FR2792862A1 - Multi-sized tape for manufacturing connection grid, terminal, etc., has different hardness values on thin and thick section, with their ratio between zero point nine and one fifty - Google Patents

Abstract

Multi-sized tape has several thin section (2) and several thick section (3). Tape is laminated so that constraints spread varies from hardness H1, at thin section, to hardness H2, at thick section, with ratio H1/H2 between 0.9 and 1.5. This ratio illustrates how equally spread constraints are.

Description

MULTIPLE CALIBER TAPE AND METHOD FOR

EQUALIZE IT

  The present invention relates to a multiple gauge strip and a method for leveling it, said multiple gauge strip being a strip which varies in steps in thickness in the direction of its width. It is used to form electronic parts such as connection grids (for power transistors), terminals, connectors, relay contacts, etc. More particularly, the present invention relates to a multi-gauge strip and a method for leveling it, said multiple-gauge strip being a strip which has a low stress value and is suitable for use for electronic parts. A multi-gauge strip is formed such that its cross section varies in thickness along its width, the cross section being uniformly continuous in the length direction. As shown in Figures 1 and 2, it has one or two thick parts depending on its cross section. There are several known methods for manufacturing said multi-gauge strip. They include, for example, rolling with pilgrim steps (Japanese patent made available to the public N 42150/1984), tandem rolling (Japanese patents made available to the public Ns 60010/1985 and 299701/1989), V-cutter molding (Japanese patent made available to the public N 10849/1977), forging (Japanese patent made available to the public N 54462/1987), and cut from a thick strip uniform. Their choice depends on the required productivity and quality. These processes, to

2 2792862

  with the exception of cutting, establish the final multi-gauge cross section by a

plastic deformation.

  A multi-caliber strip is worked for a power transistor in the following manner. First, it is stamped in a form prescribed by stamping and is divided into two parts across the width. In the stamping process, the edge of the thin part of the multi-gauge strip is split over a width of 0.5 to 2.0 mm. Then it receives nickel plating and gold point plating. It is cut by lengths (200 to 300 mm). It undergoes welding, wire welding, and resin molding for the transistors to be mounted. The process ends with a plating of

  soldering and cutting of the connecting bars.

  Multi-gauge bands are usually produced by plastic deformation. The entire process consists of rough shaping from a flat strip, annealing, and finishing rolling. Therefore, the resulting multi-gauge strip varies in thickness reduction and in structure from the thick parts to the thin parts and therefore also varies for the distribution of residual stresses from the thick parts to the thin parts. The residual stress which is due to the approximate shaping is

  almost completely eliminated by subsequent annealing.

  However, another constraint arises during the finish rolling which produces compression in thickness, expansion in width, and elongation.

lengthways.

  Conventional multi-gauge tapes produced by the above-mentioned method pose the following problems. Multiple gauge bands with improperly distributed residual stress are subject to deformation (such as elongation, contraction, camber, transverse curvature, and twist) during stamping and cutting for manufacture of electronic parts (such as connection grids and terminals). This deformation takes place when an unequal stress is released and during variations in stress distribution. Excessive deformation that occurs during machining causes the multi-gauge strip to clog the die, thereby reducing the punching speed or making press machining difficult. In addition, the deformation of the multi-gauge strip decreases the accuracy of the dimensions of the

stamped product.

  Unevenly distributed residual stress worsens the coplanar positioning of the conductors and the accuracy of the positions of the conductors due to the camber, transverse curvature, torsion, etc., when the multi-gauge strip is manufactured in connection grids. This leads to offset wire welding and an uneven welding resistance of the conductors in the step of mounting the transistors. In addition, bent conductors and unevenly spaced conductors cause difficulty when mounting terminated transistors on a printed circuit board. Thus, multi-gauge bands with unevenly distributed residual stress

  pose many problems as mentioned above

  above. The present invention has been made in order to deal with the above mentioned problems. Thus, it is an object of the present invention to provide a multi-gauge strip and a method for equalizing it. This object is achieved by manufacturing a multi-gauge strip having only a small amount of stress, by examining it to look for a distribution of residual stress under prescribed conditions, by performing a stamping without causing deformation, and subjecting it to an adequate leveling in order to reduce the stresses. The first aspect of the present invention is a multi-gauge strip having a cross section which has one or more thin parts and thick parts formed by rolling across its width, said cross section being uniformly continuous in length, which is characterized in that the thin part has a hardness Hi and the thick part has a hardness H2, the ratio H1 / H2 being

0.9 to 1.15.

  The multi-gauge strip formed as mentioned above has a very small difference in residual stress between the thin part and the thick part (this residual stress appears because the degree of machining and the structure vary from the thin part thick part during rolling). The multi-gauge strip allows us to assess whether an internal stress is uniformly distributed therein or not. That is, the H1 / H2 ratio indicates the

  distribution of the residual stress.

