JP5207782B2 - Gold plating film structure, gold plating film forming method, and glass ceramic wiring board - Google Patents

Description

  The present invention relates to a gold-plated film structure, a gold-plated film forming method, and a glass-ceramic wiring board having a gold-plated film structure formed on electrodes of a wiring pattern of a low-temperature fired glass ceramic substrate.

  Conventionally, a ceramic substrate has been widely used as a wiring substrate for a package of a multichip module on which a plurality of passive elements such as semiconductor elements, capacitors, and resistors are mounted. In recent years, a low temperature fired glass ceramic substrate (Low Temperature Co-fired Ceramics substrate; Hereinafter, it is also used as an LTCC substrate). These LTCC substrates are composed of an insulating base material made of glass ceramics and a sintered body wiring pattern mainly containing silver, for example, silver. The electrodes of the wiring pattern of the LTCC substrate are electrically connected to a semiconductor element or a passive element by wire bonding, and are connected to a resin printed board as an external electric circuit via solder. The electrodes of the wiring pattern of the LTCC substrate are generally subjected to a surface treatment of a multilayer structure composed of a nickel plating film and a gold plating film that satisfies both wire bonding and solderability required for connection. Yes. Usually, as a surface treatment specification capable of wire bonding, plating with a gold plating thickness of 0.3 μm or more and a nickel plating thickness of about 2 to 6 μm is performed.

  As a method for forming a thick gold plating film having a thickness of 0.3 μm or more that can be wire-bonded on the wiring pattern of the LTCC substrate, an electroless plating method as disclosed in Patent Document 1, for example, is used.

  The method of electroless plating on a glass ceramic substrate disclosed in Patent Document 1 is composed of processes comprising surface activation, catalysis, electroless nickel plating, substitutional electroless gold plating, and reduction electroless gold plating. The Gold plating is processed in a two-step process because the substitutional electroless gold plating solution can usually only obtain a gold thickness of less than 0.1 μm, and to obtain a gold thickness of 0.3 μm or more. This is because it is necessary to treat with a reducing type electroless gold plating containing a reducing agent. In addition, since the reduced electroless gold plating solution tends to be unstable, the plating surface must be completely covered with gold before plating. doing.

  By the way, as a document related to the present invention, Patent Document 2 discloses a method of using a neutral electroless plating solution in order to prevent dissolution of a glass ceramic substrate described later.

  Non-Patent Document 1 describes that a local dissolution hole is formed in the electroless nickel plating film by the combination of electroless nickel plating and substitutional electroless gold plating, and the solder connection reliability is lowered. Yes.

JP 2004-332036 A JP 2000-297380 A Hitachi Chemical Technical Report, p21, No36 (2001-1)

  However, the conventional technology for forming a thick gold plating film on an LTCC substrate as disclosed in Patent Document 1 has the following two problems.

  The first problem is an abnormal deposition problem of gold between patterns in which gold fine particles are deposited between the wiring patterns of the LTCC substrate. When forming an electroless gold plating film having a thickness of 0.3 μm or more on the electroless nickel plating film, the electroless nickel plating is first performed, and then a substitutional electroless gold plating is formed from about 0.03 μm to about 0.1 μm. Thereafter, gold plating is performed to a desired thickness with a thickened reduction type electroless gold plating solution. This reduction-type electroless gold plating solution is very sensitive, and there may be a problem that gold is deposited not only on the electrodes but also between the wiring patterns as an insulator depending on the surface state of the LTCC substrate. If gold is deposited between the wiring patterns in this way, the insulating performance between the patterns cannot be maintained, and thus it cannot be used as a wiring board. The inventors of the present application have found that this first problem is caused by using an electroless nickel plating solution whose pH is not substantially neutral under predetermined conditions.

  The second problem is related to the gold and nickel plating film. When substitutional electroless gold plating and thickened reduction type electroless gold plating are performed on an electroless nickel plating film, depending on the combination of electroless nickel plating and substitutional and reduction type electroless gold plating, The adhesion strength between the nickel plating films is small, and a defect that the gold plating film is peeled off from the nickel plating film at the time of wire bonding may occur. In addition, when lead-free solder is used as the solder, a phenomenon that the solder is repelled may occur, or a problem that the strength of the solder joint of the electrode after soldering is weak as described in Non-Patent Document 1 may occur. there were. When the inventors of the present invention form a reduced electroless gold plating film on a crystalline nickel-phosphorus alloy film, a pinhole is formed in the reduced electroless gold plating film, which is reduced electroless gold plating. It was discovered that a void was generated when this was done, which caused a second problem.

