KR100648970B1 - Pcb terminal and manufacturing method thereof - Google Patents

Abstract

A PCB(Printed Circuit Board) and a manufacturing method thereof are provided to increase the reliability of a solder coupling by reducing a stress, which is transferred to a solder coupling interface from an end portion of a solder resist. An electronic element is connected to a terminal portion of a PCB, which includes a contact portion(1), a first nickel layer(2), a second nickel layer(3), and the terminal portion. The contact portion is electrically coupled with a circuit. The first nickel layer is laminated on the contact portion. The second nickel layer is laminated on the first nickel layer. The terminal portion includes a metal layer(4), which is formed by surface-treating an upper surface of the second nickel layer. A distance between the upper surface of the contact portion and the upper surface of the metal layer is 5 to 25 mum.

Description

Printed circuit board and its manufacturing method {PCB terminal and manufacturing method

1 is a cross-sectional view of a printed circuit board according to an embodiment of the present invention.

2 is a graph showing the degree of reliability of the solder joint according to the distance between the solder resist end and the solder joint interface.

Figure 3 is a flow chart of a manufacturing method of a printed circuit board according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

1: contact 2: first nickel layer

3: second nickel layer 4: metal layer

5: solder resist 6: solder resist end

9: insulation material

The present invention relates to a printed circuit board, and more particularly, to a printed circuit board and a manufacturing method thereof.

Electroless Nickel Immersion Gold (ENIG) is one of the widely used methods for surface finish of terminal parts and electronic parts of printed circuit boards. After that, the surface-treated terminal portion of the printed circuit board is soldered to make mechanical / electrical connection. At this time, the electroless nickel / gold plated surface and the solder bonding interface are very brittle, and many problems have been reported recently.

 For this reason, Cu OSP (Organic Solderability Preservatives) or surface treatment such as Immersion Sn has been introduced, but there are also many problems in the process. On the other hand, the electroless nickel / gold plating process has a great advantage over other processes due to long storage, uniform surface shape, excellent recognition of the recognition mark in the packaging process.

 Therefore, if only the problem of brittleness is improved, the electroless nickel / gold plating process will be the most competitive method of surface treatment.

 It has been widely recognized that nickel corrosion, such as black pads, is the most influential factor for the solder bond brittleness of electroless nickel / gold plating, and there is no particular significance in the industry.

Another factor is the failure of the solder bond interface to maintain a constant distance from the end of the stress resist solder resist. In other words, conventionally, 2-5 μm of copper etching is usually performed as a pretreatment of an electroless nickel plating process. Thereafter, electroless nickel gold plating of approximately 5 mu m is performed on the etching surface. In conclusion, the distance between the solder bonding interface and the end of the solder resist is in the range of about 0 to 3 μm. This structure becomes a structure in which the stress at the solder resist end can be easily transferred to the solder bonding interface.

The present invention is to provide a printed circuit board and a manufacturing method for reducing the stress generated from the solder resist end to ensure the reliability of the solder bonding.

According to one aspect of the invention, in the terminal portion of the printed circuit board to which the electronic device is connected, a contact electrically connected to the circuit of the printed circuit board, a first nickel layer and a first nickel layer stacked on the contact A printed circuit board includes a terminal part including a second nickel layer stacked on an upper portion of the upper surface of the second nickel layer, and a metal layer formed by surface treatment of an upper surface of the second nickel layer, wherein a distance from an upper surface of the contact point to an upper surface of the metal layer is 5 μm to 25 μm. do.

In addition, (a) forming a contact electrically connected to the circuit on the printed circuit board, (b) plating the first nickel layer on the upper surface of the contact, (c) the second nickel on the upper surface of the first nickel layer Plating the layer, and (d) replacing the surface of the second nickel layer with a metal layer by a substitution reaction according to an ionization tendency, wherein the distance from the surface of the contact point to the surface of the metal layer is 5 μm to 25 μm. Provided is a method for preparing.

The method may further include removing a portion of the contact between steps (a) and (b) to reduce the thickness of the contact. This is to remove the oxide layer on the contact surface. The metal layer may include a gold plated layer. This is to improve the solder bonding force. The first nickel layer may include low tack nickel and the second nickel layer may include high tack nickel.

