JPH08269597A - High strength lead frame material - Google Patents

Abstract

PURPOSE: To produce a lead frame material having package crack resistance capable of withstanding the increase of input and output signals into high frequencies, furthermore having a strength capable of withstanding the increase of pins into multipines and moreover combining excellent etching workability, sealability and formability. CONSTITUTION: This is a high Ni-Fe lead frame material having a compsn. contg. 55.0 to 85.0% Ni, >0.1 to 1.0% Mn and 0.001 to 0.50% Si, and the balance Fe, an in which the contents of impurities are regulated to contain <=0.015% C, <=0.01% P, <=0.005% S, <=0.010% O and <=0.005% N. The molten material is repeatedly subjected to rolling at <=90% draft and recrystallization annealing. By the recrystallization annealing executed before the final cold rolling, the average grain size is regulated to <=30μm, and the final cold rolling is executed at >=5% draft. For obtaining a grain-regulated structure, the coefficient of variation in the grain size before the final cold rolling is regulated to <=1. After the final cold rolling, if required, after the shape is modified by a leveller, residual stress relief annealing can be executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-nickel-iron lead frame material having high strength which is excellent in etching processability, sealing property and molding processability, and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Generally, in semiconductor devices, it is known that the characteristics of the lead material used have a great influence on its performance and cost. Is a Fe-42 wt% Ni alloy (so-called "42 alloy", which has a thermal expansion coefficient close to that of packaging materials such as sealing glass and ceramics and semiconductor elements and exhibits relatively good adhesion and sealing properties with them. )) Has been preferred.

Although the 42 alloy has been used as it is for a plastic package, the difference in the coefficient of thermal expansion between the mold resin used for the plastic package and the 42 alloy is large. It is unavoidable that thermal stress is applied between the resin and the lead material when it is mounted on the printed circuit board and when it is subjected to a temperature cycle in the usage environment. , The package may crack, or the adhesive interface between the resin and the lead material may peel off,
It causes a defect.

It is well known that semiconductor devices are used not only in home electric appliances but also in electric components of vehicles such as automobiles and railways, and in the heart of various heavy machinery for functioning cities. Reliability is an area of particular importance because its defects sometimes affect life.

The current mainstream package with 200 pins or less has a low defect rate even with a normal 42 alloy and can sufficiently cope with it, but with the advent of the advanced information society, the processing capacity which will be required more and more in the future will increase. There is a possibility that a package that takes into consideration the tendency to change may not be able to deal with it from the viewpoint of the defective rate. That is, in order to increase the processing capacity, it is necessary to deal with the increase in the frequency and the degree of integration of the input / output signals. Increasing the frequency of input / output signals means that the package itself is heated to a higher temperature, and a more severe thermal cycle is realized, so the problem of package cracks pointed out above cannot be ignored. there is a possibility. Therefore, in order to cope with the high frequency of the input / output signals, a lead frame material having a further excellent package crack resistance is required.

High integration means that the lead frame has a large number of pins, and a stronger material is required. This is because when the lead frame has a large number of pins, the pin interval inevitably becomes narrower and the width of the pins themselves becomes smaller, but in order to realize this, etching or pressing with higher accuracy is required. However, there is a concern that the thickness becomes thicker than the pin width, and the processing becomes more difficult. Therefore, it becomes necessary to make the material thinner in order to cope with it, but in order to make it thin, a lead frame material having a strength higher than that of the conventional material is required.

Further, in the case of a lead frame material for multi-pins or ultra-multi-pins, etching is the main processing for molding, and it is also an important required property that "etching workability" is excellent. Here, in the step of etching the lead frame material, a photoresist is applied to both surfaces of the degreased lead frame material, a pattern is baked and developed, and then an etching solution containing ferric chloride as a main component is used for etching. After that, it is generally composed of a step of removing the resist.

The "etching workability" is specifically as follows.
"Etching rate", "Etching processing cross-section property",
It means "etching factor" and "processing accuracy".

That is, it is more preferable that the etching rate is faster because the processing time can be shortened. Further, it is more preferable that the etched cross section is smooth. This is because surface treatment such as chemical polishing and plating is performed in a later step, but if the etching processed section is rough, uniform surface treatment cannot be performed.

Further, a higher etch factor is more advantageous for increasing the number of pins. Since the etching process is a process in which the corrosive liquid dissolves and removes the metal, the process proceeds not only in the depth direction of the workpiece but also in the lateral direction. The etch factor is a concept peculiar to etching processing, and is a ratio of the progress in the depth direction to the progress in the lateral direction. In other words, the higher the etch factor, the harder it is to proceed in the lateral direction, and the easier it is to proceed in the depth direction. To increase the number of pins means that the pin spacing becomes narrower,
The fact that the etching factor is high-the etching process is less likely to proceed in the lateral direction-means that it is easier to secure the pin width of each pin, which is more advantageous for increasing the number of pins.

