backup roller was 1.4 mm, and the transfer speed was 400 mm / s using a coating roll for resist for medium and high viscosity (manufactured by Dainippon Screen). Then, after leaving it to stand horizontally for 20 minutes, it was dried at 70 ° C. to form an adhesive layer 2 having a thickness of about 50 μm (FIG. 1).
(C)).

(H) The substrate (see FIG. 1 (c)) on which the adhesive layer 2 was formed was immersed in an oxidizing agent composed of a 500 g / l chromic acid (CrO ₃ ) aqueous solution at 70 ° C. for 15 minutes to form the adhesive layer 2 After the surface was roughened, it was immersed in a neutralization solution (manufactured by Shipley) and washed with water. The surface of the adhesive layer 2 was activated by applying a palladium catalyst (manufactured by Shipley) to the substrate having the roughened adhesive layer 2 (see FIG. 1D).

(I) Next, the substrate subjected to the treatment (h) was subjected to a heat treatment for immobilizing the catalyst at 120 ° C. for 30 minutes in a nitrogen gas atmosphere (10 ppm).

(J) Next, a resin solution obtained by imparting photosensitivity to the adhesive solution prepared in the above (f) is applied to the substrate treated in the above (i) using a roll coater in the same manner as in the above (g). Applied. The obtained coating layer was subjected to a heat treatment at 80 ° C. for 30 minutes in order to remove the solvent, then exposed through a mask for pattern formation, developed with an Eterna IR (manufactured by Asahi Kasei), and then irradiated with ultraviolet rays (UV Cure) and heat-treated
A plating resist 3 (40 μm thick) was formed (FIG. 1).
(E)).

(K) The substrate obtained in (j) above, on which the plating resist 3 has been formed, is immersed in an electroless copper plating solution having the composition and conditions shown in Table 1 for 11 hours to form a conductor. Electroless copper plating (0.15mm, 0.3mm, 0.5mm) with electroless copper plating with a plating film thickness of 25μm (0.15mm TAB,
An additive type printed wiring board having a Cu pad for mounting 0.3 / 0.5 mm QFP) was formed on the same substrate (see FIG. 1 (f)). At this time, the resist 3 and the plating film
The level difference from the Cu pad 4 was 15 μm.

(2) Pretreatment Next, this electroless copper plated Cu for mounting electronic parts
Printed wiring board having pads 4 (see FIG. 2A)
Was treated with a degreasing solution (alkylate manufactured by Shipley) at 70 ° C. for 5 minutes, washed with water, and then treated with an activating solution (usually soft etch) at room temperature for 10 seconds to obtain a solder-supplied plating substrate.

(3) Formation of Sn thin film layer 5 (see FIG. 2 (b)) The substrate obtained in the above (2) is prepared by dissolving a borofluoride solution of thiourea and tin (Sn (BF ₄ ) ₂ ) in water. By immersing for about 1 minute in the adjusted electroless Sn-substituted plating solution having the composition and conditions shown in Table 1, the Cu surface was replaced with a Sn layer, and the thickness of the Sn-plated film was 0.3 to 0.5 μm. Was given.

(4) Formation of Sn crystal layer 6 (see FIG. 2 (c)) After the substrate subjected to the plating treatment of the above (3) is washed with water, a solution of sodium hydroxide in water is added to tin chloride ( A solution prepared by dissolving stannous chloride / dihydrate in water was added with stirring, and finally, formalin was added as a stabilizer to adjust the composition and conditions of the electroless Sn thick plating solution (Table 3). (Using a disproportionation reaction of Sn) for 3 hours to form a Sn crystal layer on the Sn thin film 5 obtained in the above (3), and the maximum height of the layer becomes 100 to 150 μm. Electrolytic Sn thick plating was applied. According to the observation of the surface and the fracture surface, the obtained thickened Sn crystal layer was an aggregate of crystal particles. The average size of the crystal grains was about 50 μm. The deposition rate of Sn crystal particles is 25μ in terms of thickness after melting.
m / hr.

