JPH02104654A - Production of surface treated steel sheet for high-effeiciency 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, 3-10.5% Cr, 0.0003-0.005% B, further 0.03-0.8% of one or more elements among Ti, Nb, Zr, and V, 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 characteristics, such as stamping property and corrosion resistance, can be obtained.

Description

Detailed Description of the Invention (Field of Application in Industry A) The present invention has excellent corrosion resistance, as well as excellent material performance, plating performance, or solder performance necessary for punching workability (stamping performance) in the lead frame manufacturing process. The present invention relates to a method for manufacturing surface-treated steel sheets for lead frames.

(Prior art) Recently, in the electronics field, integrated circuits (ICs)
) 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 solder or electric solder plating) is applied to the surface, and then Ag, Au, etc. are plated. It is then used as an IC material by bonding silicon chips (wire bonding).

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, Fe-42%Ni alloy has been mainly used as a lead frame material due to its strength and thermal expansion characteristics, and copper alloy has also been used due to its cost and conductivity advantages. There is. However, although this copper alloy has excellent conductivity and heat dissipation, it lacks strength compared to the Fe-42%Ni alloy, so it has been reported that actuator leads may bend when inserted into components during the automatic IC assembly process. There was an inconvenience.

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

Low carbon steel is the most advantageous from a cost point of view, but cannot be used due to its tendency to rust. On the other hand, stainless steel, which has excellent corrosion resistance and strength, has problems in plating and solderability because it contains a large amount of Cr. Materials for lead frames that solve these problems are introduced in, for example, Japanese Patent Laid-Open Nos. 57-50457, 59-9149, and 60-103158. These contain 4 to 11% Cr as a basic component, and also include Ni, Mo, Cu, Ti, 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 can provide a certain performance improvement effect, they do not necessarily provide sufficient performance as materials for lead frames. In other words, the plating adhesion of Cu plating was insufficient, and there was a drawback in that the Cu plating layer partially bulged in the blister plating layer, particularly in the heating process during wire bonding. 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 obtained by applying old or Ni alloy plating, or Cu or Cu alloy plating to a steel plate having the above-mentioned known steel components is disclosed in Japanese Patent Application Laid-Open No. 61-2849.
It is introduced in Publication No. 48. The material is Fa-Cr alloy steel plate, i.e. Cr in weight%; 5.0-10.5
%, C, 0.10% or less, Si; 2.0% or less,
Mn: 2.0% or less, Au2, 0.10% or less of the basic components, and Ni, 3.0% or less, if necessary.
Cu: 2.0% or less.

Mo: 1 fl or 2 or more of 4.0% or less,
Or 1 ffi of Nb, Ti, Ta, Zr
Or, two or more types are added at 0.6% or less, and the remainder is substantially Fe.
This is a steel plate obtained by applying a coating layer of 3 to 5 microns of Ni or Ni alloy plating, or Cu or Cu alloy plating to a steel plate, and then cold rolling the steel plate.

The steel plate is used as a lead frame material either as cold rolled or after strain relief annealing, but if the Au or Ag plating property or solderability is high, if it is used as a Fe-Cr base material. This is considerably improved compared to .

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 the Sn metal and the N 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 particularly when heated during wire bonding or when the plated layer of Ni or old alloy becomes thick.

, and when Cu or Cu alloy is applied, C
U or Cu alloys are metals or alloys that are significantly more sensitive than the Fe-Cr based steel sheets used for the base, so they cannot be used in humid environments or in corrosive environments where corrosive factors such as CJZ-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. Even when a plating layer of Ni or Ni alloy is applied, this tendency causes a problem of poor corrosion resistance due to the same cause depending on the steel composition of the Fe-(:r-based 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 acid soluble ^x: o, oos ~ o, to%, CrH3 ~ in weight%, c, o, oi% or less
10.5%, B; 0.0003-0. Contains 5% OQ and further contains Ti, Nb, and Zr.

