JPH0515785B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a surface-treated steel sheet for semiconductor lead frames, which is a Cu-based coated steel sheet with excellent corrosion resistance, solderability, adhesion of a coating layer, etc. [Conventional technology] Traditionally, materials for lead frames for ICs, etc.
For example, as introduced on page 683 of ``Surface Treatment Technology Overview/Anodizing Edition, June 15, 1980, Published by Koshinsha Co., Ltd.'', Cu-Fe-
P, Cu-Fe-Co-Sn-P, Cu-Ni-Sn alloys, etc. have been used, and Fe-42%Ni high alloy materials have been used as Fe-based materials. These lead frame materials have mechanical strength, electrical conductivity, thermal conductivity,
It has excellent corrosion resistance, and also has excellent handling properties and plating properties when manufacturing lead frames. However, due to the high cost of these materials, recently the use of cooling steel plates as an inexpensive material for lead frames has been considered and is being used in some cases. However, such materials do not satisfy the various performances required for lead frame materials, especially corrosion resistance, solderability,
There is a need to develop steel materials with improved thermal conductivity. [Problems to be Solved by the Invention] Generally, Fe-based materials such as Fe-42% Ni alloy and cold-rolled steel sheets are made into lead frame products through the following processing steps. In other words, after punching the lead frame material into a predetermined shape, the entire surface is plated with Cu, where necessary Ag is plated, and then soldered, and the Au wire is bonded to the Ag-plated areas. The product is then finished sheared. It is then packaged according to usage conditions. Further, depending on the manufacturing process, soldering may be performed first after processing into a predetermined shape. In these processes, Cu plating is a surface treatment to improve the rust prevention ability of the material and improve the adhesion and coverage of Ag plating, and also provides thermal conductivity and electrical conductivity. The Ag plating performed for this purpose is thermal bonding with the Au wire (approximately
°C), solder is applied to improve the bondability of the joint with the IC board. Considering these processes, Fe-based materials (a) are processed into a predetermined shape and then immediately plated in the lead frame manufacturing process;
(b) The material must have excellent rust resistance for this purpose; (b) It must have excellent solderability even after being processed into the specified shape; (c) Simple pretreatment (surface cleaning and activation treatment)
(d) Excellent corrosion resistance after Cu plating.
In particular, it has excellent corrosion resistance even when the thickness of Cu plating is reduced; (e) The adhesion of Cu plating is excellent, especially after heating during thermal bonding with Au wire; (f) It is required to be able to improve thermal conductivity and electrical conductivity after manufacturing lead frames. In response to these demands, the present inventors investigated various types of steel sheets and found that using cold-rolled steel sheets as they are does not necessarily provide sufficient rust resistance and solderability during storage. . In addition, even after Cu plating treatment, since Cu metal is more noble in potential than steel sheets, Fe from pinholes, plating defects, etc.
Red rust occurs significantly due to preferential corrosion, and corrosion resistance is insufficient. In particular, the corrosion resistance of end faces, cut parts, etc. with poor Cu plating may be markedly poor. In addition, even if Cu plating is thickened to reduce pinholes, plating defects, etc., it is difficult to completely reduce pinholes, etc., and adhesion may deteriorate or blisters may occur during thermal bonding. There's a problem. The present invention solves these problems and provides a lead frame material with excellent performance, particularly excellent corrosion resistance, solderability, and adhesion, that can satisfy the performance requirements described in items (a) to (f) above. This is what we provide. [Means for solving the problem] The gist of the present invention is as follows: In weight%, C: 0.30% or less, Al: 0.005 to 0.10
%, Si; 0.6% or less, Mn; 1.5 or less, Cu; 0.05~
A Cu coating layer having a Cu diffusion layer is applied to the surface of a steel plate containing 1.0% Ni and, if necessary, 0.05 to 3.0% Ni with the remainder being Fe and unavoidable impurities. This is a surface-treated steel sheet for lead frames with excellent corrosion resistance, solderability, and adhesion, with a Cu diffusion layer and a Cu coating layer having a thickness of 0.1 to 3μ and a thickness of 0.5 to 15μ. [Operation] The present invention will be explained in detail below. Molten steel produced in a melting furnace such as a converter or electric furnace is subjected to a continuous casting method, ingot making, or blooming method, and then hot rolled, cold rolled, and annealed as a slab; C;
Produces plated base plates containing small amounts of components such as Al and Si at 0.3% or less. C is economically advantageous as an element for improving mechanical strength, and from this point of view, the higher the C content, the more effective it is, but as the content increases, coating layer defects such as pinholes in the Cu coating layer increase. Deteriorates corrosion resistance. In other words, when a large amount of cementite is precipitated in the steel, even when a diffusion layer is formed after a coating treatment such as copper plating, the effect of eliminating plating defects due to the uniform formation of a diffusion layer is reduced. There is a corrosion-resistant product that deteriorates. Therefore, the C content in the plated original plate is 0.30% or less, preferably 0.15% from the viewpoint of corrosion resistance.
