JPH0288796A - Surface-treated steel sheet for high-performance lead frame having excellent corrosion resistance, solderability, and platability - Google Patents

Abstract

PURPOSE:To produce the title surface-treated steel sheet having excellent corro sion resistance, etc., by providing a coating layer of an Ni-Fe alloy in a specified amt. on the surface of a steel sheet contg. specified contents of C, acid-soluble Al, Cr, B, Ti, Nb, Zr, and V. CONSTITUTION:A steel sheet contg., by weight, <=0.01% C, 0.005-1.10% acid soluble Al, 3-20% Cr, 0.0003-0.005% B, 0.03-0.8% of one or >=2 kinds among Ti, Nb, Zr, and V, the balance Fe, and inevitable impurities is prepared. The content of Si is preferably controlled to <= about 0.6%, that of Mn to <= about 1.5%, and those of P and S to <= about 0.02%. A coating layer consisting of a (10-90%)Ni-Fe alloy, a (10-90%)Co-Fe alloy, or a (10-90%)<Ni+Co>-Fe alloy is provided on the surfaces of the steel sheet in the amt. of 100-3000mg/m<2> per surface. By this method, a surface-treated steel sheet for a high-performance lead frame having excellent corrosion resistance, solderability, and platability is obtained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a surface-treated steel sheet for IC lead frames that has excellent corrosion resistance and excellent solderability or Cu plating properties applied in the lead frame manufacturing process. It is related to.

(Prior art) Recently, with the development of the electronics field, 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.

Generally, lead frame material is made into a strip material, then cut and punched, and its surface is plated with Cu or solder (immersion solder or electric solder plating).
, Au, etc. are plated, and a silicon chip is bonded thereto (wire bonding) to be used as an IC material. Therefore, the lead frame material should have good punching and forming processability, excellent plating properties,
Excellent solderability is required. In particular, since the terminal portion of the lead frame is soldered to an IC board or the like, excellent solderability is required. Furthermore, the material is also required to have excellent rust resistance before being subjected to the above-mentioned plating, soldering, etc. or during storage, and also for the product to have excellent rust resistance after each treatment.

(Problem to be Solved by the Invention) Conventionally, lead frame materials have a F
e-42%Ni alloy is mainly used. 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 has the disadvantage of bending when inserting outer leads into components in the automatic IC assembly process. was there.

Furthermore, with the recent miniaturization of ICs, lead frame materials are becoming increasingly thinner, and higher strength is required.

Low carbon steel is the most advantageous in terms of cost, but it cannot be used because it easily rusts and has poor corrosion resistance. on the other hand,
Stainless steel, which has corrosion resistance and strength, has problems with plating and solderability because it contains a large amount of C.

Materials for lead frames that solve these problems have been introduced in Japanese Patent Application Laid-open Nos. 57-50457, 59-9149, and 1987-103158, for example. These contain 4 to 11% Cr as a basic component, and others include Nj, Mo, Cu, Ti, Nb,
A material for lead frames that contains less than a few percent of each component such as V and Zr to improve the rust resistance required for lead frame materials, and also improves plating and solderability, which are disadvantages of stainless steel. be. 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 is insufficient, and blisters (
A drawback was observed: partial blistering of the plating layer.

It is also widely used in the electronics field (, fl
- In soldering work using non-halogen type blacks that do not contain halogen ions such as ions, there was a problem that the solder did not adhere sufficiently.

Furthermore, a lead frame material obtained by plating a steel plate with the above-mentioned known steel components and plating with Ni or old alloy, or plating with Cu or Cu alloy is disclosed in Japanese Patent Application Laid-Open No. 61-284948.
It is stated in the No. This is a Fe-Cr alloy steel sheet, i.e. Cr: 5.0-10.5% by weight.

C, 0.10% or less, Si; 2.0% or less, M
In addition to the basic components of n: 2.0% or less, Au2: 0.10% or less, Ni: 3.0% or less, Cu: 2.0% or less, Mo: 4.0% or less. One or more types, or Nb, Ti, Ta
, one or more of Zr is added in an amount of 0.6% or less,
3 to 5 times each of Ni or Ni alloy plating or Cu or Cu alloy plating is applied to the steel plate, the remainder of which is essentially Fe.
This is a steel plate that is laminarly plated and then cold rolled.

