JPS596395A - Method for preventing dimensional shrinkage of lead frame strip material - Google Patents

Abstract

PURPOSE:To prevent the generation of dimensional shrinkage in post-treatment, by preliminarily imparting a small amount of displacement by a roll leveller prior to partial plating while a strip material made of an Fe-Ni alloy is bent. CONSTITUTION:In continuously applying surface treatment such as plating, etching or stamping treatment while a thin strip material such as a lead frame made of an Fe-Ni alloy is bent, the dimension of a product after treatment is reduced as compared to the dimension prior to the treatment thereof and the product is often departed from the dimensional standard thereof. In order to prevent the dimensional reduction, if the above mentioned surface treatment is applied after displacement of 0.1-0.5mm. is preliminarily imparted to the lead frame by passing th same through a roll leveller prior to applying the above mentioned surface treatment, the dimension thereof is not reduced even if the lead frame receives bending processing in a surface treating process.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for applying surface treatments such as partial plating to iron-nickel alloy lead frame strips while bending them. This invention relates to a method for preventing dimensional shrinkage of materials.

Conventionally, thin strip materials such as lead frame materials are subjected to continuous processing such as partial plating, etching, and stamping, and are repeatedly bent using rollers while applying tension. Depending on the quality of the material, the dimensions of the product after processing may be smaller than the dimensions before processing, and the product specifications may not be met.

For example, as a lead frame strip material, 42 eyes (1142
weight%, balance we), 52 alloy (Ni52% by weight)
, the remainder Fe) was partially plated while bending, the length of 160 mm before processing was reduced by about 50 μm after processing.

The object of the present invention is to eliminate the above-mentioned phenomenon and to obtain a lead frame strip that does not undergo dimensional reduction even when subjected to continuous bending processing.

In order to achieve this object, the present invention involves passing a nickel-iron alloy lead frame strip through a roll leveler in advance before subjecting it to the desired surface treatment.
By applying a displacement of 1 to 0.5 trtm to cause dimensional reduction in the strip material, it is constructed so that dimensional reduction does not occur even when subjected to bending processing in the surface treatment process. .

The displacement given by a roll leveler is usually about 10 to 20 rolls with a small diameter arranged in two stages, upper and lower, in a staggered manner when viewed from the side, and when a strip material is passed between them, it passes through the central axis of the upper roll. If the distance between the horizontal plane and the horizontal plane passing through the center axis of the lower roll is less than or equal to the sum of the diameter of the roll and the thickness of the strip, the strip passes through the bending process, but the horizontal plane passes through the center axis of the lower roll. This is the value of how much the spacing is reduced from the total value of the roll diameter and the thickness of the strip on the inlet side of the strip, and this value is set to exactly 0 on the outlet side of the strip, and In the middle of the sides, the rolls are arranged in such a way that this value decreases successively, ie the strip leaves the roll leveler without being bent.

The reason for setting the displacement amount to 0.1 to 0.5 is that when processing strips with a thickness of 0.1 to 0.5, which are generally used as lead frame materials, if the displacement is less than 0.1, the surface treatment will be insufficient. Reduction in the rear dimension will occur, and if it exceeds 0.5 tm, the strip after passing through the roll leveler will have a tendency to warp in the direction of initial biting, which is undesirable.

The preferred amount of displacement is 0.2 to 0.4 mm.

Examples will be described below.

Example 1 A cast steel roll with an outer diameter of 10 mm and a length of 100 m with a horizontal axis of rotation was rotated alternately up and down at a pitch of 13 WrM in the horizontal direction.
Nine rolls are installed to reduce the displacement of the upper and lower rolls to 0 at the entrance side of the strip.
．． 02 to 0.42 sam was set to 0 on the exit side, and in the middle, each roll was driven at a circumferential speed of 0.2"4 so that the amount of displacement gradually decreased toward the exit side. 52 alloy with a width of 0.1 and 18 fins (
After passing through a 0-roll leveler, a lead frame strip containing 52% Ni (52% by weight, remaining RE) was continuously passed through, and the strip was wound into a coil at the exit side so that there was no slack in the strip.
The size reduction amount per 160 gates of the original length before passing through the roll leveler, and the diameter of the coil after passing through the roll leveler are
When partial plating is performed by passing through a route that repeats bending 5 times around the circumferential surface of crn, the amount of dimensional reduction per length 160 mm after passing through roll lay 2 is calculated as follows: Shown in the table.

From the results shown in Table 1 above, it can be seen that when a lead frame strip passes through a roll leveler and is displaced, it is recognized that after passing through the roll leveler, there will be a slight reduction in dimension compared to the original dimension, but the amount of displacement It has been found that if 0.1- or more is not applied, further dimensional reduction occurs in the surface treatment step performed while bending.

Example 2 Using the same apparatus as in Example 1, a 52 alloy strip of the same size was passed through. However, after passing through a roll leveler with a displacement of 0.02 to 0.42 wa for the first time, it was further passed through a roll leveler with a displacement of 0.42 rran, and then surface treatment was performed while being bent. The results are shown in Table 2.

(Margins below page 6) From the results in the table above, if the roll leveler is passed twice, even if the first displacement is small, if the second displacement is large, the displacement after the second pass through the roll labeler will be the same. The amount of dimensional reduction showed a value with no significant difference, and no dimensional reduction was observed after surface treatment.

Example 3 Using the same equipment as in Example 1, a thickness of 0.25 mm and a width of 2
A lead frame strip of 4270I (42% by weight of Ni, remainder of Fθ) of Gokaku was passed through continuously, and the same surface treatment as in Example 1 was performed. The results are shown in Table 3.

From the results shown in the upper table of Table 6, it was found that the same results as in Example 1 were obtained in this example as well.

As explained in detail above, if the lead frame material made of iron-nickel alloy is subjected to repeated bending in advance to cause a slight dimensional reduction, the surface of the lead frame made of iron-nickel alloy will be Since dimensional changes no longer occur even after processing, it is possible to obtain a product free from grains that cause problems even when the requirements for product dimensional accuracy are strict.

Patent applicant: Sumitomo Metal Mining Co., Ltd.

Claims (1)

[Claims] In a surface treatment process in which partial plating, etc. is performed while bending an iron/nickel alloy strip, the strip is passed through a roll leveler beforehand to give a coating thickness of 0.1 to 0.5 tta.
A method for preventing dimensional reduction of a lead frame strip, the method comprising performing a bending process to give a displacement of n.