% or less. Further, impurity components inevitably contained in the plated original plate are not particularly defined, but the following ranges are preferable for the main components listed below. Al is the amount of acid-soluble Al (Sol Al) remaining in the steel.
If the content is less than 0.005%, it is difficult to prevent the formation of bubbles due to oxygen gas, which significantly increases the incidence of surface defects in steel and becomes the starting point for deterioration of the corrosion resistance and mechanical properties of the steel material itself. Not desirable. Also, excess acid-soluble Al exceeding 0.10%
This is not preferable because it causes Al-based oxides to be scattered on the steel surface, which becomes a starting point for deterioration of corrosion resistance, and also because it inhibits the uniform coating properties of Cu coating layer treatment. Therefore, Sol Al contained in steel is
The amount that can stably ensure the performance of the surface-treated steel sheet targeted by the present invention is 0.005 to 0.10%, preferably 0.01 to 0.08%. Si is preferably 0.6% or less. Although Si is effective in increasing mechanical strength, when the Si content increases excessively, Si-based oxides are scattered on the steel surface, which inhibits uniform coating in the Cu coating process of the present invention. Therefore, it is not preferable in terms of corrosion resistance.
Therefore, it is 0.6% or less, preferably 0.3% 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 should preferably be contained in an amount of 0.02% or less within the range contained in normal steelmaking methods. In addition, in the heating process of the plated original plate, 0.5% or less of Cr may be added for the purpose of preventing graphite-like C from precipitating on the surface and inhibiting the uniform coverage of the coating layer. . Furthermore, in the present invention, Cu: 0.05 to 1.0% is added alone, or Cu and Ni: 0.05 to 3.0% are added in combination.
The addition of Cu has the effect of improving the corrosion resistance of the steel sheet itself, cathodicizing the potential of the steel sheet and bringing the potential difference with the Cu diffusion layer closer, and improving the rust resistance of defective parts of the coating layer or exposed Fe parts on the end face. The effect of preventing deterioration can be obtained. Furthermore, the end face of the steel plate and
In the Fe exposed area, Cu in the steel precipitates and concentrates on the steel plate surface, and together with the potential proximity effect with the Cu coating layer,
Improves corrosion resistance. Such an effect can be obtained when the amount of Cu added is 0.05% or more, preferably 0.10% or more. In addition, if the amount of Cu added exceeds 1%, cracks due to red hot embrittlement or scale defects may occur due to Cu concentrating on the steel sheet surface during the hot rolling process of the original sheet manufacturing process, so it should be kept below 1%, preferably below 0.5%. regulate. Furthermore, in the present invention, the combined addition of Ni and Cu is
Red brittleness caused by Cu addition is prevented and the corrosion resistance of steel sheets is improved. Such an effect of Ni addition cannot be obtained at less than 0.05%, and reaches saturation when it exceeds 3%. Therefore, the amount of Ni added is 0.05 to 3.0%, preferably 0.1 to 3.0%.
