The present invention relates to a method of manufacturing a lead frame which is suitable for use as a chip mounting substrate, a circuit substrate, and the like.
FIGS. 9(a) to 9(e) show a conventional method of manufacturing a lead frame. In the method, a preform is made of a metallic foil provided with an adhesive stripe and a heat treatment is carried out at a temperature (300 to 350 degrees C.) lower than that at which the adhesive stripe is melted to thus prevent the adhesive from being melted, followed by peeling-off the preform.
FIGS. 9(a) and 9(b) illustrate a process of making the preform. In this process, as illustrated in FIG. 9(a), a metallic foil 11, which is a material of a lead frame, is fed between a pair of rolls 12 in a first direction indicated by an arrow xe2x80x9c1xe2x80x9d. The rolls 12 are rotated in the same direction while the metallic foil 11 is fed.
As a result, the metallic foil 11 is rolled to form the preform in which the metallic foil 11 is flattened. The flattened preform 14 is then fed to a heat treatment furnace, as shown in FIG. 9(b).
FIG. 9(c) illustrates a state of the preform which is heated in the furnace. The heat treatment of the preform is carried out at a temperature (300 to 350 degrees C.) lower than that at which the adhesive is melted. Thus, the adhesive is prevented from being melted.
FIG. 9(d) illustrates a state of the preform after the heat treatment. The adhesive is peeled off the preform 14 by a pair of peeling rolls 13 which are rotated in a direction indicated by an arrow xe2x80x9c2xe2x80x9d.
FIG. 9(e) illustrates a state of the peeled-off preform. The preform 14 is then cut into desired lengths, thus obtaining a lead frame.
However, the conventional method has the following drawbacks.
Since the heat treatment is carried out at a temperature (300 to 350 degrees C.) lower than that at which the adhesive is melted, a metallic foil is sintered to a high density in the heat treatment. Accordingly, the lead frame is easily affected by the change in ambient conditions such as temperature.
For example, the conventional method has the following problems.
First be359ba680
Related links: