JPH1131754A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to connect electrically electrodes of a semiconductor element with a prescribed wiring conductor reliably and firmly via connection pads, without making gold plated layers not peeled from electroless nickel plated layers, by a method wherein the surface roughness of the plated layers is specified. SOLUTION: The mean roughness in the center lines of the surfaces of electroless nickel plated layers 10 is (Ra) and the surface roughness of the layers 10 is set in the extent of 0.5 μm<=Ra<=1.5 μm. Thereby, the adhesive areas of the layers 10 to gold-plated layers 11, which are adhered on these layers 10, become wide and the adhesive strength of both layers 10 and 11 is increased. As the result, even though electrodes 8 under a semiconductor element 3 are connected with connection pads 7 via conductive bonding materials 9 consisting of a solder ball or the like, no peeling is caused between the layers 10 and 11 and the electrodes 8 can be electrically connected with a prescribed metallized wiring layer reliably and firmly via the pads 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board used for a package for housing a semiconductor element for housing a semiconductor element or a hybrid integrated circuit board, and more particularly to a wiring for mounting and connecting a semiconductor element by a flip-chip method. It relates to a substrate.

[0002]

2. Description of the Related Art In recent years, as a method of mounting a semiconductor element on a wiring board used for a package for housing a semiconductor element, a hybrid integrated circuit board, or the like, a semiconductor element is mounted on a connection pad connected to a wiring conductor provided on the surface of the wiring board. A so-called flip-chip type bonding in which the above-mentioned electrodes are directly connected via a conductive bonding material such as solder or silver paste has been frequently used.

[0003] In general, a wiring board used for a package for storing a semiconductor element for use in flip chip bonding or a hybrid integrated circuit board includes an insulating base made of an electrically insulating material such as an aluminum oxide sintered body, and an insulating base made of the insulating base. A wiring conductor made of a refractory metal such as tungsten, molybdenum, or manganese inside and / or on the surface, and an electrical connection with the wiring conductor on the upper surface of the insulating base;
A connection pad made of a metal material such as tungsten, molybdenum, and manganese.The semiconductor element is connected to the connection pad on the surface of the insulating base via a conductive bonding material such as a solder ball. Each electrode of the semiconductor element is mounted on a wiring board and connected to a wiring conductor.

The metal material such as tungsten, molybdenum, manganese or the like which forms the connection pad has poor wettability with a conductive bonding material such as a solder ball, so that the conductive bonding material is strongly bonded to the connection pad. Since the connection pad cannot be formed, a gold plating layer having good wettability with a conductive bonding material is attached to the surface of the connection pad with an electroless nickel plating layer interposed therebetween.

[0005]

However, in this conventional wiring board, the nickel plating layer deposited on the connection pads is formed by an electroless plating method, and the surface roughness of the electroless nickel plating layer is reduced. The surface is extremely smooth with a center line average roughness (Ra) of Ra <0.4 μm. Therefore, when a gold plating layer is applied on this electroless nickel plating layer, the adhesion area between the electroless nickel plating layer and the gold plating layer becomes small, and the adhesion strength between the two becomes weak. When the electrodes of the semiconductor element are connected to each other via a conductive bonding material such as a solder ball, the gold plating layer is peeled off from the electroless nickel plating layer, and the electrodes of the semiconductor element are electrically connected to predetermined wiring conductors via the connection pads. However, there was a drawback that the connection could not be established.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has as its object to increase the adhesion strength between an electroless nickel plating layer and a gold plating layer adhered on a connection pad, and Even when the electrodes of the semiconductor element are connected via a conductive bonding material such as a solder ball, the gold plating layer does not peel off from the electroless nickel plating layer, and the electrodes of the semiconductor element are connected to the predetermined wiring via the connection pads. Secure to conductor,
An object of the present invention is to provide a wiring board capable of firmly connecting electrically.

[0007]

SUMMARY OF THE INVENTION The present invention provides an insulating substrate,
A wiring conductor adhered to the inside and / or the surface of the insulating base; and an electroless nickel plating layer and a gold plating layer formed on the surface of the insulating base so as to be electrically connected to the wiring conductor. A wiring board comprising: electrodes of a semiconductor element which are sequentially applied; and connection pads connected via a conductive bonding material, wherein the electroless nickel plating layer has a surface having a center line average roughness. (Ra) 0.5 μm ≦ Ra ≦
The thickness is 1.5 μm.

