JPH10130741A - Strain removal annealing method of copper alloy sheet material and bright annealing furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove the warp developed in the width direction and to increase the line speed by controlling the temp. and the time at the time of continuously executing a strain removal annealing of a wide lead frame material by using a forcedly connection heating type bright annealing furnace. SOLUTION: After heating the lead frame sheet material composed of 2% Sn-0.2% Ni-0.15% Zn-0.04% P-Cu and having 0.05-0.4mm thickness and 400-700mm width at 500-700 deg.C for 5-18sec in an ammonia heating decomposed gas atmosphere in a heating zone 10, slow cooling is executed in the temp. range of 300-500 deg.C for 7-26sec in a slow cooling zone 20. Further, while passing the slow cooling zone 30, this material is cooled at 20-50 deg.C for 5-18sec. The slow cooling zone 20 in this bright annealing furnace 1 is extended to about 8.5m length from 1.9m in the conventional furnace and this furnace is made to the forcedly convention type using a pusher pad. Further, in the inlet and the outlet of the slow cooling zone 20, a rail 200 in the furnace is arranged, and the sheet material is flattened before the strain-removal in the slow cooling zone 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is required to suppress warpage (distortion) in the width direction as much as possible, such as a copper alloy strip continuously manufactured by rolling, particularly a copper alloy strip for a lead frame. The present invention relates to a strain relief annealing method for a copper alloy strip and a bright annealing furnace which can be suitably used for the strain relief.

[0002]

2. Description of the Related Art A copper alloy strip continuously manufactured by rolling generates warpage (distortion) in the width direction, and after rolling, annealing is performed to remove the distortion. For example,
Copper alloy (for example, 2% Sn-0.2% Ni-0.15% Zn-0.0) used as a lead frame material
The 4% P-remaining Cu) strip has a width of 40 after rolling.
This is a so-called wide thin plate having a wide width of 0 to 700 mm and an extremely thin thickness of 0.05 to 0.4 mm. Further, since this thin plate is used as a material for a lead frame, it is extremely important that it is flat.

Conventionally, such a rolled thin sheet has been subjected to annealing in a bright annealing furnace connected to a rolling mill. As shown in FIG. 6, the bright annealing furnace is a so-called vertical radiant heating furnace in which heating and slow cooling processes are performed by a radiant heating / cooling source. Annealing is performed while the furnace is continuously supplied vertically upward from below.

[0004] To explain further, this radiant heating furnace 1A
Is a heating zone 10 for heating the continuously supplied strip 2, a slow cooling zone 20 for gradually cooling the heated strip 2, and a cooling zone for cooling the strip 2 from above to below. In the furnace, hydrogen (H ₂ ) 75% (Vol) and nitrogen (N ₂ ) 25% (Vo)
1) is supplied. Further, for example, a radiant heating furnace 1A for annealing the copper alloy strip 2 for lead frames having a thickness of 0.2 mm and a width of 630 mm.
The length of the heating zone 10 (L ₁ ) is 8.2 m,
The length (L ₂ ) is 1.9 m, the length (L ₃ ) of the cooling zone 30 is 5.4 m, and the feed rate (line speed) of the strip 2 is 15.5 m / min. ). At this time, a muffle furnace provided with a burner 11 for radiating radiant heat is arranged in a heating zone 10 of the radiant heating furnace 1A, the atmosphere temperature is maintained at 750 ° C., and a gradual cooling zone 20 is provided.
, An air cooling tube 12 is arranged and the ambient temperature is maintained at 200 to 300 ° C. The heating zone 10 and the slow cooling zone 20 are of a radiant heating type, while the cooling zone 30 is of a forced convection type, in which a cooling fluid flows and the ambient temperature is 20 °.
５０50 ° C.

The conventional radiant heating furnace 1 has a structure in which one set of four in-furnace rolls 13 are provided in a cooling zone 30 as shown in FIG.