It is 0.5%. Next, for the plated original plate of the above steel composition,
It is necessary to provide a Cu coating layer having a Cu diffusion layer with a predetermined thickness. The method of providing this Cu-based coating layer is as follows:
Although not particularly specified, the coating layer may be provided by the following method. The surface of cold-rolled material (As Cold material) or cold-rolled steel plate (Full Finished material) is degreased, surface cleaned by pickling, and activated, followed by Cu plating treatment. As an example of this Cu plating process, the plating process is performed under the following conditions. Plating bath composition K <sub>4</sub> P <sub>2</sub> O <sub>7</sub> Cu <sub>2</sub> P <sub>2</sub> O <sub>7</sub>・3H <sub>2</sub> O NH <sub>4</sub> OH PH256g/ 64g/ 2.2g/ 8.5 Current density 10A/dm <sup>2Plating</sup> bath temperature 55℃ After Cu plating coating treatment, In the present invention, N <sub>2</sub>
A heating diffusion treatment is performed in a non-oxidizing atmosphere such as an atmosphere, a reducing atmosphere such as a MiX gas atmosphere consisting of 5% <sub>H2</sub> - <sub>N2</sub> , an AX gas atmosphere consisting of 75% <sub>H2</sub> - <sub>N2</sub> , or a vacuum atmosphere, A Cu diffusion layer is provided on the steel surface. This diffusion treatment condition corresponds to the thickness of each of the Cu diffusion layer and Cu coating layer and the mechanical properties of the material, which are the objectives of the product of the present invention, and the Cu plating coating layer applied prior to the heating diffusion treatment. The thickness, heating temperature, and heating time are set. For example, in the continuous annealing method,
30-180 seconds at 600-850℃, 450-180 seconds with box annealing method
Heat treatment is performed at 650°C for several to 30 hours.
By this heating diffusion treatment, a Cu diffusion layer is formed.
Providing a Cu coating layer with a predetermined thickness is extremely important in order to obtain a product with excellent performance as a lead frame material. That is, the following advantages can be obtained compared to the case where only the Cu plating coating treatment is applied to the plated original plate used in the present invention. In other words, if only A Cu plating coating layer is used, plating defects such as pinholes are likely to occur, rusting from pinholes etc. is likely to occur, and corrosion resistance is deteriorated.
Red rust occurs from exposed Fe parts such as punched edges. On the other hand, as shown in FIG. 1, in the present invention, an alloy diffusion layer consisting of Cu and Fe is generated at the interface of the plating original plate and the Cu plating layer due to mutual diffusion between the plated original plate and the Cu plating layer. Reduces plating defects such as holes and improves corrosion resistance of flat parts. Furthermore, Cu is also applied to the punched end face.
Due to the formation of a diffusion layer, the exposed area of Fe is reduced, and the potential difference between the Fe and Cu plating layer is alleviated by the presence of the Cu-Fe alloy diffusion layer as an intermediate layer, resulting in red rust due to preferential corrosion of Fe. is significantly suppressed. Figures 1a and b are cross-sectional concentration analysis (glow discharge emission spectrometry) results and cross-sectional schematic diagrams of Cu plating (0.5μ thickness), and Figures 1c and d are similar to that of a Cu coating layer with a Cu diffusion layer. These are the analysis results (equivalent to 0.1μ with sputtering time of 1.6 seconds) and a schematic cross-sectional view. FIG. 2 shows an example of the corrosion resistance evaluation results of the flat part and the punched end face part by an accelerated test. Figure 2 is
This figure shows an example of the corrosion resistance of a Cu-based coating material with a Cu-diffusion layer for storage. A 3-cycle test was conducted, with 1 cycle being ``30 minutes of freezing → 60 minutes of humidity bath → 24 hours of leaving indoors''. It is a thing,
The end plate thickness of the test material was 0.25 mm. B The present invention has fewer plating defects at the interface between the Cu plating layer and the plating original plate, and an alloy diffusion layer that alleviates the potential difference between the Cu plating layer and the Cu plating layer is generated. Even when applied to the case where a scorching treatment is performed, the corrosion resistance of the flat portion and the end surface portion is improved, as shown in FIG. Figure 3 shows an example of corrosion resistance (SST 24 hours) by salt spray test when Cu plating treatment is applied in the lead frame manufacturing process. Evaluation material A is a Cu-based coating material with a Cu diffusion layer (thickness 1.2μ)
Evaluation material B is a covering material having a similar thickness of 2.2μ. After stamping this, each 2.8μ
It has Cu plating. On the other hand, comparative materials A and B were stamped from the same plated original plate.
