JPH02104655A - Production of surface treated steel sheet for high-efficiency lead frame excellent in corrosion resistance, plating suitability, and solderability - Google Patents

Abstract

PURPOSE:To produce a surface treated steel sheet for high-efficiency lead frame excellent in corrosion resistance, plating suitability, and solderability by coating a Cr- containing cold rolled steel sheet having a specific composition with Ni or Co by a specific coating weight and then applying specific homogenizing treatment to the above sheet. CONSTITUTION:A Cr-containing steel sheet which has a composition consisting of, by weight, <=0.01% C, 0.005-0.10% acid-soluble Al, 4-10.5% Cr, 0.0003-0.005% B, and the balance Fe with inevitable impurities and further containing, if necessary, one or more kinds among 0.05-1% Cu, 0.05-3% Ni, and 0.05-0.5% Mo is cold rolled. A coating layer of Ni, Co, or alloy of both in which coating weight per side is regulated to 100-3000mg/m<2> is provided to the surface of the above cold rolled steel sheet. Subsequently, the above steel sheet is subjected to homogenizing treatment at a temp. in the range between 450 deg.C and the recrystallization temp. for <=180sec in a nonoxidizing atmosphere. By this method, the surface treated steel sheet for high-efficiency lead frame excellent in various properties, such as stamping property and corrosion resistance, can be obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention has excellent corrosion resistance, and also has excellent material performance, metallization performance, or solder performance necessary for punching workability (stamping performance) in the lead frame manufacturing process. The present invention relates to a method for producing an excellent surface-treated steel sheet for lead frames.

(Prior Art) Recently, in the field of electronics, integrated circuits (I
The demand for C) has increased significantly, and the demand for lead frame materials has also increased, and there is a strong desire to develop lead frame materials with excellent performance.

In general, these lead frame materials are made into strips, then cut and punched, and then Cu plating or solder plating (immersion soldering or electric solder plating) is applied to the surface, and then Ag, Au, etc. are plated on the surface. It is then bonded to a silicon chip (wire bonding) and used as an IC material.

Therefore, these lead frame materials are required to have good punching and forming processability, excellent plating properties, and excellent solderability. In particular, since the terminal portion of the lead frame is soldered to an IC board or the like, it is important to have excellent solderability.

Furthermore, the material is required to have excellent rust resistance during storage before being subjected to the above-mentioned plating, etc., and furthermore, the product after the treatment is required to have excellent rust resistance.

(Problems to be Solved by the Invention) Conventionally, Fa-42%Ni alloy has been mainly used as a lead frame material due to its strength and thermal expansion characteristics.
Copper alloys are also used due to their cost and conductivity advantages. However, although this copper alloy has excellent conductivity and heat dissipation, it lacks strength compared to Fe-42%N1 alloy, so it may bend when inserting the actor lead into a component during the automatic IC assembly process. There was this inconvenience.

Furthermore, in view of the recent miniaturization of ICs, lead frame materials are also becoming extremely thin, and high strength is required.

Low carbon steel is the most effective in terms of cost, but cannot be used because it easily rusts.On the other hand, stainless steel, which has excellent corrosion resistance and strength, has poor plating properties and poor plating properties because it contains a large amount of Cr. There is a problem with solderability. Materials for lead frames that can solve these problems are introduced in, for example, Japanese Patent Laid-Open Nos. 57-50457, 59-9149, and 80-103158. These contain 4 to 11% Cr as a basic component, and also include Ni, Mo, Cu, Tl, Nb,
This is a lead frame material that contains V, Zr, etc. in a few percent or less to improve the rust resistance required for lead frame materials, and also improves the plating and solderability, which are disadvantages of stainless steel.

Although these materials have a certain performance improvement effect, they do not necessarily have sufficient performance as lead frame materials.In other words, the adhesion of Cu plating is not sufficient, especially in the heating process during wire bonding. A defect was observed in which blisters (partial swelling of the plated layer) occurred in the Cu plated layer. Further, in soldering work using a non-halogen type flux that does not contain halogen ions, such as CfL- ions, which are often used in the electronics field, there is a problem that the solder does not adhere sufficiently.

Furthermore, a lead frame material in which a steel plate having the above-mentioned known steel components is plated with Ni or an old alloy, or plated with Cu or a Cu alloy is disclosed in Japanese Patent Application Laid-Open No. 61-2849.
It is introduced in Publication No. 48. The material is a Fa-Cr alloy steel plate, that is, Or; 5.0 to 10.5 in weight%.
%, C, 0, 10% or less, 51; 2.0% or less, Mn;
In addition to the basic components of 2.0% or less, 0.10% or less, Ni; 3.0% or less, Cu;
2.0% or less, Mo: 1 out of 4.0% or less
species or two or more species, or Nb, TI, Ta, Zr
One or more of these are added in an amount of 0.6% or less, and a 3-5 μm coating layer of Ni or Ni alloy plating, or Cu or Cu alloy plating is applied to a steel plate with the remainder substantially consisting of Fe. It is a strained and cold rolled steel plate.

The steel plate is used as a material for lead frames either as cold rolled or after annealing to remove strain, but the Au or Ag plating or soldering properties are Fa-11:r.
This is a considerable improvement over the case where the base material is used as is.

However, this steel plate has many problems in terms of manufacturing, such as the fact that the plated metal adheres to the rolling roll during cold rolling after plating, requiring complicated maintenance to obtain a product with a smooth appearance.