  The first problem and the second problem are both problems related to the electroless plating film, and the risk of occurrence of the above problem increases depending on the selection of the plating solution for forming the plating film.

  The present invention has been made in view of the above, such as abnormal precipitation of gold between wiring patterns of such LTCC substrate, poor adhesion between gold and nickel plating film, solder repelling phenomenon, and deterioration of solder joint strength, etc. An object of the present invention is to obtain a gold-plated film structure of an LTCC substrate, a method of forming a gold-plated film, and a glass ceramic wiring board with reduced occurrence of problems.

In order to solve the above-mentioned problems and achieve the object, the present invention is a gold plating film structure formed on a glass ceramic wiring substrate having a metal sintered body wiring pattern on a glass ceramic insulating substrate, First layer structure of nickel-phosphorus alloy formed on the metal sintered body wiring pattern using an electroless nickel plating solution having a substantially neutral hypophosphite as a reducing agent, and a layer to be formed Amorphous, sulfur-free nickel-phosphorus formed on the first layer structure using a weakly acidic electroless nickel plating solution containing at least 7 weight percent phosphorus and not containing a sulfur component A second layer structure of an alloy, a third layer structure of gold formed on the second layer structure using a substitutional electroless gold plating solution, and a third layer structure using a reduced electroless gold plating solution. Fourth of gold formed on the layer structure And having a structure.

  According to the present invention, the first problem is caused by forming the first layer structure of the nickel-phosphorus alloy using the electroless nickel plating solution containing the substantially neutral hypophosphite as the reducing agent. The time to use an electroless nickel plating solution containing a hypophosphite other than substantially neutral as a reducing agent is reduced, and the layer structure formed contains 7 weight percent or more of phosphorus and does not contain a sulfur component. A third layer structure of a substitutional electroless gold plating formed on the second layer structure of an amorphous nickel-phosphorus alloy containing no sulfur using an electroless nickel plating solution and the third layer Since the fourth layer structure of reduced electroless gold plating film formed on the structure is formed, the interface between the second layer structure of nickel-phosphorus alloy and the third layer structure of substitutional electroless gold plating Pinholes and voids As a result, the LTCC board has reduced the occurrence of problems such as abnormal gold deposition defects between wiring patterns, poor adhesion between gold and nickel plating film, solder repellency, and solder joint strength deterioration. A gold plating film structure can be obtained.

  First, knowledge on the first and second problems obtained through the investigation and research by the inventors of the present application will be described.

  First of all, the cause of abnormal precipitation of gold fine particles precipitating between the wiring patterns of the LTCC substrate, which is the first problem, is due to the deterioration of the plating solution and the residual Pd catalyst due to lack of water washing. The inventors of the present application have found that the pH of the plating solution is greatly related.

  The electroless nickel plating solution generally used is weakly acidic with a pH of about 4.5 to 5.0. However, in order to form a nickel plating film with a thickness of about 3 to 6 μm, the LTCC base material portion is contained in the plating solution for 15 to 30 minutes. Will be exposed. According to experiments by the inventors, abnormal deposition was likely to occur when treatment for 10 minutes or more was performed in a weakly acidic electroless nickel plating solution or when an electroless nickel plating having a thickness of 2 μm or more was formed. On the other hand, it was found that the use of a neutral type electroless nickel plating solution having a pH of 6 to 7.5 significantly suppresses the occurrence of abnormal precipitation.

  LTCC has the property of easily dissolving in acidic or alkaline high-temperature solutions because its base material is glass ceramic. According to the studies by the inventors, even a weakly acidic solution having a pH of about 4.5 to 5.0 partially dissolves the glass component on the surface of the LTCC substrate when exposed to a long time, and the surface of the LTCC substrate is uneven. become. Further, the silver diffused from the silver sintered body is deposited on the surface of the substrate inside the glass ceramic near the wiring pattern, and fine silver particles of about 0.05 to 0.2 μm are formed on the surface. It was found that the deposition of gold on the silver particles caused abnormal gold deposition on the surface of the glass ceramic substrate near the wiring pattern. Further, it has been found that the roughened LTCC base material surface easily retains abnormally precipitated gold particles, thereby causing abnormal precipitation defects more remarkably.