Contains 0.03 to 0.8% of one or more of (2), and if necessary Cu; 0.05 to 1%, 1.0
．． 05-3%, Mo; 0.05-0.5% 1
fi or 2 f! ! After cold-rolling a Cr-containing steel plate containing the above, with the remainder being Fe and unavoidable impurities, the amount of adhesion per side is 100 to 3000a+g/m"
Corrosion resistance by providing a coating layer of Nl, Co, or an alloy of Ni and Co, and then performing 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,
This is a method for manufacturing surface-treated steel sheets for high-performance lead frames with excellent plating and solderability.

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

Even if the non-oxidizing atmosphere is strictly controlled during heat treatment, a steel plate containing Cr forms a dense and stable oxide film containing Cr2bs 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, and it becomes a cause of inhibiting 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, and the heating temperature and heating time in the heat treatment are set respectively. A manufacturing method has been developed that satisfies the characteristics required for the material.

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.

CrzO5 (P type (
In the positive 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
r, 03 lattice, monovalent 8 instead of trivalent Cr''
When a portion is replaced with 0, the concentration of holes increases to maintain electrical neutrality, and the concentration of cation vacancies decreases, and as a result, the oxidation rate due to the movement of cation vacancies decreases. be reduced.

In addition, in the case of extremely low Ct14 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. Prevents strength reduction of lead frame products.

Furthermore, according to the present invention, appropriate amounts of Ti, Nb, Zr
.

By adding one fil or two or more of (2), the following effects can be obtained. That is, these elements prevent the formation of chromium carbide and improve rust resistance, and these precipitates increase the crystal coarsening temperature to expand the heating temperature range.

By subjecting such a Cr-B containing steel sheet to heat treatment after coating, Ni- containing Fe is formed through mutual diffusion between the Nl, Co, Ni-Co alloy coating layer and the steel material.
A diffusion layer mainly composed of Fe, C-Fe, or (Ni+Co)-Fe is generated. As a result, the diffusion coating layer has a smaller potential difference with the base steel sheet than the individual coating layers of Ni, Co, and Ni-Co alloy, 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 treatment layer significantly improves rust resistance compared to a steel plate coated with a Ni-Fe alloy.

Furthermore, compared to a base steel sheet containing Cr, the diffusion coating layer is easily activated by the pickling bath applied prior to plating treatment such as Cu plating in the lead frame manufacturing process, and furthermore, the diffusion coating layer is activated by the pickling bath applied prior to plating treatment such as Cu plating in the lead frame manufacturing process. By selecting the following, plating performance with excellent plating adhesion and uniform coverage can be obtained.

Furthermore, these diffusion alloy coating layers have solder wettability and spreadability of Cr even when a flux that does not contain halogen ions is used for immersion solder having a Pb-Sn composition.
It is extremely superior compared to steel sheets containing Sn, and since Fe is alloyed, the alloy layer formed between these diffusion coating layers and Sn is smaller compared to a single layer of Ni etc. Furthermore, even if it is heated over a long period of time or during wire bonding, its formation is suppressed and the solderability is improved.

Figure 1 shows the solder wettability when a Ni-based diffusion coating layer and a Ni plating layer of 800 mg/m' are applied to a Fe-Cr steel plate containing 7% Cr, and the adhesion over a long period of time after solder adhesion. An example of evaluation of solder adhesion when an accelerated heating test was conducted 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, flaking property, and solderability, by applying a coating layer to a Fe-Cr alloy steel plate. It is something that is done by being done.

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 processed through the processes of hot rolling, pickling, and cold rolling to reduce C, 0°01% or less. , acid soluble^i
;0.005~0.10%+Cr;3~10.5%
and further contains: Ti, Nb, Zr, v flea species or 2 f! ! ! A steel plate containing 0.03 to 0.8% of the above is manufactured.

C is economically advantageous as a strength-improving element, but if its content increases too much, pinholes and defects in the coating layer of Nl, Co, and Ni-Co alloys will increase, and it will also become difficult to heat diffusion treatment. However, uniform diffusion is impaired, and corrosion resistance, plating performance in the lead frame manufacturing process, and solderability deteriorate.

That is, C combines with other elements to precipitate titanium carbide, niobium carbide, chromium carbide, etc. on the steel surface, and Ni.

