JP2002118223A - Copper-based lead material for semiconductor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper-based lead material for a semiconductor that does not easily warp even if etching machining is made, and to provide a method for manufacturing the lead material. SOLUTION: In this copper-based lead material for the semiconductor device composed by a copper-based sheet bar that is subjected to rolling or correction machining after the rolling, curvature (k) in warpage is set to 0.003 or less when the etching machining with arbitrary thickness is carried out in the range of a plate thickness of 0 to 2/3 from the surface of the copper-based sheet bar. The k is obtained by substituting height y (mm) and the shortest distance x (mm) between ends for the following expression k=1/ρ,ρ=(y/2)+(x2/8y) when a sample is arranged while a projection side faces upward as shown in figure 1. In this case, the sample is cut from the copper- based sheet bar, and has a length in parallel with a rolling direction of 100 to 200 mm and a width at right angle to the rolling direction of 20 mm. The lead material can be easily manufactured by applying an elongation percentage of 0.01% or more and less than 0.30% to the copper-based sheet bar for performing the correction machining A, and by applying a tension of 5 N/mm2 or more and less than 50 N/mm2 for performing the correction machining B in a heating oven.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper-based lead material for a semiconductor, which is unlikely to be warped even by etching, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Copper alloy or 4
A strip of 2 alloy (Fe-Ni alloy) is used. These strip materials are press-punched into a lead frame-shaped body including a die pad portion for mounting the semiconductor chip and a lead portion, and the surface of the die pad portion is half-etched in a dimple shape to enhance the bonding between the semiconductor chip and the bonding wire. Is done.

[0003] Incidentally, the copper-based strip material is obtained by hot rolling a copper alloy ingot and then repeatedly performing cold rolling and annealing.
Finally, it was manufactured by subjecting it to finish temper rolling, but with the recent miniaturization and high integration of electronic devices, semiconductor lead materials have been required to be thin, high-strength and high flatness. Therefore, the strip material after the finish temper rolling has been straightened by a multi-roll leveler or the like.

[0004]

However, in order to sufficiently correct a copper-based strip using a multi-roll leveler,
It is necessary to set the intermesh amount on the entry side to be 3.0 mm or more and the unit tension to be 50 N / mm ² or more. For this reason, a large internal residual stress (hereinafter abbreviated as residual stress) occurs in the copper strip. Then, when this copper-based plate material is used, for example, the die pad portion of the lead frame-shaped body is warped when the above-described dimple-shaped half etching is performed,
There is a problem that the bondability of a semiconductor chip or a bonding wire is significantly reduced. SUMMARY OF THE INVENTION An object of the present invention is to provide a copper-based lead material for a semiconductor that is unlikely to be warped even by etching, and a method for manufacturing the same.

[0005]

According to the first aspect of the present invention,
In a lead material made of a copper-based strip material that has been rolled or straightened after rolling, from the surface of the copper-based strip material, a thickness of 0 to
A copper-based lead material for semiconductors, wherein a curvature k of a warp when etched to an arbitrary thickness in a range of 2/3 is 0.003 or less. Here, k is a length (parallel to the rolling direction) of 100 to 200 m cut from the copper-based strip material.
A sample having a width of 20 mm and a width of 20 mm (perpendicular to the rolling direction) was prepared as shown in FIG.
As shown in the figure, the height y (m
It is a numerical value obtained by substituting m) and the shortest distance x (mm) between the ends into the following equation. k = 1 / ρ, ρ = (y / 2) + (x ² / 8y) Here, the sample has a length of 100 to 200 for convenience of measurement.
mm and a width of 20 mm, and any value is acceptable.

According to a second aspect of the present invention, the copper material after rolling is subjected to straightening A by giving an elongation of 0.01% or more and less than 0.30%, and then 1 N / mm ² in a heating furnace. above, a method of manufacturing a semiconductor for copper-based lead material of claim 1, wherein that the copper-based plate strip member subjected to straightening B by applying a tension of less than 50 N / mm ^2.

[0007]

According to the first aspect of the present invention, the curvature k of the warp when the copper-based strip material is etched from the surface of the copper-based strip material to an arbitrary thickness within a range of 0 to 2/3 of the plate thickness. 0.
The reason for defining 003 or less is that if the curvature k exceeds 0.003, for example, a semiconductor chip or a bonding wire cannot be satisfactorily bonded to the die pad portion.

[0008] The invention according to claim 2 is to provide a straightening process A by applying a predetermined tension to the copper-based strip material after rolling, and then to perform a straightening process B by applying a predetermined tension in a heating furnace. This is a method of further correcting the copper-based strip while removing the residual stress generated in the correcting process A. Since the straightening B is performed in a heating furnace, residual stress hardly occurs.