Furthermore, in terms of performance, there are the following problems. In other words, materials coated with a Ni or Ni alloy plating layer have improved plating and solderability, but when immersion soldering is performed, a diffusion reaction occurs between Sn metal and Ni metal in the solder composition, and the hard and brittle Ni -5n alloy is produced.

When the amount of solder generated increases, the solder layer becomes brittle and easily breaks when subjected to impact or bending (so-called
(solder brittleness), and this drawback tends to occur especially when heated during wire bonding or when the plated layer of Ni or Ni alloy becomes thick.

In addition, when Cu or Cu alloy is applied, it is a metal or alloy that is significantly more sensitive than the Fe-Cr based steel sheet used for the base, so it cannot be used in a humid environment or In a corrosive environment where corrosive factors such as C1- ions are present, the base steel plate is preferentially corroded, and red rust or perforation corrosion may occur from pinholes in the plating layer or from flawed areas during processing. This tendency also poses a problem in that even when a Ni or Ni alloy facing layer is applied, poor corrosion resistance may occur due to the same cause depending on the steel composition of the Fe--Cr steel sheet.

The present invention was made in view of the above problems, and has corrosion resistance,
Provided is a method for manufacturing a surface-treated steel sheet for lead frames with excellent plating and solderability.

(Means for Solving the Problems) The present invention provides, in weight percent, C, 0.01% or less, acid-soluble AJ
2; 0.005-0.10%, Cr; 4-1
Contains 0.5%, B; 0.0003 to 0.005%,
Or further Cu; 0.05-1%, Ni; 0.
05-3%, Mo; 0.05-0.5% or 21
After cold rolling a Cr-containing steel plate containing 11 or more and the balance consisting of Fe and unavoidable impurities, the amount of adhesion on the surface is 10
0~3000mg/m'' of Ni, Co or Ni and C
A high-performance lead with excellent corrosion resistance, plating properties, and solderability, which is coated with a coating layer of alloy o and then subjected to heat diffusion treatment for 180 seconds or less in a temperature range of 450°C to recrystallization temperature in a non-oxidizing, neutral atmosphere. This is a method for manufacturing a steel plate on the peripheral surface of a frame.

As described above, in the present invention, a coating layer of Ni, Co, or N1-Cu alloy of an appropriate thickness is applied to the surface of a cold-rolled steel sheet having the above composition, and a heating diffusion treatment is performed.

In the present invention, an appropriate amount of Cr is contained in steel from the viewpoint of improving corrosion resistance and strength characteristics.

However, even if the non-oxidizing atmosphere is strictly controlled in the heat treatment of the steel plate containing Cr, a dense and stable oxide film containing Cr and 03 is generated due to the trace amount of oxygen contained in the atmosphere. Generally, it is difficult to uniformly remove and activate this oxide film by surface activation treatment such as pickling.
This may impede plating or solderability in the lead frame manufacturing process. Therefore, it is important to suppress the formation and growth of oxide films as much as possible during heat treatment of Cr-containing steel sheets.

Therefore, in the present invention, B is added to the steel in order to suppress the formation and growth rate of the oxide film on the Cr-containing steel sheet itself,
Furthermore, we have developed a manufacturing method that satisfies the characteristics required for lead frame materials by setting the heating temperature and heating time in the heat treatment.

By adding B to steel, Cr can be added in the same heating atmosphere.
The oxidation rate of the contained steel plate is suppressed. The present inventors believe that the reason for this is as follows.

Cr-containing steel plate is oxidized and generated (:r203 (
In the P-type (Po5itive type) oxide], cation vacancies lacking metal ions as lattice defects and holes corresponding to the number of cation vacancies for maintaining electrical neutrality are generated.

The oxidation rate of this P-type oxide is dominated by the movement of cation vacancies when the oxygen partial pressure of the heating atmosphere is the same.

Therefore, by adding B to Cr-containing steel, C
When a part of the r2Q3 lattice is replaced with monovalent B9 instead of trivalent Cr30, the hole concentration increases to maintain electrical neutrality, and the cation vacancy concentration decreases. As a result, the oxidation rate due to the movement of cation vacancies is reduced.

In addition, in the case of ultra-low C steel as in the present invention, B strengthens the grain boundaries by precipitating at the grain boundaries and prevents the growth and coarsening of grains in the heat affected zone during wire bonding heating. , prevent the strength of lead frame products from decreasing.

By subjecting such a Cr-B-containing steel plate to a heating diffusion treatment after coating, Ni- containing Fe is formed through mutual diffusion between the Ni, Co, and N1-Co alloy coating layers and the steel material.
Fe, Co-Fe, or (Ni+Co)-Fe
A diffusion layer mainly composed of N1-Co and N1-Co gold alloys is generated, and as a result, the diffusion coating layer has a smaller potential difference with the base steel sheet than the individual coating layers of N1-Co and N1-Co gold alloys, so
Ni-Fe has the effect of preventing corrosion of the base steel plate in plating defects and the occurrence of red rust.

Since the Co-Fe, (Ni+Co)-Fe diffusion alloy layer itself has excellent corrosion resistance, it protects the base steel material from corrosion and improves corrosion resistance mainly due to rust resistance. In particular, the diffusion treated layer significantly improves the rust resistance compared to a steel plate coated with a Ni-Fe alloy.

In addition, compared to a base steel sheet containing Cr, the diffusion coating layer is easily activated by the pickling bath applied prior to the polishing treatment such as Cu plating in the lead frame manufacturing process, and is further activated under the diffusion conditions. By appropriately selecting , it is possible to obtain excellent plating adhesion and uniform coverage.