It has Cu plating of 4μ and 5μ. Therefore,
This also provides the advantage of reducing the Cu plating thickness during the lead frame manufacturing process. C. For the soldering work that is essential during lead frame manufacturing, especially for the solderability after punching of the end face and storage over time, the exposed Fe part is reduced due to the formation of an alloy diffusion layer, and the effect is As shown in Fig. 4, the improvement is excellent. Figure 4a shows a Cu-based coating material with a Cu diffusion layer.
This is a diagram comparing the solder wettability of Cu-plated materials.
Figure 4b shows the method for measuring solder wetting stress.
After applying rosin alcohol as a flux to the test piece, it was immersed in a solder bath of Sn:Pb=6:4,
Solderability was evaluated by measuring wetting stress using a solder checker tester using the method shown in the figure. D Cu-plated materials generally do not necessarily have good adhesion to steel plates, and this tendency is particularly pronounced as the thickness of the Cu-plated layer increases. However, as in the present invention, since a Fe-Cu alloy diffusion layer with strong adhesion is generated at the interface between the plating original plate and the Cu plating layer, the adhesion of the Cu plating coating layer is extremely excellent. . At the same time, since the plating layer itself has good adhesion, the heat-resistant adhesion during thermal bonding is also extremely excellent. E Since there are few plating defects such as pinholes, the steel plate of the present invention has excellent thermal conductivity and electrical conductivity on the surface of the material, which are required for other materials for lead frames. The following effects can be mentioned. Therefore, in order to obtain the effects of the present invention, Cu and
The thickness of the Cu coating layer with the Fe diffusion alloy layer is important. In order to obtain this effect, the thickness of the coating layer in the present invention is such that the thickness of the Cu diffusion layer is 0.1 to 3μ and the thickness of the Cu diffusion layer is 0.1 to 3μ.
The thickness of the Cu coating layer is 0.5 to 15μ. In other words, if the thickness of the Cu diffusion layer is less than 0.1μ,
Even if the thickness of the upper layer is as described above, the desired effect of the present invention cannot be obtained, and in particular, the effect of covering the exposed portion of the Fe surface by the diffusion layer at the punched end face is small, and the corrosion resistance of the end face is , performance improvement effects such as solderability cannot be obtained. In addition, even if the thickness of the diffusion layer is within the above range, if the total thickness with the upper Cu coating layer is less than 0.5μ (maximum thickness of the upper Cu coating layer itself is less than 0.4μ), the end surface Although the effect of improving the performance of the flat part is obtained, the uniformity of the Cu coating layer on the flat part is poor, and corrosion resistance deteriorates due to rusting from the Fe-containing diffusion alloy layer. On the other hand, when the thickness of the diffusion alloy layer exceeds 3μ,
Due to the hardness of this alloy layer, it is damaged during processing, causing cracks and deterioration in corrosion resistance. Furthermore, if the total Cu coating layer of the upper layer and the diffusion layer exceeds 15μ within the composition range of the alloy layer mentioned above, this effect will be saturated and the interface between the Cu coating layer and the plating original plate will be affected by the formation of the diffusion alloy layer. Although the adhesion is good, the adhesion of the Cu coating layer itself, which is the upper layer of the diffusion alloy layer, deteriorates and is partially peeled off during processing. Therefore, in the present invention, Cu having a Cu diffusion layer
The thickness of the coating layer is such that the thickness of the Cu diffusion layer is 0.1 to 3μ, preferably 0.5 to 2μ, and the thickness of the Cu diffusion layer and the Cu coating layer is 0.1 to 3μ, preferably 0.5 to 2μ.