[0006]

In such a conventional radiant heating furnace, the width warpage (distortion) of the copper alloy strip 2 can be extremely effectively removed to a predetermined value or less. For example, it is desired to further reduce the warpage of a lead frame strip or the like.

The present inventors have conducted a number of research experiments on a conventional radiant heating furnace, and have found that, in particular, a slow cooling zone 2 in the furnace.
0 has a great effect on the warpage of the strip,
Further, (1) the length of the slow cooling zone 20 is longer than the conventional length of 1.9 m, for example, about 8.5 m, and the slow cooling process is performed longer. The method is changed from a radiation method to a forced convection method using a pressure pad, which will be described in detail later, and the material shape before distortion can be removed in the annealing zone 20 is flattened as much as possible.
(3) Using a roll in the furnace at the entrance and exit of the annealing zone 20,
It is important that the material shape before the distortion is removed in the annealing zone 20 is fixed on the roll surface and flattened, and the line speed of the strip material is increased by using an annealing furnace having a configuration satisfying the above conditions. It has been found that the warpage of the strip material, that is, the distortion, can be greatly improved while increasing the width. The present invention is based on such novel findings of the present inventors.

[0008] Accordingly, an object of the present invention is to provide a warp of a strip,
That is, it is an object of the present invention to provide a method for annealing a copper alloy strip capable of greatly improving distortion and a bright annealing furnace.

It is another object of the present invention to provide a method of annealing a copper alloy strip and a bright annealing furnace which can greatly increase the line speed of the strip.

[0010]

The above objects can be attained by the method for annealing a copper alloy strip according to the present invention and a bright annealing furnace. In summary, the present invention relates to a method for performing annealing for removing strain of a continuously supplied copper alloy strip using a bright annealing furnace, comprising: (a) a continuously supplied copper alloy; Heating the strip at 500 to 700 ° C. for 5 to 18 seconds; (b) subjecting the heat-treated copper alloy to 350 to 50 seconds;
Copper, comprising: a step of gradually cooling at 0 ° C. for 7 to 26 seconds; and (c) a step of cooling the slowly cooled copper alloy strip at 20 to 50 ° C. for 5 to 18 seconds. This is a method for annealing a strip of alloy material. In each of the above-mentioned processing steps, hydrogen (H ₂ ) 75% and nitrogen (N ₂ ) 2
It is performed in a mixed gas atmosphere of 5% and by forced convection.

The method according to the present invention has a width of 400-700.
mm and a thickness of 0.05 to 0.4 mm. or,
The lead frame material is 2% Sn-0.2% Ni-
It is a copper alloy strip composed of 0.15% Zn-0.04% P-remainder Cu.

According to another aspect of the present invention, there is provided a bright convection heating type bright annealing furnace having a substantially closed structure,
(A) from the lower side to the upper side, a heating zone for heating the continuously supplied strip, a slow cooling zone for gradually cooling the heated strip, and a cooling zone for cooling the strip are provided; b) In the furnace,
(C) In the heating zone, a plurality of injection nozzles are provided on both sides of the strip to be transferred along the strip transfer path, and a furnace is provided at the outlet of the heating zone. At least one set of inner rolls is arranged, and a heating gas is injected from the injection nozzle to both surfaces of the strip at a predetermined injection pressure so that the strip is heated at 500 to 700 ° C. for 5 seconds.
After heating for 18 seconds, the heated strip is transferred to the slow cooling zone through the in-furnace roll disposed at the outlet of the heating zone, and (d) the slow cooling zone includes A furnace roll is disposed at an inlet and an outlet of a slow cooling zone, and a heated strip material from the heating zone is introduced into the slow cooling zone through the furnace roll arranged at the inlet. At least 3 in a staggered arrangement on both sides of the transported strip along the transport path
A set of pressure pads is provided, and a heating gas is injected from the pressure pad to both surfaces of the strip at a predetermined injection pressure, thereby causing the strip to be heated at a temperature of 350 to 500 ° C. for 7 to
After slowly cooling for 26 seconds, the slowly cooled strip material is transferred to the cooling zone through the in-furnace rolls arranged at the outlet of the slow cooling zone, and (e) the cooling zone includes strips. By arranging a plurality of injection nozzles on both sides of the strip to be transferred along the transfer path of the strip, and injecting a cooling gas from the injection nozzle to both surfaces of the strip at a predetermined injection pressure. The strip material transferred from the slow cooling zone is heated at
A bright annealing furnace is provided, wherein the furnace is cooled for 18 seconds. Ammonia pyrolysis gas is supplied into the furnace by gas supply means.

