JP4214690B2 - Corrosion resistant resist adhesion evaluation method on metal - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for evaluating the adhesion between a metal such as a lead frame, a cathode ray tube shadow mask, a printed wiring board, and the like and a corrosion resistant resist, by forming a corrosion resistant resist on the metal and manufacturing the product by etching.
[0002]
[Prior art]
For example, in a method in which a corrosion-resistant resist is formed on a metal such as a lead frame, a shadow mask of a cathode ray tube, or a printed circuit board and a product is manufactured by etching, the adhesion between the metal 1 and the corrosion-resistant resist 2 is the quality of the product, such as the standard size Is an important factor to ensure.
[0003]
In a state in which the resist adhesion is lowered, the etching solution 5 penetrates into the interface 4 between the corrosion resistant resist 2 and the metal 1 and the surface of the metal 1 is corroded, and a desired external dimension and etching shape cannot be obtained. In some cases, it may cause peeling.
[0004]
In general, as a method for evaluating the corrosion resistance resist adhesion, a method for evaluating physical adhesion between the metal 1 and the corrosion resistance resist 2 such as a peel test and a tensile test is used, but the metal 1 and the corrosion resistance of the etching solution 5 are used. It is difficult to say that this is an appropriate method for evaluating the adhesion of the corrosion resistant resist where penetration into the resist 2 interface 4 becomes a problem. In general, since the adhesion between the corrosion resistant resist 2 and the metal 1 is large, when physical adhesion evaluation such as a tensile test is performed, the contact between the metal 1 or the corrosion resistant resist 2 and the measuring device (mainly using an adhesive). The corrosion resistant resist 2 itself is likely to break, and it is difficult to purely measure the adhesion of the corrosion resistant resist 2 to the metal 1.
[0005]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and an object thereof is to provide an appropriate evaluation method for the adhesion between the corrosion-resistant resist 2 and the metal 1.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, a metal having a corrosion-resistant resist formed on the surface is subjected to constant potential polarization in an electrolyte, and the change in the current value with time is observed to etch the corrosion-resistant resist and the metal interface. It is a corrosion resistance resist adhesion evaluation method on metal characterized by evaluating liquid penetration .
[0007]
According to the second aspect of the present invention , a corrosion resistant resist is formed on a metal, surface treatment for removing impurities is performed on the metal, and constant potential polarization is performed in the electrolyte to expose the metal other than the corrosion resistant resist and the metal interface. Corrosion-resistant resist adhesion evaluation method on metal characterized by forming a passive film on the part, observing changes in current density while continuing constant potential polarization, and evaluating the penetration of the etchant into the corrosion-resistant resist and metal interface It is.
[0008]
The invention according to claim 3 of the present invention is an Fe-Ni alloy mainly composed of Ni of 30 to 50% by weight of Ni and the balance of Fe, and the surface treatment for removing the impurities is a cathode in a sulfuric acid solution and The corrosion resistance resist adhesion evaluation method on metal according to claim 2, wherein the method is anodizing, and the electrolyte is a mixed aqueous solution of sodium sulfate and sodium chloride .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In order to solve this problem, the mechanism of the corrosion resistance resist adhesion was examined. A model of the interface between the corrosion-resistant resist 2 and the metal 1 at the time of etching is shown in FIG. The progress of etching at the interface between the corrosion resistant resist 2 and the metal 1 is promoted by the penetration of the etchant 5 into the interface between the corrosion resistant resist 2 and the metal 1, and the corrosion resistant resist 2 is in a state where the adhesion between the corrosion resistant resist 2 and the metal 1 interface 4 is low. It can be said that the penetration of the etchant 5 into the metal 1 interface 4 is likely to proceed.
[0011]
Therefore, focusing on this phenomenon, a method for monitoring the penetration of the etching solution 5 into the corrosion resistant resist 2 and the metal 1 interface 4 was sought. In the present invention, the principle of “crevice corrosion” is applied to find out that the penetration of the etching solution 5 into the interface 4 between the corrosion resistant resist 2 and the metal 1 is quantified. Here, the principle of crevice corrosion will be described. The crevice corrosion occurs due to a concentration difference caused by a change with time of the corrosion reaction species between the gap portion 7 and the vicinity 8 of the normal portion. In the gap portion 7, the reaction species concentration is reduced because the exchange rate of the reaction species and the reaction product is slow. However, in the normal portion 8, the reaction species and the reaction product are sufficiently exchanged. Therefore, a potential difference is generated between the gap portion 7 and the normal portion 8, and the gap portion 7 becomes a local anode, so that the corrosion of the gap portion 7 proceeds as compared with the normal portion 8.