According to the wiring board of the present invention, the surface of the electroless nickel plating layer adhered to the connection pad is appropriately adjusted to have a center line average roughness (Ra) in the range of 0.5 μm ≦ Ra ≦ 1.5 μm. Because of the roughening, the adhesion area between the electroless nickel plating layer and the gold plating layer deposited on the electroless nickel plating layer becomes large, and the adhesion strength between the two becomes strong,
As a result, even if the electrodes of the semiconductor element are connected to the connection pads via a conductive bonding material made of solder balls or the like, no separation occurs between the electroless nickel plating layer and the gold plating layer. The electrodes of the semiconductor element can be reliably and firmly electrically connected to predetermined wiring conductors via the connection pads.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1 and 2 show an embodiment in which the wiring board of the present invention is applied to an insulating base of a package for housing a semiconductor element. In the drawings, reference numeral 1 denotes an insulating base, and 2 denotes a lid.
The insulating base 1 and the lid 2 constitute a container 4 for housing the semiconductor element 3.

The insulating base 1 functions as a support member for supporting the semiconductor element 3, and the semiconductor element 3
Is mounted.

The insulating substrate 1 is made of an electrically insulating material such as an aluminum oxide sintered body, a mullite sintered body, an aluminum nitride sintered body, a silicon carbide sintered body, a glass ceramic sintered body, and the like. When it is made of an aluminum oxide sintered body, an appropriate organic binder, a solvent, etc. are added to and mixed with raw material powders of aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, etc. to form a slurry, and the slurry is doctored. A ceramic green sheet (ceramic green sheet) is formed by employing a blade method or a calender roll method. Thereafter, the ceramic green sheet is subjected to an appropriate punching process and a plurality of the green sheets are laminated, and a temperature of about 1600 ° C. It is manufactured by firing.

A plurality of wiring conductors 5 are formed on the upper surface of the insulating substrate 1 from the region where the semiconductor element 3 is mounted and mounted on the upper surface to the lower surface through the inside, and the wiring conductors 5 are exposed on the upper surface of the insulating substrate 1. Each electrode of the semiconductor element 3 is connected to the portion, and an external lead terminal 6 is brazed to a portion extending to the lower surface of the insulating base 1 via a brazing material such as silver brazing.

The wiring conductor 5 functions as a conductive path for connecting each electrode of the semiconductor element 3 to an external lead terminal 6 connected to an external electric circuit, and connects each electrode of the semiconductor element 3 to the wiring conductor 5. As a result, each electrode of the semiconductor element 3 is connected to an external electric circuit via the wiring conductor 5 and the external lead terminal 6.

The wiring conductor 5 is made of a metal having a high melting point, such as tungsten, molybdenum, or manganese. For example, a metal paste such as tungsten or molybdenum is added to an appropriate organic binder and a solvent to form a metal paste. The paste is printed and filled in a predetermined pattern by screen printing into the upper and lower surfaces of the ceramic green sheet to be the insulating substrate 1 and the through holes formed in the ceramic green sheet in advance, so that the paste passes from the upper surface of the insulating substrate 1 to the inside. A predetermined pattern is formed over the lower surface.

As shown in FIG. 2, the region of the wiring conductor 5 exposed on the upper surface of the insulating substrate 1 constitutes a connection pad 7, on which an electrode 8 provided on the lower surface of the semiconductor element 3 is soldered. The electrodes 8 of the semiconductor element 3 are electrically connected to the wiring conductors 5 via the connection pads 7 and the conductive bonding material 9. .

The connection pad 7 is further provided with an electroless nickel plating layer 10 and a gold plating layer 11 sequentially on the upper surface thereof, and the electroless nickel plating layer 10
1 is a connection pad 7 made of tungsten, molybdenum, etc.
The gold plating layer 11 functions to firmly join the electrodes 8 of the semiconductor element 3 to the connection pads 7 via the conductive bonding material 9.

The electroless nickel plating layer 10 is made of, for example, nickel sulfate 20 to 40 g / l, sodium succinate 40 to 60 g / l, boric acid 25
~ 35 g / l, ammonium chloride 25 ~ 35
Grams / liter, dimethylamine borane 2.5-4.
An electroless nickel plating solution of 5 g / liter or the like is prepared, the surface of the connection pad 7 is degreased and acid-treated, and then immersed in a solution containing a catalyst agent to perform an activation treatment. 7 is immersed in the electroless nickel plating solution set at 60 to 65 ° C. for 30 to 60 minutes, so that the surface of the connection pad 7 has a predetermined thickness (2
μm to 8 μm).