[0013] Preferably, the strip has a width of 400-7.
This is a lead frame material having a thickness of 00 mm and a thickness of 0.05 to 0.4 mm, for example, 2% Sn-0.2%.
It is a copper alloy strip composed of Ni-0.15% Zn-0.04% P-remainder Cu.

Preferably, the injection pressure of the pressure pad is 10 to 20 mm (H ₂ O).

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The bright annealing furnace according to the present invention will be described below in more detail with reference to the drawings.

1 to 5 show one embodiment of a bright annealing furnace according to the present invention. In this embodiment, the bright annealing furnace is the same as the conventional FIG.
Unlike the radiant heating furnace described in connection with the above, a so-called forced convection heating furnace in which heating and slow cooling are performed in a forced convection method. In this embodiment, the strip supplied to the bright annealing furnace is a strip for lead frame, that is, 2% Sn.
A copper alloy strip having a thickness of 0.2 mm and a width of 630 mm made of -0.2% Ni-0.15% Zn-0.04% P-remaining Cu was used. However, it should be understood that the strip treated in the present invention is not limited to this.

More specifically, referring to FIG. 2, in the present embodiment, the bright annealing furnace 1 has a substantially closed structure,
As before, the heating zone 10 for heating the continuously supplied strip 2, the slow cooling zone 20 for gradually cooling the heated strip 2, and the cooling of the strip 2 from above to below. In the furnace, 75% of hydrogen (H ₂ ), which is an ammonia pyrolysis gas, is supplied from a gas supply source (not shown).
A mixed gas G composed of (Vol) and nitrogen (N ₂ ) 25% (Vol) is supplied, and is returned to a gas supply source by a circulation means (not shown). The strip material 2 is heat-treated in the heating zone 10 for 5 to 18 seconds under the temperature conditions described later in detail, gradually cooled in the slow cooling zone 20 for 7 to 26 seconds, and cooled in the cooling zone 30 for 5 to 18 seconds. It is important to be cooled, and in the present embodiment, the strip 2 passes through the heating zone 10, the slow cooling zone 20 and the cooling zone 30 from above to below, and at a supply speed (line speed) of 40 m / min. Was transferred continuously.

In the heating zone 10, a plurality of spray nozzles 3 are arranged on both sides of the strip to be transferred along the transfer path of the strip 2. The heating system of the heating zone 10 is a forced convection system unlike the conventional one. That is, for example, a heating chamber 4 having a radiant tube 100 as a radiant heat source is provided adjacent to the heating zone 10, and an atmosphere gas (ie, ammonia pyrolysis gas) G in the heating zone 10 is heated in the heating chamber 4. Then, the heated gas is supplied to the injection nozzle 3. Injection nozzle 3
Is injected to both surfaces of the strip 2.
Then, the heating gas in the heating zone 10 is returned to the heating chamber 4 by using the fan means 5. Injection pressure of the heating gas from the injection nozzle 3 is a 0.5~10.0mm (H ₂ O), in the present embodiment is a 4.0mm (H ₂ O).
The temperature of the heating gas from the injection nozzle 3, that is, the temperature in the heating zone 10 is maintained at 400 to 750 ° C. If the temperature in the heating zone 10 is out of this range, there arises a problem that mechanical properties such as tensile strength and elongation cannot be satisfied with respect to the target. In this embodiment, the temperature of the heating gas was 550 ° C. The heating by the forced convection type of the present invention has an advantage that heat transfer to the strip is improved as compared with a radiant heating method in which the strip is directly heated by a radiant tube as a radiant heat source. Therefore, it is possible to increase the line speed of the strip material as compared with the related art.

