KR100733252B1 - Printed circuit board having high reliable terminals for surface mounting, and manufacturing method thereof - Google Patents

Abstract

A printed circuit board having high reliable surface mounting terminals and a manufacturing method thereof are provided to prevent the interfacial separation phenomenon between a gold layer and an Ni layer or between the Ni layers. In a printed circuit board having a wire bonding terminal for mounting a semiconductor and a soldering terminal for connecting with external parts, the wire bonding terminal and the soldering terminal are composed of a metal layer and an Ni layer formed on the metal layer. The Ni layer includes triple layers having different phosphorus contents.

Description

Printed circuit board having high reliable terminals for surface mounting, and manufacturing method

1 is a schematic illustration of an apparatus for electrolytic metal plating.

2 is a cross-sectional view schematically illustrating a connection state between a mounting terminal and a plating lead wire during electrolytic metal plating.

3 is a cross-sectional view schematically showing a cross section of the mounting terminal in order to explain the connection state during electroless metal plating.

4 is a cross-sectional view schematically illustrating a layer structure of a printed circuit board surface mount terminal according to an exemplary embodiment of the prior art.

5 is a cross-sectional view schematically illustrating a layer structure of a printed circuit board surface mount terminal according to another exemplary embodiment of the prior art.

6 is a schematic cross-sectional view of a layer structure of a printed circuit board surface mount terminal according to another exemplary embodiment of the prior art.

7 is a schematic cross-sectional view of a layer structure of a printed circuit board surface mount terminal according to another exemplary embodiment of the prior art.

8 is a schematic cross-sectional view of a layer structure of a printed circuit board surface mount terminal according to another exemplary embodiment of the prior art.

9 is a schematic cross-sectional view illustrating a layer structure of a printed circuit board surface mounting terminal according to an exemplary embodiment of the present invention.

10 is a schematic cross-sectional view of a layer structure of a printed circuit board surface mount terminal according to another exemplary embodiment of the present invention.

11 is a schematic cross-sectional view of a layer structure of a printed circuit board surface mounting terminal according to another exemplary embodiment of the present invention.

※ Explanation of code about main part of drawing ※

1 plating bath 2 anode

3: electrolyte solution 4: substrate (cathode)

6: power

10: mounting terminal 20: plating lead wire

110: Au plating layer 120: Ni plating layer

130: Cu layer 140: corrosion pores

150: solder 160: black spot

170: barrier layer 180: low P-containing Ni plating layer

190: high P-containing Ni plating layer 200: pure nickel layer

210: bonding wire 220: intermetallic compound layer

The present invention relates to a printed circuit board having a high reliability surface mount terminal and a method of manufacturing the same. More specifically, in the surface mount terminal including the copper layer and the nickel layer, the nickel layer may be composed of triple layers having different phosphorus contents to prevent corrosion and black spots of the surface mount terminal. The present invention relates to a printed circuit board having a high reliability surface mount terminal capable of providing a smooth bonding surface at the time of bonding and preventing interfacial separation of terminals.

Manufacturing printed circuit boards that drive electronics is a collection of numerous processes and the steps are very complex. Among them, a key role for delivering current, voltage, and signal to electronic devices is a wire bonding pad or solder joint pad for mounting a chip on a printed circuit board.

Recently, as printed circuit boards are becoming thin and thin, the size of metal wirings is getting smaller, and electroless plating is preferred to electrolytic plating requiring plating lead wire. In addition, a method of satisfying both types of terminal manufacturing is a method in which nickel (Au) plating after nickel (Ni) plating on copper terminals is common.

The metal plating process for outermost chip mounting of a printed circuit board can be roughly divided into the following two types. First, the electroplating method in which an electrode is plated on a printed circuit board and a plated ion source of a metal to be plated, and a method of depositing metal ions in an aqueous solution state, is used by a self-catalytic method without using any electricity from the outside. There is an electroless plating method in which a desired metal is plated on a plated body.

An apparatus for applying the above-described electrolytic plating is schematically shown in FIG.

Referring to FIG. 1, the electrolytic solution 3 is filled in the plating bath 1, and the anode 2 and the substrate 4, which is a cathode for plating, are connected to the power source 6. In the case of using such a method, there is an advantage in that a metal having corrosion resistance can be formed, but as shown in FIG. 2, a plating lead wire 20 is required to plate the mounting terminal 10. Generally, mounting terminals having a diameter of 200 to 400 μm are used to mount chips. In addition, the distance (a) between the terminal has a limit of 500 μm if a mounting lead and a free space of about 100 μm (b) are used to prevent the plating lead wire having a width of 100 μm (c) and ion migration.