  As a method for preventing this abnormal precipitation, it is effective to use a neutral type electroless nickel plating solution having a pH of 6 to 7.5. The neutral type electroless nickel plating solution does not dissolve the LTCC base material during the plating process even if the plating time is long, and as a result, the risk of abnormal precipitation can be greatly reduced. Patent Document 2 discloses a method using a neutral electroless plating solution in order to prevent dissolution of the glass ceramic substrate.

  On the other hand, the cause of poor adhesion between the gold and nickel plating films and the deterioration of the strength of the solder joints, which is the second problem, is mainly due to voids generated in the nickel plating film during thick reduction electroless gold plating. It is thought that there is.

  Substitution-type electroless gold plating film has many pinholes, so the substitution reaction where nickel partially dissolves during reduction-type electroless gold plating treatment continues, and electroless nickel plating film under gold plating An infinite number of voids may occur. In this case, there is no problem on the appearance of the gold plating, but if only the gold plating film is dissolved and peeled, a black mesh-like crack may occur on the surface of the electroless nickel plating. It is called a black pad.

  When a plating film with many voids is formed at the interface between such electroless nickel plating and gold plating, the adhesion strength between the gold and nickel plating films decreases, for example, the gold plating film peels off from the nickel plating during wire bonding. This causes a failure to occur. In addition, when lead-free solder is used to solder a plating film with many voids, gold easily diffuses and disappears inside the solder, but the nickel and tin do not get wet and the solder is repelled. Sometimes happened. Furthermore, many voids are generated in the diffusion layer (tin-nickel compound layer) between nickel and solder, and there is a problem that the strength of the solder joint is lowered. Non-Patent Document 1 describes that a combination of electroless nickel plating and substitutional electroless gold plating forms local dissolution holes in the electroless nickel plating film, resulting in low solder connection reliability. .

  The inventors have found that such a black pad is generated by a combination of electroless nickel plating and electroless gold plating, in particular, an electroless nickel plating containing a neutral type low phosphorus concentration or a sulfur-based additive. It has been found that this phenomenon occurs remarkably when a liquid is used. That is, since the electroless nickel plating film structure with a low phosphorus concentration is crystalline, a substitutional electroless gold plating reaction is likely to occur at the crystal grain boundary, and the part where the nickel dissolves such as the crystal grain boundary is covered with gold. It is considered that non-uniformity occurs in the portion, and many voids and pinholes in which nickel continues to elute are formed. Moreover, since the electroless nickel plating film containing a sulfur component has poor corrosion resistance, it is considered that similar voids are likely to be generated.

  On the other hand, when electroless nickel plating is performed while controlling the phosphoric acid concentration in the film to be 7 wt% or more, a nickel-phosphorus alloy plating film having an amorphous film structure can be obtained. It has been found that when the nickel plating film is amorphous and does not contain sulfur, the substitutional electroless gold plating reaction occurs uniformly and gently, and the formation of voids and pinholes can be suppressed.

  However, in order to perform electroless nickel plating so that the phosphoric acid concentration in the film is 7 wt% or more, it is currently necessary to use a weakly acidic type electroless nickel plating solution. When this plating solution is used, the first problem cannot be solved.

  Therefore, in the gold plating film structure and the gold plating film forming method of the embodiment of the present invention, after forming most of the thickness of the desired nickel plating film using a neutral type electroless nickel plating solution, An amorphous nickel plating film containing 7 wt% or more of phosphorus and not containing sulfur is thinly formed on the nickel plating film to form a nickel plating film having a desired thickness as a whole. The first and second problems were solved by devising to perform electroless gold plating. Embodiments of the present invention will be specifically described below with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
A gold plating film forming method according to an embodiment of the present invention and a gold plating film structure created by the method will be described with reference to three comparative examples created for comparison. FIG. 1 is a diagram illustrating the gold plating film forming method of the present embodiment and a comparative example for comparison. The gold plating film structure created by the gold plating film forming method of the present embodiment is sample 1, and the gold plating film structures created by the comparative gold plating film forming method are samples 2, 3, and 4. .