It is 0.5-15μ, preferably 1.5-7.5μ. Therefore, a method for obtaining a Cu-based coated steel sheet with this coating structure is, for example, by performing a heating diffusion treatment after Cu plating on the surface of the steel sheet, so that a part of the Cu plating layer is diffused.
Set the thickness, heating temperature, and heating time of the Cu plating layer so that the remaining part remains as the Cu plating layer.
The method of providing a two-layer coating layer of the present invention consisting of a diffusion layer and a Cu coating layer is adopted. In addition, after the entire Cu plating layer applied before the heating diffusion treatment is interdiffused with the plating original plate to generate a diffusion layer, a Cu plating coating layer is applied as a surface layer of the diffusion layer by electroplating. may be provided to constitute the coating of the present invention. However, the manufacturing method is simplified and the diffusion layer
From the viewpoint of the adhesion of the Cu coating layer itself, it is preferable to provide the diffusion layer and the Cu coating layer all at once in the heat diffusion treatment step. Furthermore, rather than using cold-rolled steel sheets, the plating base plates used are as-cold-rolled (As Cold materials), and are annealed and diffused at the same time to ensure the required mechanical properties. This is desirable because diffusion is promoted by the effect of processing strain on the cold-rolled material and the process is simplified. Of course, a cold-rolled steel sheet may be used to perform Cu plating and diffusion treatment, and then rolling or skin pass may be performed to adjust the mechanical properties. In particular, when considering the stamping workability into the shape of a lead frame, high-strength materials with low ductility are superior, and lead frame products are required to have strength and bending workability. As a result of various studies from these points of view, the strength was 45
~85Kg/ ^mm2 , elongation 3~90%, preferably 55~80
It was found that mechanical properties of Kg/mm ² and elongation of 5 to 15% are good. Regarding the steel component materials used in the present invention,
Using the above-mentioned As Cold material, it is preferable to perform a heating diffusion treatment at a temperature lower than the recrystallization temperature, in which the Cu plating layer can be diffused and softening due to recrystallization is difficult to occur, that is, in the temperature range of 450 to 550°C. In addition, in the present invention, the method for obtaining the coating layer has been mainly explained using electric Cu plating and diffusion treatment. A method may also be adopted in which an aqueous solution of a surfactant is applied, dried, and then heated and diffused. However, from the viewpoint of uniform coverage of the Cu coating layer and method for adjusting the thickness, the method using electroplating is industrially preferable. In addition, as a material for the steel plate and lead frame in the method of the present invention, the surface of the Cu-based coating layer may be cleaned and activated by pretreatment in the lead frame manufacturing process, and then Cu plating is further performed. Often, the Cu plating process is omitted and soldering is done.
It may be used as a lead frame product by only performing work such as Ag plating. As described above, the steel plate of the present invention has extremely excellent performance characteristics as a material for lead frames. (Example) Using cold-rolled As Cold material or cold-rolled and annealed full-finish finish material, using plating base plates with steel components shown in Table 1, surface cleaning by degreasing, pickling, After the activation treatment, the Cu-based coating layer according to the present invention shown in Table 1 was provided. In addition, the treated material of the present invention is an As Cold material that has been subjected to heat diffusion treatment below the recrystallization temperature.