Hereinafter, a preferred embodiment of a printed circuit board and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings, in the following description with reference to the accompanying drawings, the same or corresponding components regardless of reference numerals The same reference numerals will be given, and redundant description thereof will be omitted.

1 is a cross-sectional view of a printed circuit board to improve the reliability of the solder joint according to an embodiment of the present invention. Referring to FIG. 1, a contact 1, a first nickel layer 2, a second nickel layer 3, a metal layer 4, a solder resist 5, a solder resist sheet end 6, an insulating material 9 The printed circuit board 10 and the terminal portion 20 are shown.

The terminal unit 20 is a portion to which an external device is connected, and is formed by plating the first nickel layer 2, the second nickel layer 3, and the metal layer 4 on the upper surface of the contact 1.

The contact point 1 is located on the upper surface of the insulating material and is connected to the circuit. In general, copper is used as a part formed when the circuit is formed.

The first nickel layer 2 is positioned on the upper surface of the contact 1. As shown in the drawing, the first nickel layer 2 has a predetermined thickness inserted into the contact 1. This is a phenomenon caused by electroless plating after etching the contact 1. On the other hand, the reason for etching the contact 1 is to remove the oxide layer on the surface. If this process is not used, there is a possibility that an oxide or the like remains on the surface of the metal layer. In addition, even if the surface oxide is not completely removed, a non-uniform plating layer is formed on the surface due to the surface roughness, etc., and there is a possibility that a recognition failure of the machine may occur in a later process.

However, if the surface of the contact 1 is processed so that the etching process does not need to be performed, the first nickel layer 2 may be plated directly on the contact 1. The 1st nickel layer 2 is performed by electroless plating, and is a process performed in order to make a fixed thickness. The low nickel nickel is used for the 1st nickel layer 2, and low nickel nickel is a nickel / phosphorus alloy layer containing 5 weight% or less of phosphorus content.

The 2nd nickel layer 3 is located in the upper surface of the 1st nickel layer 2, and is performed by electroless plating. The second nickel layer 3 is made of high phosphorus nickel, which is a nickel / phosphorous alloy layer containing 9 wt% or less of phosphorus. In general, high tack nickel is used in the surface treatment process. However, in the present invention, the first nickel layer 2, which is a low tack nickel layer, is plated before the second nickel layer 3 is formed.

The first nickel layer 2 is to secure a constant thickness, and to form such a thickness layer, the first nickel layer 2 may be electroplated, but there is a need to insert an electric lead wire. Therefore, it is to perform a low-dollar nickel plating that can achieve the fastest speed of the direct plating method. However, the first nickel layer 2 may have a problem such as a black pad. Therefore, when a certain thickness is secured, plating the second nickel layer 3 resistant to the black pad phenomenon may increase corrosion resistance.

The metal layer 4 is positioned on the upper surface of the second nickel layer 3, and the metal layer 4 forms the second nickel layer 3 by a substitution reaction by an ionization reaction. The metal layer 4 is preferably gold.

The solder resist end 6 is positioned on the contact 1 surface, and stress is generated at the solder resist end 6 and transferred to the solder bonding interface 20 and the metal layer 4 surface.

This stress has a certain relation to the distance between the solder resist end 6 and the solder joint interface 20, that is, the distance between the contact 1 surface and the metal layer 4 surface. .

2 is a graph showing the degree of reliability of solder bonding according to the distance between the solder resist end and the solder bonding interface.

As shown in FIG. 2, the reliability of solder bonding is the best at the site where the distance between the solder resist end and the solder bonding interface is 15 μm to 20 μm. When the thickness is 15 μm or less, the stress is transferred from the solder resist end to the solder bonding interface, and the reliability of the solder bonding is not good. When the thickness is too thick, the stress can propagate on the surface, making stress transfer easier. Therefore, the reliability of solder bonding improves in the appropriate distance. However, the first nickel layer of a certain thickness is effective in dispersing the stress at the solder resist end.

The graph of FIG. 2 illustrates a case where the thickness of the solder resist is 35 μm, and the optimum range may be somewhat fluid when the thickness of the solder resist changes.