Furthermore, these diffusion alloy coating layers have solder wettability and spreadability of Cr even when Franks, which does not contain halogen ions, is used for immersion solder consisting of Pb-5% composition.
It is extremely superior to steel sheets containing Sn, and since Fe is alloyed, less alloy layer is formed between these diffused N layers and Sn compared to a single layer of N1 etc. Moreover, even if it is heated over a long period of time or during wire bonding, its growth is suppressed and the solderability is improved.

Figure 1 shows a Fe-Cr steel plate containing 7% Cr containing Ni.
-Fe-based diffusion coating layer and old plating layer 800 mg/m
An example of evaluation of solder wettability when applying each of 2 and solder adhesion when conducting a heating acceleration test targeting adhesion over a long period of time after solder adhesion is shown below.

As described above, the present invention provides performance characteristics required for lead frame materials, that is, excellent performance characteristics in corrosion resistance, plating performance, and solderability, by applying a coating layer to a Fe-Cr alloy steel plate. This was done by

(for production) The present invention will be explained in detail below.

Molten steel melted in a melting furnace such as a converter or electric furnace is made into a slab through continuous casting, ingot making, or a blooming method, and then subjected to hot rolling, pickling, and cold rolling to reduce C; 0.01% or less. , acid-soluble Af
L, 0.005-0.10%, Cr; 4-10.5
Produce a steel plate containing %.

Although C is economically advantageous as an element for improving mechanical strength,
If the content increases too much, Ni, Co, N1-G.

This increases pinholes and defects in the alloy coating layer, and also impairs uniform diffusion during heat diffusion treatment, resulting in deterioration of corrosion resistance, plating properties, and solderability in the lead frame manufacturing process. In other words, the amount of precipitation of cementite or chromium carbide on the surface of the base steel sheet increases, and Ni, C
The uniform coverage and plating adhesion of coating layers such as o etc. deteriorate,
In addition, for heat diffusion treatment, these become diffusion inhibiting factors and inhibit uniform diffusion, making it impossible to obtain a good diffusion coating layer with uniform performance. From the viewpoint of forming a diffusion coating layer, the content is 0.01% or less, preferably o, ooa% or less.

Ai is acid-soluble AIt (Soi) remaining in the steel.

If the amount of Aλ) is less than 0.005%, it is difficult to prevent the formation of bubbles due to oxygen gas, which significantly increases the rate of occurrence of surface defects in the steel, and deteriorates the corrosion resistance of the steel material itself.
This is not desirable because it becomes the starting point for mechanical deterioration.

Excessive acid-soluble Ail exceeding 0.10% causes helium-based oxides to be scattered on the steel surface, becoming a starting point for deterioration of corrosion resistance.
Furthermore, S contained in steel is not preferable because it becomes a factor that inhibits uniform coating properties in coating layer treatment.
oi and 8u are 0.005 to 0.10%, preferably 0.005 to 0.10%, as amounts that can ensure stable performance of the surface-treated steel sheet.
01-0.08%.

Cr is added in the present invention as an element that improves the corrosion resistance and strength of the plated original plate.

In a corrosive environment, the potential is brought close to that of a Ni-Fe based, Co-Fe based, or (Ni+Co)-Fe based diffusion coating layer. As a result, excellent rust resistance and corrosion resistance can be obtained from the corrosion resistance improvement effect of the steel plate itself, the corrosion resistance improvement effect of the coating layer, and the combined synergistic effect of the steel plate and the coating layer.

Furthermore, by containing Cr in the steel, mechanical strength and corrosion resistance can be obtained. In the present invention, if the Cr content is less than 4%, the desired corrosion resistance and strength cannot be obtained, and if the Cr content exceeds 10.5%, the following drawbacks occur. That is, the Ni coating treatment performed prior to the diffusion treatment requires a pre-activation treatment to obtain a coating layer with good adhesion. Furthermore, even after the diffusion treatment, when the Cr content of the base steel sheet increases, the amount of Cr diffused onto the surface of the diffusion coating layer increases, and the surface Cr-containing Ml-Cr-Fe system or Co-Cr-Fe system A coating layer that is difficult to activate by pretreatment such as pickling or the like is likely to be formed. Therefore, in the lead frame manufacturing process, it becomes difficult to obtain a cover layer or a plating layer with good plating adhesion due to excellent uniform coverage, and the solder wettability, spreadability, etc. are also significantly deteriorated, resulting in a decrease in solder performance. Furthermore, from the viewpoint of the electrical conductivity and thermal conductivity required for the lead frame material, it is preferable that the Cr content be small. Therefore, the Cr content ranges from 4 to 10.5%, preferably from 6 to 10%.

B is a decrease in the oxidation rate during heating of the steel plate, ``especially Cr2O3
It is added to reduce the production rate of system oxides and improve the strength of steel sheets and high-temperature strength during wire heat bonding. In order to obtain these effects, the amount of B added should be 0.0
003% or more, preferably o,oos% or more.

On the other hand, when the amount of B added increases, the effect becomes saturated and cracks occur in the steel sheet during hot rolling. Therefore, in the present invention, the upper limit of the amount of B added is O.005%, preferably 0.002%.

Regarding unavoidable impurity elements in the plating original plate,
Although not particularly specified, the content as described below is preferable.

S [ is preferably 0.6% or less. Si is effective in increasing mechanical strength, but if the S1 content increases excessively,
This is not preferable in terms of corrosion resistance, since the system oxides are scattered on the steel surface and impede uniform coating properties in the alloy plating treatment of the present invention.

Therefore, it is 0.066% or less, preferably 0.15% or less.