On the other hand, electroless plating can be divided into a substitution plating method in which a metal ion to be plated is plated by a substitution reaction with a metal of a plated body and an external reducing agent, or a reduction plating method in which a metal ion to be plated is reduced and plated by itself. have.

The substitution plating method is mainly used for electroless gold plating, and oxidation and reduction reactions as shown in Reaction Schemes 1 and 2, respectively, occur in the plating bath as an example.

Ni ⁰ → Ni ²⁺ + e ^-

Au ^{+ +} e ^- → Au ⁰

In addition, the reduction plating method is mainly used for nickel plating, as an example, the oxidation reaction and the reduction reaction occur as shown in the reaction schemes 3 and 4, respectively, in the plating bath.

^{_{H 2 PO 2 - + H 2}} O → H 2 PO 3 - + 2H + + 2e -

Ni ²⁺ + 2e ^- → Ni ⁰

At this time, as a reducing agent of nickel, sodium hypophosphite, sodium borohydride, hydrazine, etc. are used, and the first and second chemicals are generally used.

The Ni layer plated through this process may contain phosphorus (P) and boron (B). In the case of boron, microcrystalline and ferromagnetic materials exhibit weak surface hardness and poor electrical properties. In addition, when phosphorus is used, the crystal structure is amorphous and the surface hardness becomes strong. At this time, when the components constituting the bath is alkaline, the porosity is not good because it is acidic. In addition, the content of phosphorus in the plating layer is adjusted according to pH. In the case of acidic, for example, pH 4-5, the phosphorus content increases, and in the basic case, the phosphorus content decreases at pH 8 or higher. The hardness varies according to the phosphorus content of the plated layer controlled as described above, which plays an important role in the substitution reaction of the gold plating, which is subsequently carried out, and the higher the hardness, the better the erosion of the nickel surface.

On the other hand, when the mounting terminal is made by the electroless plating method, the plating lead wire is not required as shown in FIG. 3. In this case, even when the diameter of the terminal is 200 to 400㎛, the distance between the terminal and the terminal can be maintained at 300㎛ (a), so that a large number of I / O connections are possible, thereby enabling fine pitch mounting.

However, as shown in FIG. 4, if the substitution reaction is excessive during the gold plating on the nickel layer 120 or the hardness of the nickel layer is not large, corrosion pores 140 called pin holes are formed. Corrosion pores formed in this way may cause separation or deterioration of electrical characteristics by weakening the coupling force of terminals when mounting electronic devices in the future. The cause of the corrosion pores is generated when the content of phosphorus in the nickel plating layer is low.

On the contrary, as shown in FIG. 5, when the phosphorus content is increased to increase the hardness of the nickel layer 120, the black spot 160 is called a black spot 160 on the outer portion of the nickel layer 120 when soldering for component mounting. P-rich layer is formed. The black spot 160 also weakens the bonding force of the mounting terminal and degrades the electrical characteristics of the substrate. In addition, if the content of phosphorus in the nickel plating bath is increased, it is impossible to obtain a uniform plating layer by a heterogeneous substitution reaction of gold.

In order to solve such a problem, as shown in FIG. 6, a barrier layer 170 having a high corrosion resistance and no porosity may be used between the nickel layer 120 and the gold plating layer 110.

For example, the barrier layer 170 may be coated with palladium (Pd) and tin (Sn). However, tin has limited use due to alloy layer formation problem with Ni, and palladium has advantages in corrosion resistance and low porosity, but its price fluctuation is severe and expensive.

On the other hand, in order to solve the above-mentioned problems, for example, Japanese Patent Laid-Open No. 11-354685 discloses a technique in which a nickel layer of a surface mounting terminal is composed of a double layer.

That is, as shown in FIG. 7, a Ni layer 180 having a low phosphorus content is formed on the Ni layer 190 having a high phosphorus content. In this case, when the gold plating thickness for wire bonding is performed, for example, 0.5 μm or more. In the case of gold plating, the corrosion pores 140 as shown in FIG. 4 cannot be avoided, and when the reflow is two or more times, the black spots 160 as shown in FIG. 5 cannot be essentially avoided. .

In addition, as shown in FIG. 8, when the Ni layer 190 having a high phosphorus content is formed on the Ni layer 180 having a low phosphorus content, a rough plating layer is formed when the phosphorus content is high, resulting in uneven gold plating interface. Bad effects on wire bonding. In addition, when the reflow melting the solder several times, the phosphorus is exposed in the high phosphorus-containing layer to form a black spot 160.