In addition to deteriorating the uniform coating properties and plating adhesion of coating layers such as Co, carbide also deteriorates during heat diffusion treatment.
This becomes a diffusion inhibiting factor and inhibits uniform diffusion, making it impossible to obtain a diffusion coating layer with uniform performance.

Therefore, the C content in the base steel sheet is 0.01% or less, preferably 0.0% from the viewpoint of corrosion resistance and formation of a uniform diffusion coating layer.
0.08% or less.

AfL is an acid-soluble ^JZ (Son.

If the amount of An) is less than 0.005%, it is difficult to prevent the formation of bubbles due to oxygen gas, which will significantly increase the incidence of surface defects on the steel, resulting in deterioration of the corrosion resistance of the steel material itself.
An excess of acid-soluble Aj2 exceeding 0.10% is not preferable because it becomes a starting point for deterioration of mechanical properties.
This is not preferable because the helical oxides are scattered on the steel surface, which becomes a starting point for deterioration of corrosion resistance, and furthermore, it becomes a factor that inhibits uniform coating properties in coating layer treatment. Therefore, the amount of Son,^L contained in the steel is 0.005 to 0.10%, preferably 0.01 to 0.08%, as an amount that can stably ensure the performance of the surface-treated steel sheet.

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

Cr-containing steel sheets have superior rust resistance and corrosion resistance compared to steel sheets without Cr, and they also have superior rust and corrosion resistance in corrosive environments.
o) The potential is brought close to that of the -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 3%, the desired corrosion resistance and strength cannot be obtained. 'Furthermore, when 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. 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 becomes Cr-containing Ni-Cr-Fe or Co-Cr-Fe. Pretreatment of the system, etc. A coating layer that is difficult to activate by pickling or the like is likely to be formed. For this reason, it becomes difficult to obtain a plating layer with excellent uniform coverage or a plating layer with good adhesion in the lead frame manufacturing process, and the solder wettability, spreadability, etc. are also significantly deteriorated, leading to 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. The Cr content therefore ranges from 3 to 10.5%, preferably from 5 to 10%.

B is added to reduce the oxidation rate during heating of the steel plate, particularly to reduce the production rate of Cr and 03-based oxides, and to improve the strength of the steel plate and the high-temperature strength during wire heat bonding. In order to obtain these effects, the amount of B added is 0.00.
03% 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, oos%, preferably 0.
．． 002%.

Ti, Nb, Zr, and V are components that combine with C or N contained in the plated original plate to prevent the formation of carbides or nitrogen substances of Cr, thereby effectively exerting the corrosion-resistant effect of Cr. In addition, carbides such as TI or nitrogen substances are finely precipitated at grain boundaries to prevent coarsening of the crystal grains of the plating original plate and ensure strength. In particular, it has the effect of expanding the heating temperature range for adjusting mechanical properties.

In order to obtain such an effect, Ti, Nb, Zr,
It is necessary to contain 0.03% or more of one or more types of V, and if the content exceeds 0.8%,
If the amount of precipitates increases too much, the material becomes brittle, cracks occur during molding, and electrical conductivity and thermal conductivity tend to deteriorate. The preferred range is 0.05-0.5%.

In addition, the unavoidable impurity elements in the original plate material are not particularly defined, but the content as described below is preferable.

Sl is preferably 0.6% or less. St is effective in increasing mechanical strength, but when the St content increases excessively, Si
The system oxides are scattered on the steel surface and inhibit the uniform coating properties of the plating treatment in the present invention, which is not preferable in terms of corrosion resistance.

Therefore, it is 0.6% 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 should be contained within the range of 0.02% or less in normal steelmaking methods.In particular, in order to improve the rust resistance of the parts where the original plate material is exposed such as the end face, S
is preferably o, ooa% or less.

Furthermore, in the second aspect of the present invention, the plating original plate composed of the above-mentioned components is made to contain one or more of Cu, Ni, 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 to 1.0
%, Nl is 0.05-3.0%, Mo is 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, Mi-Cu is 0.05 to 1.0%, preferably 0.1 to 1.0%.
It is 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, making it difficult to obtain a thin material such as a lead frame. The rolling process becomes 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-5% alloy in the lead frame manufacturing process, or solderability will be poor. It is insufficient as a material for frames, and therefore Ni-Fe, Co-Fe, or (
A Ni+Co)-Fe based diffusion coating layer is provided.