  The second aspect of the present invention is a multi-gauge strip defined in the first aspect, in which the thick part is formed only at the center of the width and the thin parts are formed at both edges, and the cross section is uniform so only when the multi-gauge strip is cut lengthwise (1.2 times its width), in five positions, one in the center of its width, one on each side at the limit between the thin part and the part thick, and one on each side at the edges of the thin part to be split, the variability in size between the two points (symmetrical with respect to the center of the width) of the cutting surface is less than 0.15 mm per end

o begins cutting.

  The value specified above allows us to assess whether a residual stress is adequately distributed or not. Residual stress tends to accumulate at a particular position in the case of multi-gauge bands which have a thick part and two thin parts on both sides thereof. Thus, it can be assessed whether the given multiple gauge strip is suitable or not for another production. The third aspect of the present invention is a multi-gauge strip defined in the first aspect, in which two thick parts are formed symmetrically, a thin part being formed at the center of the width, and thin parts are formed at the two outer edges of the thick parts, and the cross section is uniform so that when the multi-gauge strip is cut lengthwise (1.2 to 5 times its width) in five positions, one in the center of the width, one of each side at the outer limit between the thin part and the thick part, and one on each side at the edge of the thin part to be split, the variability in size between the two points (symmetrical with respect to the center of the width) of the surface cutout is less than 0.15 mm at the end

o begins cutting.

  The value specified above allows us to assess whether a residual stress is adequately distributed or not. Residual stress tends to accumulate at a specific position in the case of multi-gauge bands which have two thick parts formed symmetrically, a thin part being between them. Thus, it can be assessed whether the given multi-gauge strip is suitable or not for machining. The fourth aspect of the present invention is a multi-gauge strip defined in the first aspect, in which the thick part is formed only at the center of the width, the thin parts are formed at both edges, and the cross section is uniform so only when the multi-gauge strip is cut lengthwise (1.2 to 5 times its width) in five positions, one in the center of the width, one on each side at the limit between the thin part and the part thick, and one on each side at the edge of the thin part to be split, the angle of inclination of the cut thin part is less than 4 compared to the horizontal base line at

  the end o begins cutting.

  The value specified above allows us to assess whether a residual stress is adequately distributed or not. Residual stress tends to accumulate at a specific position in the case of multi-gauge bands which have a part

  thick and two thin parts on both sides of it

  this. Thus, it is possible to minimize the transverse curvature, the torsion and the camber during the

  manufacture of multi-gauge bands.

  The fifth aspect of the present invention is a multi-gauge strip defined in the first aspect, in which two thick parts are formed symmetrically, a thin part being formed in the center of the width, and the thin parts are formed at the two outer edges of the thick parts, and the cross section is uniform so that when the multi-gauge strip is cut lengthwise (1.2 to 5 times its width) in five positions, one in the center of the width, one of each side at the outer limit between the thin part and the thick part, and one on each side at the edge of the thin part to be split, the angle of inclination of the cut thin part is less than 4 with respect to the line horizontal

  at the end o begins cutting.

  The value specified above allows us to assess whether a residual stress is adequately distributed or not. Residual stress tends to accumulate at a specific position in the case of multi-gauge bands which have two thick parts formed symmetrically, with a thin part between them, and two thin parts on both sides thereof. Thus, it is possible to minimize the transverse curvature, the torsion and the camber during

  the manufacture of multi-gauge bands.

  The sixth aspect of the present invention is a multi-gauge strip having a cross section which has one or more thin parts and thick parts formed by rolling across its width, said cross section being uniformly continuous in length, said multi-gauge strip being equalized after rolling by application of a tensile stress which produces a corresponding plastic deformation of 0.05 to 1% of

  elongation in the longitudinal direction.

  Equalizing in this way frees the multi-gauge bands from the unevenly distributed residual stresses. Thus, it is possible to minimize the deformation of multi-gauge bands

which takes place during machining.

BRIEF DESCRIPTION OF THE DRAWINGS

  Figure 1 is a perspective view showing the multi-gauge strip according to the

present invention.

  FIGS. 2A and 2B are perspective views showing the important parts of the strip to be

  multiple calibers according to the present invention.

  Figure 3 is a perspective view showing another design of the gauge strip

  multiple according to the present invention.

  FIGS. 4A and 4B are perspective views showing the important parts of another strip with

  multiple calibers according to the present invention.

  FIGS. 5A and 5B are simplified diagrams showing the cross section of the multi-gauge strip according to the present invention, said cross section appearing after cutting. FIG. 6A is a plan view of the multi-gauge strip of the present invention which has been stamped, and FIG. 6B is a perspective view showing the grid of connections formed from

  the multi-gauge band stamped.

  Figures 7A and 7B are perspective views showing another design of the gauge strip

  multiple according to the present invention.