The heat-diffusion treated materials were cold-rolled at a reduction rate of 20 to 40% below the recrystallization temperature using full-finish materials, and evaluation materials with a thickness of 0.754 mm were obtained for each material. The results of various performance evaluations for these evaluation materials are summarized in the second
Shown in the table. As a result, the product of the present invention (Example) exhibits extremely superior performance as a lead frame material, such as stable solderability, compared to comparative materials. Evaluation test method Evaluation of adhesion of coating layer The Cu-based coating layer of the present invention was evaluated using the following method and evaluation criteria. Adhesion evaluation method and evaluation criteria A Cu-based coated steel plate was repeatedly bent at 90 degrees, and the following evaluation criteria were used to evaluate the occurrence of peeling or cracking in the coating layer and the number of repetitions. ◎...No peeling or cracking of the coating layer occurs when the number of repetitions is 10 or more ○...Peeling or cracking of the coating layer occurs when the number of repetitions is 6 or more to 9 times △...Peeling of the coating layer when the number of repetitions is 3 or more to 5 times Or cracks occur ×…Peeling of the coating layer or cracks occur after repeating less than 2 times Adhesion evaluation method and evaluation criteria For the purpose of evaluating the adhesion of a Cu-based coating layer during thermal bonding of Au wire, etc. Heat to 2
The film was held for 1 minute and then rapidly cooled, and the adhesion was evaluated based on the number of repetitions and the peeling of the coating layer or the occurrence of pristals using the following evaluation criteria. ◎...No defects such as peeling of the coating layer or generation of blisters occur when the number of repetitions is 5 or more. ○...No defects such as peeling of the coating layer or generation of blisters occur when the number of repetitions is 2 or more to 4.△...Heating Blisters occur in the coating layer after one heating. ×… Peeling occurs in the coating layer after one heating. Corrosion resistance evaluation for rust resistance during storage. When punching the evaluation material into a predetermined lead frame shape, the lead frame manufacturing process The rust resistance performance during storage until surface treatment was applied was evaluated using the following accelerated test method and evaluation criteria for flat parts and punched end faces. Corrosion resistance evaluation for rust resistance of lead frame products After punching the evaluation material of the present invention into a lead frame shape, pre-treatments such as degreasing and pickling are performed in the surface treatment process, and a 3μ thick Cu plating is applied. By applying and salt spray test (JIS-C-5028),
The corrosion resistance was evaluated on the flat surface portion and the end surface portion using the following evaluation criteria. Corrosion resistance of flat parts ◎...No red rust occurrence after 24 hours of salt spray test ○...Red rust occurrence rate less than 3% after 24 hours of salt water spray test △...Red rust occurrence rate after 24 hours of salt water spray test 3% or more to less than 5% ×... Red rust occurrence rate after 24 hours of salt spray test 5% or more Corrosion resistance of end face ◎... Red rust occurrence rate after 24 hours of salt water spray test less than 10% ○... Red rust occurrence rate after 24 hours of salt water spray test 10 % or more and less than 15% △...Incidence of red rust after 24 hours of salt spray test 15% or more and less than 20% ×...Incidence of red rust after 24 hours of salt spray test 20% or more Evaluation of Solderability About the solderability of the evaluation materials Assuming that soldering is performed after punching and before Cu plating in the lead frame manufacturing process, we evaluated the solderability, especially the solderability of the punched end face. Wetting stress and wetting time when rosin alcohol flux is applied to the evaluation material sheared into a 50 mm wedge shape and immersed vertically in a Pb-60%Sn solder bath with the 10 mm sheared surface 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 3 months. ◎...Solder wettability and wetting speed are both extremely good when wetting stress is 450mg or more and wetting time is less than 6 seconds ○...Both solder wettability and wetting speed are good when wetting stress is 350mg or more and less than 400mg and wetting time is less than 7 seconds Good quality △... Either the solder wettability or the wetting speed is slightly inferior when the wetting stress is 250 mg or more and less than 350 mg or the wetting time is 7 seconds or more and less than 8 seconds. ×: If the wetting stress is less than 250 mg or the wetting time is 8 seconds or more, either the solder wettability or the wetting speed is extremely poor. Evaluation of electrical conductivity The electrical conductivity of the surface of the evaluation material was measured by the potential difference method, and evaluated using the following evaluation criteria. Note that the measurements were performed at room temperature (30°C). ◎…Electrical conductivity 7×10 ⁶ (Ωm) ^-1 or more ○…Electrical conductivity 6×10 ⁶ (Ωm) ^-1 or more ~ 7×10 ⁶