This steel plate is used as a lead frame material as it is cold rolled or after being annealed to remove strain, but if it is used as it is as it is as a Fe-Cr based material, the plating property or solderability of 8U or Ag improved compared to

However, since the plated metal adheres to the rolling roll during cold rolling after plating, this steel plate has many problems in manufacturing, such as requiring complicated maintenance to obtain a product with a smooth appearance. In addition, there are the following problems in terms of performance.Although materials plated with Ni or Ni alloy have improved plating and solderability, when immersion soldering is performed, Sn metal in the solder composition and Ni metal cause a diffusion reaction, producing a hard and brittle Ni--Sn alloy. When the amount of solder produced increases, the solder layer becomes brittle and has the disadvantage of being easily broken when subjected to impact, bending, etc. (solder brittleness). In particular, this defect tends to occur when the wire is heated during wire bonding or when the plating layer of Ni or Ni alloy becomes thick.

In addition, when Cu or Cu alloy is applied, it may be exposed to a humid environment or CJZ- because Cu or Cu alloy is a metal or alloy that is significantly more sensitive than the Fe-Cr based steel sheet used for the base. In a corrosive environment where corrosive factors such as 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 old or old alloy is applied, there is a problem of poor corrosion resistance due to the same cause depending on the steel composition of the Fe-Cr steel sheet.

The present invention focuses on Cu coating applied in the lead frame manufacturing process of Fe-Cr-B yarn material, which contains Cr to improve corrosion resistance and further contains B to suppress the formation and growth of an oxide film on the steel plate surface as much as possible. To provide a surface-treated steel sheet for a lead frame, which has excellent plating properties such as electroplating, excellent solderability, and corrosion resistance such as rust resistance.

(Means for Solving the Problems) The present invention provides an acid-soluble composition in which, in weight %, C; 0.01% or less, JZ, o, oos to o, to %, Cr; 3
~20%, B: 0.0003~0.005%,
One or more of Ti, Nb, Zr, and V in an amount of 0.
03-0.8%, further Cu; 0.05-0.05% as necessary
1%, Ni; 0.05-3%, Mo; 0.0
The surface of a Cr-containing steel plate containing 5 to 0.5% of one or more of the following, the balance consisting of Fe and unavoidable impurities, has an adhesion amount of 100 to 3000 mg/m2 (10 to 9
0%) former -Fe alloy, (10-90%) Co-Fe alloy, or (10-90%) <Ni+Co> - Provided with a coating layer made of -Fe alloy with excellent corrosion resistance, solderability, and plating performance. This is a surface-treated steel sheet for high-performance lead frames.

The gist of the present invention is to apply a Ni or Go-Fe based alloy plating layer to the surface of a steel plate containing Cr. Even when adjusted to It is difficult to
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, 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.

Cr203 (P type (
In the positive type oxide], cation vacancies lacking metal ions as lattice defects and a number of holes corresponding to the 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 r2O3 lattice is replaced with monovalent B+ instead of trivalent C "3"", the concentration of holes increases to maintain electrical neutrality, and the concentration of cation holes increases. 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.

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

By adding one 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.

According to the present invention, together with the above-mentioned Cr and B, T1Nb,
By providing a (Ni or Go) -Fe alloy plating layer on the surface of a steel sheet with one or more of Zr and V as essential components, a steel sheet for lead frames having excellent properties can be obtained.

(Function) The present invention provides a steel plate having the above composition with an F of an appropriate composition and an appropriate thickness.
e −Ni, Fe −Go, Fe −(Ni+ G
o) An alloy plating layer is provided, but these alloy plating layers are
Since Fe is alloyed with Ni and Co, the potential difference with the base steel plate is smaller than that of Ni and Go gold metal plating layers, so the base steel plate in the plating defects is preferentially corroded and red rust occurs. At the same time, the coating layer itself prevents corrosion of the base steel plate and improves corrosion resistance, mainly rust resistance.

In addition, these alloy plating coating layers are easily activated by pickling performed prior to plating treatment such as Cu plating in the lead frame manufacturing process, and are a plating layer with excellent plating adhesion and uniform coverage. is obtained, improving plating properties.

Furthermore, these alloy coating layers have extremely superior solder wettability compared to Cr-containing steel sheets even when using flux that does not contain halogen ions for immersion solder consisting of Pb-Sn composition, and Because it is alloyed, there is less alloy layer formed between these coating layers and Sn compared to a single Ni layer, and furthermore, its growth is suppressed even if it is heated over a long period of time or during wire bonding. It has characteristics such as not causing solder brittleness and greatly improves solderability.

Figure 1 shows a Fe-Cr-B steel sheet containing 7% Cr coated with a Ni-Fe alloy plating layer and a Ni plating layer of 100%.
The solder wettability when applied at 0 mg/m2 and the solder adhesion according to a heating accelerated test for adhesion after a long period of time after solder adhesion are shown.

Note that evaluation of solderability and solder adhesion was performed as follows.

(1) Regarding the solderability of the solderability evaluation material, apply rosin alcohol flux to the evaluation material sheared into a 10mm x 50mm wedge shape, and place the Pb-6
By measuring the wetting stress and wetting time when vertically immersed in a 6% Sn-based solder bath, 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 2 months. The evaluation criteria are as follows.

◎...Solder wettability and wetting speed are extremely good when wetting stress is 450 mg or more and wetting time is less than 5 seconds.○...Solder wettability and wetting speed are extremely good when wetting stress is 300111 g or more and less than 450 mg and wetting time is less than 8 seconds. Wetting speed is also fairly good △... Wetting stress of 250 mg or more to less than 300 mg or wetting time of 8 seconds or more to less than 10 seconds either the solder wettability or the wetting speed changes slightly ×... Wetting stress of less than 250 mg Alternatively, if the wetting time is 10 seconds or more, either the solder wettability or the wetting speed is extremely poor.

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 mm/5 ec). The samples were immersed for 30 seconds at an immersion depth of 4 mm, and the wetting stress and wetting time were evaluated by meniscograph measurements as shown in FIG.

(2) Solder adhesion A non-halogen type flux (flux containing 13% rosin in isopropyl alcohol) was applied to each evaluation material, immersed in a Pb-60%Sn solder bath at 230°C, and after lifting the rice. The solder was applied with an air blow to a target thickness of 8μ. The evaluation material was heat-treated at 100°C for 90 minutes assuming adhesion after long-term aging, and subjected to impact processing (a hemisphere with a diameter of 12.5 mm and a height of 9 mm was applied to the evaluation surface at a speed of 2 m/sec). After applying and peeling off the tape, the 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% ×; Solder peeled area is 30% or more and extremely large. By applying a coating layer to Cr alloy steel plate,
The performance characteristics required for lead frame materials, that is, excellent performance characteristics in corrosion resistance, solderability, and solderability can be obtained.

The present invention will be explained in detail below.

Molten steel produced in a melting furnace such as a converter or electric furnace is made into a slab through continuous casting, ingot making, or blooming, and then hot rolled, cold rolled, and annealed to produce a C, 0.01% or less, acid soluble A
n, 0.005-0.10%, Cr; 3-20%
Contains 1. :Ti, Nb, Zr, V(0
A steel plate containing 0.03 to 0.8% of one or more types is manufactured.

C is economically advantageous as a strength-improving element, but if its content is too high, pinholes and defects in the coating layer of gold alloys such as Ni-Fe and Go-Fa will increase and corrosion resistance will deteriorate. do. That is, C combines with other elements to precipitate titanium carbide, niobium carbide, chromium carbide, etc. on the steel surface, which deteriorates the uniform coverage, plating adhesion, etc. of the plating coating layer. Furthermore, an increase in C content makes the material itself brittle and has an adverse effect on electrical conductivity or thermal conductivity, which is not preferable. Therefore, from this point of view, the C content in the plating original plate is 0.01% or less, preferably o.ooa% or less.

AIL is the acid-soluble AJZ (Son.

If the amount (8°C) 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, deteriorate the corrosion resistance of the steel material itself, and cause mechanical damage. It becomes the starting point of property deterioration. In addition, excess acid-soluble A2 exceeding 0.10% causes J2-based oxides to be scattered on the steel surface, becoming a starting point for deterioration of corrosion resistance, and is also a factor that inhibits uniform coverage during plating treatment. becomes. Therefore, the amount of Soβ and Aj2 contained in the steel is 0.005 to 0.10% to ensure stable performance of the surface-treated steel sheet.
Preferably it is 0.01 to 0.08%.