Although Mn does not adversely affect corrosion resistance, an increase in Mn content increases mechanical strength and deteriorates rolling workability, so it is preferably 1.5% or less.

In addition, P and S are preferably contained within the range of 0.02% or less in a normal steel manufacturing method. In particular, in order to improve the rust resistance of parts such as end faces where the original plate material is exposed, S
is preferably o, ooa% or less.

Furthermore, in the second aspect of the present invention, the plating base plate composed of the above components contains 1 ffl or two or more of Cu, Nf, and Mo. These elements improve the rust resistance and corrosion resistance of the steel sheet itself, and in a corrosive environment, as mentioned above, when combined with Cr, the potential becomes cathodic, and the potential difference with the diffusion coating layer is brought closer. , deterioration of rust resistance and corrosion resistance due to preferential corrosion of Fe is further prevented.

Therefore, the addition of these elements is such that Cu is 0.05~L, 0
%, Ni 0.05-3.0%, Mo 0.05-0.
It is 5%. If the amount of Cu added is less than 0.05%, the above-mentioned corrosion resistance effect cannot be obtained, and if it exceeds 1.0%, Cu may cause cracking due to red rust brittleness or concentrate on the steel surface during the hot rolling process during the production of the original sheet. , scale defects are more likely to occur.

Therefore, Cu is 0.05 to 1.0%, preferably 0.1%
~0.5%.

If the amount of Ni added is less than 0.05%, no corrosion resistance effect will be obtained, and if it exceeds 3.0%, the corrosion resistance improvement effect will be saturated, and the coexistence effect with Cr will reduce the quality of the coating layer. Pretreatment of the steel surface to obtain good adhesion becomes complicated. Therefore, the amount added is 0.05 to 3.0%
, preferably 0.1 to 1.5%.

If the amount of Mo added is less than 0.05%, the effect of improving corrosion resistance cannot be obtained, and if it exceeds 0.5%, the effect is saturated and the material becomes hard, resulting in a thin material such as a lead frame. This makes rolling processing difficult. Therefore, the amount added is 0.05 to 0.50%, preferably 0.1 to 0.50%.
It is 0.3%.

Furthermore, if a steel plate (plated original plate) with the above-mentioned composition is used as is, corrosion resistance such as rust resistance, plating properties such as Cu and Pb-5n alloy in the lead frame manufacturing process, or solderability will be poor. N1-Fe is insufficient as a frame material.

A Co-Fe-based or (Ni+Co)-Fe-based diffusion coating layer is provided.

In the present invention, for the base steel plate after cold rolling,
A predetermined thickness of Ni, Co, and N1-Co alloy is coated. Prior to this coating treatment, the surface of the material is first degreased by a method such as immersion or electrolysis, and activated using an acid solution. This activation treatment includes pickling treatment by dipping, spraying, etc., or electrolytic pickling treatment.
In order to uniformly remove and reduce the oxide film on the surface peculiar to Cr-containing steel sheets, electrolytic pickling treatment is desirable.

In other words, activation treatment is performed by reducing the oxide film by cathodic electrolytic pickling using a steel material as the cathode in a pickling bath, activation treatment is performed by dissolving and removing the oxide film in anodic electrolytic pickling using the steel material as the anode, or anodic electrolysis Therefore, a method is adopted in which the surface is further activated by cathodic electrolysis after the oxide film is dissolved and removed.

Among these, a method in which cathodic electrolytic treatment is further performed after anodic electrolytic treatment is particularly preferable for removing and reducing the strong oxide film formed during the annealing process peculiar to Cr-containing steel and activating the surface. Methods for performing these electrolytic pickling include, for example, H2SO4 bath, ) 12s
It is preferable to use an O4 bath containing F- ions, a current density of 10 to 6°A/dm', a temperature of room temperature to 80°C, and an electrolysis time of 0.5 to 10 seconds.

Regarding the subsequent coating treatment method of Ni, Co, and Ni-Co alloy, it is preferable to perform the coating treatment by, for example, an electroplating method under the following conditions.

(a) Example of Ni plating plating bath composition Nickel sulfate 240 g/JZ Nickel chloride 45 g/jZ Boric acid 40 g/u Current density 7.5 A/dm2 Plating bath temperature
40℃ (b) Example of Co plating bath composition Cobalt sulfate 75g/u Cobalt chloride 140g/f1 Boric acid 25g/A Current density 50A/d+++2 plating bath temperature 55℃ (c) Example of N1-Co alloy plating bath composition Nickel sulfate 50g/j2 Cobalt sulfate 25g/l Nickel chloride 100g/11 Cobalt chloride 50g/jQ Boric acid 30g/IL Current density 30A/di2 plating bath temperature
The coating treatment is carried out by electroplating under conditions such as 65°C.

Next, in the present invention, heating is carried out to obtain a diffusion coating layer that secures the mechanical properties required for the lead frame material and has excellent corrosion resistance, and excellent performance in waxing and solderability in the lead frame manufacturing process. Diffusion processing is performed.

That is, after cold-rolling a base steel sheet with the above components and subjecting it to pretreatment such as degreasing and pickling, and activation treatment,
Coating amount (per one side) N in the range of 0111g/l112
Co, Nf--Co alloy coating treatment is performed, and then heat treatment is performed for 180 seconds or less in a non-oxidizing atmosphere at a temperature higher than 450° C. and lower than the recrystallization temperature.

By applying such a coating layer, oxidation of the steel plate is prevented during heating. As a result, heat treatment is more advantageous than using a steel plate as is in terms of heating atmosphere, heating time, etc.