The straightening process A is performed by a multi-roll leveler 1 as shown in FIG. The multi-roll leveler 1 is composed of five work rolls 2 having a diameter of 10 to 20 mm.
Up to 25 pieces are arranged, and the upper and lower surfaces of the copper-based plate material 3 are successively brought into contact with the surface of the work roll 2 in a state where tension is applied, and the copper-based plate material 3 is straightened. The tension is controlled by bridle rolls 4 arranged before and after the multi-roll leveler 1.

In the present invention, the reason why the elongation percentage in the straightening A is specified to be 0.01% or more and less than 0.30% is that if the elongation percentage is less than 0.01%, the effect cannot be sufficiently obtained. If the elongation is 0.30% or more, the residual stress becomes large, and it becomes difficult to remove the residual stress in the next straightening process B.

In the straightening process B, the copper-based strip material 3 is applied with a tension by a single straightening roll 6 (FIG. 3A) placed in a horizontal heating furnace 5 under tension. Straightening is performed by two straightening rolls 6 (FIG. 3B) arranged in the furnace 9. Here, three straightening rolls 6 may be arranged (FIG. 3C) or three or more straightening rolls. The larger the number of straightening rolls 6, the better the straightening. The tension is controlled by an uncoiler 7 and a coiler 8. FIG.
In (b), 10 is a guide roll. Fig. 3 (a),
The diameter of the straightening roll 6 shown in (b) is desirably 100 mm or more.

[0012] The straightening B in the tension applied to the copper-based plate strip member 1N / mm ² or more, the reason for defining less than 50 N / mm ^2, the effect is insufficient at less than 1N / mm ^2, If it is 50 N / mm ² or more, wrinkles occur in the material, and the flatness decreases. The reason for applying the tension in the heating furnace is that when the tension is applied at a high temperature, the residual stress is easily removed and the residual stress is hardly generated. The heating furnace temperature in the straightening process B is appropriately selected depending on the type, shape, dimensions, and the like of the copper-based plate material.

In the present invention, the straightening process A and the straightening process B
The productivity can be improved by performing the process continuously or by inserting a slitter process between the straightening process A and the straightening process B.

[0014]

The present invention will be described below in detail with reference to examples. (Example 1) 0.25 wt% of Sn and 0.30 w of Cr
t%, and the remainder is ingot-melted by casting a copper alloy consisting of unavoidable impurities and Cu by a conventional method.
Hot rolling, then cold rolling and annealing are repeated, and cold rolling after final annealing (final finish temper rolling) is performed at a rolling ratio of 40.
% To obtain a copper material having a thickness of 0.2 mm, and this copper material is subjected to a straightening process A by the method shown in FIG.
The straightening process B was continuously performed by the method shown in (a) to produce a copper-based strip. 150mm in diameter in straightening B
Was used. The tensions in the straightening processes A and B were variously changed within the specified values of the present invention. In the straightening process B, the heating furnace temperature was set to 500 ° C., and the passage time of the copper-based sheet material in the furnace was set to 5 seconds.

(Example 2) A copper-based strip was manufactured in the same manner as in Example 1 except that the straightening B was performed by the method shown in FIG. 150mm in diameter in straightening B
2 straightening rolls were used.

(Comparative Example 1) A copper-based strip was manufactured in the same manner as in Example 1, except that the tension was applied in the straightening process A or B in excess of the value specified in the present invention.

(Comparative Example 2) Straightening A or / and B
To apply tension in excess of the specified value of the present invention, and straightening B
A copper-based strip was manufactured in the same manner as in Example 1 except that the straightening roll was not used.

Examples 1, 2, Comparative Example 1, and Comparative Example 2
(1) Steepness,
(2) The curl (straightness), (3) the curvature k of the warpage before and after the etching (surface removal), and (4) the amount of warpage of the die pad portion after the etching into a dimple shape were examined. (1) As shown in FIG. 4, the steepness is a percentage ((h / h / h) of the undulation height h of the copper-based strip 3 divided by the pitch p.
p) × 100%). When the steepness was 0.3% or less, it was judged as pass, and when it exceeded 0.3%, it was judged as reject. (2) As shown in FIG. 5, the curl is such that a copper-based strip 3 having a length of 1 m (parallel to the rolling direction) is hung on a wall, and the lower end of the copper-based strip 3 curled away from the wall. It was represented by the distance a from the wall. When the distance a was 50 mm or less, it was judged as acceptable, and when it exceeded 50 mm, it was judged as unacceptable.