Cr is added as an element that improves the corrosion resistance and strength of the plated original plate. Cr-containing steel sheets have superior corrosion resistance and resistance to corrosion as compared to steel sheets that do not contain Cr.
, or approach the potential of the (Ni+Go)-Fe alloy coating layer. As a result, excellent rust resistance and corrosion resistance can be obtained from both the corrosion resistance improvement effect of the steel plate itself, the corrosion resistance improvement effect of the coating layer, and the composite/synergistic effect of the steel plate and the coating layer.

Furthermore, by including Cr in the steel, mechanical strength and corrosion resistance can be obtained. If the Cr content is less than 3%, corrosion resistance and strength cannot be obtained, and if the Cr content exceeds 20%, it is difficult to obtain good adhesion with the Ni-Fe alloy plating layer, etc. Even if a layer is provided, there are drawbacks such as insufficient solderability on the end face. Also, from the viewpoint of the electrical conductivity and thermal conductivity required of the lead frame material, it is preferable that the Cr content is small. Therefore,
Cr content ranges from 3 to 20%, preferably from 5 to 10%
It is.

Further, depending on the method of manufacturing the lead frame, a method of manufacturing the lead frame shape by a dissolution etching method using an acid-based corrosive solution is adopted. In this etching method, the Cr content is reduced to 1 because of the ease of uniform etching of the material.
It is preferably 0% or less.

B decreases the oxidation rate during heating of the steel sheet, especially Cr2O.

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
0.003% or more, preferably 0.0005% or more.

On the other hand, when the amount of B added increases, its effect becomes saturated and cracks occur in the steel sheet during hot rolling. Therefore,
In the present invention, the amount of B added is 0.005% or less, preferably 0.002% or less.

Ti, Nb, Zr, and V are components that combine with C or N in steel to prevent the formation of Cr carbides or nitrides, thereby effectively exerting the corrosion-resistant effect of Cr. In addition, carbides or nitrides such as Ti are finely precipitated at grain boundaries,
Prevents the crystal grains of the plated original plate from becoming coarser and ensures strength. In particular, it has the effect of expanding the range of heating temperatures for adjusting mechanical properties.

In order to obtain such an effect, Ti, Nb, Zr,
V's 1ff! Or, it is necessary to contain two or more types at 0.03% or more, and if the content exceeds 0.8%, there will be too much precipitate and the material will become brittle and cracks will occur during molding. Electrical conductivity and thermal conductivity also 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. Sl is effective in mechanically increasing strength, but if the St content is excessive, Si-based oxides will be scattered on the steel surface and will inhibit uniform coating in alloy plating treatment, so it will have a negative effect on corrosion resistance. So it's not desirable. Therefore, it should be 0.6% or less, preferably 0.15% or less.

Although Mn does not have a negative effect on 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 the portions where the original plate material is exposed, such as the end faces, it is preferable that S be 0,00% or less.

Furthermore, in the second aspect of the present invention, one or more of Cu, Ni, and Mo are contained in addition to the above components. These elements improve the rust resistance and corrosion resistance of the steel sheet itself, and in a corrosive environment, Cr
The combined addition of Fe makes the potential more noble (cathodic), bringing the potential difference with the plating coating layer closer, and further preventing deterioration of rust resistance and corrosion resistance due to preferential corrosion of Fe.

The addition of these elements includes Cu from 0.05 to 0.1%, N
i h<0.05-3.0%, Mo is [1,05-0.
It is 5%. If the additive content of Cu is less than 0.05%, the above corrosion resistance effect cannot be obtained, and if it exceeds 1.0%, cracks due to red hot embrittlement or Cu will concentrate on the steel surface during the hot rolling process during original sheet manufacturing. This makes it easier for scale defects to occur. Therefore, Cu is 0.05 to 1.0%, preferably 0.1 to 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 effect of improving corrosion resistance will be saturated, and the coexistence effect with Cr will improve the adhesion of the coating layer. The pretreatment work on the steel surface to obtain this 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 thin materials such as lead frames. 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%.

