JP3153115B2 - Circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a computer C
The present invention relates to a circuit board provided with an insulating film made of an organic polymer, such as a PU module.

[0002]

2. Description of the Related Art
As a wiring conductor of a circuit board, a wiring material having a gold surface is often used. Also, as an insulating material for wiring,
Insulating organic polymer compounds, especially polyimide resins, are widely used.

When a wiring material having a gold surface is used and a polyimide resin is directly used as an insulating film on the gold, the adhesion between the gold and the polyimide resin is not good. Peeling occurs with the resin,
The characteristics and reliability of the circuit board may be reduced. In addition, when a polyimide resin is once formed on gold on the surface of the wiring member and then removed to expose the gold, the exposed portion is exposed to solder wettability or wire bonding property (hereinafter, referred to as “wire bonding property”) due to the residue of the polyimide resin. W / B property ”).

[0004] In view of this point, various studies have hitherto been made. That is, JP-A-63-148659 discloses that a wiring material is covered with a metal film having good adhesion to a polyimide resin (such as titanium, chromium, titanium nitride, silicon nitride, silicon oxide) and then coated with a polyimide resin. A disclosed structure is disclosed. JP-A-59-167096 discloses a structure in which gold as a wiring material is covered with palladium and then covered with a polyimide resin.

However, when a wiring material having a gold surface is used and titanium, chromium, titanium nitride or palladium is used as a metal coating, these metals forming the metal coating are cured at the curing temperature (curing temperature) of the polyimide resin. In this case, there is a problem that heat is diffused into gold. When the metal film thermally diffuses into the gold, not only does the property of the gold change,
From the viewpoint of the metal coating, the properties of the metal coating also changed because gold diffused into the metal coating. For this reason, when the gold is exposed by removing a part of the metal film, the exposed portion may not have sufficient solder wettability and W / B property, or the adhesion of the metal film to the polyimide resin may be reduced. There was something. On the other hand, when silicon nitride or silicon oxide is used as the metal coating, there is a problem that cracks occur when the polyimide precursor is cured.

Japanese Patent Application Laid-Open No. 59-198795 discloses that
There is disclosed a structure in which gold as a wiring material is covered with nickel having good adhesion to a polyimide resin and then covered with a polyimide resin. However, since nickel is a ferromagnetic material, there is a problem that transmission loss increases in a high frequency region due to a skin effect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a circuit board which does not cause swelling or peeling of an insulating film, cracks of a metal film, and lowers high frequency characteristics. The purpose is to provide.

[0008]

Means for Solving the Problems, Embodiments of the Invention, and Effects of the Invention In order to solve the above problems, the present invention provides a wiring member formed on a substrate so as to have a predetermined pattern, In a circuit board provided with a metal film to be coated and an insulating film made of an organic polymer covering the wiring material and the metal film, the wiring material has a gold surface, and the metal film has the insulating property. excellent adhesion to the membrane and gold, said and cracks do not diffuse into the gold at a curing temperature of the organic polymer does not occur, moreover a coating not ferromagnetic material, the distribution
Part of the gold on the surface of the wire is
The coating is removed and exposed .

As the wiring material used in the present invention, for example,
Titanium-palladium-gold, titanium-copper-nickel-gold (all with gold on the surface) and the like. Examples of the organic polymer forming the insulating film include a polyimide-based resin, benzocyclobutene (BCB), a cyclic olefin-based resin, and a modified polyimide (such as one containing a fluorinated polyimide or siloxane). These may be photosensitive or non-photosensitive.

In addition, the fact that the adhesiveness to the insulating film and the gold is excellent means that a pattern is processed (for example, when holes are formed in the insulating film).
No peeling or floating, or 85 ° C, 85%
It means that there is no peeling or floating of the polyimide in the high temperature and high humidity test at Rh. Specifically, due to the nature of the metal that forms the metal film, an adhesion strength test (a film is formed on gold on the substrate with the metal and a polyimide is applied thereon (20 μm).
m) to prepare a cured sample as a test sample,
In this test for measuring the adhesion strength with respect to a width of 5 mm of the polyimide, it means that the polyimide has an adhesion strength of 2 kg / mm or more. If the metal film of the present invention is formed of a metal having an adhesion strength of 2 kg / mm or more, the insulating film does not peel or swell. This adhesion strength is 8 for molybdenum.
~ 15kg / mm, 7-13kg / for tungsten
mm, chromium> 20 kg / mm (polyimide breaks), no coating (ie gold only) 0.2-0.3
kg / mm.