  FIG. 8 is a simplified diagram showing the method of equalizing the multi-gauge band

according to the present invention.

  Figure 9 is a simplified diagram showing the design of the matrix used to equalize the multi-gauge strip according to the present invention. FIG. 10 is a simplified diagram showing the variation in cross section and hardness which takes place during rolling during the manufacture of

the multi-gauge band.

  The embodiments will be described in

  referring to the accompanying drawings.

  (1) Material and shape of the multi-gauge strip The multi-gauge strip is formed so as to have one or more thick parts and thin parts across its width, its cross section being uniformly continuous in the longitudinal direction. Certain characteristic structures of the multiple-gauge strip are shown in Figures 1 to 4. The multiple-gauge strip 1 shown in Figure 1 is composed of a thick part 3 at the center of its width W and thin parts 2 and 2 on both sides of the thick part 3. The thick part 3 is formed in such a way that its walls have a particular angle (E) of inclination which is from 0 to 100. The multi-gauge strip 11 shown in FIG. 3 is composed of two thick parts 13 and 13 and three thin parts 12. The two thick parts 13 and 13 are formed, with the thin part 12b interposed between them. Two thin parts 12a and 12a are formed outside the two thick parts 13 and 13. The thick parts 13 and 13 are formed in such a way that their walls have an angle

  particular (D) of inclination which is from 0 to 100.

  The multi-gauge strip 1 or 11 is transformed into electronic parts such as connection grids intended for power transistors (see FIG. 6), terminals, connectors, and relay contacts. The multi-gauge strip 1 or 11 for the connection grids is made of pure copper, such as oxygen-free copper (C1020), oxygen-containing copper (C1100), and deoxidized phosphorus copper (C1201 ), or a copper alloy, such as Cu-0.1Fe-0.03P. The multi-gauge strip 1 or 11 for terminals is made of a copper alloy (of higher strength), an Fe-Ni alloy, an Fe alloy, or an Ni alloy. She is

  also made of any other alloy.

  As shown in Figures 1 and 3, the multi-gauge strip 1 or 11 differs from a flat strip having a uniform thickness. It is manufactured by approximate shaping (rolling or forging), annealing, and finishing rolling. The thick parts 3 and 13 as well as the thin parts 2 and 12 vary widely in hardness and in grain dimensions according to the conditions (such as the reduction in thickness and the annealing temperature and the time) of the approximate shaping and of

finish rolling.

  Likewise, as indicated in FIGS. 1 and 3, the multi-gauge strip 1 or 11 has one or two thick parts 3 or 13 on one side thereof. These

  parts have the following dimensions.

  Thickness T, of thin part 2 or 12: 0.1 to

1.5 mm.

  Thickness T2 of the thick part 3 or 13: 3 to

20.2 mm.

  Width W of the multi-gauge strip 1 or 11: 30 to 200 mm Width D1 of the thick part 3 or 13: 5 to mm (or else the sum of the widths if the multi-gauge strip has two thick parts 13 and 13) . Incidentally, as shown in Fig. 7A, the multi-gauge strip 51 can be formed such that the thick portion is curved both up and down. In addition, as indicated in FIG. 7B, the multi-gauge strip 61 may have grooves 64 and 64 which run lengthwise on the opposite face near the limit between the thick part 63 and the thin part 62. In other words, the present invention relates to any multi-gauge strip which is used for electronic parts. The multiple gauge strips 51 and 61 shown in FIGS. 7A and 7B constitute examples comprising a thick part. The same idea applies to those with two thick parts

(not shown).

  (2) Hardness measurements According to the present invention, the multi-gauge strip 1 or 11 is characterized in that the thin part 2 or 12 has a certain hardness and the thick part 3 or 13 has another certain hardness, the ratio of the first to the second being specified. Because the thick part 3 or 13 and the thin part 2 or 12 are formed from a flat strip (of uniform thickness), they differ in hardness according to their reduction in thickness even if the raw material is the same . The hardness can be measured according to the hardness test method (Vickers, Rockwell, or Brinell) provided for in the Japanese standards JIS Z2244, JIS Z2465, and JIS Z 2243. In the case of the multi-gauge strip 1 having a thick part 3, the hardness Hi of the thin part 2 is measured on the line S1 and the hardness H2 of the thick part 3 is measured on the axial line CL, represented in FIG. 1. The hardness is expressed as a function of a

  average of five measurements on each line.

  In the case of the multi-gauge strip 11 comprising two thick parts 13 and 13, the hardness Hi of the thin part 12 is measured on the axial line CL of the multi-gauge strip 11 and the hardness H2 of the thick parts 13 and 13 is measured on the axial line S2 of one or other of the thick parts, as shown in FIG. 3. The hardness is expressed in

  based on an average of five measurements on each line.