Of course, it is desirable that the machining accuracy is high in order to increase the number of pins. The processing accuracy in the etching process is affected by the homogeneity and anisotropy of the work material and the adhesion between the work material and the photoresist. That is, it is preferable that the material to be processed is homogeneous, has small anisotropy, and has good adhesion to the photoresist. Here, “homogeneous” means that the structure is uniform, the segregation of components is small, and there is no coarse precipitate or inclusion. Further, the anisotropy which is regarded as a problem in the etching process is the in-plane anisotropy of the processing speed of the material to be processed. Since there is a difference in the etching rate depending on the crystal orientation, if a certain kind of texture is developed, the intended processed shape printed on the photomask pattern may not be obtained.

So far, the characteristics required for the lead frame material in order to cope with future package trends have been described. In addition to these, various characteristics required for the lead frame material from the standpoint of reliability than before. Has a wide variety of properties such as solder wettability, solder heat-resistant peeling property, die bonding property, wire bonding property, plating property, corrosion resistance, and the like, all of which are important properties that cannot be ignored. However, since the number of items required is too large, it is extremely difficult to achieve the same level of reliability as the conventional 42 alloy and further improve the characteristics to meet future needs.

For example, JP-A-2-159348, JP-A-3-39446, JP-A-3-39447, JP-A-3-173748, JP-A-3-207834, JP-A-3-207835 and JP-A-3. -219051 and Japanese Patent Laid-Open No. 3-219054 achieve high strength by adding Be, but since Be is an active metal, it is difficult to melt and cast, and inclusions are likely to occur. Further, the oxide film on the surface of the material formed of Be significantly deteriorated the solder wettability. Further, since Be is a metal harmful to the human body, there is a drawback that alloys containing Be are generally difficult to recycle.

Japanese Patent Laid-Open No. 3-166340, Japanese Patent Laid-Open No. 4-120245, Japanese Patent Laid-Open No. 4-176844, etc. reduce the Ni content as compared with the usual 42 alloy and add Co by that amount. The austenite phase is made unstable and the strength is increased by utilizing the work-induced martensite. However, since it is a two-phase mixed structure, it is difficult to control the structure, and it is difficult to obtain a certain characteristic, so that there is a problem in stable manufacturability. There is also a drawback that the plastic anisotropy is large.

Further, JP-A-57-207154, JP-A-2-58338, JP-A-3-2353 and JP-A-4
-99251, JP-A-4-120245, JP-A-4
No. 202642, etc. are V, Zr, Al, Hf, T
Although trace elements such as i, Nb, Ta, and W have been added to increase the strength by precipitation hardening, these elements tend to generate coarse inclusions and precipitates, which roughens the etched cross section. It became a result.

On the other hand, among the copper alloy lead frame materials, a material having a strength higher than that of ordinary 42 alloys has been developed and has been attracting attention. This is because the copper alloy has a thermal expansion coefficient close to that of the mold resin and is superior in conductivity and heat dissipation compared to the 42 alloy. However, the copper alloy is 4
Inferior in press workability, adhesion to mold resin, corrosion resistance, and moisture resistance reliability, etc.
There was a problem in reliability as a multi-pin package.

[0017]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The object of the present invention is to provide a package crack resistance capable of withstanding the high frequency of input / output signals required in the near future without deteriorating the high level of reliability of the conventional 42 alloy, and further increasing the number of pins. With the strength to withstand
An object of the present invention is to provide a lead frame material having both excellent etching processability, sealing property and molding processability.

[0018]

In order to achieve the above object,
In particular, paying attention to the high reliability as a lead frame material originally possessed by Fe-Ni alloys, and investigating the relationship between the Ni content and various properties required for the lead frame material in detail,
As a result of further detailed research on the relationship between the trace elements and the manufacturing process, new knowledge has been obtained in addition to the conventionally known knowledge.

That is, the generally known matters in the region where the Ni content of the Fe-Ni alloy is higher than that of the 42 alloy are as follows: 1) As the Ni content increases, the strength increases. Improved, N
When the i content is 77% by weight, the strength becomes maximum. This produces an ordered phase when the Ni content is 75% in atomic%,
This is because the crystal structure becomes the most stable. 2) The conductivity improves as the Ni content increases. 3) The coefficient of thermal expansion increases as the Ni content increases. 4) The corrosion resistance improves as the Ni content increases.