Further, the curing temperature of the organic polymer is from 200 to
400 ° C., for example, when the organic polymer is a polyimide resin, about 350 ° C. for non-photosensitive and about 4 ° C. for photosensitive
00 ° C. If the metal film diffuses into the gold at the curing temperature of the organic polymer, the metal film is deteriorated at the same time as the gold is deteriorated. Then, when gold is exposed by removing a part of the metal film, the exposed portion may have poor solder wettability or W / B property, or may have poor adhesion of the metal film to the insulating film. . For this reason, it is required that the metal film does not diffuse into gold at the curing temperature of the organic polymer. In addition, when cracks occur at the curing temperature of the organic polymer, the metal film and the gold are peeled off, or the surface becomes uneven, so that the transmission loss of a high-frequency signal occurs. For this reason, it is required that the metal film does not crack at the curing temperature of the organic polymer. Furthermore,
When the metal film is made of a ferromagnetic material, transmission loss increases in a high-frequency region due to a skin effect. Therefore, the metal film is required not to be a ferromagnetic material.

The metal coating of the present invention may be a single layer or a multilayer. When the metal film is a single layer, the metal film is preferably formed of molybdenum, tungsten, or an alloy composed of two components of molybdenum-tungsten. Tantalum oxide is not preferred because cracks occur at the curing temperature of the organic polymer. On the other hand, when the metal coating is a multilayer, it has at least two layers, a layer in contact with the gold surface of the wiring member and a layer in contact with the insulating film. The layer of the wiring material that contacts the surface of gold must be formed of a metal that has excellent adhesion to gold, does not diffuse into gold at the curing temperature of the organic polymer, and does not crack. For example, molybdenum, tungsten, and molybdenum Alloys comprising two components of tungsten; Further, the layer in contact with the insulating film must have excellent adhesion to the insulating film, do not crack at the curing temperature of the organic polymer, and be formed of a metal that is not a ferromagnetic material. For example, molybdenum, tungsten, molybdenum -In addition to the two-component alloy of tungsten,
Titanium, chromium and the like can be mentioned. Of these, chromium is preferable in consideration of adhesion to an insulating film (particularly polyimide). Incidentally, titanium and chromium thermally diffuse to gold due to their properties, but since they do not come into contact with the surface of gold of the wiring material, there is no risk of thermal diffusion to gold.

According to the circuit board of the present invention, the following effects can be obtained. Since the metal coating covering the gold on the surface of the wiring member has good adhesion to the gold and the insulating film, the insulating film does not swell or peel off. The metal coating does not thermally diffuse into gold at the curing temperature of the organic polymer. For this reason, the metal film does not deteriorate and keeps its original properties, and the adhesion to the insulating film does not deteriorate. Also, since the gold does not deteriorate, when the gold is exposed by removing a part of the metal film, the exposed portion is excellent in solder wettability and W / B property. For this reason, I
Brazing C, connecting the IC with wires,
When soldering an electronic component such as a capacitor, brazing and soldering operations can be performed smoothly and the component can be mounted with sufficient strength. When the organic polymer is cured, no cracks are generated in the metal coating, so that the reliability is high. Since it does not have ferromagnetism, the high-frequency characteristics are not reduced by the skin effect.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. The embodiments of the present invention are not limited to the following examples at all, and it goes without saying that various embodiments can be adopted as long as they belong to the technical scope of the present invention. [Reference Example 1] will be described with reference to the circuit board of the multilayer of Example 1 in Figure 1. FIG. 1 is a schematic sectional view of a circuit board of Reference Example 1 . The circuit board 10 is made of a substrate 11 mainly composed of alumina.
And a plurality of circuit layers 12, 12 laminated on the substrate 11.
……. The circuit layer 12 provided on the upper surface of the substrate 11 includes a titanium thin film 13 formed on the substrate 11.
(Thickness of about 2000 mm) and a palladium thin film 14 (thickness of about 3000) formed as an upper layer of the titanium thin film 13.
Å), a gold plating 15 (about 5 μm thick) formed as an upper layer of the palladium thin film 14,
(Copper) 16 formed as an upper layer, a molybdenum coating 17 (about 3000 mm thick) covering the surface of the gold plating 15 and the via plating 16, and a molybdenum coating 1
7 and a polyimide insulating film 18 covering the side surfaces of the gold plating 15
It is composed of Here, the titanium thin film 13, the palladium thin film 14, and the gold plating 15 correspond to the wiring material of the present invention, and the molybdenum coating 17 corresponds to the metal coating of the present invention.