  The H1 / H2 ratio must be in a range between 0.9 and 1.15, where Hi represents the hardness of the thin part 2 or 12 and H2 represents the hardness of the thick part 3 or 13. The reason why the ratio H1 / H2 should be in the range between 0.9 and 1.15 is as follows. If the ratio is less than 0.9 or greater than 1.15, the multi-gauge strip 1 or 11 has such a large value of uneven residual stress that it is subjected to deformation (camber, transverse curvature, and torsion) during stamping (Figure 6A), mounting the transistors, or assembling the terminals. This greatly degrades productivity and yield. The H1 / H2 ratio should be 0.9 to 1.15, preferably 0.95 to 1.10, more preferably 0.98 to 1.05. The number of measurements can be lower or

greater than 5.

  The multi-gauge tape is usually made from a flat tape (or raw material) through an intermediate product. The figure shows the rolling steps used for the manufacture of the multi-gauge strip of the present invention. The flat strip (raw material) must undergo an approximate rolling and a finishing rolling with an adequate thickness reduction under adequate heat treatment conditions in accordance with its alloy composition and the finished cross section (thickness of the thick parts and thin parts) so that the resulting multi-gauge strip has satisfactory mechanical properties (hardness, tensile strength, elongation limit, elongation, etc.) and good conductivity

electric.

  e Flat strip (or raw material): A copper or copper alloy slab is produced by continuous casting or semi-continuous casting. The slab is formed into a sheet by hot rolling, cold rolling, and heat treatment. The sheet is split into flat strips of desired dimensions. The flat strip can be either in laminated form or in annealed form. The flat strip thus obtained has a uniform hardness (H0) both in the length direction and the direction of the

  width. The flat strip has a thickness of TO.

  * Intermediate product: The flat strip undergoes an approximate rolling thanks to a Pilger rolling mill or a rolling mill composed of a grooved roller and a flat roller, so that it has a thick part (with a thickness T12) and a thin part (with a thickness T11). The approach rolling is carried out in such a way that the reduction in thickness is small in the thick part and large in the thin part. The thick part has a H12 hardness and the thin part has a H11 hardness. So Hll is larger than H12 because the thin part has a reduction value

  thicker than the thick part.

  The intermediate product thus obtained is annealed in order to regain its ductility. The thick part has a hardness H22 and the thin part has a hardness H21. Then, H22> H21 because the thin part has a thickness reduction value greater than the thick part and is more softened by

annealing it.

  * Strip with multiple gauges finished: The annealed intermediate strip undergoes a finishing rolling with a rolling mill composed of a grooved roller and a flat roller (the grooved roller has a concave part of desired depth at a prescribed position in the direction of the width). The thick part has a thickness

  T32 and the thin part present with a thickness T31.

  The thick part has an H32 hardness and the thin part has an H31 hardness. The hardness values

  depend on the thickness reduction.

  In accordance with the present invention, the H31 / H32 ratio must be from 0.9 to 1.15. To this end, it is necessary to choose suitable rolling conditions for the reduction of thickness and annealing. (3) Cutting method and offset measurements In accordance with the present invention, the multi-gauge strip 1 or 11 must have a particular offset after cutting. The cuts are made at the specific positions shown in Figures 1 to 4. A sample of length L2 (from 200 to 500 mm) is taken from the multi-gauge strip 1 or 11 of standard length L. The cuts are made with five positions as shown in Figures 2 and 4. The length L, of the cutout is 1.2 to 5 times the width

  of the multi-gauge band 1 or 11.

  The offset value and angle are measured at the end at which cutting begins. The five positions intended for cutting (in the case of the multi-gauge strip 1) are shown in FIG. 2. The first position e is at the center of the width W. The second and third positions b1 and b2 are at the limit between the thin part and the thick part 3. The fourth and fifth positions cl and c2 must be 0.5 to 2.5 mm relative to the two edges in the thin part 2. These positions correspond to those which must be split when of the stamping process to produce the grid of connections. The cutting must be carried out by machining with electric discharges or chemical etching so as to prevent new stresses from

  enter the multi-gauge strip 1.

  The length (L;) of cut should be 1.2 to 5 times the width W of the multi-gauge strip 1 or 11 (if the sample is cut over its entire length, it is impossible to measure the amplitude of the offset). If the cutting length is less than 1.2 times the width W, the offset due to the residual stress does not appear. If the cutting length is greater than 5 times the width W, the offset due to the stress

  residual is affected by gravity.

  The offset is measured as follows. Assuming that the multi-gauge strip 1 has a width (W) of 65 mm, a sample with a length (L2) of 200 mm is taken and sections (about 150 mm long lengthwise) are made by EDM machining in five positions (e, bl, b2, cl, c2). Before cutting, marks are made in a, and a2 (2 mm inside with respect to the shoulders of the thick part 3) in a symmetrical manner with respect to the central cutting line e. The distance Ad between ai and a2 is measured before and after cutting using a projector

  (with a magnification of 30 to 100).

  The multiple gauge strip 11 shown in FIGS. 3 and 4 is tested in the same way as the multiple gauge strip 1. That is to say that they are of the same sample length L2, width W, cutting length , and cutting method. The cuts are made in five positions. The first position e is at the center of the width W. The second and third positions b1 and b2 are at the border between the outer thin part 12 and the thick part 13. The fourth and fifth positions c, and c2 are in the thin part 12 at both edges to be split. Before cutting, marks are made in ai and a2 (2 mm inside with respect to the shoulders of the thick parts 13 and 13) symmetrically with respect to the central cutting line e. The distance Ad between a. and a2 is measured before and after cutting using a projector

  (with a magnification of 30 to 100).

  The value of the offset es_ obtained from

equation (1) below.

  d - Ad (1) (where d is the length of the distance before cutting, and Adest the length of the distance after cutting). According to the present invention, the value calculated according to equation (1) must be smaller than

0.15 mm.

  The offset value between the two points a, and a2 on the thick part of the multi-gauge strip is proportional to the amplitude of the residual stress stored in the multi-gauge strip 1 or 11. If the offset value is greater at 0.15 mm, then the following drawbacks appear in the multiple-gauge strip 1 comprising a thick part 3 or else the multiple-gauge strip 11 comprising two thick parts 13 and 13. The multiple-gauge strip (in the form of a blank 1A) does not allow regular stamping for manufacture in a grid of connections (IB), shown in Figure 6A and Figure 6B. During the stamping, the main body 3A and the terminals 2B obstruct the stamping matrix. Likewise, poor wire welding and deformed terminals appear during assembly of the transistors and assembly of the terminals. Therefore, the offset value should be less than 0.15mm, preferably less than 0.1mm, and more than

  preferably less than 0.05 mm.

  The offset angle is measured as follows: e. FIG. 5 is a simplified diagram showing the cross section of the multi-gauge strip 1 which has been cut (the cross section is seen in the direction of the cut). The symbol 0 represents the angle of inclination with respect to

  the horizontal base line SL of the thin part 2.

  The angle 0 is determined by measuring the positions P1 and P2 shown in FIG. 5B. For measurement, a sample of the multi-gauge strip 1, in which cuts have been made, is placed on a movable plate 5 and is moved under the projector 7 (with a magnification of 30 to 100). In other words, length A and length B are calculated from positions P1 and P2 and angle 0 is obtained from

equation (2) below.

  0 = tan '(B / A) (2) The same procedure as that mentioned above is also applied to the multi-gauge strip 11 shown in FIGS. 3 and 4. That is to say that the thin part outside 12a, which has been cut at the outer limit b2 between the thick part and the thin part, is examined under the projector, and the angle 0 is

  calculated from equation (2) above.

  According to the present invention, the angle 0 thus measured must be less than 4. The reason for this is explained below. The angle of inclination relative to the horizontal base line SL of the thin part after cutting is proportional to the value of the residual stress stored in the multi-gauge strip 1. If the angle O is greater than 4, then the following drawbacks appear in the multi-gauge strip 1 comprising a thick part 3 or else in the multiple-gauge strip 11 comprising two thick parts 13 and 13. The multiple-gauge strip (in the form of a blank 1A) does not allow regular stamping for manufacture in a grid of connections (IB), shown in FIG. 6A. During the stamping, the main body 3A and the terminals 2B obstruct the stamping matrix. Likewise, poor wire welding and deformed terminals appear during assembly of the transistors and assembly of the terminals. Therefore, the tilt angle should be less than 4, preferably less than 3, and more preferably

less than 20.

  The direction of the angle 0 can be upwards relative to the horizontal base line SL. In this case too, the angle of inclination must be less than 4. In this connection, the horizontal base line SL coincides with the lower surface of the strip to

multiple calibers 1 or 11.

  (4) Equalization process Figure 8 is a simplified diagram showing the traction equalization machine for the multi-gauge strip 1 or 11. The multi-gauge strip 1 or 11, which has undergone a final rolling, a slitting and a winding passes through the equalization machine which performs the equalization by application

  of a tensile stress in the following manner.

  As indicated in FIGS. 8 and 9A, the multiple-gauge strip 1 is unwound from the supply reel 38 and is wound on the tension reel 39 (first step). This state is preserved while the advance of the multi-gauge strip 1 is suspended (second step). The gripping cylinders 34 and 36 are lowered so that the thick part 3 and the thin parts 2 and 2 of the multi-gauge strip 1 are gripped by the die 30 (third step). The left die 30 is moved to the left by means of the stretching cylinder 35 (fourth step). Because the right die 30 is fixed, the multi-gauge strip 1 receives a tensile force. The left die 30 is moved a prescribed distance (necessary for equalization), and then the drawing cylinder 35 is stopped (sixth step). The stretching cylinder 35 is actuated again so that the die 30 is restored (seventh step). The left and right gripping cylinders 34 and 36 are raised to open the dies 30 and 30, so that the multi-gauge strip 1 is released (eighth step). The tension reel 39 is rotated to wind the equalized multi-gauge strip, which is as long as the distance between the left and right dies 30 and 30 (ninth step). The third step and the following steps are repeated. In this regard, the distance between the two dies 30 and 30 represents the length of the multi-gauge strip 1 to be equalized at the same time. The upper and lower dies are indicated by 31 and 32. The equalization machine shown in FIG. 8 has left and right dies 30 and 30, which grip the thick part 3 and the thin parts 2 and 2 of the strip. multi-gauge 1 at the same time, thereby applying a tensile force lengthwise, causing the multi-gauge strip 1 to undergo plastic deformation. The longer the distance between the left and right matrices 30 and, the longer the multiple gauge strip which can be equalized at the same time. This contributes to productivity and facilitates the control of the dies 30 and 30 to obtain the same elongation. On the other hand, the gripping cylinders 34 and 36 and the stretching cylinder 35 must have a large capacity and therefore the equalization machine needs a large installation surface. If the distance between the left and right dies 30 and 30 is small, the equalization machine is of poor productivity and cannot apply uniform plastic deformation to the multi-gauge strip. For this reason, the distance between the left and right matrices 30 and 30 must be

about 3 to 10 m.

  The die 30 which comes into contact with the multi-gauge strip 1 can be formed from tool steel. Its contact surface must be covered with a urethane coating so that it does not damage the multiple gauge strip 1. For the multiple gauge strip 11, the matrix 30a or 30b as shown in the figure 9B or 9C, respectively, must be used, which follows the shape of the multi-gauge strip 11 and fits on the thick parts 13 and

13 and the thin part 12.

  The amount of plastic deformation (or elongation) to be added to the multi-gauge strip 1 or 11 must be 0.05 to 1%. The value of the elongation is controlled by the distance AL over which the matrix moves, and the distance AL is approximately represented by equation (3) below. AL = x LO (3) (where LO represents the distance between the left and right matrices, and 6 represents the value (0, 0005

  at 0.001) of plastic deformation).

  The effect of the equalization treatment can be confirmed by cutting a sample from the multi-gauge strip 1 or 11 at five positions (e, bl, b2, cl, c2), explained above (in paragraph (3) , cutting process and offset measurements). If the desired equalization effect is not produced, it is possible to repeat a stretching equal to the previous one or a stretching greater than the previous one as long as the value of the plastic deformation is less than 1% (on the basis of the length before equalization ). The application of a tensile stress to the multi-gauge strip 1 or 11 should preferably be carried out after the final step (or slitting) of the manufacturing, however, the equalization may be followed by a slitting. The equalized multi-caliber band 1

  or 11 can be split before stamping.

  With insufficient equalization (less than 0.05%), the multi-gauge tape will cause problems with stamping and mounting the lead frame (see Figure 6) in the following steps. With excessive equalization (more than 1%), the multi-gauge strip is of poor dimensional accuracy or has residual stress in the lengthwise direction, which adversely affects the following steps. Therefore, the adequate value of plastic deformation (or tensile equalization) must be from 0.05 to 1%, preferably from 0.1 to 0.6%, more preferably from 0.2 to 0, 5%. Pull equalization can be repeated two or more times as long as the total equalization value is

  below the value mentioned above.

  The invention will be described in more detail with reference to the following examples, which are not

  intended to restrict its scope.

Example 1

  (Preparation of a multi-gauge strip)

  A slab of deoxidized phosphorus copper (Cu-

  0.035P) is produced by semi-continuous casting. The slab is hot rolled and is cold rolled into a rolled sheet, with a thickness of 2, 1 to 3.2 mm and a width of 600 mm. The sheet is split into a 70 mm wide strip. The strip is made up of a gauge strip

  multiple (shown in Figure 1) specified above

below as follows.

  Width W: 65 mm, width Dl of the central thick part: 34 mm, thickness Ti of the thin part: 0.4 mm, thickness T2 of the thick part: 1.27 mm, angle a of the slope of the part

  thick: 10 (80 relative to a horizontal line).

  Manufacturing stage: Approximate shaping (by Pilger rolling), annealing (at 350-450 C for 2

  hours), finish rolling, and slitting.

  The hardness of the thick and thin parts is controlled by modifying the reduction in thickness during the approximate shaping, the annealing temperature and

  the reduction of the thickness during the finishing rolling.

  The multi-gauge strip thus obtained has a

  hardness (Hv) which is indicated in table 1.