Through this treatment, the material has high strength and has the necessary ductility for bending workability, and the combined effect of the material steel plate and the diffusion coating layer improves corrosion resistance, mainly rust resistance, plating performance, and solder performance. It becomes possible to efficiently manufacture lead frame materials that can improve the performance.

Regarding the heating conditions, it is important to control the amount of the Ni, Co, and N1-Co gold alloy coating layer in order to obtain a diffusion coating layer with excellent performance. That is, the amount of these coating layers is 100 m
If it is less than g/la', many coating defects such as pinholes in the coating layer will be generated, making it difficult to produce a uniform diffusion coating layer even after heating and diffusion treatment, and the material steel sheet will be removed from the defective areas during the heating treatment. Oxidation also occurs easily. Therefore, due to an increase in the area of the exposed portion of the material steel plate, etc., it is difficult to obtain an effect of improving corrosion resistance, plating property, or solderability.

In addition, if the amount of the coating layer exceeds 3000 mg/m'', the effects of improving corrosion resistance, plating properties, solderability, etc. of the material subjected to heat diffusion treatment after forming these coatings are saturated, and the shearing process When subjected to such processing, cracks are generated in the coating, or phenomena such as partial peeling occur.

Furthermore, when the amount of coating increases as described above, it is difficult to perform the diffusion treatment sufficiently, and Ni and Co are added to each surface diffusion coating layer.
Alternatively, a diffusion coating layer is formed in which the content ratio of Ni and Co to Fe is large, for example, the concentration of each exceeds 90%. As a result, the corrosion resistance and solder wettability of the coating itself can be improved, but as the amount of Ni, Co, etc. increases, the potential moves in the negative direction, increasing the potential difference with the original plate material and causing defects in the coating. As a result, red rust is likely to occur due to preferential corrosion of the original plate material, and corrosion resistance tends to deteriorate.

Furthermore, since Ni and Co form a stable and dense oxide film, a diffusion coating layer with a large content of Ni and Co should be treated with acid prior to plating (Cu or Pb-5n electric solder plating, etc.) in the lead frame manufacturing process. Since it tends to make washing and activation treatment difficult, it is not preferable in order to obtain uniform plating coverage and wipe adhesion.

Furthermore, the most important problem is that when the concentration of diffusion alloying elements for Fe is high (for example, exceeding 90%), the wettability, spreadability, etc. effects of molten Pb-5n solder are saturated, and the solder The amount of Nt-5n and Co-5n alloys produced by reaction or diffusion between the Sn metal inside and these alloying elements increases, and the formation of these hard and brittle alloy layers may cause the soldered part to be subjected to impact or bending. They are more likely to be destroyed if Therefore, from the viewpoint of preventing solder brittleness, Ni and C are applied prior to heat treatment.
o, The amount of coating layer of Ni and Co alloy is 300hg/m'
It is as follows. Therefore, prior to heating and diffusion treatment, Ni, Co
Alternatively, the amount of coating layer of Ni and CO alloy is t OO ~ 30
QQmg/m2. Preferably 300-2000mg/m
'is.

Next, heat treatment is performed to obtain the mechanical properties and required performance (corrosion resistance, plating properties in the lead frame process, solderability) required for the lead frame material. Heat treatment conditions are regulated for the following reasons. That is,
After cold-rolling the base steel sheet, pre-treatments such as degreasing and pickling are applied.
After the activation treatment, a coating layer such as N1 is provided, and a heat treatment is performed.

The mechanical properties required for the lead frame material are as follows, considering the punching processability into the lead frame shape.
High-strength materials with low ductility are excellent, and lead frame products require both strength and bending workability.

As a result of various studies from these points of view, the strength was 45 to 85.
kg/+m2, preferably 55-80 kg/mm2,
Good mechanical properties are elongation of 3 to 20%, preferably 5 to 15%. In other words, the strength is 45kg/lll
If it is less than 112, the hardness of the material is low and soft, so it is difficult to extract the processed material from the punch or die of the punching machine, which has a negative effect on the punching speed, and the strength is 85 kg/aha2. If it exceeds the hardness of the material, the hardness of the material increases, causing cracks in the material during punching and forming, and wear and tear on the punch and die of the forming machine. Therefore, the strength of the material is 45-85 kg/am2, preferably 55-8
0 kg/m+a2.

In addition, the lead frame product needs to have sufficient strength in the bent leg portion and to withstand repeated bending during bending. Therefore, if the elongation rate of the material is less than 3%, the material will crack during bending. If the elongation rate exceeds 20%, bending workability is good, but it is difficult to obtain high strength, and the strength of the lead frame product is insufficient, and it is also unfavorable for punching formability. The elongation is between 3% and 20%, preferably between 5 and 15%.

Therefore, by using a material provided with an N layer in the steel component material used in the present invention, these mechanical properties are ensured, and the corrosion resistance, plating properties, and solderability required for lead frame materials are achieved. A heating diffusion treatment is used as a manufacturing method that can provide excellent properties.

In order to improve the above-mentioned mechanical properties and various performances as a material for lead frames, it is necessary to simultaneously perform heat treatment and diffusion treatment at a heating temperature of 450°C or higher and lower than the recrystallization temperature, and to hold the material in a non-oxidizing atmosphere. Heat treatment is performed for a time of 180 seconds or less.