Next, a method for forming the circuit board 10 will be described with reference to FIG. FIG. 2 is a manufacturing process diagram of the circuit board 10. First, sputtering is performed on the substrate 11 in the order of titanium and palladium (see FIG. 2A). Subsequently, a negative type rubber-based resist 21 is applied, exposed and developed,
A predetermined pattern P1 is formed on the resist 21 (see FIG. 2B). Subsequently, the predetermined pattern P1 is plated with gold (see FIG. 2C), and after removing the resist 21, a positive type novolak type resist 22 is applied, exposed and developed to form a predetermined pattern P2 on the resist 22. (See FIG. 2D). Subsequently, via plating (copper) 16 is applied to the predetermined pattern P2 (see FIG. 2 (e)). After the resist 22 is removed, portions of the titanium thin film and the palladium thin film which are not subjected to gold plating are removed by etching (FIG. 2 (f)). Thereafter, molybdenum is sputtered (see FIG. 2 (g)), a negative type resist 23 is applied, exposed and developed, and a predetermined resist is applied on the resist 23 so as to cover the surface of gold plating and via plating (copper). A pattern is formed (see FIG. 2 (h)). Then, molybdenum not covered with the resist 23 is etched, and then the resist 2
3 is removed (see FIG. 2 (i)). The etchants for molybdenum etching are potassium ferricyanide (100 g / l) and potassium hydroxide (100 g / l).
Use a mixture of Subsequently, a polyimide precursor is applied,
After curing at a predetermined temperature (about 350 ° C.), a polyimide insulating film 18 is formed (see FIG. 2J). Thereby, one circuit layer 12 is formed. Thereafter, the surface is polished to expose the via plating 16 on the surface, and the same procedure is again performed (however, Ti-Pd sputtering is performed using Cr (250 °)).
−Pd (change to 3000 °) sputtering) to form the circuit layer 12.

When the gold plating 15 has a large solid pattern (for example, a solid pattern having a size of 2 to 3 cm square), the molybdenum coating 17 is present because the contact area with the polyimide insulating film 18 is large, so that peeling or swelling is likely to occur. Is particularly effective. Such a multilayer circuit board 10 is
It can realize high-density wiring and high-speed signal transmission on a board on which an LSI is mounted, and can be used for a CPU module or the like of a computer.

According to the multilayer circuit board 10, the following effects can be obtained. Via plating 16 and gold plating 1
5 is covered with a polyimide insulating film 18
Relatively good adhesion to polyimide insulating film 1
8 does not swell or peel off. Since the polyimide precursor is not thermally diffused into gold when curing, the molybdenum coating 17 does not deteriorate and keeps its original properties. Therefore, the adhesion between the molybdenum film 17 and the polyimide insulating film 18 does not deteriorate. The molybdenum film 17 does not crack when the polyimide precursor is cured, and does not lower the high-frequency characteristics because it is not a ferromagnetic material. It will be described with reference to Reference Example 2 multilayer circuit board 20 of the reference example 2 in FIG. FIG. 3 is a schematic sectional view of the circuit board of Reference Example 2 .
The circuit board 20, except having a chromium coating 17 'on the upper layer of molybdenum coating 17 of the circuit board 10 of Example 1, is the same as in Reference Example 1, and the same elements are denoted by the same reference numerals, The description is omitted. In Reference Example 2 ,
The molybdenum coating 17 and the chromium coating 17 'correspond to the metal coating of the present invention.

In the circuit board 20 of the reference example 2 , the chromium film 17 'provided on the molybdenum film 17 adheres more closely to the polyimide insulating film 18, but chromium adheres more closely to the polyimide insulating film 18 than molybdenum. Due to the high strength, the reliability is further improved. In addition, when chromium is in direct contact with gold, it thermally diffuses into gold when curing the polyimide precursor, but in this reference example , chromium does not contact with gold, so it may diffuse into gold. There is no. Further, the molybdenum film 17 and the chromium film 17 'do not crack when the polyimide precursor is cured, and do not deteriorate the high frequency characteristics because they are not ferromagnetic materials.