In the present invention, for the base steel plate after cold rolling,
Ni, Co, and Ni-Co gold alloys are coated to a predetermined thickness. 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.

That is, activation treatment by reducing the oxide film by cathodic electrolytic pickling in a pickling bath with the steel material as the cathode, activation treatment by dissolving and removing the oxide film in anodic electrolytic pickling with the steel material as the anode, or anode A method is adopted in which the oxide film is dissolved and removed by electrolysis, and then the surface is further activated by cathodic electrolysis.

Among these, a method in which cathodic electrolytic treatment is further combined after anodic electrolytic treatment is particularly preferable in order to activate the surface by removing and reducing the strong oxide film formed during the annealing process peculiar to Cr-containing steel. These electrolytic pickling methods include, for example, H2SO, bath, H2S
It is preferable to use a bath containing F- ions, a current density of 10 to 60^/dm'', a temperature of room temperature to 80°C, and an electrolysis time of 0.5 to 10 seconds.

The Ni, Co, and Ni--Co gold alloy coating method to be performed subsequently is preferably performed by electroplating under the following conditions, for example.

(a) Ni plating Example of plating bath composition Nickel sulfate 230 g/jl! nickel chloride
40g/j2 Boric acid 40 g/u Current density 7.5A/dm2 Plating bath temperature
40°C (b) Co plating Example of plating bath composition Cobalt sulfate 75 g/fL Cobalt chloride 145 g/f Boric acid 25 g/fL Current density 50 A/dm' Plating bath temperature
55℃ (c) Ni-Co gold alloy plating bath composition - Example Nickel sulfate 45g/i Cobalt sulfate 25g/fl Nickel chloride 100 g/i Cobalt chloride 45g/j2 Boric acid 30g/ft Current density 30A/di" Mefuki bath temperature
The coating treatment is carried out by electroplating under conditions such as 65°C.

Next, in the present invention, the material for the lead frame has the required mechanical properties and corrosion resistance.

A heating diffusion process is performed to obtain a diffusion coating layer having excellent plating or solderability in the lead frame manufacturing process.

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,
Ni, C with adhesion amount (per one side) in the range of 0 mg/m'
o, Ni-Co alloy coating treatment, then 45
Heat treatment is performed for 180 seconds or less in a non-oxidizing atmosphere at a temperature higher than 0° C. and lower than the recrystallization temperature. By applying such a coating layer, oxidation of the Cr-containing steel sheet 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 ductility necessary 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 materials for lead frames that can be improved.

Regarding this heating condition, in order to obtain a diffusion coating layer with excellent performance, it is important to control the amount of coating layer of Ni, Co, and Ni-Co alloy. That is, the amount of these coating layers is 100 r
ag/m", many coating defects such as pinholes are generated in the coating layer, making it difficult to produce a uniform diffusion coating layer even after heat diffusion treatment, and the material steel sheet is removed from the defective areas during heat treatment. Oxidation is also likely to occur.Therefore, due to an increase in the area of the exposed portion of the material steel plate, it is difficult to obtain the effect of improving corrosion resistance, plating performance, 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 that has been heat-diffused after providing these coatings are saturated, and the shearing process When subjected to such processing, cracks are generated in the coating or partial peeling occurs.

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 tends to shift 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.

In addition, since Nl and Co form a stable and dense oxide film, a diffusion coating layer with a large content of these is required prior to plating (Cu or Pb-Sn electric solder plating, etc.) in the lead frame manufacturing process. Since it tends to make pickling activation treatment difficult, it is not preferred for obtaining uniform plating coverage and plating 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 Ni-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. easily destroyed if Therefore, from the viewpoint of preventing solder brittleness, Ni, which is applied prior to heat treatment,
The coating layer amount of Co, Ni and Co alloy is 3000mg/
a” or less. Therefore, Ni prior to heating and diffusion treatment,
The coating layer amount of Co or an alloy of Nf and Co is 100 to 3
000mg/a”, preferably 300-2000II
Ig/m2.