The heating temperature is lower than 450℃ and the retention time is 18
Heat treatment for less than 0 seconds has the problem that the composition of the base steel sheet is limited in order to obtain mechanical properties that can withstand bending.
There is a problem in that it is difficult to sufficiently diffuse the coating layer such as i, Co, etc. Therefore, it is difficult to obtain desirable mechanical properties as a material for a lead frame over the entire composition range of the steel material components mentioned above, and the diffusion coating layer is made of Ni, Co, etc.
Since the coating layer or surface with a high concentration of Ni or Co remains as a Ni or Co layer, the desired effects of the present invention cannot be achieved in terms of corrosion resistance, plating properties in the lead frame manufacturing process, solder brittleness, etc. I can't.

When the heating temperature exceeds the recrystallization temperature, the strength of the base steel sheet becomes soft, making it difficult to obtain the desired mechanical strength. Furthermore, when the heating temperature becomes high, the amount of Cr diffused increases, and even if the heat treatment is performed in a non-oxidizing atmosphere, the surface of the diffusion coating layer is oxidized due to the high temperature, forming a dense and strong oxide film, which leads to the formation of a lead frame. Impairs plating and solderability in the manufacturing process. Therefore, from these viewpoints, the heating temperature is higher than 450° C. and lower than the recrystallization temperature. The recrystallization temperature of the base steel sheet varies slightly depending on the steel composition and degree of reduction, but
It is approximately 580°C, and in the present invention, it is 475 to 550°C.
It is preferable that the heat treatment is performed within the range of .

In addition, if the heating time exceeds 180 seconds, the amount of diffusion of additional elements such as Cr in addition to Fe due to diffusion from the base steel sheet to the coating layer increases due to treatment within the above heating temperature range, and as described above, heating Even if the atmosphere is adjusted quite strictly, a strong and dense oxide film is likely to be formed on the surface of the diffusion layer. As a result, pretreatment and activation treatments during plating work in the lead frame manufacturing process become extremely difficult, making it difficult to obtain Cu plating or electric Pb-5-hole solder plating with excellent uniform coverage and plating adhesion. This makes it difficult to solder, and also deteriorates the wettability and solder spreadability of immersion solder.

In addition, the lower limit of the retention time is not particularly specified, but in order to perform the diffusion treatment uniformly, it is 10 seconds or more, preferably 20 seconds or more.
It is preferable to heat the heating for more than a second.Furthermore, a non-oxidizing atmosphere is used as the heating atmosphere for such heat treatment, and N2 gas, ammonia decomposition gas (AX gas), and 5%) 12-N2-based Mix gas are used.

Still heating up! After performing A process, a light pressure treatment may be performed to correct the shape, and in the process of coating with Ni etc., impurities inevitably contained from the plating bath or electrodes, such as S, Even if a small amount (less than about 1%) of B or the like is contained, this does not pose a problem to the present invention.

As mentioned above, N1. Provide a coating layer such as Co,
Due to its combined effects, the steel plate material manufactured by the above heat treatment method has excellent rust resistance, punching processability, uniformity of plating film in the lead frame manufacturing process, adhesion, and solderability. Demonstrates excellent effects on performance, etc.

(Example) A raw steel plate having the steel components shown in Table 1 was cold rolled, subjected to surface activation treatment by degreasing and pickling, and then subjected to coating treatment and heat treatment to produce a lead frame material.

The following performance evaluation tests were conducted on the evaluation materials regarding the main performances required for lead frame products.
The performance evaluation is shown in Table 2.

Regarding the evaluation material, the evaluation material was adjusted to each Kashihara during hot rolling, and the cold rolling reduction rate was changed to obtain a thickness of 0.254.
111 m of evaluation material was obtained. Further, the cold rolled material used for comparison was subjected to the same heat treatment without providing a coating layer.

As a result, the steel plate manufactured by the manufacturing method of the present invention exhibits extremely superior performance as a lead frame material compared to comparative materials.

[Evaluation test method]

■ Adhesion of the diffusion coating layer of the present invention Providing a coating layer of Ni, Co or an alloy of Ni and CO,
The heat-treated evaluation material was repeatedly bent so that the radius of curvature was the same as the plate thickness, and then cellophane tape was applied and peeled off to investigate the degree of peeling of the coating layer.

The evaluation criteria were as follows.

◎... No peeling of the plating coating layer after 11 or more repetitions ○... No peeling of the plating coating layer after 8 or more to 10 repetitions △... No peeling of the plating coating after 4 or more repeats to 7 times No peeling of layer The punching formability was evaluated using the following evaluation criteria, and the molding processability was evaluated.

◎...There is almost no occurrence of burrs on the punched end face or cracks in the material, and the punching and sewing formability is extremely good.O...The punching and sewing formability of the evaluation material is as good as above, but there is some molding. Abrasion damage occurs due to continuous operation of punches and dies of the machine △... Some burrs may occur on the punching end face, or the ability to remove the molded material from the device is poor, so troubles are likely to occur during punching and forming. ×...Cracks occur considerably in the evaluation material due to punching, or the wear of punches, dies, etc. is considerably large due to long-term continuous operation■ Corrosion resistance (a) Evaluation method A The resistance of the evaluation material during storage In order to evaluate rust performance, after punching the evaluation material into a predetermined lead frame shape (48 bottle shape), rust resistance performance was evaluated during storage until surface treatment was applied in the lead frame manufacturing process. The plane part and punched end face part were evaluated using the following accelerated test method and evaluation criteria.

(60 minutes freezing/condensation (-5℃) - 90 minutes high temperature and humidity (49℃)
℃, humidity ≧98%) → 24 hours, left indoors (30℃))
A 7-cycle evaluation test was conducted with 1 cycle as 1 cycle, and the rust resistance performance was relatively evaluated using the following evaluation criteria.