There are no particular regulations regarding the material of the original plate, but
It is recommended to make the following material adjustments. For example, when looking at punching workability into lead frame shapes, high-strength materials with low ductility are superior, and lead frame products are required to have strength and bending workability. From these points of view, the strength is 45 to 85 kg/mm2, preferably 55 to 80 kg/mm2.
kg/mm2, elongation is 3-20% (7.5-15%)
The steel plate is excellent. The steel material is an original sheet that has been heat-treated at a temperature below the recrystallization temperature of a cold-rolled steel sheet and subjected to a skin pass treatment to adjust the shape, or a rolled sheet,
An original plate obtained by further cold rolling an annealed original plate at a rolling reduction of about 20 to 40% may be used.

Prior to the plating process, such plating base plates are subjected to pickling treatment by dipping, spraying, etc., or electrolytic pickling treatment to activate the surface of the material prior to the plating treatment, but surface oxidation, which is unique to Cr-containing steel sheets, In order to uniformly remove and reduce the film, electrolytic pickling treatment is desirable. That is, activation treatment by reducing the oxide film by cathodic electrolytic pickling using the steel material as the cathode in a pickling bath, activation treatment by dissolving and removing the oxide film by anodic electrolytic pickling using the steel material as the anode, or activation treatment by anodic electrolysis. A method that combines oxide film dissolution and removal with surface activation treatment using cathodic electrolysis is employed. Among these, a method in which cathodic electrolytic treatment is further performed 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.

As a method for carrying out these electrolytic pickling methods, for example, H2S
Using an O4 bath, a H2SO4 bath containing F- ions, etc., the current density is 10 to 60 A/d, ~2. It is preferable that the temperature ranges from room temperature to 80°C and the electrolysis time ranges from 0.5 to 10 seconds.

Furthermore, if a steel plate (plated original plate) with the above-mentioned composition is used as it is, it may have poor corrosion resistance such as rust resistance, plating properties for Cu or Pb-5n alloy in the lead frame manufacturing process, or solderability for immersion soldering. is insufficient as a material for lead frames, and Ni-Fe, Co-Fe
, or (Ni+Go)-Fe alloy plating treatment is performed. The combined effect of the plating base plate and the alloy plating coating layer improves corrosion resistance, mainly rust resistance, plating properties,
Improves soldering performance.

Ni-Fe, Go-Fe, (Ni+Go)
-Fe alloy plating is preferably carried out under the following plating conditions, for example.

(a) Example of Ni-Fe alloy plating plating bath composition NiSO4.6H2070g/IL NiCu2.8H20i 40g/ItFeSOa
4N20 170 g / 421-13B03
40 g/jQ Current density 10 to 100 A/dm2 Plating bath temperature Room temperature to 60°C (b) Example of Go-Fe alloy plating plating bath composition CO3O4.6H2055g/It Coin 2.6H20160g/u FeSO4.7H20180g/II.

)13B0330 g/J2 Current density 10~1008/dm2 Plating bath temperature Room temperature~60℃ (c) Example of (Ni+Go)-Fe alloy plating plating bath composition NiSO4・8820 45 g/JZCoS
04・0H2025g/, Q NiCjZ 2・6H20100g/11CoCft
2.66H2O5o/ILFeSO4.7H20 HsBOs 35 g/It Current density 10-100A/dm' Plating bath temperature
Room temperature to 60° C. By changing the content ratios of Ni2'' ions, Go'' ions, and Fe2+ ions in the above-mentioned plating, it is possible to obtain alloy plating layers each having a predetermined alloy composition.

In the present invention, by applying a coating treatment such as a old -Fe alloy plating layer to the original plate, as described above, effects such as improving corrosion resistance, plating performance in the lead frame process, or solderability can be obtained. In order to obtain these effects, the alloy composition of the plating coating layer and the thickness (deposition amount) of the coating layer are important and are regulated as follows. That is, N
i-Fe.

Ni in Go-Fe or (Ni+Go)-Fe alloy plating layer.

If the content of Co or Ni+Go is less than 10%, the corrosion resistance of the alloy plating layer is insufficient due to the large Fe content, and although the plating properties and solderability are improved in the lead frame manufacturing process, coatings with these alloy compositions Even if the treatment is performed, the effect of improving corrosion resistance cannot be obtained because red rust occurs from the surface of the alloy plating layer in a corrosive environment. From the point of view of improving corrosion resistance, the old alloy joint composition was Co or Ni and Co.
It is desirable that the coating layer has an alloy composition with Fe and containing 20% or more of Fe.