The following new findings have been obtained this time: 5) Trace elements (especially S) which are easily segregated at the grain boundaries or surface.
In the Fe-Ni-based alloy in which (i, P, S) is suppressed to a certain concentration or less, the adhesion with the mold resin improves as the Ni content increases. Further, the adhesiveness is further improved by performing residual stress relief annealing after cold rolling. 6) Trace elements (especially S
In the Fe-Ni alloy in which (i, P, S) is suppressed to a certain concentration or less, even if the Ni content is increased, the etching rate and the etch factor are 42 when etched with a high temperature etching solution of 50 ° C. or higher. Almost the same as the alloy, and if the specific gravity of the etching liquid is 1.5 or more, a good etching cross section can be obtained as with the 42 alloy. 7) Trace elements that are easily segregated at the grain boundaries or surface (especially S
In the Fe-Ni based alloy in which (i, P, S) is suppressed to a certain concentration or less, the solder wettability is almost the same as that of the 42 alloy even if the Ni content is increased. In addition, in the case of performing Ni undercoating and performing various platings, the undercoating is stabilized with an increase in the Ni content, and thus the plating property is improved. 8) When the ordered phase of the Fe-Ni alloy system develops, not only a good shape is easily obtained by performing residual stress relief annealing after shape correction, but also the spring limit value is significantly improved. However, to make this effect more noticeable,
It is necessary to make the crystal grains of the material as fine as possible, and to make the orientation of each crystal grain random. 9) When the Fe-Ni alloy-based ordered phase develops, the press punchability becomes good. That is, in press working, the generation of harmful "burrs" is reduced, and the ratio of the fracture surface to the shear surface is increased. At the same time, the "twist" of the machined part is also reduced.

Up to now, alloys having a Ni content of 55% or more have been used for magnetic materials such as permalloy, heat-resistant materials such as Inconel, and high corrosion-resistant materials such as Hastelloy. Was not done. This is because it is considered that the die bonding property is inferior because the etching workability and the solder wettability are inferior and the coefficient of thermal expansion is larger than that of the semiconductor element as compared with the conventional 42 alloy.

However, as described above, the Ni content is 5
In alloys of 5% or more, it was found that if the trace elements were reduced to below a certain concentration, the etching workability equivalent to that of the 42 alloy could be obtained by properly controlling the temperature and specific gravity of the etching solution. In addition, it was found that the solder wettability and the plating property were equivalent to those of the 42 alloy. Also, F
Since a copper alloy having a thermal expansion coefficient significantly higher than that of an e-Ni alloy has been studied as a lead frame material,
A die-bonding agent for a semiconductor element has been developed that can withstand extreme thermal cycles, and the die-bonding property, which has been a concern in the past, has almost disappeared.

Based on these findings, the present invention provides, in weight%, Ni: 55.0 to 85.0%, Mn: more than 0.1 to 1.0%, and Si: 0.001 to 0.001. 0.50%
And the balance consists of Fe and inevitable impurities, and the impurities are C: 0.015% or less, P: 0.01% or less, S: 0.005% or less, O: 0.010% or less, and N: characterized by being regulated to 0.005% or less,
Provided is a high-strength lead frame material excellent in etching processability, sealing property and molding processability.

If the average value of the crystal grain size of the lead frame material before the final cold rolling is 30 μm or less, the material has higher strength, and the variation coefficient (standard deviation / average value) of the crystal grain size at that time is If it is 1 or less, the material has a better press workability.

The high-strength lead frame material excellent in etching processability, sealing property and molding processability according to the present invention has a Ni content of 55.0 to 85.0% and a Mn content of more than 0.1% by weight. ~ 1.0%, and Si: 0.001 to 0.50%
And the balance consists of Fe and inevitable impurities, and the impurities are C: 0.015% or less, P: 0.01% or less, S: 0.005% or less, O: 0.010% or less, and N: In the material melted so as to be 0.005% or less,
Repeated rolling and recrystallization annealing with a workability of 90% or less, and an average crystal grain size of 30μ by recrystallization annealing performed before the final cold rolling.
It can be manufactured by adjusting to m or less and performing the final cold rolling at a working ratio of 5% or more.

In addition, after the final cold rolling, if residual stress relief annealing is performed, the plastic anisotropy is reduced, and the etching processability and sealing property are improved. Furthermore, if shape correction is performed after the final cold rolling, a material having a good shape can be obtained even if the strain is released by subsequent residual stress relief annealing.

The lead frame material manufactured in this manner has a high strength that can withstand the increasing number of pins that is desired to be realized in the future, and also has a high sealing property that can withstand a severe thermal cycle. ing. Further, in other various properties as a wide variety of lead frame materials, the same level of reliability as the conventional 42 alloy is maintained as it is, and the great improvement of the present invention is that the above improvement is achieved without any defects. is there.

[0028]

[Function] The lead frame material is obtained by melting and casting a material having a required component composition, for example, hot forging or hot rolling, and the first cold rolling-the first annealing, the second cold rolling. Rolling-Second annealing, cold rolling and annealing are repeated, and final cold rolling is performed to obtain a required thickness. Next, the reason why the component composition of the material alloy and the manufacturing process are defined as described above in the present invention will be explained together with its action.

(A) Material composition of the material [Ni]: Ni determines the coefficient of thermal expansion, adhesion and strength with the molding resin, and shape fixability (press moldability, easiness of shape correction). Is an important ingredient in. It guarantees excellent sealing property and moisture resistance reliability that can withstand the severe thermal cycles that will be realized in future high-speed processing packages, and also secures high strength that can withstand the high pin count realized in highly integrated packages. In order to achieve this, the Ni content should be 55.0-8.
It is necessary to adjust the range to 5.0%. For this reason, N
Although the i content is set to 55.0 to 85.0%, a particularly preferable range is 65.0 to 82.0%, and more preferably,
It is 75.0 to 80.0%. [Mn]: Mn is an element added to secure deoxidation and hot workability, but if the content is less than 0.1%, not only the desired deoxidation effect cannot be obtained, The hot workability also becomes poor. On the other hand, even if the Mn content exceeds 1.0%, the effect is saturated and meaningless, so the Mn content was set to 0.1 to 1.0%. [Si]: Si is an element generally added as a deoxidizer, but on the other hand, it has a great influence on etching processability and solder wettability. That is, the Si content is 0.50%
If it exceeds, a stable oxide film is formed on the surface of the material, and the adhesiveness with the photoresist and the etching processing rate are significantly deteriorated. In addition, this oxide film also reduces solder wettability. Therefore, in order to secure good etching processability and solder wettability, it is necessary to adjust the amount of Si added to 0.50% or less. Since Si tends to segregate on the surface due to annealing, it is desirable to reduce the content to 0.15% or less in order to stably obtain good solder wettability and etching workability. However, the Si content is 0.001
If it is reduced to less than%, the deoxidizing effect described above cannot be recognized. Therefore, the Si content is 0.001
Although it was set to 0.50%, as mentioned above, if possible,
It is desirable to adjust it to 0.001 to 0.15%. The smaller the amount of Si, the better the etching property and solder wettability, so a more preferable range is 0.0
It is 01 to 0.05%.

[C]: C subtly affects the strength of the material. The higher the content of C, the more preferable it is only to increase the strength. However, if it exceeds 0.015%, coarse carbides precipitate and the etched cross section becomes rough. Therefore, the content of C is set to 0.015% or less. However, since C reduces the etching processing rate even in a solid solution state, it is preferably 0.
It is desirable to regulate it to 005% or less. [P]: P is an extremely harmful element to the lead frame material, and it is desirable that P is not present at all. P has the effect of segregating at grain boundaries and facilitating the formation of coarse inclusions, resulting in embrittlement of the material and deterioration of corrosion resistance, solder wettability, plating properties and etching processability. Bring If the P content is set to 0.01% or less, these adverse effects are acceptable to the lead frame material, so the P content was defined as 0.01% or less. Further P
To minimize the adverse effects of the
It is desirable to be 001% or less. [S]: S, along with P, is an extremely harmful element for the lead frame material. That is, S impairs hot workability, and P
Similarly, it causes deterioration of corrosion resistance, solder wettability, plating property and etching processability. Further, S also impairs hot workability. Therefore, it is most desirable not to have it at all,
If the content is controlled to 0.005% or less, these adverse effects are acceptable as a lead frame material, so the S content was specified as 0.005% or less. Further, in order to make the adverse effect of S small enough to be ignored, it is desirable to set it to 0.001% or less. [O]: When the O content exceeds 0.010%, oxide-based inclusions increase in the material, which adversely affects etching workability and press workability. 01
It was defined as 0% or less. [N]: When the content of N exceeds 0.005%, the etching processability is significantly deteriorated, so the upper limit of the N content is set to 0.005% or less.

(B) Average Crystal Grain Size and Recrystallization Annealing Before Final Cold Rolling The crystal grain size in the lead frame material of the present invention is adjusted by recrystallization annealing performed before the final cold rolling. The crystal grain size is an important factor for ensuring the desired strength, and also has a great influence on the etching cross-sectional properties and press workability. That is, the smaller the crystal grain size is, the higher the strength is, the smoother the cross section is etched, and the better the press workability is. Therefore, a more desirable material can be obtained for the purpose of the present invention. If the average value of the crystal grain size after the recrystallization annealing performed before the final cold rolling is 30 μm or less, the above effect becomes remarkable. Therefore, the average that should be adjusted in the recrystallization annealing performed before the final cold rolling. The crystal grain size was defined as 30 μm or less. More preferably, it is 20 μm or less.

(C) Grain Size Structure and Recrystallization Annealing Further, if the crystal grains are sized rather than mixed grains, press workability and easiness of shape correction are improved. Since it is often determined by visual judgment whether the crystal grains are mixed grains or sized grains, here, in order to quantitatively evaluate the degree of mixed grains, the coefficient of variation of the crystal grain size ( The concept of (standard deviation / mean value) was used. If the coefficient of variation of the crystal grain size is 1 or less, it can be said that the particles are in a sized state, so that the above effect becomes more remarkable, and the material is more preferable for the purpose of the present invention. In order to obtain such a grain size, it is impossible to adjust only by the final recrystallization annealing, and it is necessary to make the grain size uniform from the upper step as much as possible. Therefore, in the present invention, it is necessary to adjust the crystal grain size to 30 μm or less even in the recrystallization annealing in the upper step, preferably hot rolling or hot forging. That is, unless the crystal grain size of the raw material is constantly controlled to a certain value of 30 μm or less from the above step, the final product cannot be sized. In the recrystallization annealing from the above step, it was found that if the average value of the crystal grain size is always controlled to 30 μm or less, a sufficient grain size control structure can be obtained, and more preferable results can be obtained for the purpose of the present invention. The average value of the crystal grain size to be adjusted by recrystallization annealing was specified to be 30 μm or less. However, it is more preferable to control to 20 μm or less in all recrystallization annealing. Since the crystal grain is not a circle, the grain diameter in this case is preferably a circle equivalent diameter (diameter of a circle having the same area as the target crystal grain). The equivalent circle diameter can be easily measured with an image processing device such as LUZEX.

(D) Workability in final cold rolling A higher workability in the final cold rolling gives a material having higher strength. In particular, the component system of the present invention has a high work hardening index, so that a material having high strength can be easily obtained by adding a small amount of working. If the workability in the final cold rolling is 5% or more, sufficient strength can be obtained for the purpose of the present invention. Therefore, the workability in the final cold rolling is set to 5% or more. However, when the workability in the final cold rolling exceeds 90%, bending workability is deteriorated, and especially the roughened surface of the bent portion is apt to be remarkable, so the preferable range is 5 to 90%. The most preferable range for obtaining more stable quality is 30 to 80%.

(E) Workability in cold rolling in the upper step before final cold rolling On the other hand, in cold rolling in the upper step before final cold rolling, if a high workability is constantly added, a texture develops. . As a result, the plastic anisotropy becomes large, the press workability deteriorates, and the work hardening ability decreases in the final rolling. In addition, there is a drawback that it becomes difficult to correct the shape. If the cold rolling workability is always controlled to 90% or less from the above process, the development of texture can be suppressed to a negligible range, and in the final cold rolling, the work hardening ability to sufficiently reach the target strength can be obtained. Since it was proved that it could be obtained, the cold rolling workability was always controlled to 90% or less from the above process. However, it is preferably always 70% or less.

(F) Shape correction performed after final cold rolling In order to obtain a package with higher reliability, it is desirable that the lead frame material has a good shape (high flatness). This is because the material shape affects the processing accuracy of the lead frame. In order to improve the material shape, it is common to correct the shape with a roller leveler or stretcher leveler. However, when these treatments are applied to conventional 42 alloy, processing strains become uneven, and then residual stress is removed. When annealing is applied, the release of strain becomes uneven, and the shape rather deteriorates. However, in the component system of the present invention,
It has been found that if a sufficient grain size control structure and random crystal orientation are obtained, a good shape can be maintained even if residual stress relief annealing is performed after shape correction. Should be used.

(G) Final Annealing (Residual Stress Relief Annealing) As described above, a severe thermal cycle is applied to the lead frame. In the cold-worked material, this releases residual stress and changes the material dimensions slightly.
Therefore, it is desirable that the residual stress relief annealing be performed after the final cold rolling or after the shape correcting process is added. The material having the component system of the present invention, if subjected to residual stress removal annealing after cold rolling, tensile strength and hardness are hardly reduced,
Ductility is restored, plastic anisotropy is reduced, and the spring limit value is further improved. In addition, as described above, the material having the component system and the structure of the present invention is extremely small in size change due to release of strain, and therefore deterioration of the material shape due to residual stress relief annealing is almost negligible. Rather, if a continuous annealing line is used and residual stress relief annealing is performed while tension is applied to the material, a better shape can be obtained. In addition, the material having the component system of the present invention has an advantage that the ordered phase is developed by the residual stress removal annealing and the adhesion with the mold resin is further improved.

[0037]

EXAMPLES Next, the effects of the present invention will be specifically described by showing Examples and Comparative Examples. First, predetermined components were mixed, melted, and cast to obtain various ingot samples with a thickness of 30 mm. Hot rolling is applied to them, and then cold rolling and annealing are repeated to obtain a plate thickness of 0.1.
The material of mm was obtained. The chemical components, main manufacturing steps and manufacturing conditions at this time were as shown in Table 1.

Regarding the chemical components, the gas components such as C and N slightly changed even by annealing, so they were confirmed after the final step. The crystal grain size after annealing was confirmed by observing the structure from the surface of the material. However, the confirmation of the crystal grain size may be performed after cold rolling. Even if cold rolling is performed after recrystallization annealing, the crystal grains do not stretch in the direction perpendicular to the rolling direction.Therefore, when observing after cold rolling, measure the maximum width of each crystal grain in the direction perpendicular to the rolling direction. May be.

Then, with respect to various samples, the characteristics which are considered to be particularly necessary as the lead frame material are investigated,
I confirmed the effect. The evaluation items, evaluation conditions, and established acceptance criteria are shown below.

(A) Mechanical Properties Regarding mechanical properties, tensile strength (N / mm ² ), Vickers hardness (Hv 0.5) and: Spring limit value (N / mm)
We investigated 3 items of ² ). The tensile strength and the spring limit were compared with the rolling parallel direction (//) and the rolling orthogonal direction (⊥), and the plastic anisotropy was also evaluated. The Vickers hardness was evaluated by making a dent on the surface of the material with a load of 500 g. Since the evaluation of mechanical properties is for confirming the achievement of high strength which is one of the objects of the present invention, the acceptance criteria set this time is 30% more than the strength of the conventional 42 alloy. Value. a-1: Tensile strength (N / mm ²⁾ Pass Criteria: 800 N / mm ² or more a-2: Vickers hardness (Hv 0.5) Pass Criteria: 260Hv0.5 or a-3: Spring limit (N / Mm ² ) Acceptance criteria: 650 N / mm ² or more

(B) Press workability An investigation was conducted from the viewpoint of punchability and formability. Regarding the punching property, the QFP type lead frame was actually punched, the sheared surface was observed, and the fracture surface ratio was measured. Here, the “fracture surface area ratio” means the plate thickness of the workpiece,
It is the ratio of the thickness of the fracture surface. The sheared surface consists of a sheared surface that has undergone shear deformation and a fractured surface that has fractured.If the ratio of sheared surfaces is large, it means that there is a large amount of plastic deformation that occurs before fracture. It means that the press punching property is poor. Therefore, it can be said that the higher the fracture surface ratio is, the better the press punching property is.

Further, the maximum values of the generated "burr height" (burr protrusion amount in the plate thickness direction) and "burr thickness" (burr protrusion amount in the direction perpendicular to the sheared surface) are Measured. As mentioned above, it is desirable that there be no burrs in the press working.

Furthermore, the "up and down of the tip of the inner lead" was measured, and the difference between the maximum height and the minimum height was calculated. The reason for this evaluation is that poor flatness of the inner leads leads to poorer wire bonding. That is, if the press punching property is poor, "twisting" occurs in each lead and the lead flatness deteriorates. The mold clearance at this time was 10% of the plate thickness of the material to be processed.

The moldability is V of JIS Z 2248 standard.
A bending test was performed by the block method, and "spring back" and "roughness of the bent portion" were observed and evaluated. In this test, the rolling load was 5 tons, the sample width was 10 mm, the angle of the V block was 90 deg, and the radius of curvature of the tip of the push fitting was less than 0.01 mm.
Good press formability, in other words, means that the shape of the press die is more faithfully transmitted to the workpiece, and the smaller the springback, the better. In addition, the plastic deformation in the vicinity of the bent portion must be performed without difficulty, and the less rough the skin of the bent portion, the more desirable.

The acceptance criteria were set as follows: b-1: fracture surface ratio (%) acceptance criteria: 20% or more b-2: burr height (μm) acceptance criteria: maximum value of 3 μm or less b-3: Burr thickness (μm) Acceptance standard: Maximum value is 10 μm or less b-4: Ups and downs of lead (μm) Acceptance criterion: Difference between maximum height and minimum height is 20 μm or less b-5: Springback (deg) Acceptance criterion: Deviation from 90 deg is 1.0 deg or less b-6: Rough skin condition of the bent part (○, ×) Pass criteria: Rough skin is equal to or less than the conventional 42 alloy

(C) Etching processability The etching processability was also evaluated by actually etching the T-SOP type lead frame. As the photomask pattern, we chose a type that allows perforation of an array of perfect circles on one side of the die pad. The etching depth was measured by measuring the center (the deepest part) of the circle punched in the lead frame after etching. The "etching rate" was obtained as a value obtained by dividing the etching depth by the time required for processing. Similarly, the side etch amount was measured, and the "etch factor" was calculated as (etching depth / side etch amount).