Accordingly, the present invention solves the above-mentioned problems of the prior art, and has extensively researched a method for forming a surface mount terminal of a printed circuit board which can prevent Ni corrosion that may occur during the manufacturing or mounting process of a bonding or soldering terminal. As a result, by forming a triple layer when forming the Ni layer, a printed circuit board for a package exhibiting excellent characteristics during wire bonding or soldering for chip mounting was fabricated, and the present invention was completed based on this.

Accordingly, a first aspect of the present invention is to provide a printed circuit board having a highly reliable surface mount terminal capable of preventing corrosion and black spots of the surface mount terminal and a manufacturing method thereof.

A second aspect of the present invention is to provide a printed circuit board having a high reliability surface mount terminal capable of providing a smooth bonding surface during bonding and a method of manufacturing the same.

A third aspect of the present invention is to provide a printed circuit board having a high reliability surface mount terminal capable of preventing the interface separation phenomenon of the terminal and a manufacturing method thereof.

According to one preferred embodiment of the invention:

In a printed circuit board having a predetermined circuit pattern, including a wire bonding terminal for semiconductor mounting and a soldering terminal for coupling with external components,

The wire bonding terminal and soldering terminal is:

A metal layer, and

A nickel layer is formed on the metal layer, and the nickel layer is provided with a printed circuit board comprising a triple layer having a different phosphorus (P) content.

Here, the nickel layer preferably contains phosphorus, which is formed between the first and second nickel-phosphorus alloy layers containing phosphorus but having different phosphorus contents, and the first and second nickel-phosphorus alloy layers. It consists of a pure nickel layer that does not contain.

The nickel layer is preferably formed by sequentially forming a first nickel-phosphorus alloy layer, a pure nickel layer containing no phosphorus, and a second nickel-phosphorus alloy layer on the metal layer, and the first nickel-phosphorus alloy layer The phosphorus content is higher than the silver second nickel-phosphorus alloy layer.

More preferably, the first nickel-phosphorus alloy layer contains 10 to 20% by weight of phosphorus, and the second nickel-phosphorus alloy layer contains 9 to 20% by weight of phosphorus.

On the other hand, it is preferable that the thickness of the said 1st and 2nd nickel- phosphorus alloy layer is 3-10 micrometers, and the thickness of the said pure nickel layer is 1-3 micrometers.

The pure nickel layer is preferably an electrolytic plating layer, a sputter deposition layer, or a nickel metal foil. On the other hand, the nickel-phosphorus alloy layer is preferably an electroless plating layer.

Preferably, it may further include a gold plating layer on the nickel layer.

According to another preferred embodiment of the present invention:

(a) providing a printed circuit board comprising a wire bonding terminal for semiconductor mounting and a soldering terminal for coupling with external components, the circuit board having a constant circuit pattern formed thereon;

(b) forming a photosolder layer on portions of the printed circuit board other than wire bonding terminals and soldering terminals;

(c) forming a first nickel layer on the wire bonding terminal and the soldering terminal;

(d) forming a second nickel layer on the first nickel layer; And

(e) forming a third nickel layer on the second nickel layer;

Provided is a method of manufacturing a printed circuit board comprising a.

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

For reference, the same components and the same reference numerals are assigned to the same components as the conventional components in the drawings, and detailed description thereof will be omitted.

As described above, according to the present invention, there is provided a printed circuit board having a high reliability surface mount terminal that can prevent Ni corrosion that may occur during the manufacturing or mounting process of the bonding or soldering terminal.

The present invention is characterized in that a triple layer having a different phosphorus content is formed at the time of forming the Ni layer. In particular, by adjusting the content of phosphorus (P) contained in the Ni layer can control the change in hardness and volume of the nickel layer to prevent corrosion when forming a corrosion-resistant Ni layer near the terminal that actually requires bonding or on the solder terminal surface can do.

Since recent flip chip mounting packaging substrates require multiple soldering, a large amount of P-containing Ni layer also forms a black spot, which is a deterioration factor of reliability. Therefore, in the present invention, by forming a triple layer having a different phosphorus content to form a corrosion-resistant Ni layer, and more preferably, by inserting a pure Ni layer between the bilayers having a controlled phosphorus content when bonding or soldering for chip mounting A printed circuit board having a high reliability surface mount terminal showing excellent characteristics can be provided.

9, the high-P-containing Ni plating layer 190, the pure nickel layer 200, the low-P-containing Ni plating layer 180, and the gold plating layer on the Cu layer 130 according to one preferred embodiment of the present invention. 110) schematically shows the layer structure of the surface mount terminal of the printed circuit board formed sequentially.

