Papers in JOURNAL OF THE JAPAN SOCIETY
FOR TECHNOLOGY OF PLASTICITY

(Vol.41 No.471 April 2000)


Effect of Surface Hardening and Grain Size on Punchability of Fe-Ni
Lead Frame Alloy


Hiroshi YAMADA, Kento SUGIURA,
Takashi ISHIKAWA and Takashi JIMMA

(Received on April 21, 1999)

The authors reported that it was effective to add sulfur to typical IC lead frame material, Fe-42%Ni alloy, in order to reduce burrs and shear drop. In the case of industrial production, it appears that the sulfur addition is limited to approximately 0.01% considering hot workability and solderability. Furthermore in order to reduce burrs and shear drop, the effect of surface hardening on burrs and shear drop was investigated. It was confirmed that the volume of burrs and the width of shear drop in the blanking of an IC lead frame were reduced by the formation of a hardened surface layer of a few ƒÊm thickness. The effect of grain size on the volume of burrs and the width of shear drop was also investigated; it was found that the strength and elongation of the Fe-42%Ni alloy were increased by refining the grain size. On the other hand, the burrs and shear drop increased. Then it was confirmed that both refining the grain size and surface hardening were effective for increasing the strength of the Fe-42%Ni alloy and for reducing burrs and shear drop.
Key words : shearing, ferrous metal (Fe-Ni alloy), burrs, shear drop, surface hardening, grain size

Influence of Inclusion on Punchability of Fe-Ni Lead Frame Alloy


Hiroshi YAMADA, Takuo OH-ISHI
Takashi ISHIKAWA and Takashi JIMMA

(Received on April 21, 1999)

As a result of the miniaturization of IC packages, the interval and width of leads have decreased, and it has necessary to reduce burrs which cause short circuits and shear drop which causes resin leakage. Further, because IC packages have been getting thinner, thinner lead frame strips are required; thus, it is necessary to increase the strength of the lead frame strip itself. The effect of adding sulfur to a typical lead frame alloy, Fe-42%Ni, on burrs and shear drop was investigated. On adding sulfur to The Fe-42%Ni alloy fine MnS inclusions formed in the matrix. Burrs and shear drop decrease as the rate of MnS inclusion in an area increases. frame alloy A similar result was obtained in the case of adding sulfur to an inexpensive Fe-34%Ni alloy lead . Then, for the purpose of solution hardening, niobium was added to the Fe-34%Ni used as the high-strength lead frame alloy. Then NbC inclusions formed in the matrix and the reduction of burrs and shear drop was observed, but the reduction by adding sulfur is greater than that by adding niobium.
Key words : shearing, ferrous metal (Fe-Ni alloy), IC lead frame, burrs, shear drop, inclusion, MnS, NbC

Investigation of Measurement of Burr and Shear Drop
in Blanking IC Lead Frame


Hiroshi YAMADA, Takuo OH-ISHl
Takashi ISHIKAWA and Takashi JIMMA

(Received on April 21, 1999)

IC lead frames are mainly produced by blanking or photoetching. Because burrs in blanking IC lead frames cause short circuits and cracks in resin, it is necessary to reduced burrs. In order to investigate burrs, they must be measured quantitatively. Thus far a micrometer and a focal depth meter have been used in measuring burrs. It is difficult to measure burrs with accuracy using a micrometer or a focal depth meter, because the height of burrs on the lead frame is less than 10ƒÊm. Similarly it is necessary to reduce shear drop because shear drop in blanking IC lead frames causes resin leakage. Therefore the use of a laser microscope to measure the burrs and shear drop was investigated. It is considered that measuring the volume of burrs of constant area is more accurate than measuring the width and height of burrs. On the other hand it appears to be sufficient to measure the width and height of shear drop, because the scatter of the width and height of shear drop is smaller than the scatter of the width and height of burrs.
Key words : shearing, ferrous metal (Fe-Ni alloy), IC lead frame, burrs, shear drop, laser microscope


Stress-Strain Characteristics and Accuracy of Measurement
of m-Value in Superplastic TensionTest Using R-Type Specimen


Hajime TAKAHASHI, Susumu MIZUNUMA, Toshitaro MIMAKI
Yoshimasa TAKAYAMA and Norio FURUSHIRO

(Received on May 7, 1999)

A new tensile testing method using an R-type specimen has been proposed for evaluating effectively the superplastic properties of sheet metals. However, as the stress state in this specimen is assumed to be more or less biaxial, the degree of the influence of the bixiality on the superplastic properties must be understood quantitatively. In the experiment, two types of aluminum alloys are used and the strain distribution in the specimen is measured to clarify the extent of the influence of the biaxiality on the accuracy of the measurement of the m-value, which is one of the most important superplastic properties. The result obtained is as follows. The deformation concentrates in the central region of the specimen, where the stress state derived from the measured strain is nearly uniaxial rather than plane strain. The extent of the error of the m-value measured using an R-type specimen is estimated to be 4-8% at most. If more than one specimen is used, the error will decrease markedly.
Key words : material testing, tension test, superplasticity, R-type specimen, stress-strain relationship, zinc-aluminum alloy, 7475 aluminum alloy, strain rate sensitivity exponent


Basic Property of Martensitic Microalloyed Steel
- Development of Microalloyed Steel for Forgmg Usmg Ausforming I -

Hiroaki YOSHIDA, Sachihiro ISOGAWA and Takashi ISHIKAWA

(Received on May 27, 1999)

Currently, the demand for reductions in the weight of cars is increasing. However, most steels, which are mainly microalloyed steels, used for car parts do not have sufficient mechanical properties. It is effective to apply thermomechanical treatments such as controlled rolling and ausforming to microalloyed steels. However, in the case of applying ausforming to forging, some properties such as forgeability and the ability of the steel to harden under quenching are degraded. In this research, ausforming is applied to martensitic microalloyed steel which has been developed. By ausforming, martensite lath and block become finer, and the density of dislocations increases without the formation of cell structures. As a result, mechanical properties of this developed steel such as strength, proof stress, fatigue strength and toughness were improved.
Key words : forging, material property, ausforming, microalloyed steel


Effect of Consolidation Process on the Density
of Al-20Si P/M Alloy Containing SiC Particles

Nobukazu HAYASHI

(Received on June 10, 1999)

To fabricate good P/M alloy from aluminum powder, it was thought that high pressure and large straining were needed. Extrusion appears to be the process which satisfies these conditions. However, there are reports that a P/M alloy fabricated by extrusion performs more poorly than that fabricated by powder forging. This study aims to explain the contradiction. Al-20Si powder mixed with SiC particles was tested, and an estimation of the processing was performed on the basis of the density change. During the forging process, the powder was hot-pressed and then upset. The alloy remained above a 99.9% relative density if the upsetting temperature was higher than 673K and the SiC content was smaller than 5mass%. In powder extrusion at 773 K, the alloy had, at most, a relative density of 99.7% in SiC=0% and was inferior to that fabricated by forging. The mechanism was studied by FEM analysis. During upsetting, the maximum tensile stress of ƒÐ=0.28 appeared at the outside surface. In extrusion, the maximum of ƒÐ=1.0 was the longitudinal stress at the die bearing. The very high tension in extrusion was considered to be the reason for the density reduction.
Key words : powder forming, powder forging, density, upsetting, aluminum powder, SiC, powder extrusion

Lubricating Oil less Deep Drawing Assisted by Water Pressure

Kazuhiko NAKAMURA

(Received on July 30, 1999)

The utilization of water pressure as an environmental-friendly lubrication technology is investigated. Specifi- cally, instead of lubricating oil, water is utilized as the pressure medium for hydraulic counterpressure deep drawing (HCP) method and radial-pressure-assisted hydraulic counterpressure deep drawing (RHCP) method. In the cylindrical deep drawing of A5182 and SUS304 sheets, the two methods can yield a higher limiting drawing ratio than the conventional method of applying high-viscosity lubricating oil. In particular, by utilizing a water pressure of 10 to 15 MPa, the RHCP method achieves as high a limiting drawing ratio for the above two types of material as the conventional method of applying high-viscosity lubricating oil. When a press with a small outer slide capacity is used, the HCP method yields a higher limiting drawing ratio than the RHCP method, because the former can produce a higher water pressure than the latter. When a press capable of applying water pressure suitable for a drawn material is used, however, the RHCP method yields a higher limiting drawing ratio than the HCP method. The reason is that the former has the effect of pushing flange ends and of decreasing the friction between the blank and the blank holder.
Key words : sheet metal forming, deep drawing, hydraulic counterpressure, lubricant, water pressure, environment, forming limit


Processing of Transition Region from a Fine
to a Coarse Mesh in Finite-Element Analysis

Mitsuru ICHISHIMA, Yasuto YOKOUCHI and Takashi IZUMI

(Received on August 19, 1999)

In a typical finite-element analysis, a model having a locally fine and coarse mesh is often used. In this study, we examine how the quality of a finite-element solution depends on the method of connection from a fine mesh region to another region that is twice as coarse, in the case of plane strain with the use of the four-node quadrilateral element. The following three classes of the method are discussed: I ) a primitive method which fills the transition region with the same type of element as in other regions, but with irregular element shapes; 2) a direct-joint method which introduces a constraint equation among the related variables in order to prevent incompatibility of interelement displacement; and 3) a method which places special transition elements in the transition region. In numerical examples, each solution is compared with the reference one which is obtained as the most exact solution using a uniformly fine mesh over the entire region. Consequently, method I ) and a transition element having five nodes with a piecewise linear shape function in method 3) give good results.
Key words : numerical analysis, elastoplastic FEM, mesh refinement, five-node element, transition element, incompressibility, plane strain analysis