Further, in order to evaluate the "etching anisotropy", the roundness of the preceding hole was measured. Here, "roundness" is a concept introduced here for the first time, and is defined as follows. That is, the roundness is "a scale representing the closeness of a figure having a shape close to a circle, and is a value obtained by dividing the minimum value of the diameter by the maximum value of the diameter". According to this definition, the higher the roundness is, the closer the figure is to the circle, and the roundness is 1 in the roundness. 1 when roundness is expressed as a percentage
You just have to multiply by 00. Further, the "roughness of the cross section subjected to etching" was observed to confirm the rough skin condition.

The etching solution used was an aqueous solution of ferric chloride, the temperature of the solution was 50 ° C., and the specific gravity at that temperature was adjusted to 1.5. As the etching method, an etching process was performed by spraying with an etcher having a nozzle with a spray pressure of 30 N / cm ² .

The acceptance criteria were set as follows: c-1: etching rate (μm / sec) acceptance criterion: 0.2 μm / sec or more (equal to or more than the conventional 42 alloy) c-2: etch factor (dimensionless) ) Acceptance criteria: equivalent to or more than the conventional 42 alloy c-3: Etching anisotropy (%) Acceptance criteria: Roundness is 95% or more c-4: Etching cross-section property (○, ×) Acceptance criteria: Conventional Smoother than 42 alloy

(D) Micro shape The micro shape of the lead frame material is a factor that becomes more important as the package size becomes smaller. This is because the deviation from the target shape affects the assembling accuracy at the time of packaging, and the smaller the package size, the higher the accuracy required. The defective shape of the lead frame material easily causes a package crack.
As an evaluation of the micro shape, the "amount of warpage of the die pad" of the lead frame etched in (c) above was measured. Here, the "warpage amount" is an amount that represents a slight depression or swell of the die pad. That is, it is the maximum value of the distance between the straight line connecting both ends of the die pad and the point at which the foot of the perpendicular line drawn from the straight line to the die pad intersects the die pad. The length of the die pad of the lead frame used in this evaluation was 14 mm, and the acceptance criteria were as follows. d-1: Amount of tie pad warp Acceptance criteria: Maximum warp is 5 μm / 14 mm or less

(E) Corrosion resistance Regarding the corrosion resistance, a salt spray test according to JIS Z 2371 was carried out for 100 hours to confirm the presence or absence of rust, and the result was taken as the acceptance criterion. e-1: Salt spray test (○, ×) Pass criteria: No rust generation

(F) Solder wettability With respect to the solder wettability, T ₂ (time until the solder gets wet) was measured according to the meniscograph method defined by MIL-STD-883D. The acceptance criteria are as follows. f-1: T ₂ (seconds) in the meniscograph method Pass criteria: 1 second or less (equal to or less than the conventional 42 alloy)

(G) Sealing property Regarding the sealing property, "adhesion test" and "temperature cycle test" between the material and the molding resin were conducted. First, a mold resin having a glass transition temperature of 175 ° C. is molded and cured on a material, a shear load is gradually applied, the maximum load until peeling is measured, and the adhesion strength (N /
mm ² ) was determined. In addition, the lead frame pressed in the above (b) is used as it is without mounting a semiconductor element or the like.
Packaged in FP, temperature difference 230 ° C (160 ° C)
The temperature cycle test (° C. → −70 ° C.) was performed 1000 cycles at a rate of 1 cycle per hour to confirm the occurrence of cracks. In addition, the temperature cycle test that is normally performed is performed at a temperature difference of 215 ° C. (150 ° C. → −65 ° C.).
If no cracks occur in the 00 cycle, it is often passed. Therefore, it can be said that the test conditions of the temperature cycle test set this time are more severe test conditions for meeting future needs with a margin. The acceptance criteria are as follows. g-1: Adhesion test (N / mm ² ) Pass criteria: 10 N / mm ² or more (12 of conventional 42 alloy)
0% or more) g-2: Temperature cycle test (○, ×) Pass criteria: No cracks occur at all

Table 2 shows the above test results. As is clear from the results of Tables 1 and 2, the materials of the present invention have sufficient strength and hardness, and exhibit excellent etching property, press workability and sealing property, while the composition of the components is It can be seen that the comparative material which does not satisfy the conditions defined by the present invention does not satisfy any of the characteristic acceptance criteria required for the lead frame material.