The length (L ₁ ) of the heating zone 10 is 6.6 m in this embodiment. Further, a set of in-furnace rolls 200 is arranged at the outlet of the heating zone 10. As shown in FIG. 2, the in-furnace roll 200 is provided at a position shifted by a distance (A ₁ ) in the transport direction of the strip 2, and this distance (A
₁ ) was set to 330 mm in this embodiment. Further, each of the in-furnace rolls 200 can be moved so as to be separated from and in contact with the strip 2, and in this embodiment, the distance (A ₂ ) in FIG.
5 mm.

Next, the slow cooling zone 20 will be described. According to the present invention, one feature is that the length (L ₂ ) of the annealing zone 20 is configured to be longer than that of the conventional furnace. In the present embodiment, the conventional furnace has a length of 1.9 m. On the other hand, about 4 times L ₂ =
It was 8.5 m.

Another feature of the present invention is that the annealing zone 2
The point is that the pressure pad 21 is adopted in the first embodiment. The pressure pad 21 is commercially available from Chugai Furnace Industry Co., Ltd., and is well known to those skilled in the art, and a detailed description thereof will be omitted.

Referring briefly to FIGS. 3 to 5, the pressure pad 21 is provided on both sides of the support portion 22.
Connecting rod 23 driven by screw jack 24
Is connected. The screw jack 24 is connected to the slow cooling zone 20.
Of the pressure pad 21 by driving the screw jack 24.
Is movable relative to the strip 2 as shown by the imaginary line in FIG. Further, in this embodiment, a guide member 26 provided on the furnace wall 25 and a slide means 27 sliding along the guide member 26 are provided to smoothly guide the movement of the pressure pad 21.

The pressure pad 21 is connected to a heating gas supply means (not shown), and a high-temperature heating gas from the heating gas supply source, that is, an ammonia pyrolysis gas G is sprayed onto the surface of the strip 2. Is done. The pressure applied to the strip 2 is the distance (C) of the pressure pad 21 to the strip 2
Can be freely adjusted by adjusting.
In the present embodiment, the distance (C) between the pressure pad 21 and the strip 2 was set to 50 mm.

The heating gas G in the slow cooling zone 20 is returned to the heating gas supply means by using a fan means (not shown). In this embodiment, the injection pressure of the heating gas G from the pressure pad 21 is set to 5 to 20 mm (H ₂ O).
The temperature of the heating gas G, that is, the temperature in the annealing zone is 350 to 500.
° C, and in this example, it was maintained at 350 ° C. If the pressure and temperature in the slow cooling zone 20 are out of this range, problems such as generation of burrs and wrinkles on the strip 2 occur. In this embodiment, the injection pressure of the heating gas G is 10.0 m
m (H ₂ O), and the temperature was 350 ° C.

Further, according to the present invention, the pressure pad 21 can be arranged in any number of sets on both sides of the strip 2 to be transferred, but preferably, three or more sets are provided. As shown in an enlarged manner in FIG. 2, three sets are arranged. Further, the pressure pads 21 forming a pair are shifted in a so-called staggered arrangement so that the center position is shifted by a distance (B) with respect to the strip 2 to be transferred, and in this embodiment, B is shifted by 500 mm. Was installed. By arranging in this manner, there is an advantage that a wavy shape is given to the strip member 2 to suppress warpage in the width direction.

Further, according to the present invention, a pair of in-furnace rolls 200 similar to those provided at the outlet of the heating zone 10 are arranged at the inlet and the outlet of the annealing zone 20, respectively. That is, the furnace rolls 200 is provided at a position shifted in the transport direction of the elongated member 2 by a distance (A _1), the distance (A ₁₎ is in this example was a 330 mm. Further, each of the in-furnace rolls 200 can be moved so as to be separated from and in contact with the strip material 2. In this embodiment, the distance (A ₂ ) is set to 15 mm in FIG. The in-furnace roll 200 works in cooperation with the pressure pad 21 to eliminate the warpage of the strip 2.