(Ωm) Less than ^-1 △…Electrical conductivity 5×10 ⁶ (Ωm) ^-1 or more ~ 6×10 ⁶
(Ωm) Less than ^-1 ×…Electrical conductivity 5×10 ⁶ (Ωm) Less than ^-1 Evaluation of thermal conductivity The thermal conductivity of the surface of the evaluation material was measured by the optical alternating current method and evaluated using the following evaluation criteria. . The measurements were conducted at room temperature (30℃). ◎…Thermal conductivity is 0.15 (cal/sec・cm・℃) or more ○…Thermal conductivity is 0.10 (cal/sec・cm・℃) or more and less than 0.15 (cal/sec・cm・℃) △…Thermal conductivity Thermal conductivity is less than 0.05 (cal/sec・cm・℃) or more and less than 0.10 (cal/sec・cm・℃) ×…Thermal conductivity is less than 0.05 (cal/sec・cm・℃) Performance of lead frame products over time Evaluation 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 maker at a pressure of 2 Kg/cm ² and a temperature of 120°C. These products were encapsulated in boiling hot water and subjected to a 500-hour aging test, and their external appearance was evaluated based on the following evaluation criteria. still,
Cu plating was carried out at 2μ. ◎...Excellent condition with no change in surface appearance △...Slight rust on the end face ×...Significant rust on the flat and end faces Punching formability (stamping property) The following evaluations were made of the stamping formability into the shape of the lead frame. The moldability was evaluated based on the criteria. ◎...There is almost no occurrence of burrs on the punched end face or cracks in the material, and the punching formability is extremely good. ○...The punching formability of the evaluation material was as good as above, but some wear and tear occurred due to the continuous operation of the punch and die of the molding machine. △: Slight burrs occur on the punched end face, or the ability to remove the molded material from the device is poor, so some troubles tend to occur during punching. ×...A considerable amount of cracking occurs in the evaluation material due to punching and forming, or wear and tear on punches, dies, etc. is significant due to long-term continuous operation.

【table】

【table】

【table】 [Brief explanation of the drawing]

Figures 1a and b are the results of cross-sectional concentration analysis (glow discharge emission analysis) and a schematic cross-sectional view of the Cu-plated layer, and Figures 1c and d are the cross-sectional concentration analysis (glow discharge emission analysis) of the Cu-plated layer. Results and cross-sectional schematic diagrams. Figure 2 shows an example of the corrosion resistance of a Cu-based coating material with a Cu diffusion layer for storage. Figure 3 shows the results obtained by applying Cu plating treatment during the lead frame manufacturing process. Figure 4a shows an example of corrosion resistance after 24 hours of salt spray test (24 hours SST), Figure 4a shows the solder wettability of Cu-based coating material with Cu diffusion layer and Cu plating material, Figure 4b FIG. 3 is an explanatory diagram of the wetting stress measurement method in FIG. 1: Steel plate, 2: Cu plating layer, 3: Steel plate, 4:
Cu coating layer.

Claims (1)

[Claims] 1% by weight, C: 0.30% or less, Al: 0.005 to 0.10
%, Si; 0.6% or less, Mn; 1.5 or less, Cu; 0.05~
A Cu coating layer having a Cu diffusion layer is applied to the surface of a steel plate containing 1.0% Fe and unavoidable impurities, and the thickness of the Cu diffusion layer is 0.1 to 3μ and
A surface-treated steel sheet for lead frames with excellent corrosion resistance, solderability, and adhesion, characterized by a diffusion layer and a Cu coating layer having a thickness of 0.5 to 15μ. 2 In weight%, C: 0.30% or less, Al: 0.005 to 0.10
%, Si; 0.6% or less, Mn; 1.5 or less, Cu; 0.05~
1.0%, further contains Ni: 0.05 to 3.0%, and the balance is Fe.
Cu on the surface of the steel plate, which consists of
Corrosion resistance and solderability characterized by applying a Cu coating layer having a diffusion layer, the thickness of the Cu diffusion layer being 0.1 to 3μ, and the thickness of the Cu diffusion layer and the Cu coating layer being 0.5 to 15μ, Surface-treated steel plate for lead frames with excellent adhesion.