(5) Formation of Pb film 7 (see FIG. 2 (d)) After the substrate subjected to the treatment of (4) is washed with water, adjustment is performed by dissolving a lead (II) tetrafluoroborate solution and borofluoric acid in water. Of the composition and conditions shown in Table 4
By immersing in Pb displacement plating solution for 6 minutes, the above (4)
The surface of the Sn crystal particles of the Sn crystal layer 6 obtained in the step (b) was coated with a Pb film (estimated to
(3 to 3 μm), and electroless Pb substitution plating was performed to superficially substitute.

(6) Post-processing Next, after the substrate subjected to the processing of (5) above is washed with water, dried at 80 ° C. for 10 minutes in a hot air drier, and a metal (Sn, Pb) for mounting electronic components is plated. Thus, an additive type solder pre-coated wiring board supplied on the Cu pad 4 was obtained (see FIG. 2).

The composition of the connecting metal for mounting electronic components was determined by melting the metal (Sn, Pb) supplied by simple plating and heating the solder pre-coated wiring board and alloying the same, and as a result of Sn / Pb The ratio was 6/4.

(7) Mounting of electronic components Next, without heating this additive type solder pre-coated wiring board, in the case of 0.3, 0.5 mm QFP,
It is mounted by heating it with a reflow machine after mounting it in the corresponding location, while in the case of 0.15mm TAB, it is mounted by heating it with a hot bar (pulse heating method) after mounting it in the relevant location did.

Example 2 (1) A metal for mounting an electronic component by performing the same processing as the steps (1) to (6) of Example 1 (solder after melting: Sn / Pb ratio is 6/4) Was supplied onto a Cu pad by plating to obtain an additive-type solder precoated wiring board.

(2) Next, the wiring board was immersed in an organic heat medium at 210 ° C. for 5 seconds to melt and alloy Sn and Pb supplied on copper. At this time, the solder (Sn
/ Pb ratio: 6/4) has a shape in which a chord is drawn on the resist wall portion having the Cu lead width or the same height.

(3) Next, the same process as the process shown in (7) of Example 1 was performed to mount various electronic components.

Example 3 (1) In Example 1 (5), except that in the step shown in (5), the substrate was immersed in a Pb-substituted plating solution for 2 minutes.
The same processes as in the steps (6) to (6) were performed to obtain an additive-type solder precoated wiring substrate.

(2) Next, after heat-treating and alloying this wiring board (Sn / Pb ratio: 9/1), the same processing as in step (7) of Example 1 is performed to mount various electronic components. did.

Example 4 (1) A copper-clad laminate (rolled copper foil layer having a thickness of 18 μm) was subjected to various lead pitches (0.1
A subtractive printed wiring board having Cu pads for mounting electronic components (5, 0.3, 0.5 mm) was obtained.

(2) Next, the same processing as in the steps (3) to (6) of Example 1 is performed, and a metal (solder) for mounting an electronic component on the copper and the copper side wall is supplied by plating. As a result, a subtractive type solder pre-coated wiring substrate was obtained.

(3) Next, the wiring board was immersed in an organic heat medium at 210 ° C. for 5 seconds to melt and alloy Sn and Pb supplied on the copper and the copper side wall. At this time, the solder alloyed by melting (Sn / Pb ratio: 6/4) had a shape surrounding the Cu pad.

(4) Next, the same processing as in the step (7) of Example 1 was performed to mount various electronic components.

Comparative Example 1 (1) The same process as in the step (1) of Example 1 was performed to obtain an additive-type printed wiring board on which Cu conductor portions having various pad pitches were formed.

(2) Next, the wiring board was soldered with a solder printing machine (manufactured by Yokota Seisakusho) to apply a solder paste (manufactured by Tamura Seisakusho) having a particle size of 20 to 38 μm through a metal mask at a squeegee speed of 2 to 50 μm.
Printing was performed at 3 cm / s, and 50 μm solder (Sn / Pb ratio: 6/4) was supplied. In addition, it was not possible to supply solder with high accuracy on Cu pads having a pitch of 0.3 mm or less. Also, the thickness of the solder varied due to the lead pitch.