The gold plating layer 11 may be made of, for example, potassium hydroxide 20 to 40 g / l, ethylenediaminetetraacetic acid 30 to 50 g / l, potassium dihydrogen phosphate 15 to 45 g / l, potassium cyanide 0.01 to 45 g / l. A gold plating solution (liquid temperature: 85-95 ° C.) consisting of 0.1 g / -liter, potassium gold cyanide 1-4 g / liter, etc. is prepared, and the electroless nickel plating layer 10 is adhered to the surface thereof. A predetermined thickness (0.02 μm to 0.3 μm) is formed on the electroless nickel plating layer 10 by immersing the connection pad 7 thus formed for 5 to 15 minutes.
Is adhered to.

If the thickness of the electroless nickel plating layer 10 is less than 2.0 μm, it becomes difficult to firmly attach the gold plating layer 11 to the connection pad 7.
When the thickness exceeds μm, a large stress is generated when the electroless nickel plating layer 10 is formed, and the stress is present inside the electroless nickel plating layer 10, and the connection pad 7 and the electroless nickel plating layer 10 There is a tendency that the reliability of adhesion is greatly reduced. Therefore, the electroless nickel plating layer 10 has a thickness of 2.0 μm to
It is preferable to set the thickness in the range of 8.0 μm.

If the thickness of the gold plating layer 11 is less than 0.02 μm, the gold plating layer 11 cannot completely cover the underlying electroless nickel plating layer 10, whereby the electroless nickel plating layer 10 is oxidized. When the thickness exceeds 0.3 μm, a part of the gold plating layer 11 diffuses into the conductive bonding material 9. Accordingly, the mechanical strength of the conductive bonding material 9 is reduced, and the reliability of the electrical connection between the connection pad 7 and each electrode 8 of the semiconductor element 3 tends to be deteriorated. Therefore, it is preferable that the thickness of the gold plating layer 11 be in the range of 0.02 μm to 0.3 μm.

The surface roughness of the electroless nickel plating layer 10 is 0.5 μm ≦ center line average roughness (Ra).
Ra ≦ 1.5 μm, and the surface is appropriately roughened, so that the electroless nickel plating layer 10 and the gold plating layer 11 deposited on the electroless nickel plating layer 10
And the adhesion strength between them is increased, and as a result, even if each electrode 8 of the semiconductor element 3 is connected to the connection pad 7 via the conductive bonding material 9 made of a solder ball or the like. No separation occurs between the electroless nickel plating layer 10 and the gold plating layer 11, so that each electrode 8 of the semiconductor element 3 is securely and firmly attached to the predetermined metallized wiring layer 5 via the connection pad 7. It is possible to make an electrical connection.

When the surface roughness of the electroless nickel plating layer 10 is 0.5 μm> Ra in center line average roughness (Ra), the surface area of adhesion between the electroless nickel plating layer 10 and the gold plating layer 11 is small. When the electrode 8 of the semiconductor element 3 is connected to the connection pad 7 via the conductive bonding material 9 composed of a solder ball or the like, the gold plating layer 11 Peel off,
It becomes impossible to electrically connect the electrode 8 of the semiconductor element 3 to the predetermined wiring conductor 5 through the connection pad 7, and R
When a> 1.5 μm, the surface of the gold plating layer 11 becomes rough, and the wettability of the solder balls and the like constituting the conductive bonding material 9 is hindered, and the conductive bonding material 9 is firmly bonded to the gold plating layer 11. It will be difficult to make it. Therefore, the surface roughness of the electroless nickel plating layer 10 is specified in the range of 0.5 μm ≦ Ra ≦ 1.5 μm in center line average roughness (Ra).

Further, the surface roughness of the electroless nickel plating layer 10 is determined by calculating a center line average roughness (Ra) as 0.5 μm ≦ Ra ≦
To make the thickness 1.5 μm, the electroless nickel plating layer 1
No. 1500 media on the surface of 2.0 to 2.0 to 4.0
The spraying is performed by applying a so-called blast treatment at a pressure of Kg / cm ² .

On the other hand, an external lead terminal 6 is attached to the wiring conductor 5 extending to the lower surface of the insulating base 1 via a brazing material such as silver brazing, and the external lead terminal 6 is a semiconductor element. The third electrode 8 serves to electrically connect each electrode 8 to an external electric circuit.