Referring to FIG. 9, first, a Ni layer 190 having a high content of P is plated on the Cu layer 130 for the surface mount terminal. The content of P is preferably 10% by weight or more and 20% by weight or less to increase the hardness, and preferably to maintain the pH of the plating bath at about 4 to 6 to control the content of P. In addition, in order to prevent Cu from diffusing to the mounting terminal surface, the thickness of the Ni layer 190 is suitably 3 to 10 탆. The surface of the Ni layer thus prepared becomes rough due to the high content of P, which adversely affects Au plating for wire bonding.

Therefore, the pure Ni layer 200 is coated on the high phosphorus-containing Ni layer 190. The method of coating includes a method by electroplating, a method by sputtering deposition, a method by laminating a metal thin film, and the like. The thickness of the pure Ni layer 200 is preferably 1 to 3 µm because it does not form a phosphorus (P) layer during soldering, and it is preferable because a smooth pad can be provided even during wire bonding.

Next, the Ni layer 180 containing a relatively small amount of P is plated on the pure Ni layer 200 thus obtained. At this time, the content of phosphorus is maintained at about 6 to 8% by weight, for this purpose it is preferable to maintain the pH of the bath at 8 or more, preferably 8 to 10. As for the thickness of the plating layer 180, 1-3 micrometers is suitable.

As another method for controlling the P content of the Ni layer, increasing the temperature of the plating bath decreases the P content, and lowering the temperature increases the P content. As an example, as the temperature increases from 80 ° C. to 100 ° C., the pH increases from 4 to 6, which reduces the P content by 1 to 2%.

The Au layer 110 is plated on the Ni layer 180 thus formed. The Au layer 110 prevents the corrosion of Ni, provides a smooth bonding surface during wire bonding, and improves wettability when soldering solder.

According to another preferred embodiment of the present invention in FIG. 10, a bonding wire 210 is attached to the high-P-containing Ni plating layer 190, the pure nickel layer 200, and the low-P-containing Ni plating layer on the Cu layer 130. A layer structure of the surface mount terminal of the printed circuit board 180, the gold plating layer 110, and the bonding wire 210 are sequentially formed.

In the case of a conventional low P-containing Ni plated layer, corrosion pores are likely to be generated as shown in FIG. 4, and when a single high-P-containing Ni plated layer is used, a gold plated layer and a nickel plated layer are formed due to an amorphous structure. The likelihood of delamination occurring between them increases. In addition, in the case of the layer structure as shown in FIG. 7, the low-P-containing Ni plating layer having a weak hardness at the top causes corrosion pores, and in the case of the layer structure as shown in FIG. 8, the high-P-containing Ni plating layer is formed at the top. Even when applied, the surface roughness may be increased to lower the bonding strength, or separation may occur between the gold plating layer and the Ni plating layer.

Thus, the structure provided in the preferred embodiment of the present invention provides a pure nickel layer 200 having a high hardness and no surface roughness between the low-P-containing nickel plating layer 180 and the high-P-containing nickel plating layer 190 to be corroded. It can be prevented, and the interfacial separation phenomenon caused by the change in phosphorus content can be prevented by sandwiching the pure nickel layer.

11, the high-P-containing Ni plating layer 190, the pure nickel layer 200, the low-P-containing Ni plating layer 180, on the Cu layer 130 during solder soldering, according to another preferred embodiment of the present invention. The layer structure of the surface mount terminal of the printed circuit board on which the intermetallic compound layer 220 and the solder 150 are sequentially formed is shown.

In general, the solder material may be composed of a mixed material such as tin (Sn) and silver (Ag), and copper (Cu) and bismuth (Bi). When the solder is applied and reflowed, the gold plated layer diffuses into the solder, and the solder forms a nickel layer and an intermetallic compound. In this case, in the case of the low-P-containing Ni plating layer, it is highly likely that nickel forms a black spot by forming a high-P Ni layer due to a rapid chemical reaction with the solder, or a corrosion hole called a Kirkendal void is formed. On the other hand, in the case of the high-P-containing Ni plating layer, the surface roughness is not good, and there is a high possibility of a poor surface corrosion due to the uneven substitution reaction of the gold plating. In addition, even when the double-layer of the low-P-containing Ni plating layer and the high-P-containing Ni plating layer is formed, the interfacial separation may not be prevented due to the occurrence of black spots and a difference in internal stress due to the P content.