Next, heat treatment is performed to obtain the mechanical properties and required performance (corrosion resistance, plating properties in the lead frame process, solderability) required of the lead frame material. Heat treatment conditions are regulated for the following reasons. That is, after cold rolling a base steel sheet of steel components, a coating layer is provided for degreasing, pickling pretreatment, activation treatment recovery, etc., and then 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/mm2 preferably 55-80 kg/mff1
2. Good mechanical properties are elongation of 3 to 20%, preferably 5 to 15%. That is, the strength is 45 kg/
If it is less than mm2, the hardness of the material is low and it is soft, making it difficult to remove the workpiece from the punch or die of the punching machine, which adversely affects the punching speed. Also, if the strength exceeds 85 kg/mm2, the hardness of the material will be high (the material will crack during punching and forming, and the punches and dies of the molding machine will be prone to wear and tear. Therefore, the strength of the material will be 45 to 45 kg/mm2). 85 kg/ma+”, preferably 55-8
0 kg/mm'.

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 in which a coating layer is provided on 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. Thermal diffusion treatment is performed as a manufacturing method that can obtain excellent performance.

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 closer to the recrystallization temperature 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 180℃.
Heat treatment for less than a second 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 of 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 has a high concentration of Ni, Co, etc. is Ni. Since the Cojl remains as it is, the desired effects of the present invention cannot be obtained in terms of corrosion resistance, plating properties in the lead frame manufacturing process, solder brittleness, etc.

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. Therefore, the basic component of the base steel sheet is C.
Since it contains Ti and Nb in addition to r, the recrystallization temperature shifts to the high temperature side, making it easier to obtain a diffusion coating layer. The recrystallization temperature varies slightly depending on the steel composition and degree of rolling reduction, and is approximately 650°C, but the recrystallization temperature is approximately 650°C, but
Heat treatment at 75 to 625°C is preferable.

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, in the plating work in the lead frame manufacturing process, pretreatment and activation treatments are extremely difficult, making it difficult to obtain Cu plating or electric Pb-5n solder plating with excellent uniform coverage and plating adhesion. It becomes difficult to solder, and also deteriorates the wettability and solder spreadability for 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.
A non-oxidizing atmosphere is used as the heating atmosphere for such heat treatment, and N2 gas, ammonia decomposition gas (AX gas), and 5% H2-N2-based old X gas are used.

After the heat treatment, a light pressure treatment may be performed to modify the shape, and in the process of coating with Ni etc., impurities unavoidably contained from the plating bath or electrodes, such as Even if a small amount (less than about 1%) of S, B, etc. is contained, the present invention will not be affected.

As described above, a coating layer of Ni, Co, etc. is provided on the steel component,
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 thickness of the material was changed to 0.254.
An evaluation material of mm was obtained.

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 The evaluation material, which was coated with a coating layer of Co or an alloy of Nl and CO and subjected to heat treatment, was repeatedly bent so that the radius of curvature was the same as the plate thickness, and then Apply cellophane tape and peel off 1II1. /The degree of peeling of the coating layer was investigated.

The evaluation criteria were as follows.

◎... No peeling of the plating coating layer after 11 or more repetitions O... 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 ×...Plating coating layer peels off or peels off after repeating 3 times or less ■ Stamping processability (stamping property) Evaluation material was continuously stamped into a 48-pin lead frame shape, and the lead The punching formability into a frame shape was evaluated using the following evaluation criteria, and the formability was evaluated.

0...Excellent punching formability with almost no occurrence of burrs on the punched end surface or cracking of the material 0...The punching formability of the evaluation material was as good as above, but it was slightly affected by the molding machine. Abrasion damage occurs due to continuous operation of punches and dies △... Slight burrs may occur on the punched end face, or problems may easily occur during punching and forming due to poor ability to remove the molded material from the equipment X...・Due to punching and forming, a considerable amount of cracking occurs in the evaluation material, or wear and tear on punches, dies, etc. becomes considerably large due to long-term continuous operation■ Corrosion resistance (a) Evaluation method A Rust resistance of evaluation material during storage In order to evaluate the performance, after punching the evaluation material into a predetermined lead frame shape (48 bottle shape), we evaluated the rust resistance performance during storage until surface treatment was applied in the lead frame manufacturing process. The flat part and punched end face part were evaluated using the following accelerated test method and evaluation criteria.