That is, according to the slow cooling zone 20 having the above structure,
By the three sets of pressure pads 21 provided in the annealing zone 20, the material shape before the width warping (distortion) of the strip 2 is removed in the annealing zone 20 as much as possible. In addition, slow cooling zone 20
Rolls 200 provided at the inlet and the outlet of the
At 0, the material shape before the distortion can be removed is fixed on the roll surface, and has the function of flattening. Such slow cooling zone 20
With the above structure, the warpage of the strip 2 is greatly improved.

Next, the cooling zone 30 will be described. As shown in FIG. 1, the cooling zone 30 has a forced convection type structure as in the conventional case, and the length (L ₃ ) of the cooling zone 30 is 6.0 m in this embodiment. The cooling zone 30 includes spray nozzles 3 on both sides of the transported strip 2 along the transport path of the strip 2.
1 is provided in plurality. Further, a cooling chamber 32 provided with a cooling means 33 is provided adjacent to the cooling zone 30, and the atmosphere gas in the cooling zone 30, that is, the ammonia pyrolysis gas is cooled in the cooling chamber 32, and the cooling gas is injected by the cooling chamber 32. It is supplied to the nozzle 31. The cooling gas from the injection nozzle 31 is injected to both surfaces of the strip 2 to cool the strip 2. The cooling gas in the cooling zone 30 is returned to the cooling chamber 32 by using the fan means 34. Injection pressure of the cooling gas from the injection nozzle 31 is a 15~40mm (H ₂ O), the temperature in the cooling zone is held at 20 to 50 ° C.. If the pressure and temperature in the cooling zone deviate from these ranges, problems such as burnout of the furnace top roll and generation of burrs, wrinkles, and the like on the strip 2 occur. In this embodiment, the pressure is 30 mm (H ₂ O) and the temperature is 30 to 40.
° C.

Using the bright annealing furnace 1 having the above structure, at a line speed of 40 m / min.
A lead frame material having a width of 630 mm and a width of 630 mm was annealed. Accordingly, the lead frame strip 2 was substantially heat-treated in the heating zone 10 for 9 seconds, gradually cooled in the slow cooling zone 20 for 12 seconds, and cooled in the cooling zone 30 for 9 seconds.

The width warpage of the strip produced in this manner is
When measured by the conventional width direction hanging curl method, 3 m
m or less. This is because when a conventional annealing furnace is used, the line speed is 15.5 m / min, and the warpage is 5 to 8 mm. This indicates that the warpage has been significantly reduced.

Incidentally, the above-mentioned width direction hanging curl method means that the width 6
The strip is cut at a length of 50 mm in the longitudinal direction of the strip, which is assumed to be 30 mm, to prepare an elongated measurement sample. One end of the sample having a width of 50 mm is gripped, and the other end is dropped downward. The warpage of the other end with respect to the vertical line is used as the width warpage.

[0032]

As described above, according to the method for annealing strain of copper alloy strip and the bright annealing furnace of the present invention, the continuously supplied copper alloy strip is 5 to 500 ° C. at 700 ° C. ~ 1
Heat treatment for 8 seconds, slowly cooling at 350 to 500 ° C. for 7 to 26 seconds, and then cooling at 20 to 50 ° C. for 5 to 18 seconds. It is possible to achieve a significant improvement and an effect that the line speed of the strip can be greatly increased.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a bright annealing furnace according to the present invention.

FIG. 2 is a sectional view showing details of a slow cooling zone of the bright annealing furnace according to the present invention.

FIG. 3 is an enlarged front view of a pressure pad.