On the other hand, in the case of the layer structure shown in FIG. 11 in the present invention, when the alloying proceeds at a conventional reflow temperature of 220 to 260 ° C. for 2 to 10 minutes, the low-P-containing Ni plating layer 180 having a thickness of 1 to 3 μm at the top A portion of the becomes an intermetallic compound 220 together with the gold plating layer formed on the upper portion, and since then, the thin pure Ni layer 200 having high hardness serves as an anti-corrosion barrier. In addition, since the pure nickel layer 200 does not contain phosphorus, reflow may continue or black spots may not occur even after the heat treatment. In addition, the corrosion resistance and hardness also serves to help the connection with the low-P containing Ni plating layer 180 has the advantage of preventing the interface separation.

Although the present invention has been described in detail with reference to specific embodiments, this is for explaining the present invention in detail, and a printed circuit board having a high reliability surface mount terminal according to the present invention and a manufacturing method thereof are not limited thereto. It is apparent that modifications and improvements are possible by those skilled in the art within the technical idea of the present invention.

As described above, according to the present invention, since the Ni layer is composed of triple layers having different phosphorus contents in the surface mount terminal of the printed circuit board, corrosion and black spots can be prevented, and a smooth bonding surface is provided during wire bonding. can do.

In addition, the triple Ni layer structure of the present invention has the advantage of preventing the interfacial separation that may occur between the gold layer and Ni layer or Ni layers that can occur in the conventional double Ni layer structure.

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be apparent from the appended claims.

Claims (16)

In a printed circuit board having a predetermined circuit pattern, including a wire bonding terminal for semiconductor mounting and a soldering terminal for coupling with external components, The wire bonding terminal and soldering terminal is: A metal layer, and And a nickel layer formed on the metal layer, wherein the nickel layer is formed of a triple layer having different phosphorus (P) contents. 2. The phosphorus of claim 1, wherein the nickel layer is formed between first and second nickel-phosphorus alloy layers containing phosphorus but having different phosphorus contents, and the first and second nickel-phosphorus alloy layers. A printed circuit board comprising a pure nickel layer containing no nickel. The method of claim 1, wherein the nickel layer is formed by sequentially forming a first nickel-phosphorus alloy layer, a pure nickel layer containing no phosphorus, and a second nickel-phosphorus alloy layer on the metal layer. The phosphorus alloy layer has a higher phosphorus content than the second nickel-phosphorus alloy layer. 4. A printing according to claim 3, wherein the first nickel-phosphorus alloy layer contains 10 to 20% by weight of phosphorus, and the second nickel-phosphorus alloy layer contains 9 to 20% by weight of phosphorus. Circuit board. The printed circuit board of claim 3, wherein the first and second nickel-phosphorus alloy layers have a thickness of 3 to 10 μm, and the pure nickel layer has a thickness of 1 to 3 μm. The printed circuit board of claim 2, wherein the pure nickel layer is an electrolytic plating layer, a sputter deposition layer, or a nickel metal foil. 4. The printed circuit board of claim 2 or 3, wherein the nickel-phosphorus alloy layer is an electroless plating layer. The printed circuit board of claim 1, further comprising a gold plating layer on the nickel layer. (a) providing a printed circuit board comprising a wire bonding terminal for semiconductor mounting and a soldering terminal for coupling with external components, the circuit board having a predetermined circuit pattern formed thereon; (b) forming a photosolder layer on portions of the printed circuit board other than wire bonding terminals and soldering terminals; (c) forming a first nickel layer on the wire bonding terminal and the soldering terminal; (d) forming a second nickel layer on the first nickel layer; And (e) forming a third nickel layer on the second nickel layer; Method of manufacturing a printed circuit board comprising a. The printing method according to claim 9, wherein the first and third nickel layers are nickel-phosphorus alloy layers containing phosphorus in different amounts, and the second nickel layer is a pure nickel layer containing no phosphorus. Method of manufacturing a circuit board. The method of claim 10, wherein the first nickel layer has a higher phosphorus content than the third nickel layer. The method of claim 10, wherein the first nickel layer contains 10 to 20% by weight of phosphorus, and the third nickel layer contains 9 to 20% by weight of phosphorus. The method of claim 9, wherein the first and third nickel layers have a thickness of 3 to 10 μm, and the second nickel layer has a thickness of 1 to 3 μm. The method of claim 9, wherein the second nickel layer is formed by electroplating or sputter deposition, or is formed by laminating nickel metal foil. 10. The method of claim 9, wherein the first nickel layer and the third nickel layer are each formed by electroless plating. The method of claim 9, (f) forming a gold plating layer on the third nickel layer.

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