On the other hand, Ni and C contained in these alloy plating layers.

Alternatively, the alloying element content in a state where Ni and Go coexist is regulated to 90% or less. When the content of alloying elements exceeds 90%, the corrosion resistance of the alloy layer itself is improved and the molten Pb-5n
When the effect of improving the wettability and spreadability of the alloy solder reaches saturation, the following drawbacks occur. That is, N
As the amount of i, Go, etc. increases, the potential is more favorable in the negative direction, increasing the potential difference with the original plate, making it easier for red rust to occur from plating defects due to preferential corrosion of the original plate, and corrosion resistance tends to deteriorate. It is in. In addition, since Ni and Go form a stable and dense oxide film, an alloy plating layer with a content of more than 90% should be formed prior to plating (Cu or Pb-5n electro-solder plating, etc.) in the lead frame manufacturing process. Since it tends to make pickling activation treatment difficult, uniform plating coverage and plating adhesion cannot be obtained.

Furthermore, the most important problem is that when the alloying element with respect to Fe exceeds 90%, the wettability, spreadability, etc. effects of the molten Pb-Sn solder are saturated, and the alloying elements with the Sn metal in the solder become saturated. The amount of Nj-5n and Go-5n alloys produced by reaction with elements or diffusion increases, and the formation of these hard and brittle alloy layers makes the soldered parts more likely to break when subjected to impact or bending. Therefore, in order to prevent this solder brittleness, the content of alloying elements such as the Ni--Fe alloy plating layer applied to the original plate material is regulated to 90% or less.

In order to prevent the occurrence of the above defects, these Fe
The content of alloying elements such as Nj and Co to be alloyed with is 90% or less, preferably 60% or less.

The coating amount (thickness) of the alloy plating layer with these compositions is important, and the coating amount per side is 100 to 3000 mg/
m2 must be applied. In other words, if the coating amount is less than 100 mg/m2, many coating layer defects such as pinholes in the alloy plating coating layer will be generated, and the area of the exposed part of the original plate will increase, which will reduce the effect of improving corrosion resistance, plating properties, and solderability. It is difficult to obtain improvement effects. Also, its cover lI
If the amount of U exceeds 3000 mg/m2, the effects of improving corrosion resistance, plating performance, solderability, etc. will be saturated, and when the material on which these alloy plating layers are applied is subjected to processing such as shearing, the coating will deteriorate. Phenomena such as the formation of cracks or partial peeling occur. Furthermore, Ni
- Even if the tli composition of Fe alloys, etc. is regulated, as the amount of adhesion increases, the amount of Nf or Co will increase, so the amount of alloys such as Nf-5n and Co-5n produced by reaction with Sn will increase. This results in drawbacks such as increased solder brittleness. Therefore, the coating amount of these alloy plating layers is 100 to 3000 mg/m', preferably 30
It is 0 to 2000 mg/l112.

In addition, in the process of applying these alloy plating layers, even if a small amount (less than about 1%) of impurities that are inevitably contained in the plating bath or electrode, such as S and B, are contained in the coating layer, no problem will occur. .

The present invention configured as described above has extremely excellent performance characteristics as a lead frame material.

(Example) Using the original plate material having the steel composition shown in Table 1, surface activation treatment by degreasing and pickling was performed, and then Ni-Fe, Go-Fe and ( Ni+
Go) -Fe alloy plating layer was provided. The original plate material is
Hypertension cuff made by annealing a cold rolled material and then cold rolling at a reduction rate of 20 to 30% to adjust the plate thickness to 0.25 mm, followed by strain relief annealing at a temperature below the recrystallization temperature 0 to 80
A material adjusted to kg/mm2, elongation of 5 to 8%, and hardness (Vickers hardness) of 230 to 240 was used as the original plate material.

The performance characteristics and evaluation results of these evaluation materials are shown in Table 2.

As a result, the present invention showed extremely superior performance as a lead frame material compared to comparative materials.