(Sample 1)
Sample 1 which is a gold plating film structure created by the gold plating film forming method in the present embodiment has a layer structure as shown in FIG. In FIG. 2, a sample 1 has a wiring pattern 2 made of a sintered metal mainly composed of silver on an insulating base material 1 made of glass ceramic, and a first layer structure on the wiring pattern 2 made of silver. A certain first electroless nickel plating film 3, a second electroless nickel plating film 4 having a second layer structure, a substitutional electroless gold plating film 5 having a third layer structure, and a thickness having a fourth layer structure The attached reduced electroless gold plating film 6 has a structure formed in this order. In the following, the process of creating the sample 1 created by the method of the present embodiment will be described with reference to FIG.

  First, the insulating base material 1 on which the silver wiring pattern 2 is formed is degreased and surface activated by a normal method, and the glass component and the oxide film are removed from the electrode surface of the silver wiring pattern 2.

  Subsequently, it is immersed in a catalyst solution containing palladium or the like, and a palladium catalyst is applied to the electrode surface of the silver wiring pattern 2.

  Subsequently, a nickel-phosphorus alloy plating film is formed to a thickness slightly smaller than a desired thickness using a neutral type electroless nickel plating solution as the first electroless nickel plating. The plating thickness may be equal to or greater than the thickness at which the wiring pattern of the silver sintered body is completely covered, and specifically, it is preferably 1 μm or greater. The phosphorus concentration of the plating film is not particularly limited. However, since it is neutral electroless nickel plating, the phosphorus concentration is 1 to 6 wt%, and a crystalline nickel-phosphorus alloy plating film is obtained. In Sample 1, the pH was adjusted to 7.0 on the wiring pattern, including nickel sulfate as a metal salt, sodium hypophosphite as a reducing agent, glutamates as a complexing agent, boric acid as an inorganic acid, and the like. Using the first electroless nickel plating solution, 4 μm of the first electroless nickel plating film 3 made of a nickel-phosphorus alloy having a phosphorus concentration of 4 wt% was formed under the conditions of a solution temperature of 80 ° C. and a plating time of 20 minutes.

  Since the electroless nickel plating solution used in this step is neutral, the LTCC base material surface is not affected even when immersed for a long time. Therefore, the nickel plating film can be formed to an arbitrary thickness without causing abnormal precipitation of gold in the gold plating film structure finally obtained.

  Subsequently, a nickel-phosphorus alloy plating film having a phosphorus concentration of 7 wt% or more and containing no sulfur is formed using a weakly acidic type electroless nickel plating solution as the second electroless nickel plating. Currently, a weak acid type electroless nickel plating solution capable of forming a phosphorus-nickel alloy plating film having a phosphorus concentration of 7 to 10 wt% is available. The plating thickness is such that it does not dissolve and disappear in the solder during soldering, and is preferably processed in as short a time as possible. Specifically, it is formed to be 1 μm or less. In sample 1, the second electroless nickel plating containing nickel sulfate as the metal salt, sodium hypophosphite as the reducing agent, lactic acid or propionic acid as the complexing agent, triethanolamine, etc. and adjusted to pH 4.5. Using the solution, a second electroless nickel plating film 4 made of a nickel-phosphorus alloy having a phosphorus concentration of 8 wt% was formed to a thickness of 0.8 μm under the conditions of a solution temperature of 80 ° C. and a plating time of 5 minutes.

  The second electroless nickel plating film 4 created in this step contains 7 wt% or more of phosphorus, and thus has a lot of amorphous film structure, and the reaction with the subsequent substitution type electroless gold plating is slow. Since it occurs uniformly, there are few pinholes and it does not contain sulfur. Therefore, voids and pinholes do not increase even if reduction-type electroless gold plating is performed thereafter. For this reason, in the gold plating film structure finally obtained, a gold plating film which is excellent in wire bonding property and does not deteriorate the solder joint strength even during soldering is formed. In this process, a weakly acidic type electroless nickel plating solution is used, but it is sufficient to perform the treatment in a short time so that the thickness obtained is 1 μm or less. The LTCC substrate does not corrode.