(3) The curvature k is determined by the length (pressure
200 mm in width (parallel to the rolling direction), 20 in width (perpendicular to the rolling direction)
mm sample, cut out, and cut
Etching the copper strip to 50% of its thickness
(Removed) and measured. The curvature k is, as shown in FIG.
The height y (mm) when the convex side is arranged up
The short distance x (mm) is measured, and this is k = 1 / ρ, ρ =
(Y / 2) + (x ^Two / 8y). k
Is acceptable if the value is 0.003 or less, and exceeds 0.003
Determined to be rejected. (4) The amount of warpage of the die pad portion is, as shown in FIG.
Length (parallel to rolling direction) 20mm, width (pressure
Cut a 20 mm sample (perpendicular to the direction of extension)
The height h of the warp when etched into a simple shape
It was measured and judged. The dimple depth is 0.1mm,
The sample area is 10% of the sample area (40 mm^Two )When
did. The warp height passes 10μm or less and exceeds 10μm
It was judged as failed. Table 1 shows the results. Also etching
FIG. 7 illustrates the relationship between the processed (removed) thickness and the curvature k. table
1 has a thickness of 50 μm removed by etching (initial thickness
25%) and 100 μm (50% of the initial thickness)
Is described.

[0020]

[Table 1]

As is clear from Table 1, N of the present invention example
o. In all of the samples Nos. 1 to 9, the curvature k was within the specified value of the present invention, and the warpage of the die pad portion was 10 μm of the acceptable line.
m, and the characteristics required for the lead material, such as steepness and curl, were also satisfied. On the other hand, in Comparative Example No. In all of Nos. 10 to 18, since the tension of the straightening process A and / or B is outside the specified value of the present invention, the curvature k exceeds 0.003 specified in the present invention, and therefore the die pad warpage exceeds 10 μm and is rejected. It became. In addition, No. Nos. 12, 13, and 15 are inferior in steepness and curl. 10, 11, and 14 were inferior in curl. In the case where the tension of 50 N / mm ² or more was applied in the straightening process B (No. 12, 13, 15), wrinkles occurred on the surface (not shown). Thus, all of the comparative examples were determined to be totally defective. As shown in FIG. 7, the curvature k of the present invention example (Nos. 2, 4, 7, and 9) exceeds 0.003 even when the plate thickness of 0 to 100 μm is arbitrarily removed by etching. Never. On the contrary,
In Comparative Examples (Nos. 10, 13, 15, and 18), the curvature k exceeds 0.003 when the etching removal amount is within 100 μm. In the above embodiment, the lead frame has been described. However, the present invention is not limited to the lead frame, and the effect is exhibited when applied to any semiconductor lead.

[0022]

As described above, the copper-based lead material for a semiconductor according to the present invention has a curvature k of a warp when etched to an arbitrary thickness in the range of 0 to 2/3 of the plate thickness from the surface. Is 0.003 or less, for example, in the case of a lead frame material, even if dimple-shaped half-etching is performed on the die pad portion, the die pad portion does not warp, and the semiconductor chip and the bonding wires are satisfactorily joined. The copper-based strip having a curvature k of 0.003 or less is subjected to straightening A to give an elongation of 0.01% or more and less than 0.30% to the copper-based strip after rolling, and then heated. 1N / mm in furnace
^It can be easily manufactured by performing a straightening process B for giving a tension of ² or more and less than 50 N / mm ² . Therefore, an industrially remarkable effect is achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of how to determine a curvature k of a copper-based strip material of the present invention.

FIG. 2 is an explanatory view of straightening A in the manufacturing method of the present invention.

FIGS. 3A to 3C are explanatory views of straightening B in the manufacturing method of the present invention.

FIG. 4 is an explanatory diagram of a method for measuring steepness in the present invention.

FIG. 5 is an explanatory diagram of a curl measuring method according to the present invention.

FIG. 6 is an explanatory diagram of a method for measuring a warpage amount of a die pad portion in the present invention.

FIG. 7 is a diagram showing a relationship between an etching removal thickness and a curvature k.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multi-roll leveler 2 Work roll 3 Copper-based strip material 4 Bridle roll group 5 Horizontal heating furnace 6 Straightening roll 7 Uncoiler 8 Coiler 9 Vertical heating furnace 10 Guide roll

Claims (2)

[Claims] 1. A lead material made of a rolled or straightened copper-based strip material, and having an arbitrary thickness in the range of 0 to 2/3 of the plate thickness from the surface of the copper-based strip material. A copper-based lead material for a semiconductor, wherein a curvature k of a warp when processed is 0.003 or less. Here, k is a length (parallel to the rolling direction) cut out from the copper-based strip material (1).
The height y (mm) and the shortest distance x (mm) between the ends when a sample having a size of 00 to 200 mm and a width (perpendicular to the rolling direction) of 20 mm is arranged with the convex side up as shown in FIG. It is a numerical value obtained by substituting into the expression. k = 1 / ρ, ρ = (y / 2) + (x ² / 8y) To 2. A copper material after rolling, elongation of 0.01% or more, and impart less than 0.30% of straightening A subjected to, then in a furnace 1N / mm ² or more, 50 N / mm ² 2. The method for producing a copper-based lead material for a semiconductor according to claim 1, wherein the copper-based plate material is subjected to a straightening process B by applying a tension less than or equal to the tension.