[0012]
In general, when the metal 1 such as iron or copper is anodically polarized in the electrolytic solution 3, a film of metal salt, hydroxide or oxide is formed on the surface in a certain potential region (this is referred to as passivated 15). The dissolution rate of the surface of the metal 1 in the vicinity of the normal part 8 is remarkably reduced. When the metal 9 in the state where the corrosion resistant resist 2 is formed on the metal 1 as the object this time is anodic polarized in the passive state 15 region, the exposed part of the metal 1 in the vicinity of the normal part 8 is passivated 15 and etching is slowly performed. The corrosion current does not flow so much. However, if the corrosion resistance resist 2 and the metal 1 interface 4 have low adhesion as shown by crevice corrosion, it is assumed that the electrolyte 3 permeates at the interface between the corrosion resistance resist 2 and the metal 1 (gap occurs). Oxygen, hydroxide ions, or other ion concentrations in the electrolyte 3 that have penetrated into the gaps at the interface 4 are difficult to exchange with the bulk solution in the gaps. As a result, the passive film 15 is not formed in the gap portion 7, and the etching proceeds and a relatively large corrosion current is generated. Therefore, a method for evaluating the adhesion of the corrosion-resistant resist 2 by observing the time change of the current value during anodic polarization has been found.
[0013]
As can be seen from the above-described contents, in the present invention, that is, the method for evaluating the adhesion of the corrosion-resistant resist by the constant potential polarization in the electrolytic solution 3, the vicinity of the normal portion 8 which is a portion other than the corrosion-resistant resist 2 and the metal 1 interface 4 is used. How stably the passive film 15 is formed on the exposed metal portion affects the stability and reliability of the measured value. Therefore, in the present invention, the target metal material is a large, high-definition shadow mask or an iron-nickel alloy mainly composed of 30 to 50% by weight of Ni used as a lead frame material of a semiconductor device, and a stable passive state. The polarization conditions capable of forming the film 15 and the electrolyte 3 were selected.
[0014]
As a polarization condition, it was confirmed that about 100 mV to 500 mV was a passive state 15 formation region as a voltage during constant potential polarization. The processing time is preferably about 30 to 60 minutes. Further, prior to constant potential polarization, surface treatment (pretreatment) is important for forming a passive film 15 that is stable for the purpose of removing deposits and natural oxide film on the surface of the metal 1. As pretreatment conditions, it is effective to carry out cathodic treatment in a sulfuric acid solution and subsequent anodic treatment. The treatment conditions are preferably a sulfuric acid solution concentration of about 1 kmol / m 3, a cathode treatment with a current density of about −10 A / m 2 for about 60 seconds, and an anode treatment with a current density of about +1 kA / m 2 for about 60 seconds.
[0015]
Electrolytic solution 3 at the time of constant potential polarization is the most important factor for the formation of stable passive film 15. As a result of testing various electrolytic solutions 3, when iron-nickel alloy is used as metal 1, sulfuric acid Stable measurement results could be obtained in a mixed solution of sodium and sodium chloride. The concentration is preferably about 0.1 kmol / m3 for sodium sulfate and about 0.05 to 0.001 kmol / m3 for sodium chloride.
[0016]
The evaluation of resist adhesion shown in FIG. 2 can be performed by observing the change in current density with time during constant potential polarization. When the corrosion resistance resist adhesiveness is good, the current density drops rapidly immediately after the constant potential polarization and stabilizes after a certain time (about 20 minutes), whereas when the adhesion is poor, the rapid current density immediately after the constant potential polarization. It is in a state where the current density is high without any decrease. This is because the etching at the interface between the corrosion-resistant resist 2 and the metal 1 continues to proceed because the passivation 15 at the interface between the corrosion-resistant resist 2 and the metal 1 is not promoted in a state where the adhesion of the corrosion-resistant resist is poor.
[0017]
FIG. 3 shows an example of constant potential polarization, which is a corrosion resistance resist adhesion evaluation method in the present invention.
[0018]
Specifically, a water-soluble resist (FR-17: Fuji Yakuhin Kogyo Co., Ltd.) added with 1% by weight of ammonium dichromate as the corrosion resistant resist 2 is used as an invar alloy substrate (YET36: Hitachi Metals, Ltd.) with a plate thickness of 130 μm. The product was applied by spin coating and dried at 60 ° C. for 30 minutes to form two corrosion-resistant resist layers on one side of the metal 1.
[0019]
Next, the two layers of the corrosion-resistant resist on the metal 1 shown in FIG. 3 were exposed through a negative photomask on which a desired pattern was drawn with a super-high pressure mercury lamp of 3 kW by an integrated light amount of 1500 mJ / cm ² . After the exposure, general clean water was used as a developer for 90 seconds and sprayed at a spray pressure of 0.1 MPa to remove (develop) the unexposed portion of the photoresist layer, thereby forming a desired 6-layer resist pattern. FIG. 4 shows the corrosion resistant resist pattern 6 partially enlarged from FIG.