(3) Next, the same process as the process shown in (7) of Example 1 was performed to mount various electronic components.

Comparative Example 2 (1) The same process as in (1) of Example 1 was performed to obtain an additive-type printed wiring board on which Cu conductor portions having various pad pitches were formed. In addition, to all pads,
An energizing lead was provided in advance.

(2) Next, this wiring board is subjected to electrolytic solder plating by a conventional method, and a 50 μm solder (Sn / Pb ratio: 6 /
4) supplied.

(3) Next, the same process as the process shown in (7) of Example 1 was performed to mount various electronic components.

Comparative Example 3 (1) The same processing as in each step shown in (1) of Example 1 was performed to obtain an additive-type printed wiring board on which Cu conductor portions having various pad pitches were formed.

(2) Next, after preprocessing this wiring board, room temperature electroless solder plating (Cu replacement type) was performed.
Only 〜15 μm solder (Sn / Pb ratio: 6/4) could be supplied. This is a pad with solder formed by plating
Since the substitution reaction with Cu is used, the supply thickness is limited to the solder thickness.

(3) Next, the same process as the process shown in (7) of Example 1 was performed to mount various electronic components.

Comparative Example 4 (1) The same processing as in each step shown in (1) of Example 4 was performed to obtain a subtractive printed wiring board on which Cu conductor portions having various pad pitches were formed.

(2) Next, this wiring board was subjected to the same processing as the step shown in (2) of Comparative Example 1, a solder paste was printed on the board, and solder was supplied on Cu pads having various lead pitches. Similarly, on a 0.3 mm pitch or less Cu pad,
Solder could not be supplied with high accuracy, and the supply thickness varied.

(3) Next, the same process as the process shown in (7) of Example 1 was performed to mount various electronic components.

Comparative Example 5 (1) The same processing as in each step shown in (1) of Example 4 was performed to obtain a subtractive printed wiring board on which Cu conductor portions having various pad pitches were formed. It should be noted that all the pads were provided with energizing leads in advance.

(2) Next, this wiring board is subjected to the same processing as the step shown in (2) of Comparative Example 2, and a 50 μm solder (Sn / Pb ratio: 6/4) is supplied on the substrate Cu pad by electrolytic solder plating. did.

(3) Next, the same process as the process shown in (7) of Example 1 was performed to mount various electronic components.

Comparative Example 6 (1) The same processing as in each step shown in (1) of Example 4 was performed to obtain a subtractive printed wiring board on which Cu conductor portions having various pad pitches were formed.

(2) Next, this wiring board is subjected to the same processing as the step shown in (2) of Comparative Example 3, and the board is subjected to electroless solder plating.
A solder of 10 to 15 μm (Sn / Pb ratio: 6/4) was supplied on the Cu pad.

(3) Next, the same process as the process shown in (7) of Example 1 was performed to mount various electronic components.

As described above, a solder pre-coated wiring board in which the solder is supplied onto the Cu pad by using various solder supply methods (the method of the present invention, the solder paste printing method, the electrolytic solder plating method, and the electroless displacement solder plating method) alone Table 5 shows the mounting reliability of electronic components (0.15TAB, 0.3QFP, 0.5QFP) with various lead pitches. As is evident from the results shown in this table, it was confirmed that surface mounting was possible in a wide range (rough pitch, fine pitch) in the mounting using the solder precoated wiring board of the present invention.

In addition, in the case of the electrolytic solder plating in the comparative example of Table 5, a lead for energization is required, which causes a problem that the wiring density is reduced and the productivity is very poor. Also,
In the case of electroless displacement solder plating, it is difficult to increase the thickness of the solder layer, and it is necessary to supply the solder on the rough-pitch Cu pad by some other method, so that there is a problem that productivity is very poor. Further, in the case of the solder paste printing method, there is a problem that it is difficult to supply a reliable solder onto a fine pitch Cu pad (0.3 mm or less).

In this regard, in the case of the method of the present invention, the above-described various problems do not occur, and it is understood that this is a very useful technique.