  Subsequently, substitutional electroless gold plating is performed on the second electroless nickel plating film 4. In sample 1, a substitutional electroless gold plating solution containing potassium gold cyanide, potassium cyanide, etc. was used, and the substitution type was not changed to 0.05 μm under the conditions of pH 6.8, solution temperature 90 ° C., plating time 10 minutes. An electrolytic gold plating film 5 was formed. The thickness of the substitutional electroless gold plating film 5 is not particularly specified, and may be a thickness other than 0.05 μm.

  Finally, thick gold plating is performed on the substitutional electroless gold plating film 5 by reduction electroless plating. In sample 1, using a reduced electroless gold plating solution containing potassium gold cyanide, sodium cyanide, sodium hydroxide, sodium borohydride and the like as a reducing agent, a solution temperature of 75 ° C. and a plating time of 30 minutes Thus, a 0.7 μm thick electroless gold plating film 6 was formed. Gold of the thick electroless gold plating film 6 was pure gold having a purity of 99% or more. Here, the plating thickness is not limited to 0.7 μm as long as it is a wire bondable thickness, that is, 0.3 μm or more.

(Sample 2)
Next, sample 2 created as a comparison will be described. Sample 2 was created by a creation step in which the step of forming the second electroless nickel plating film 4 was omitted from the creation step of Sample 1 in FIG. The sample 2 created by this process has a structure as shown in FIG.

  In FIG. 3, the LTCC substrate of Sample 2 is composed of an insulating base material 1 made of glass ceramic and a wiring pattern 2 made of a metal sintered body containing silver as a main component, as in Sample 1. The structure of the metal plating film on the surface of the wiring pattern 2 is in order of the first electroless nickel plating film 3, the substitutional electroless gold plating film 5, and the thickened reduction type electroless gold plating film 6 in order from the wiring pattern 2. ing. The first electroless nickel plating film 3 is a nickel-phosphorus alloy having a phosphorus concentration of 1 to 6 wt% and a thickness of 4 μm. The thickness of the substitutional electroless gold plating film 5 is about 0.05 μm, and the thickness of the thickened substitutional electroless gold plating film 6 is 0.7 μm.

(Sample 3)
Next, Sample 3 created as a comparative example different from Sample 2 will be described. In sample 3, the process of forming first electroless nickel plating film 3 is deleted from the process of creating sample 1 in FIG. 2, and the time of the process of forming second electroless nickel plating film 4 is changed to 30 minutes. The second electroless nickel plating film 4 was formed by a manufacturing process in which the thickness was 5 μm. Sample 3 created by this process includes a second electroless nickel plating film 4 of 5 μm, a substitutional electroless gold plating film 5 of 0.05 μm, and 0.7 μm on the wiring pattern 2 of the LTCC substrate. The thick reduction type electroless gold plating film 6 is formed.

(Sample 4)
Next, sample 4 created as still another comparative example will be described. Sample 4 is a phosphorous containing 1 μm sulfur using a commercially available electroless nickel plating solution for printed circuit boards containing thiourea, which is a sulfur component, in the step of forming second electroless nickel plating film 4. The preparation of the nickel-phosphorus alloy with a concentration of 7 wt% is different from the preparation process of Sample 1. That is, in sample 4, a 4 μm first electroless nickel plating film, an electroless nickel plating film containing 1 μm sulfur, and a 0.05 μm substitutional electroless gold plating film on the wiring pattern 2 of the LTCC substrate. 5 and 0.7 μm thick reduced electroless gold plating films 6 are formed.

  The samples 1 to 4 thus prepared were subjected to a comparison by appearance observation and a plating characteristic test related to the above problems 1 and 2. First, the appearance comparison results will be described. FIG. 4 is a diagram for explaining the appearance observation results of Samples 1 to 4.

  In FIG. 4, the appearance of the reduced electroless gold plating film 6 on the wiring pattern 2 is a bright gold color in any sample, but only the sample 3 is arranged in parallel with the wiring pattern 2. An abnormal precipitation of brown gold occurred between the patterns 2 and it was found that normal plating as a wiring board was not possible.

  Furthermore, the samples 1 to 4 were immersed in a gold plating stripper containing potassium cyanide (10 g / L concentration) and the electroless nickel plated surface after stripping the gold was observed. As shown in FIG. The black pad was observed almost entirely in 2 and partially in sample 4. No black appearance was observed on the electroless nickel-plated surfaces of Samples 1 and 3 after peeling off the gold plating.

  That is, only Sample 1 did not cause abnormal gold deposition and no black pad.