(60 minutes freezing/condensation (-5℃) → 120 minutes high temperature and humidity (4
9℃, humidity ≧98%) - 24 hours, left indoors (30℃)
) was taken as one cycle, and a 7-cycle evaluation test was conducted.
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 O... 〃 More than 5% to 10% or less △... 〃
More than 10% to less than 20%×... 20% Rust resistance evaluation criteria for end face ◎... Red rust occurrence rate less than 10% O... More than 10% to less than 20% Δ...
〃 More than 20% ~ 40% or less ×... 〃 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.

◎... Red rust occurrence rate after 24 hours of salt spray test less than 1% O... 〃 Red rust occurrence rate of 1% or more to less than 5% Δ... 〃 Red rust occurrence rate of 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.
Using a plating bath, the thickness is 3μ at a current density of 7.5A/dm2.
After plating, the appearance after Cu plating was inspected, and a bending test was conducted using the following method to examine the adhesion.

In other words, the bending test was performed using an actor with a plate width of 0.5 mm.
After shearing the lead part to a length of 15 mm, MIL S
In accordance with To 883G/2004, one end was fixed to the test jig, the sample was hung vertically, a 230 g weight was attached to the other end, the test jig was bent at 90°, and the process was repeated. Then, the adhesion of Cu plating was evaluated.

The evaluation was conducted 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 10 times or more.○...The Cu plating surface is uniform and smooth, with no plating defects. , No peeling of the Cu plating layer after repeated bending of 6 times or more △...Although some clear plating defects occur partially on the Cu plating surface, no peeling of the Cu plating layer after repeated bending of 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 in the same manner as evaluation method A, heating during wire bonding was performed. We investigated the occurrence of blisters (fine swells in the Cu plating layer) that occur on the Cu plating surface when heat treatment was performed at 400°C for 5 minutes, assuming that the Cu plating layer The plating performance was evaluated using the following evaluation criteria.

◎... No blisters occur Δ... 5 or less blisters occur per 5 x 5 cra" area ×... 6 or more blisters occur per 5 x 5 cm" area (c) Evaluation method C After performing the same pretreatments as above, such as degreasing and pickling, the plating properties were evaluated using an alkanosulfonic acid-based Pb-50%Sn electric soldering bath. Electrical solder plating conditions include plating bath temperature of 50°C and current density of 10°C.
Plating was performed at A/da' to a thickness of 8 μm.

The evaluation method was impact processing (the diameter of the evaluation surface was 12.5 ma).

A hemisphere of height ljom at a speed of 2 m/sec? # After applying impact load and indentation), the tape was applied and peeled off to evaluate the adhesion of the plating layer.

The evaluation criteria were as follows.

◎... No peeling of plating layer ○... Peeling area of plating layer less than 10% △... 〃
Peeling area 10% or more - less than 30%×...〃
Peeling area of 30% or more■ Soldering performance (a) Evaluation method A Regarding the solderability of the evaluation material, assume that soldering is performed after punching in the lead frame manufacturing process and before Cu plating. In particular, the solderability of the punched end face was evaluated. In other words, the wetting stress and wetting time were obtained when the evaluation material was sheared into a wedge shape of 10 μm x 50 mm, coated with rosin alcohol flux, and immersed vertically in a Pb-63%SB solder bath with the 10 mm shear plane facing downward. 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 is 450a+g or more and wetting time is less than 7 seconds, and both solder wettability and wetting speed are extremely good.○...Wetting stress is 300mg or more and less than 450mg and wetting time is less than 8 seconds, and solder wettability is excellent. and wetting speed are fairly good Δ... Wetting stress is 250 mg or more and less than 300 mg or wetting time is 8 seconds or more and less than 10 seconds, and either the solder wettability or the wetting speed is slightly poor ×... 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. Constant speed (
4 μm/5 ec) and immersed for 30 seconds at an immersion depth of 4 m+a, and as shown in FIG. 2, the wetting stress and wetting time were evaluated by meniscograph measurement.