[0020]
Next, the side sectional view shown in FIG. 5 is an electrochemical cell device. The metal 9 forming the six layers of the corrosion-resistant resist pattern was measured using an electrochemical cell device. First, the pattern formation surface 9 of the corrosion resistant resist of the measurement sample 14 is placed at the position of the sample fixing jig 16 of the electrochemical cell so as to face the inside of the electrolyte solution 3 of the electrochemical cell, and the current density is 1 kmol / m3 sulfuric acid solution. Cathodic treatment at −10 A / m 3 for 60 seconds was carried out, and anode treatment was continuously carried out at a current density of +1 kA / m 2 for 60 seconds.
[0021]
After the electrochemical cell tank 10 is washed with pure water, the dissolved oxygen removal treatment sodium sulfate 0.1 kmol / m3 sodium chloride 0.003 kmol / m3 mixed solution 3 is filled into the electrochemical cell tank 10 and the standard A constant potential was applied at a voltage of +300 mV using a silver-silver chloride electrode as an electrode.
[0022]
In the case of the sample A having good corrosion resistance resist adhesion shown in FIG. 2, it decreases immediately after the constant potential polarization, and the current density is stabilized to the order of −3 A / m 2 in about 15 to 20 minutes after the polarization. This indicates that no gap is generated between the corrosion-resistant resist 2 and the metal 1 interface, and the exposed metal portion is uniformly passivated.
[0023]
On the other hand, in Sample B with low corrosion resistance resist adhesion, no decrease in current density after constant potential polarization is observed. This is due to the progress of corrosion due to the generation of a gap between the corrosion resistant resist 2 and the metal 1 interface.
[0024]
Sample C is an oxide film in which the corrosion resistance resist 2 and metal 1 adhesion are unstable. The current density decreases suddenly immediately after constant potential polarization, but the current density suddenly increases and the current density time Change is unstable. The unstable current density change that causes this sudden current density change is a process in which the unstable oxide film is broken and the process of forming the stable passive film 15 after the current suddenly flows from that portion. It is. Also from these results, it can be seen that the time of constant potential polarization, which is the corrosion resistance resist adhesion evaluation method in the present invention, requires about 30 to 60 minutes.
[0025]
【The invention's effect】
According to the present invention, it becomes possible to legitimately evaluate the adhesion between the corrosion-resistant resist and the metal, and as a result of establishing the resist adhesion evaluation method, the management in the manufacturing process and the optimization of the process conditions, the appropriateness to the metal Corrosion resistant resists can be easily selected.
[Brief description of the drawings]
FIG. 1 is a schematic diagram relating to the relationship between temporal change in current density during constant potential polarization and adhesion to a corrosion-resistant resist in the present invention.
FIG. 2 is an example of actual measurement of the change over time of the current density of constant potential polarization in the present invention.
FIG. 3 is a plan view of a corrosion-resistant resist pattern used in an example of the present invention.
FIG. 4 is an enlarged plan view of a corrosion-resistant resist pattern used in an example of the present invention.
FIG. 5 is a schematic view of an electrochemical cell used in an example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Metal 2 ... Corrosion-resistant resist 3 ... Electrolyte (solution)
4 ... Interface 5 ... Etchant (etchant)
6 ... Corrosion-resistant resist pattern 7 ... Gap portion 8 ... Near normal portion 9 ... Metal 10 for forming corrosion-resistant resist pattern ... Electrochemical cell device tank 11 ... Electrochemical cell device cover 12 ... Pt electrode 13 ... Thin tube 14 ... Document 15 ... Passive film 16 ... Data fixing jig 17 ... Current change graph 18 when metal and corrosion resist are in poor contact 18 ... Current change graph when metal and corrosion resist are in good contact

Claims (3)

A metal with a corrosion-resistant resist formed on the surface is subjected to constant-potential polarization in the electrolyte , a passive film is formed on the exposed portion of the metal other than the interface between the corrosion-resistant resist and the metal, and the change over time in the current value of the constant-potential polarization is observed. By this, the corrosion resistance resist adhesion evaluation method on the metal characterized by evaluating the penetration of the etching solution into the corrosion resistance resist and the metal interface. Forming a corrosion resistant resist on the metal,
Metal surface treatment for removing impurities,
Conducting constant-potential polarization in the electrolyte to form a passive film on exposed parts of the metal other than the corrosion-resistant resist and metal interface,
Observe current density change while continuing constant potential polarization,
A method for evaluating adhesion of a corrosion-resistant resist on a metal, characterized by evaluating the penetration of an etching solution into the corrosion-resistant resist and the metal interface. The metal is an Fe-Ni alloy mainly composed of Ni 30 to 50% by weight and the balance Fe,
The surface treatment for removing the impurities is a cathode and anode treatment in a sulfuric acid solution,
3. The method of evaluating corrosion resistance resist adhesion on metal according to claim 2, wherein the electrolyte is a mixed aqueous solution of sodium sulfate and sodium chloride.

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