INDUSTRIAL APPLICABILITY As described above, the solder pre-coated wiring board according to the present invention has excellent characteristics as compared with the conventional surface mounting board, allows finer pitch mounting, and has excellent productivity. Therefore, in addition to mounting with a pitch width of 0.3 mm,
Further, it is used with high reliability for mounting at a narrow pitch.

In particular, since a solder pre-coated wiring substrate using an additive substrate has a unique permanent resist, the self-alignment effect of the permanent resist can be used.
As a result, it becomes easy to align the surface-mounted components at the time of assembling, and at the same time, at the time of solder reflow after mounting the components, it becomes possible to prevent solder bridges by a solder dam effect.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05K 3 / 24,3 / 34 C23C 18 / 48,18 / 52

Claims (13)

(57) [Claims] 1. A solder pre-coated wiring board in which a solder layer required for mounting is previously provided on an electronic component connecting conductor of the wiring board, wherein the solder layer is formed of a Sn thin film layer and at least a part of Sn crystal grains. A Pb-coated Sn layer containing particles coated with a Pb film,
A solder pre-coated wiring board characterized by being formed by: (2) A metal layer formed of a Sn thin film layer and a Pb-coated Sn layer containing particles in which at least a part of Sn crystal particles is coated with a Pb film, is heated and melted to form an alloy layer. The pre-coated solder wiring board according to claim 1, wherein: 3. The solder pre-coated wiring board according to claim 1, wherein the Sn thin film layer has a thickness of 0.1 to 2 μm. 4. The pre-coated solder wiring board according to claim 1, wherein the Sn crystal particles in the Pb-coated Sn layer have an average particle diameter of 1 to 100 μm. 5. The Pb film in the Pb-coated Sn layer has a thickness of
The solder pre-coated wiring board according to claim 1 or 2, wherein the thickness is 0.1 to 5 µm. 6. A method of manufacturing a solder pre-coated wiring board in which a solder layer required for mounting is previously provided on a conductor for connecting electronic components on a wiring board. Forming a Sn thin film layer on the electronic component connecting conductor of the substrate; (2) forming a Sn crystal layer by selectively depositing Sn on the Sn thin film layer by a Sn disproportionation reaction; (3) At least a part of the Sn crystal grains in the Sn crystal layer is converted to Pb by Sn-Pb substitution reaction based on ionization tendency.
Forming a Pb-coated Sn layer by coating with a film. 7. A method of manufacturing a solder pre-coated wiring board in which a solder layer required for mounting is preliminarily provided on an electronic component connecting conductor of the wiring board. A step of forming a Sn thin film layer on a conductor for connecting electronic components of a wiring board; and (2) a step of selectively depositing Sn on the Sn thin film layer by a Sn disproportionation reaction to form a Sn crystal. (3) At least a part of the Sn crystal grains in the Sn crystal layer is converted to Pb by Sn-Pb substitution reaction based on ionization tendency.
A step of forming a Pb-coated Sn layer by coating with a film, (4) a Pb coating containing particles formed by coating the Sn thin film layer formed in the above step and at least a part of Sn crystal particles with a Pb film.
And melting the Sn layer by heating, and then cooling the Sn layer to form an alloy layer. 8. The method according to claim 6, wherein the method of forming the Sn thin film layer on the electronic component connecting conductor is a Cu-Sn substitution reaction based on the formation of a Cu complex of thiourea. Manufacturing method of solder pre-coated wiring board. 9. The method according to claim 6, wherein the Sn thin film layer has a thickness of 0.1 to 2 μm. 10. The method according to claim 6, wherein the Sn crystal particles in the Pb-coated Sn layer have an average particle diameter of 1 to 100 μm. 11. The method according to claim 6, wherein the Sn crystal layer has a deposition rate of 1 to 50 μm / hr in terms of thickness after melting. 12. The method according to claim 6, wherein the Sn-Pb substitution reaction based on the ionization tendency is carried out at a normal temperature to 90 ° C. 13. The method according to claim 6, wherein the Pb film in the Pb-coated Sn layer has a thickness of 0.1 to 5 μm.