(b) Evaluation method B After shearing the evaluation material into a wedge shape of 30 mm width x 100 mm length, 27% rosin alcohol flux was applied to the evaluation material, and a solder composition of 1'b-63% Sn bath was applied from the end face to the end surface. The solder was immersed to a depth of 50 mm for 10 seconds at a temperature of 360° C. to adhere the solder.

After this, we assumed heat treatment during wire bonding, and also served as an accelerated test for aging.
The adhesion of the solder was evaluated when heat treatment was performed at 0° C. for 120 minutes.

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

◎...No peeling of solder or cracks in the solder layer after repeated bending 10 times or more○...No peeling of solder or cracks in the solder layer after repeated bending 6 times or moreΔ...No peeling of solder or cracks in the solder layer after repeated bending 6 times or more No peeling of solder or cracks in the solder layer after 3 or more bending times... No peeling of solder or cracks on the solder layer after 2 bending times or less ■ Performance evaluation of lead frame products over time Performance evaluation of lead frame products of the present invention After processing the evaluation material into a lead frame shape, Cu plating and soldering were performed in the surface treatment process, and a pressure of 2 kg/cm was applied using a pressure cutter.
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.

◎...Excellent condition with no change in surface appearance ○...Small rust on the end face △...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 indicates the solderability of the evaluation material.
Apply rosin alcohol flux to the evaluation material sheared into a 10mm wedge shape, with the 10mm sheared surface facing downward.
The solderability was evaluated based on the following evaluation criteria by measuring wetting stress and wetting time when vertically immersed in a Pb-63%Sn solder bath.

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...Wetting stress 450+++g or more and wetting time 7
Solder wettability and wetting speed are very good in less than seconds O... Wetting stress is 300 mg or more and less than 450 mg and wetting time is less than 8 seconds, both solder wettability and wetting speed are quite good Δ... Wetting stress is 250 mg More than 300 + sg,
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. ×...The wetting stress is less than 250 mg or the wetting time is 10 seconds or more, and either the solderability or the wetting speed is extremely poor. Inferior.

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

(Note) 2: Each evaluation machine is coated with non-halogen type flux (flux containing 13% rosin in isopropyl alcohol) and Pb-63 is heated at 230°C.
%Sn solder bath, and after pulling it up, it was applied with an air blow to a target 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 9I were placed on the evaluation surface).
Indentation processing by applying impact load at a speed of m/sec)
After that, the tape was peeled off and its adhesion was evaluated using the following evaluation criteria.

◎: No solder peeling ○: Solder peeled area is less than 10% △: Solder peeled area is 10% or more and less than 30% X: 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, the surface treatment for high-performance lead frames has excellent corrosion resistance, plating properties, and solderability, as well as adhesion and stamping properties of the diffusion coating layer, which can be used as lead frame materials for integrated circuits, etc. You can get steel plates.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the evaluation results of solderability and adhesion of immersion solder, and FIG. 2 is a drawing explaining a method of measuring wetting stress and wetting time using a meniscograph. 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; 3-10.5%, B; 0
．． 0003 to 0.005%, and further contains Ti, Nb
After cold rolling a Cr-containing steel plate containing 0.03 to 0.8% of one or more of Zr, V, and the balance consisting of Fe and unavoidable impurities, the surface has a coating weight of 100% per side.
~300018/m^2 Ni, Co or Ni and Co
45 in a non-oxidizing atmosphere.
A method for producing a high-performance surface-treated steel sheet for lead frames with excellent corrosion resistance, plating performance, and solderability, which is characterized by performing a heat diffusion treatment for 180 seconds or less in a temperature range of 0°C to recrystallization temperature. (2) In weight%, C: 0.01% or less, acid-soluble Al: 0
．． 005-0.10%, Cr; 3-10.5%, B: 0
．． 0003 to 0.005%, and further contains Ti, Nb
, Zr, V or more at 0.03-0.8%, Cu: 0.05-1%, Ni: 0.05-3%, Mo:
After cold-rolling a Cr-containing steel plate containing 0.05 to 0.5% of one or more Cr and the balance consisting of Fe and unavoidable impurities, the amount of adhesion on the surface is 100 to 3000 mg/m^
2. Corrosion resistance 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 plating and solderability.