  Next, the results of the plating characteristic test will be described. For the plating characteristics test, a tape test to peel off the tape by applying a tape to compare the adhesion of the gold plating, a wire bond tensile test in which wire bonding is performed with a gold wire, and the gold wire is pulled to test for breaking, and nickel The L-shaped angle of the lead was connected with lead-free solder, and the strength of the lead-free solder joint was tested to test whether this angle was pulled and broken. However, with respect to Sample 3, the gold plating film was not subjected to a characteristic test because normal gold plating was not possible due to abnormal precipitation. FIG. 5 is a diagram for explaining the results of the gold plating film characteristic test performed on samples 1, 2, and 4. FIG.

  In FIG. 5, the result of the tape test will be described first. In the tape test, a commercially available cellophane tape having a width of 20 mm was applied on the wiring pattern 2 of each of the samples 1, 2, and 4, and the appearance of the sample after being peeled off in the vertical direction was examined. Although only the sample 2 was partially peeled off the electroless gold plating films 5 and 6 and the underlying first electroless nickel plating film 3 was exposed, there was an abnormality in the LTCC substrates of the samples 1 and 4 I was not able to admit.

  Next, the results of the wire bond tensile test will be described. In the wire bond tensile test, wire bonding was performed using a gold wire having a diameter of 25 μm on the electroless gold-plated electrode of each sample 1, 2, and 4, and then a break test was performed by pulling the wire in the vertical direction. . As a result of performing a tensile test on 100 wires each, in sample 1 and sample 4, all the gold wires were broken, and no gold wire-gold plating or gold plating peeling was observed. On the other hand, in sample 2, about 1/5 of all the wires were separated from the gold plating film and the nickel plating with a strength smaller than the average value of the wire breaking strength.

  Finally, the results of strength evaluation of lead-free solder joints will be described. When evaluating the strength of lead-free solder joints, a nickel L-shaped angle was soldered to a 2 mm x 2 mm square electrode pad on an LTCC substrate, and annealed at 125 ° C for 12 hours and pulled vertically to observe the fractured part. did. The number of electrode pads subjected to the test is 50 each. Note that a lead-free solder of 96.5 wt% tin, 3 wt% silver, and 0.5 wt% copper was used as a solder material. In all samples 1, the silver sintered body wiring pattern 2 or the insulating base material 1 was broken or peeled off at the interface of the L-shaped angle, and it was not broken at the interface of the LTCC plating film. On the other hand, in samples 2 and 4, the L-shaped angle peeled off in a form in which electroless nickel plating remained, and breakage sometimes occurred at the interface of the plating film. In comparison between Samples 2 and 4, Sample 2 was more noticeable at the plating film interface.

  As is clear from the results of comparison of appearance observation and plating characteristics test, there is no abnormal gold deposition, no black pad, good adhesion between nickel plating film and gold plating film, wire The gold plating film forming method of the present embodiment satisfies both the conditions that the gold plating film does not peel in the bond tensile test and that there is no breakage at the nickel plating film interface in the peeling test of the soldered portion. Only sample 1 was prepared. That is, when performing nickel plating, the time for which the LTCC substrate is exposed to an electroless nickel plating solution other than the neutral type by performing a step of creating a nickel plating film using a neutral type electroless nickel plating solution. Since the length was shortened, the effect of preventing abnormal gold deposition between the wiring patterns was obtained. In addition, as an undercoat film for the gold plating film, an amorphous nickel-phosphorus alloy film that does not contain sulfur is formed by controlling so that the phosphorus concentration does not contain sulfur and the phosphorus concentration is 7 wt% or more. , The reaction with the displacement gold plating solution is moderated to reduce the occurrence of pinholes, the black pad is not formed, and the gold-nickel film interface with few voids is formed. The effect of increasing the strength of the joint was obtained.