Rust resistance evaluation criteria for flat parts ◎... Red rust occurrence rate 5% or less ○... 〃 More than 5% to 10% or less Δ... 〃
More than 10% to less than 20% X... n 20%
Rust resistance evaluation criteria for super end face ◎... Red rust occurrence rate 10% or less ○... 〃 More than 10% to 20% or less Δ...
〃 More than 20% ~ 40% or less X... 〃 40%
Super (b) evaluation method B As an evaluation test for the rust resistance of lead frame products, after punching into a lead frame shape (48 pin shape), degreasing and immersion pickling were performed, and a 2μ thick Cu After plating was applied, the corrosion resistance was evaluated using a salt spray test (JIS-C-5028) by observing the occurrence of red rust on the flat surface and end surfaces, and using the following evaluation criteria.

O... Red rust occurrence rate after 24 hours of salt spray test less than 1% 0... Red rust occurrence rate 1% or more to less than 5% △... Red rust occurrence rate 5% or more to less than 10% ×...・〃 Red rust occurrence rate of 10% or more ■ Plating performance In order to evaluate the plating performance in the lead frame manufacturing process, Cu plating and Pb-5n alloy electro-solder plating were performed by the following method, and the plating performance was evaluated.

(a) Evaluation method A After punching the evaluation material into a lead frame shape and degreasing (soda phosphate electrolytic degreasing), immersion pickling was performed at 30°C for 5 seconds in a 10% H2SO4 bath.
3μ thick at a current density of 7.5A/di” using a gilding bath.
After Cu plating, the appearance was examined and a bending test was conducted using the following method to examine the adhesion.

In other words, in the bending test, the outer lead part with a plate width of 0.5 mm was sheared to a length of 15IIIffi, and then MI
According to L STD 883C/2004, one end is fixed to the test fixture, the sample is suspended vertically, and the other end is
The process of bending the test jig to 90° C. with a weight of g and then returning it to its original position was repeated to evaluate the adhesion of the Cu plating.

Note that the evaluation was performed based on the following evaluation criteria.

◎...The Cu plating surface is uniform and smooth, with no plating defects, and the Cu plating layer does not peel off even after repeated bending for 10 times or more. No peeling of Cu plating layer after bending 6 times or more △... Although some clear plating defects occur partially on the Cu plating surface, no peeling of Cu plating layer after bending 6 times or more ×...・Plating defects clearly occur on the Cu-plated surface, and peeling of the Cu-plating layer occurs when repeated bending is repeated 5 times or less (b) Evaluation method B After Cu plating as in evaluation method A, heat is applied during wire bonding. We investigated the occurrence of blisters (fine swelling of the Cu-plated layer) on the Cu-plated surface when heat treatment was performed at 400°C for 5 minutes. Adhesion was evaluated, and the mating performance was evaluated using the following evaluation criteria.

◎... No blisters occur Δ... Blisters are 5 x 5 CI! 12 Points or less occur when calculated per area. After the plating, the plating properties were evaluated using an alkanosulfonic acid-based Pb-50%Sn soldering bath. The conditions for electric solder plating are a plating bath temperature of 50°C and a current density!
Plating with a thickness of 8 μm was performed using OA/da+′.

The evaluation method was impact processing (diameter 12.5 mm on the evaluation surface.

After pressing a hemisphere with a height of 9 ffia+ by applying an impact load at a speed of 2 a+/sec, the tape was applied and peeled off, and the adhesion of the abutment layer was evaluated.

The evaluation criteria were as follows.

◎... No peeling of the plating layer O... Peeling area of the plating layer is less than 10% △... 〃
Peeling area 10% or more to less than 30%
Peeling area of 30% or more ■ Solder performance (a) Evaluation method A Regarding the solderability of the evaluation material, we assumed that solder is applied after punching in the lead frame manufacturing process and before Cu plating. In particular, the solderability of the punched end face was evaluated. That is, the wetting stress and wetting time were obtained when the evaluation material was sheared into a wedge shape of 1011III1×50111I11, coated with rosin alcohol flux, with the 10 mm shear plane facing downward, and immersed vertically in a PB-63% Sn solder bath. The solderability was evaluated using the following evaluation criteria.

The above evaluation test for solderability was performed immediately after punching and after being stored indoors for 1.5 months.

◎... Wetting stress of 450 mg or more and wetting time of less than 7 seconds, both solder wettability and wetting speed are very good O... Wetting stress of 300 mg or more and less than 450 mg and wetting time of less than 8 seconds, solder wettability and Fairly good wetting speed △... Wetting stress 250 mg or more to less than 300 mg or wetting time 8 seconds or more to less than 10 seconds, either solder wettability or wetting speed is slightly poor X... Wetting stress 250 Less than mg or wet time 10
The wetting stress and wetting time described above were measured using a Resca-type solder wettability evaluation tester, and the evaluation material coated with flux was melted. It was immersed in a solder bath at a temperature of 350 t at a constant speed (4 mm/5 ec) and immersed for 30 seconds at a depth of 4 mm. As shown in Figure 2, the wetting stress and wetting time were measured by meniscograph measurement. An evaluation was conducted.

(b) Evaluation method B After shearing the evaluation material into a wedge shape of width 30III11 x length 100m + a, 27% rosin alcohol flux was applied to the evaluation material, and the length from the end surface was applied to the solder composition Pb-83% Sn bath. Immersed to a depth of 50 mm, at a temperature of 360'e for 10
The adhesion of the solder was evaluated when heat treatment was performed at 200℃ for 120 minutes to simulate heat treatment during wire bonding after dipping for seconds to adhere the solder, and also as an acceleration test for aging. evaluated.