 Therefore, the distance between the contact surface and the metal layer surface may be 5 µm to 25 µm, preferably 15 µm to 20 µm in consideration of the thickness of the solder resist.

Hereinafter, a method of manufacturing a printed circuit board having improved reliability of solder bonding according to the present invention will be described.

First, a circuit pattern and a semiconductor mounting are formed on a printed circuit board, and this process is typically performed by photolithograpy, which is well known in the art.

 Then, a solder resist is applied to the printed circuit board, the solder resist layer serves as a resist for the gold plating described later. A dry film is affixed to a soldering resist layer, and selectively peels only the solder resist layer part on a terminal part through exposure and image development.

The terminal portion is composed of a contact, a first nickel layer, a second nickel layer, and a metal layer, and is a portion that is connected to a substrate and an external element.

3 is a flowchart illustrating a method of manufacturing a printed circuit board according to an exemplary embodiment of the present invention.

In step S11 of FIG. 3, the first nickel layer is plated on the contact upper surface. It is preferable to plate a 1st nickel layer by electroless plating. The first nickel layer is a step for securing a constant thickness before plating the second nickel layer. Therefore, it is necessary to properly control the plating time to obtain the desired thickness. On the other hand, it is preferable to remove a contact to a fixed thickness before plating a 1st nickel layer. This removes the oxide film remaining at the contact point and is generally performed by an etching process. The first nickel layer is formed of low tack nickel.

If the first nickel layer is plated by a predetermined thickness, the second nickel layer is plated. (S12) Since the plating of the second nickel layer takes a long time, the first nickel layer can be relatively easily secured. After plating, the method of plating the high tack nickel was selected. The second nickel layer is made of high tack nickel.

 In general, the distance from the contact surface to the surface of the second nickel layer is preferably set to 5 µm to 25 µm.

A metal layer is plated on the upper surface of the second nickel layer. (S13) The metal layer is preferably made of gold. The plating method at this time is established by the substitution reaction according to the ionization tendency as follows.

^{_{2Au (CN) 2 - + Ni}} > 2Au + Ni 2 +

Examples of preferred electroless plating solutions used in the present invention include, but are not limited to, gold cyanide as a gold source, nitriloacetic soda as a chelating agent, and an electroless gold plating solution mainly containing citric acid as a complexing agent. . It is preferable that pH of an electroless gold plating solution is 4-7.

Although the technical spirit of the present invention has been described in detail according to the above-described embodiments, the above-described embodiments are for the purpose of description and not of limitation, and a person of ordinary skill in the art will appreciate It will be understood that various embodiments are possible within the scope.

According to the present invention having such a configuration, there is an advantage that the reliability of solder bonding is increased by reducing the stress transmitted from the solder resist end to the solder bonding interface.

Claims (7)

In the terminal portion of the printed circuit board to which the electronic device is connected, A contact electrically connected to a circuit of the printed circuit board; A first nickel layer stacked on the contact; A second nickel layer stacked on the first nickel layer; And a terminal portion including a metal layer formed by surface treatment of an upper surface of the second nickel layer, wherein a distance from an upper surface of the contact point to an upper surface of the metal layer is 5 μm to 25 μm. The method of claim 1, The metal layer is a printed circuit board comprising a gold plated layer. The method of claim 1, The first nickel layer includes a low tack nickel, and the second nickel layer comprises a high tack nickel. (a) forming a contact on the printed circuit board, the contact being electrically connected to the circuit; (b) plating a first nickel layer on an upper surface of the contact; (c) plating a second nickel layer on the upper surface of the first nickel layer; And (d) replacing the surface of the second nickel layer with a metal layer by a substitution reaction according to an ionization tendency, wherein a distance from the surface of the contact point to the surface of the metal layer is 5 μm to 25 μm. The method of claim 4, wherein And removing the portion of the contact between the steps (a) and (b) to reduce the thickness of the contact. The method of claim 4, wherein The metal layer is a manufacturing method of a printed circuit board comprising a gold plated layer. The method of claim 4, wherein The first nickel layer includes a low tack nickel, and the second nickel layer comprises a high tack nickel.

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