(Evaluation test method) ■ Adhesion of alloy coating layer Ni -Fe, Co -Fe, (Ni+Co)
-The evaluation material coated with the Fe alloy plating layer was repeatedly bent with a radius of curvature of 0.25 mm (same as the plate thickness), and then Sellotape (registered trademark) was applied and peeled off to determine the degree of peeling of the coating layer. investigated. The evaluation criteria are as follows.

◎...Repeated 10 times or more, no peeling or cracking of the plating coating layer occurred.

○: No peeling or cracking of the plating coating layer occurred after repeating 7 or more times to 9 times.

Δ: No peeling of the brushed coating layer after repeating 4 or more times to 6 times.

X: Peeling of the plating layer occurred after repeating 3 times or less.

■ Corrosion resistance performance a Evaluation method A In order to evaluate the rust resistance performance of the evaluation material during storage, after punching the evaluation material into a predetermined lead frame shape (32 pin shape), surface treatment is performed in the lead frame manufacturing process. The rust resistance performance during storage was evaluated using the following accelerated test method and evaluation criteria on the flat surface and punched end surface.

(60 minutes freezing/condensation (-5℃) - 180 minutes high temperature humidity (4
9℃, humidity ≧98%) - 24 hours, left indoors (30℃)
) was taken as one cycle, a 12-cycle evaluation test was conducted, 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 △... 〃
More than 10% to less than 2o%×... 20% Rust resistance evaluation criteria for end face ◎... Red rust occurrence rate less than 10% ○... More than 10% to less than 2o% △...
〃 More than 20% ~ 4o% 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 (32 bottle shape), degreasing and immersion pickling were performed, and a 2.5μ thick Cu
After polishing, salt spray test (JIS-C-5028
), the corrosion resistance was evaluated 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% △... 〃 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 using the following method, and the plating performance was evaluated. .

a Evaluation method A After punching the evaluation material into the shape of a lead frame, degreasing (sodium phosphate electrolytic degreasing), immersion pickling at 30°C for 5.0 seconds using a 10% 02SO bath, and cyanide. Using C, u plating bath, current density 8, OA/dm2
Cu plating was applied to a thickness of 3 μm, and the appearance after the Cu plating was examined and a bending test was performed using the following method to examine the adhesion.

That is, in the bending test, the outer lead part of the plate width 0.5 mm was sheared to a length of 15 mm, and then the MIL S
In accordance with TD 883G/2004, the process of fixing one end to a test jig, hanging the sample vertically, attaching a 230g weight to the other end, bending the test jig 90 degrees, and returning it to its original position was repeated. Then, the adhesion of Cu plating was evaluated. 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 10 times or more.

○: 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 6 times or more.

Δ...Although some clear plating defects occurred partially on the Cu plating surface, the Cu plating layer did not peel off after repeated bending 6 times or more.

×... Plating defects clearly occur on the Cu-plated surface, and the Cu-plating layer peels off when the number of repeated bending is 5 times or less.

b Evaluation method B Blisters generated on the Cu plating surface when heat treatment was performed at 400°C for 5 minutes after Cu plating similar to evaluation method A, assuming that it would be heated during wire bonding. The occurrence of (fine swelling of the Cu plating layer) was investigated, the adhesion of the Cu plating layer was evaluated, and the plating performance was evaluated using the following evaluation criteria.

◎...No blistering occurred.

△... 5 or less blisters occur per 5 x 5 cm2 area.

×: 6 or more blisters occurred per 5 x 5 cm2 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-75%Sn electro-solder plating bath. Electrical solder plating conditions include plating bath temperature of 50°C and current density of 8.5.
Plating was applied to a thickness of 5 μm at 5 μm/dm2. The evaluation method is
After impact processing (pressing a hemisphere with a diameter of 12.5 mm and a height of 9 mm onto the evaluation surface by applying an impact load at a speed of 2 m/sec), tape was applied and peeled off to check the adhesion of the plating layer. evaluated. The evaluation criteria are 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 ■ Solder performance a Evaluation method A Regarding the solderability of the evaluation material, assuming that soldering is performed after punching and before Cu plating in the lead frame manufacturing process, we especially evaluated the solderability of the material. 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 1010 mm x 50 wedge shape, coated with rosin alcohol flux, and immersed vertically in a Pb-63%Sn 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 conducted immediately after punching and after being stored indoors for 2 months. The evaluation criteria are as follows.