[0019] Incidentally, since it is etched by the same etchant as chromium and molybdenum, to form a circuit board 20 of the multilayer of the present reference example, by sputtering a molybdenum in Reference Example 1 (FIG. 2 (g) refer) Then, it is only necessary to further increase the step of sputtering chromium. Embodiment 1 A circuit board 30 according to Embodiment 1 will be described with reference to FIG. FIG. 4 is a schematic sectional view of the circuit board according to the first embodiment . Example 1
The circuit board 30 includes a substrate 31 provided with a via hole 39 made of tungsten, and a circuit layer 32 formed on the substrate 31. The circuit layer 32 includes a titanium thin film 33 (thickness of about 2000 Å) formed on the substrate 31,
A palladium thin film 34 (thickness of about 3000 Å) formed as an upper layer of the titanium thin film 33 and a gold plating 35 (thickness of about 5 μm) formed as an upper layer of the palladium thin film 34.
m), a polyimide insulating film 38 covering a portion of the substrate 31 not covered with the gold plating 35 and a part of the surface of the gold plating 35, and a polyimide insulating film 3
8 and a metal coating (molybdenum or tungsten) 37 formed between the gold plating 35 and the surface. The portion of the surface of the gold plating 35 that is not covered with the metal coating 37 is referred to as a gold plating exposed surface 35a. Here, the titanium thin film 33, the palladium thin film 34, and the gold plating 35 correspond to the wiring member of the present invention.

An IC 41 is brazed to a certain gold plating exposed surface 35a of the circuit board 30 by gold-tin.
The adjacent gold-plated exposed surfaces 35a are bonded by wires 42, 42. A chip-type capacitor 43 is arranged on the surface of a certain insulating film 18, and the electrodes of this chip-type capacitor 43 are connected to the adjacent gold plating exposed surface 35a by soldering.

Next, a method for forming the circuit board 30 will be described with reference to FIG. FIG. 5 shows the circuit board 30 of the first embodiment .
FIG. First, sputtering is performed on the substrate 31 having the tungsten via hole 39 in the order of titanium and palladium (see FIG. 5A). Subsequently, a negative type rubber-based resist 51 is applied, exposed and developed, a predetermined pattern is formed on the resist 51, and then the predetermined pattern is plated with gold (see FIG. 5B). Subsequently, the resist 51 is removed, and a portion of the palladium thin film / titanium thin film that is not covered with the gold plating is removed by etching (see FIG. 5C). After that, molybdenum (or tungsten) is sputtered, a resist is applied, exposed and developed, a pattern is formed on this resist in which only the surface of gold plating is covered with molybdenum (or tungsten), and molybdenum not covered with resist is formed. (Or tungsten) is removed by etching (see FIG. 5D). Thereafter, a polyimide precursor is applied and cured at a predetermined temperature (about 350 ° C.).
A predetermined pattern is formed by dry etching such as E,
A polyimide insulating film 38 is formed (see FIG. 5E).
Then, the molybdenum (or tungsten) film that is not covered with the polyimide insulating film 38 is removed by etching to expose the gold plating, thereby forming a gold plating exposed surface 35a (see FIG. 5F). Thus, the circuit board 30 of the first embodiment is formed.

According to the circuit board 30, the following effects can be obtained. Since the metal coating (molybdenum or tungsten) 37 covering the gold plating 35 has good adhesion to the polyimide insulating film 38, the polyimide insulating film 38 does not swell or peel off. Since molybdenum (or tungsten) does not thermally diffuse into gold when curing the polyimide precursor, when the metal coating is removed to form the gold-plated exposed surface 35a after curing, the soldering of the gold-plated exposed surface 35a occurs. Properties and W / B properties are in a favorable state (see Test Examples described later). Molybdenum (or tungsten) has high reliability because cracks do not occur during curing of the polyimide precursor, and does not lower high-frequency characteristics because it is not a ferromagnetic material. [Test Example] Solder wettability and W / B property (1) Solder wettability test A test sample was subjected to Sn-Pb (60% / 4) at 260 ° C.
0%) for 10 seconds, the exposed gold plating surface is 90%
If the solder is wet, it is suitable, otherwise it is unsuitable (N
G). The flux used was a rosin-based flux. (2) W / B test A 30 µm aluminum wire was ultrasonically bonded to a test sample, and then this wire was pulled. The wire was broken, and the wire was broken. It was determined. (3) Test samples ( Examples 1-1 and 1-2 , Comparative Example 1)
3) The test sample is shown in Fig. 5 (a) on a 50mm square substrate.
The one provided with 100 exposed surfaces of 1 × 2 mm gold plating by the same method as (f) was used.