  As described above, according to the embodiment of the present invention, the first layer structure of the nickel-phosphorus alloy is formed by using the electroless nickel plating solution using the substantially neutral hypophosphite as the reducing agent. Therefore, the time for using an electroless nickel plating solution having a non-neutral hypophosphite that causes the first problem as a reducing agent is reduced, and the formed layer structure is 7 weight percent or more. A second layer structure of an amorphous, non-sulfur-containing nickel-phosphorous alloy is formed using an electroless nickel plating solution that contains phosphorus and does not contain a sulfur component. Since the fourth layer structure of the reduced-type electroless gold plating film formed on the third-layer structure and the third-layer structure is formed, the second-layer structure of the nickel-phosphorus alloy and the replacement-type electroless gold Piping generated at the interface with the third layer structure of the plating The generation of holes and voids has been reduced, resulting in problems such as abnormal gold deposition between wiring patterns, poor adhesion between gold and nickel plating film, solder repellency, and solder joint strength deterioration. It is possible to obtain a gold-plated film structure of an LTCC substrate with reduced resistance.

  As described above, the gold plating film structure, the gold plating film forming method, and the glass ceramic wiring board according to the present invention include a gold plating film structure, a gold plating film forming method, and a gold plating film forming method that are formed on the electrodes of the wiring pattern of the low-temperature fired glass ceramic substrate. It is suitable for application to a glass ceramic wiring board.

It is a figure explaining the gold plating film formation method of an embodiment and a comparative example of the present invention. It is a figure explaining the layer structure of the sample 1 formed by the gold plating film forming method of this Embodiment. It is a figure explaining the layer structure of the sample 2 formed by the gold plating formation method of the comparative example. It is a figure explaining the result of appearance comparison of samples 1-4. It is a figure explaining the result of the plating characteristic test of samples 1, 2, and 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation base material 2 Wiring pattern 3 1st electroless nickel plating film 4 2nd electroless nickel plating film 5 Substitution type electroless gold plating film 6 Reduction type electroless gold plating film

Claims (6)

A gold plating film structure formed on a glass ceramic wiring substrate having a metal sintered body wiring pattern on a glass ceramic insulating base material,
A first layer structure of a nickel-phosphorous alloy formed on the metal sintered body wiring pattern using an electroless nickel plating solution containing a substantially neutral hypophosphite as a reducing agent;
The formed layer structure contains 7% by weight or more of phosphorus and contains amorphous sulfur formed on the first layer structure using a weakly acidic electroless nickel plating solution containing no sulfur component. A second layer structure of a nickel-phosphorus alloy that does not
A third layer structure of gold formed on the second layer structure using a substitutional electroless gold plating solution;
A gold-plated film structure comprising a gold fourth-layer structure formed on the third-layer structure using a reduced electroless gold plating solution.   In the electroless nickel plating for forming the second layer structure, when a plating solution having a pH other than substantially neutral is used as the electroless nickel plating solution, the thickness of the second layer structure is 1 μm or less. The gold plating film structure according to claim 1.   The gold plating film structure according to claim 1 or 2, wherein the fourth layer structure has a thickness of 0.3 µm or more.   The said substantially neutral is the range of pH 6-7.5, The gold plating film structure as described in any one of Claims 1-3 characterized by the above-mentioned. A method for forming a gold plating film on a glass ceramic wiring board having a metal sintered body wiring pattern on a glass ceramic insulating substrate,
First electroless plating for forming a first layer structure of a nickel-phosphorus alloy on the metal sintered body wiring pattern using an electroless nickel plating solution containing a substantially neutral hypophosphite as a reducing agent Process,
The formed layer contains 7% by weight or more of phosphorus, and uses a weakly acidic electroless nickel plating solution containing no sulfur component. A second electroless plating step to form a second layer structure of the phosphorus alloy;
A third electroless plating step of forming a gold third layer structure on the second layer structure with a substitutional electroless gold plating solution;
And a fourth electroless plating step of forming a gold fourth layer structure on the third layer structure with a reduced electroless gold plating solution. A glass ceramic insulating substrate having a metal sintered body wiring pattern;
A first layer structure of a nickel-phosphorous alloy formed on the metal sintered body wiring pattern using an electroless nickel plating solution containing a substantially neutral hypophosphite as a reducing agent;
The formed layer structure contains 7% by weight or more of phosphorus and contains amorphous sulfur formed on the first layer structure using a weakly acidic electroless nickel plating solution containing no sulfur component. A second layer structure of a nickel-phosphorus alloy that does not
A third layer structure of gold formed on the second layer structure using a substitutional electroless gold plating solution;
A glass ceramic wiring board comprising: a fourth layer structure of gold formed on the third layer structure using a reduced electroless gold plating solution.

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