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  (Sample preparation) Three multi-gauge strips (designated by

  numbers 1 to 3 in table 1) are prepared.

  Three pieces (about 300 mm long) are taken from each of the multiple gauge strips. Each piece has its ends (about 50 mm) cut by an EDM machine (with a wire diameter of 0.5 mm). Thus, a 200 mm sample is obtained. Two marks are made on the cut surface, each 2 mm inside with respect to the shoulder of the thick part. The distance between the two marks is measured

  using a projector fitted with a movable X-shaped plate

  Y. Five marks are made on the cut surface (one in the center of the width, one on each side at the border between the thick part and the thin part, and one on each side 1 mm inside with respect to at the edges). The cuts (150 mm long) are made lengthwise at the five marks using an EDM machine (with a wire diameter of

0.5 mm).

  (Press punching test and deformation measurement) Each of the coils (N 1 to 3) is punched into connection grids using a punch press. The punched product is divided in half crosswise. The grid cut in half is cut over a length of 200 mm. The resulting sample is examined for a transverse curvature. Each sample is examined with regard to the distance of the marks and the inclination of the thin part using a projector (with a magnification of 100), provided with a movable plate in X-Y. The distance of the benchmarks is expressed as an average of three measurements. The sample is examined for A and B (shown in Figure 5) using a

23 2792862

  projector fitted with a movable X-Y platform. The angle (0) of inclination of the thin part is calculated from A and B. It is expressed in terms of an average of six

  measures (three of each for right and left).

Table 1

  N Hardness H1 Hardness H2 H1 / H2 Curvature Variability of the Inclination of the transverse dimensions at the part part part of the level grid of the thin thin thick connections shoulders of the thick part Example 1 1 1.23 1.17 1, 05 none +0.03 0.7 2 1.18 1.19 0.99 none +0.05 0.8 3 1.12 1.22 0.93 very low +0.09 1.2

Example

  Exempale4 1.09 1.24 0.88 significant +0.38 5.8 No-a: For the variability of dimensions at the shoulders of the thick part, the sign + indicates dilation and the sign - indicates a

contraction.

  (Results) The table shows the results of the measurements of the transverse curvature and the deformation of the connection grid divided in two. Samples N 1 to 3 of Example 1 have a very small or undetectable transverse curvature and a very small deformation (variability of the dimensions between two points at the shoulders and inclination of the thin part). On the contrary, sample N 4 of the comparative example has a remarkable transverse curvature (likewise of a twist of conductors). It presents a significant deformation due to the imbalance between the hardness of the thick part and the hardness of the thin part (the result is a great variability of the

  dimensions and a large tilt angle).

Example 2

  (Equalization) Multi-gauge bands N 1 to 4 pass

  by a traction equalization machine specified above

  below for a specific equalization value. The

  resulting samples are designated by N 1-2, 2-

  2, 3-3, 2-3, and 4-2. * Distance between the dies: 6 m * Width of the die: 85 mm * Length of the die: 200 mm (Preparation of samples and deformation measurements) The same procedure as that of Example 1 is repeated.

Table 2

  NN Value Hardness Hardness H1 / H2 Curvature Variation of the equalization inclination H1 of the H2 of the transverse dimensions to of the part by traction part of the level grid of thin (%) thin thick connections shoulders of the thick part 1- 2 0.3 1.23 1.17 1.05 none +0.01 0.4 Example 2 2-2 0.3 1.18 1.19 0.99 none +0.02 0.6 3- 2 0 , 4 1.12 1.22 0.92 very low +0.06 0.8 Example 2-3 1.5, 1.18 1.19 0.99 none -0.16 0.9 Comparative example 4-2 0 , 4 1.09 1.24 0.88 significant +0.22 4.3 (Results) The samples N s 1-2, 2-2 and 3-2 of Example 2 show reduced deformation after cutting thanks to the equalization treatment. On the contrary, the sample N 4-2 of the comparative example has a greater value of deformation than the samples of Example 1 although the value of the deformation itself decreases after equalization. In addition, the sample N 4-2 undergoes a transverse curvature after manufacture in a grid of connections. Sample N 2-3 of the comparative example shows a variation (contraction) in the dimensions between two points at the shoulders and an increase in the angle of inclination of the thin part. This is due to the fact that the plastic strain value for tensile equalization is greater than 1%. Example 3 (Preparation of a multi-gauge strip)

  A slab of deoxidized phosphorus copper (Cu-

  0.035P) is produced by semi-continuous casting. The slab is hot rolled and is cold rolled into a rolled sheet, 2.1 to 3.2 mm thick and 600 mm wide. The sheet is split into a 110 mm strip

wide.

  This strip is transformed into a multiple gauge strip (shown in Figure 3)

  specified below as follows.