FIG. 4 is a sectional view taken along line IV-IV in FIG. 1;

FIG. 5 is a sectional view taken along line VV in FIG. 3;

FIG. 6 is a sectional view showing a schematic configuration of a conventional bright annealing furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bright annealing furnace 2 Copper alloy strip 3 Injection nozzle 4 Heating chamber 5 Fan means 10 Heating zone 20 Slow cooling zone 21 Pressure pad 30 Cooling zone 200 Roll in furnace

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁶ Identification symbol FI // C22F 1/00 624 C22F 1/00 624 661 661 682 682 682 691 691B 691C 692 692B 693 693A 693B

Claims (9)

[Claims] 1. A method for performing annealing for removing strain of a continuously supplied copper alloy strip using a bright annealing furnace, comprising the steps of: (a) removing the continuously supplied copper alloy strip. 500-7
(B) subjecting the heat-treated copper alloy to a heat treatment at 350 to 500 ° C. for 7 to 18 seconds.
A step of gradually cooling the copper alloy strip for 26 seconds; and (c) a step of cooling the cooled copper alloy strip at 20 to 50 ° C. for 5 to 18 seconds. Method. 2. Each of the treatment steps is carried out in a mixed gas atmosphere comprising 75% of hydrogen (H ₂ ) and 25% of nitrogen (N ₂ ), which are ammonia pyrolysis gases, and by forced convection. 2. The method of claim 1 wherein the copper alloy strip is annealed. 3. The copper alloy strip has a width of 400 to 700.
The method of claim 1 or 2, which is a lead frame strip having a thickness of 0.05 to 0.4 mm. 4. The lead frame material is 2% Sn.
4. The method of annealing a copper alloy strip according to claim 3, which is a copper alloy strip comprising -0.2% Ni-0.15% Zn-0.04% P-remainder Cu. 5. A bright annealing furnace of a forced convection heating type having a substantially closed structure, wherein: (a) a heating zone for heat-treating a continuously supplied strip from above to below. A cooling zone for gradually cooling the heated strip and a cooling zone for cooling the strip; (b) the furnace is maintained in an ammonia pyrolysis gas atmosphere; and (c) the heating zone includes A plurality of injection nozzles are provided on both sides of the material to be transferred along the material transfer path, at least one set of in-furnace rolls is provided at the outlet of the heating zone, and heating gas is supplied from the injection nozzle. The strip is heated at 500 to 700 ° C. for 5 to 18 seconds by injecting it onto both surfaces of the material at a predetermined injection pressure, and the heated strip is placed in the furnace placed at the outlet of this heating zone. (D) the slow cooling zone is transferred to the slow cooling zone through an inner roll; Placing the furnace rolls at the inlet and outlet of the zone, introducing the heated strip from the heating zone to the slow cooling zone through the furnace rolls arranged at the inlet,
Further, at least three sets of pressure pads are arranged in a staggered arrangement on both sides of the strip to be transferred along the transfer path of the strip, and a heating gas is supplied from the pressure pad to both surfaces of the strip in a predetermined manner. By injecting the material at the injection pressure,
The material is gradually cooled at 50 to 500 ° C. for 7 to 26 seconds, and the slowly cooled strip is transferred to the cooling zone through the in-furnace roll disposed at the outlet of the annealing zone, and (E)
In the cooling zone, a plurality of spray nozzles are arranged on both sides of the strip to be transferred along the transfer path of the strip, and a predetermined amount of cooling gas is injected from the spray nozzle to both surfaces of the strip. A bright annealing furnace, characterized in that the strip material transferred from the slow cooling zone by injecting under pressure is cooled at 20 to 50C for 5 to 18 seconds. 6. The bright annealing furnace according to claim 5, further comprising gas supply means for supplying an ammonia pyrolysis gas into the furnace. 7. The strip has a width of 400 to 700 mm,
7. The bright annealing furnace according to claim 5, which is a lead frame material having a thickness of 0.05 to 0.4 mm. 8. The lead frame material is 2% Sn.
The bright annealing furnace according to claim 7, wherein the bright annealing furnace is a copper alloy strip composed of -0.2% Ni-0.15% Zn-0.04% P-remainder Cu. 9. The injection pressure of the pressure pad is 10
The bright annealing furnace according to any one of claims 5 to 8, wherein the bright annealing furnace has a thickness of ２０20 mm (H ₂ O).