[0023] those in Example 1 -1 using molybdenum as the metal film, Example 1 -2 is obtained using tungsten as the metal film. Comparative Example 1 used a chromium coating as a metal coating, Comparative Example 2 used a palladium coating as a metal coating, and Comparative Example 3 did not form a metal coating (that is, the surface of the gold plating was directly polyimide-insulated). After being covered with the film, the surface was exposed to gold plating by dry etching). (4) Test results Table 1 shows the test results.

[0024]

[Table 1]

As apparent from Table 1 above, Example 1
The gold-plated exposed surfaces of Nos. 1 and 1-2 showed very good results in both solder wettability and W / B property. On the other hand, in Comparative Examples 1 and 2, good results were not obtained in both the solder wettability and the W / B property, but this was at a temperature (about 350 ° C.) at which the polyimide precursor was cured. This is because the properties of the exposed surface of the gold plating changed from the original properties of gold because chromium or palladium thermally diffused into gold. In Comparative Example 3, good results were not obtained either in the solder wettability or the W / B property, but this was because the polyimide insulating film that was not removed by dry etching remained on the gold plating exposed surface. Other Embodiments In the above embodiments, the wiring material was formed by Ti / Pd / sputtering + gold plating.
i-Cu sputtering + Cu-Ni-Au plating (2
000Å-5000Å-5μm-2μm-3μm) or C
r-Pd sputtering + Au plating (250Å-50
Any wiring material having gold on the outermost surface, such as (00Å−5 μm), can be used without particular limitation.

In each of the above embodiments, Mo was used as the metal coating.
A -W alloy coating may be used, and in this case, the same effects as those of the above embodiments can be obtained. Further, the metal coating of Example 1 was
As in Reference Example 2 , two layers may be used (a layer in contact with gold is molybdenum (or tungsten), and a layer in contact with the insulating film is chromium).

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a multilayer circuit board of Reference Example 1 .

FIG. 2 is a manufacturing process diagram of the multilayer circuit board of Reference Example 1 .

FIG. 3 is a schematic sectional view of a multilayer circuit board of Reference Example 2 .

FIG. 4 is a schematic sectional view of a circuit board according to the first embodiment .

FIG. 5 is a manufacturing process diagram of the circuit board according to the first embodiment .

[Explanation of symbols]

10, 20, 30 ... circuit board, 11, 31, ...
Substrate, 12, 32 ... circuit layer, 13, 33 ...
Titanium thin film, 14, 34 ... palladium thin film, 15, 35 ...
Gold plating, 16: Via plating, 17: Molybdenum coating, 18, 38: Polyimide insulating film, 21, 22, 23
... Resist, 35a ... Exposed surface of gold plating, 37 ... Metal coating,

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 1/09 H05K 3/24 H05K 3/46

Claims (3)

(57) [Claims] 1. A wiring member formed on a substrate in a predetermined pattern, a metal film covering the wiring member, and an insulating film made of an organic polymer covering the wiring member and the metal film. In the provided circuit board, the wiring member has a surface of gold, the metal film has excellent adhesion to the insulating film and gold, and does not diffuse into gold at the curing temperature of the organic polymer and cracks. It is a film that is not generated and is not a ferromagnetic material, and a part of the gold on the surface of the wiring material is formed before forming once.
A circuit board, wherein the metal film is removed and exposed . 2. The circuit board according to claim 1, wherein the metal film is formed of molybdenum, tungsten, or an alloy including two components of molybdenum-tungsten. 3. The metal film includes a first film provided as an upper layer of the wiring material, and a second film provided as an upper layer of the first film, wherein the first film is molybdenum, tungsten, or the like. 2. The circuit board according to claim 1, wherein the second coating is formed of any one of a two-component alloy of molybdenum and tungsten, and the second coating is formed of chromium.