That is, although the target values of the characteristics set this time are significantly stricter than the standard values of ordinary lead frame materials, all the materials of Examples 1 to 10 of the present invention achieved the target. are doing. In particular, the present invention example No. Comparing No. 1 to No. 3, Since the component composition is controlled in a more preferable range in order, the strength and sealing property are accordingly
You can see that it is improving. Next, the present invention example No. 3-
Comparing No. 10 with each other, there is no great difference in component composition, but No. Since the manufacturing process in turn becomes a more preferable condition, each characteristic value is also improved accordingly.

For example, the present invention No. 4 and No. 6 ~
In No. 10, the average value of the crystal grain size before the final cold rolling is controlled in a more preferable range, so that the strength is improved. The invention example No. In Nos. 5 to 10, the coefficient of variation of the crystal grain size before the final cold rolling is controlled in a more preferable range, so that the press formability such as springback and lead flatness is improved. Among them, the present invention example No. 7
In Nos. 10 to 10, the crystal grain size is controlled in a more preferable range from the stage of hot rolling, so it can be seen that the press formability is further improved.

The present invention example No. In Nos. 8 to 10, after residual cold stress annealing was performed after the final cold rolling, the plastic anisotropy was reduced, and the micro shape and sealing property were also improved. Among them, the present invention example No. In Nos. 9 and 10, after the final cold rolling, the shape was corrected and then the residual stress relief annealing was applied, so that the micro shape was dramatically improved.

On the other hand, Comparative Example 11 is a typical 42 alloy, but since the Ni content is small, strength, press workability,
Micro shape and inferior sealing property. In Comparative Example 12,
Since P and Si are more than specified values, solder wettability, corrosion resistance, sealing property, and etching property are poor. In Comparative Example 13, since S is larger than the specified value, solder wettability and corrosion resistance are poor. In Comparative Example 14, since C is larger than the specified value, coarse carbides are deposited and the bent portion and the etched cross section are rough. In addition, the fact that the N content is higher than the specified value also promotes the deterioration of the etching property. Further, since the workability in cold rolling before the final recrystallization annealing is extremely high, a recrystallization texture develops and etching anisotropy appears. In Comparative Example 15, since O is larger than the specified value,
Coarse oxide-based inclusions appear, and the bent portion and the etched cross section are rough.

[0059]

[Table 1]

[0060]

[Table 2]

[0061]

As described above, according to the present invention,
Excellent etching workability, press workability and sealability,
In addition, it is possible to provide a lead frame material having high strength, and it is possible to stably manufacture such a lead frame material, which contributes to higher functionality and higher integration of semiconductor devices, which is extremely useful in industry. Be brought.

Claims (8)

[Claims] 1. Ni: 55.0 to 85.0% by weight
%, Mn: more than 0.1 to 1.0%, and Si: 0.
001 to 0.50%, the balance consisting of Fe and inevitable impurities, and C: 0.015% or less, P: 0.01% or less, S: 0.005% or less, O:
A high-strength lead frame material excellent in etching processability, sealing property and molding processability, which is regulated to 0.010% or less and N: 0.005% or less. 2. The lead frame material according to claim 1, wherein the average value of the crystal grain size before the final cold rolling is 30 μm or less. 3. The lead frame material according to claim 1, wherein the variation coefficient (standard deviation / average value) of the crystal grain size before the final cold rolling is 1 or less. 4. Ni: 55.0 to 85.0% by weight
%, Mn: more than 0.1 to 1.0%, and Si: 0.
001 to 0.50%, the balance consisting of Fe and inevitable impurities, and C: 0.015% or less, P: 0.01% or less, S: 0.005% or less, O:
By recrystallization annealing performed before the final cold rolling, rolling with a working degree of 90% or less and recrystallization annealing are repeated on the material melted to 0.010% or less and N: 0.005% or less. A high-strength leadframe material excellent in etching processability, sealing property and molding processability, which is characterized by adjusting the average crystal grain size to 30 μm or less and performing the final cold rolling at a workability of 5% or more. Manufacturing method. 5. The method for producing a lead frame material according to claim 4, wherein the coefficient of variation (standard deviation / average value) of the crystal grain size before the final cold rolling is adjusted to 1 or less. 6. The crystal grain size is adjusted to 30 μm or less by recrystallization annealing in a step above the recrystallization annealing performed before the final cold rolling, and if necessary, hot rolling or hot forging. Lead frame material manufacturing method. 7. The method for manufacturing a lead frame material according to claim 4, wherein after the final cold rolling, residual stress relief annealing is performed. 8. After the final cold rolling, after shape correction with a stretcher leveler or roller leveler,
The method for manufacturing a lead frame material according to claim 4, wherein residual stress relief annealing is performed.