The external lead terminals 6 are made of a metal material such as an iron-nickel-cobalt alloy or an iron-nickel alloy.
For example, it is formed into a predetermined shape by subjecting an ingot made of an iron-nickel-cobalt alloy or the like to a conventionally known metal working method such as a rolling method or a punching method.

The external lead terminals 6 are attached to the wiring conductor 5 by placing the external lead terminals 6 on the wiring conductor 5 with a brazing material foil made of silver brazing or the like interposed therebetween. This is performed by heating to a temperature of about 900 ° C. to melt the brazing material foil.

In this case, nickel having good wettability with respect to the brazing material is previously plated on the surface of the wiring conductor 5 with a plating method.
If it is applied to a thickness of μm, the attachment of the external lead terminal 6 to the wiring conductor 5 via the brazing material becomes strong. Therefore, nickel having good wettability to the brazing material is preferably applied to the surface of the wiring conductor 5 to which the external lead terminals 6 are attached via the brazing material to a thickness of 1 to 20 μm by plating. preferable. The external lead terminals 6 attached to the wiring conductors 5 are made of a metal such as nickel or gold having good conductivity and excellent corrosion resistance on the surface thereof by a plating method of 1 to 20 μm.
When it is adhered to the thickness, the external lead terminal 6 can be effectively prevented from being oxidized and corroded, and good electrical connection with an external electric circuit can be achieved. Therefore, it is preferable that nickel, gold, or the like is applied to the surface of the external lead terminal 6 by plating to a thickness of 1 to 20 μm.

The insulating substrate 1 to which the external lead terminals 6 are attached is further joined to the outer periphery of the upper surface thereof by a lower surface of a bowl-shaped lid 2 via a sealing material made of glass, resin, brazing material or the like. Thereby, the container 4 comprising the insulating base 1 and the lid 2
Is hermetically sealed.

The lid 2 has a semiconductor element 3 inside a container 4.
It is made of a metal material such as copper, an iron-nickel-cobalt alloy, an iron-nickel alloy, or a ceramic sintered body such as an aluminum oxide sintered body.

Thus, according to the package for housing a semiconductor element described above, the semiconductor element 3 is provided on the upper surface of the insulating base 1, the electrodes 8 of the semiconductor element 3 are connected to the connection pads 7 via the conductive bonding material 9 made of solder balls or the like. Then, the bowl-shaped lid 2 is joined to the upper surface of the insulating base 1 via a sealing material made of glass, resin, brazing material, or the like. A semiconductor device as a final product is obtained by hermetically housing the semiconductor element 3 in the container 4 composed of

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. Although the case where the substrate is applied to a semiconductor element housing package for housing a semiconductor element has been described as an example, the same applies to a case where the substrate is applied to a hybrid integrated circuit board on which a semiconductor element is mounted.

[0032]

According to the wiring board of the present invention, the surface of the electroless nickel plating layer adhered to the connection pad has a center line average roughness (Ra) of 0.5 μm ≦ Ra ≦ 1.5 μm. Since the surface is appropriately roughened, the adhesion area between the electroless nickel plating layer and the gold plating layer deposited on the electroless nickel plating layer is large, and the adhesion strength between the two is increased. As a result, the connection Even when the electrodes of the semiconductor element are connected to the pads via a conductive bonding material made of solder balls or the like, no separation occurs between the electroless nickel plating layer and the gold plating layer. Can be reliably and firmly electrically connected to a predetermined wiring conductor via the connection pad.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an embodiment of a wiring board of the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating base 2 ... Lid 3 ... Semiconductor element 4 ... Container 5 ... Wiring conductor 6 ... External lead terminal 7 ... ···· Connection pad 8 ····· Electrode of semiconductor element 9 ··· Conductive bonding material 10 ··· Electroless nickel plating layer 11 ··· Gold plating layer

Claims (1)

[Claims] An insulating substrate, a wiring conductor adhered to the inside and / or the surface of the insulating substrate, and a surface formed on the surface of the insulating substrate so as to be electrically connected to the wiring conductor. A wiring board comprising: a connection pad to which an electrode of a semiconductor element to which an electrolytic nickel plating layer and a gold plating layer are sequentially applied is connected via a conductive bonding material, wherein the electroless nickel plating layer has a surface Is the center line average roughness (R
a) a wiring board, wherein 0.5 μm ≦ Ra ≦ 1.5 μm in a).