As an adhesion evaluation method, a repeated bending test with a radius of curvature of 0.25 ma+ (same thickness as the plate thickness) was performed, and the solder peeling state was investigated to evaluate the solder performance.

◎...No peeling of solder or cracks in the solder layer after repeated bending 10 times or more O...No peeling of solder or cracks in the solder layer after repeated bending 6 or more timesΔ...No peeling of solder or cracks in the solder layer after repeated bending 6 times or more Peel the solder more than 3 times.
・・Solder peels off and cracks occur in the solder layer when the number of repeated bending is 2 times or less ■ Performance evaluation of lead frame products after time After processing the evaluation material of the present invention into a lead frame shape, Cu plating and For items that have been soldered, apply a pressure of 2 kg/cm" using a pressure solder.
These products were sealed in a temperature of 120 DEG C. and a relative humidity of -85% and subjected to a 1000 hour aging test, and their appearance was observed and evaluated relatively based on the following evaluation criteria. Note that Cu plating was performed to a thickness of 3.5μ.

0...Excellent condition with no change in surface appearance ○...Small rust on the end face Δ...Blisters on the Cu-plated surface ×...Significant rust on the flat surface and end face Figure 1 is a graph showing the solderability and solder adhesion evaluation results of immersion solder. (Note) 1 is a graph showing the solderability of the evaluation material.
Measurement of wetting stress and wetting time when applying rosin alcohol flux to the evaluation material sheared into a wedge shape of III11 and immersing it vertically in a Pb-63%Sn solder bath with the 10 mm shear plane facing downward. The solderability was evaluated according to the following evaluation criteria.

The above evaluation test for solderability was conducted immediately after punching and after being stored indoors for 1.5 months. The evaluation criteria are as follows.

O...Solder wettability and wetting speed are extremely good when wetting stress is 450 mg or more and wetting time is less than 7 seconds O...Solder wettability and wetting speed are extremely good when wetting stress is 300 mg or more and less than 450 mg and wetting time is less than 8 seconds. Wetting speed valve fairly good △... Wetting stress 250mg or more - less than 300a+g,
Or, if the wetting time is 8 seconds or more and less than 10 seconds, either the solder wettability or the wetting speed is slightly inferior. Wetting stress is less than 250 mg or the wetting time is 10 seconds or more, and either the solder wettability or the wetting speed is slightly inferior. is extremely inferior.

The above wetting stress and wetting time were measured using a Resca-type solder wettability evaluation tester, and the evaluation material coated with flux was immersed at a constant speed (4 mm/5 ec) into a melted solder ball at a temperature of 350°C. The samples were immersed for 30 seconds at a depth of 4 cm, and as shown in FIG. 2, the wetting stress and wetting time were evaluated by meniscograph measurements.

(Note) 2: Non-halogen type flux (flux containing 13% rosin in isopropyl alcohol) was applied to each evaluation material and PB-A o% was applied at 230℃.
It was immersed in a Sn solder bath, pulled up, and then air blown to achieve a solder adhesion thickness of 8 μm. The evaluation material was heat-treated at 100°C for 60 minutes assuming adhesion after long-term aging, and impact-treated (two hemispheres with a diameter of 12.5 mm and a height of 9 mm were placed on the evaluation surface).
After applying an impact load at a speed of m/sec to indentation), the tape was applied and peeled off, and its adhesion was evaluated using the following evaluation criteria.

◎: No solder peeling O: Solder peeled area is less than 10% △: Solder peeled area is 10% or more and less than 30% ×: Solder peeled area is 30% or more, extremely large (effects of the invention) As explained above. According to the manufacturing method of the present invention, a high-performance surface-treated steel sheet for lead frames, which has excellent corrosion resistance, plating properties, and solderability, as well as adhesion and stamping properties of the diffusion coating layer, can be used as lead frame materials for integrated circuits, etc. Obtainable.

[Brief explanation of the drawing]

FIG. Agent: Patent attorney Masamitsu Akizawa and 1 other person

Claims (2)

[Claims] (1) In weight%, C: 0.01% or less, acid-soluble Al: 0
．． 005-0.10%, Cr; 4-10.5%, B; 0
．． After cold rolling a Cr-containing steel plate containing 0003 to 0.005% and the balance consisting of Fe and unavoidable impurities, the amount of adhesion per side on the surface is 100 to 3000 mg/m^2
Corrosion-resistant plating characterized by providing a coating layer of Ni, Co, or an alloy of Ni and Co, and then subjecting it to a heat diffusion treatment in a non-oxidizing atmosphere at a temperature range of 450°C to the recrystallization temperature for 180 seconds or less. A method for manufacturing surface-treated steel sheets for high-performance lead frames with excellent solderability and solderability. (2) In weight%, C: 0.01% or less, acid-soluble Al: 0
．． 005-0.10%, Cr; 4-10.5%, B; 0
．． 0003 to 0.005%, and further contains Cu; 0.005%.
05~1%, Ni; 0.05~3%, Mo; 0.05~
After cold-rolling a Cr-containing steel plate containing 0.5% of one or more of the following, the balance consisting of Fe and unavoidable impurities, the amount of Ni deposited on the surface is 100 to 3000 mg/m^2,
For Co, a coating layer of an alloy of Ni and Co is provided, and then 1
A method for producing a high-performance surface-treated steel sheet for lead frames with excellent corrosion resistance, plating properties, and solderability, characterized by applying heat diffusion treatment for 80 seconds or less.