◎...Solder wettability and wetting speed are extremely good when wetting stress is 400 mg or more and wetting time is less than 7 seconds ○...Solder wettability and wetting speed are extremely good when wetting stress is 300 mg or more and less than 400 mg and wetting time is less than 8 seconds Wetting speed is also fairly good △... Wetting stress of 250 mg or more to less than 300 mg or wetting time of 8 seconds or more to less than 10 seconds either the solder wettability or the wetting speed changes slightly ×... Wetting stress of less than 250 mg Or, if the wetting time is 10 seconds or more, either the solder wettability or the wetting speed is extremely poor.In addition, the above wetting stress and wetting time can be measured by applying flux using a Resca solder wettability evaluation tester. The evaluated material was immersed in a melted solder bath at a temperature of 350°C at a constant speed (4 m/sec), and the immersion depth was 4 mm.
Dipping was carried out for seconds, and wetting stress and wetting time were evaluated by meniscograph measurement as shown in FIG.

b Evaluation method B After shearing the evaluation material into a rectangular shape with a width of 30 mm and a length of 100 mm, 27% rosin alcohol flux was applied to the evaluation material, and a length of 5 from the end face was applied to a solder composition Pb-63% Sn bath.
The solder was immersed to a depth of 0 mm for 10 seconds at a temperature of 360° C. to adhere the solder. Thereafter, heat treatment was performed at 175° C. for 5 hours to evaluate the adhesion of the solder, assuming heat treatment during wire bonding and also as an acceleration test against aging. As a method for evaluating adhesion, a repeated bending test with a radius of curvature of 0.25 mm (same as the plate thickness) was performed, and the state of solder peeling was investigated to evaluate the solder performance.

◎...No solder peeling or crack formation in the solder layer after repeated bending 10 times or more.

○...No solder peeling or crack formation in the solder layer after repeated bending 6 times or more.

△...No solder peeling or crack formation in the solder layer after repeated bending 3 times or more.

×...Solder peeled off and cracks formed in the solder layer when repeated bending was repeated 2 times or less.

■ Performance evaluation of lead frame products over time After processing the evaluation material of the present invention into a lead frame shape, Cu plating and soldering were performed in the surface treatment process.
Using a pressure puller, apply a pressure of 2 kg/cm'
These products were sealed in a room with a temperature of 120° 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 O...Small rust on the end face △...Blisters on the Cu-plated surface ×...Significant rust on the flat and end faces (no Effects) As explained above, the surface-treated steel sheet according to the present invention can be used as a lead frame material for integrated circuits, etc., and has excellent adhesion of the alloy coating layer and performance after aging as a product, as well as excellent corrosion resistance, solderability, A high-performance steel plate for lead frames with excellent plating properties.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing the solderability and solder adhesion evaluation results of immersion solder, and FIG. 2 is a drawing showing the solder wettability evaluation method.

Claims (2)

[Claims] (1) C in weight%: 0.01% or less, acid-soluble Al: 0.005 to 1.1
0%, Cr; 3-20%, B; 0.0003-0.00
The surface of the Cr-containing steel sheet contains 5% of Ti, Nb, Zr, and V, and 0.03 to 0.8% of one or more of Ti, Nb, Zr, and V, and the balance is Fe and unavoidable impurities. The adhesion amount is 100 to 3000 mg/m^2 (10 to 90
%) Ni-Fe alloy, (10-90%) Co-Fe alloy, or (10-90%) <Ni+Co>-Fe alloy, providing high performance with excellent corrosion resistance, solderability, and plating properties. Surface-treated steel sheet for lead frames. (2) C in weight%: 0.01% or less, acid-soluble Al: 0.005 to 0.1
0%, Cr; 3-20%, B; 0.0003-0.00
5%, one or more of Ti, Nb, Zr, and V; 0.
0.03 to 0.8%, and further Cu; 0.05 to 1%
, Ni; 0.05 to 3%, Mo; 0.05 to 0.5%, and the remainder is Fe and unavoidable impurities. is 1
00-3000mg/m^2 (10-90%) Ni-
Fe alloy, (10-90%) Co-Fe alloy, or (1
A surface-treated steel sheet for high-performance lead frames with excellent corrosion resistance, solderability, and plating properties, provided with a coating layer made of <Ni+Co>-Fe alloy (0 to 90%).