  Width W: 130 mm, width D3 of the central thin part: 36 mm, width Dl of each of the thick parts: 34 mm, width D2 of each of the parts

thin outer: 15.5 mm.

  A rolled sheet, 2.1 to 3.2 mm thick and 110 mm wide, is formed by approximate shaping (by Pilger rolling), annealing from 350 to 450 C for 2 hours , a finish rolling, and a slitting. The multi-gauge strip has a hardness of the thick part and a hardness of the thin part which vary according to the reduction in thickness during the approximate shaping, the annealing temperature and the reduction in thickness during rolling finishing. Table 3 shows the hardness (Hv) of multi-gauge bands (N 5 to 8)

thus obtained.

  (Press punching test) Each of the coils (N 5 to 8) is punched in connection grids using a punch press. The punched product is divided into four parts across the width. The divided grid is

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  cut over a length of 200 mm. The resulting sample is examined for curvature

  transverse (see Figures 3 and 5).

  (Cutting of the samples for the measurement of deformation) Three multi-gauge bands designated by N s 5 to 8 in table 3) are prepared. Three pieces (about 300 mm long) are taken from each of the multi-gauge strips. Each piece has its end (about 50 mm) cut by an EDM machine (with a wire diameter of 0.5 mm). Thus, a sample with a length of 200 mm is obtained. Two marks are made on the cut surface, each outside the thick outer part (see Figure 3). The distance between the two marks is measured using a projector fitted with a movable X-Y plate (see Figure 5). Five marks are made on the cutting surface (one in the center of the width, one of each at the border between the thick outer part and the thin outer part, and one of each at 1 mm inside with respect to edges). The cuts (150 mm long) are made lengthwise at the five marks using an EDM machine (with a diameter

0.5 mm wire).

  (Measurements of the deformation of the cut sample) The same procedure as in Example 1 is repeated.

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Table 3

  N Hardness H1 Hardness H1 / H2 Curvature Variation of the Inclination of the part H2 of the transverse dimensions to the of the thin part level of the level of the thin thick connections shoulders of the thick part 1.23 1.18 1.04 none + 0.03 0.6 Example 3 6 1.17 1.18 0.99 none +0.06 0.9 7 1.12 1.20 0.93 very low +0.08 1.5

Example 8

  Example 8 1.09 1.25 0.88 significant + 0.45 6.2 comparative (Results) Table 3 shows the results of the measurements of the transverse curvature and of the deformation of the connection grid divided into four. Samples N s 5 to 7 of Example 3 have a very small or undetectable transverse curvature and a very small deformation (variability of the dimensions between two points at the level of the outer shoulders and inclination of the thin part). On the contrary, sample N 8 of the comparative example has a remarkable transverse curvature due to the imbalance between the hardness of the thick part and the hardness of the thin part (the result is a great variability of the

  dimensions and a large tilt angle).

Example 4

  (Equalization) Multi-gauge bands N s 5 to 8 pass

  by a traction equalization machine specified above

  below to obtain a specific equalization value.

  The resulting samples are designated by N 5-2,

6-2, 7-2, 6-3, and 8-2.

  * Distance between the dies: 6 m * Width of the die: 120 mm * Length of the die: 200 mm (Preparation of samples and measurement of transverse curvature and deformation) The same procedure as that of Example 1 is repeated to prepare samples and to measure the

  transverse curvature and deformation.

  Table 4 Value Hardness Hardness Curvature Variability Inclination of equalization H1 of H2 of the transverse of of the part by traction part of the grid dimensions thin N (%) thin thick H1 / H2 of at the level of the shoulders connections of the thick part -2 0.3 1.23 1.18 1.04 none +0.02 0.5 Example 4 6-2 0.35 1.17 1.18 0.99 none +0.04 0.6 7-2 0.4 1.12 1.20 0.93 none +0.06 0.9 Example 6-3 1.3 1.17 1.18 0.99 none -0.11 0.9 comparative 8-2 0, 4 1.09 1.25 0.88 significant +0.32 4.8 (Results) The samples N s 5-2, 6-2 and 7-2 of example 4 show a deformation which decreases after cutting thanks to equalization processing. On the contrary, sample N 8-2 of the comparative example has a greater deformation value than samples 5 to 7 of Example 3, although the value of the deformation itself decreases after equalization. Sample N 6-3 of the comparative example shows a variation (contraction) of the dimensions between two points at the shoulders and an increase in the angle of inclination of the thin part. This is due to the fact that the plastic strain value for equalization by

traction is greater than 1%.

Example 5

  (Preparation of a multi-gauge strip) A slab (150 mm thick, 500 mm wide, and 4,000 mm long) of

  C19210 (Cu-0, lFe-0.03P) is produced by semi-casting

  keep on going. The slab is hot rolled into a hot coil 15 mm thick. The hot winding is cold rolled into a sheet with a thickness of 2.6 mm, which is then subjected to a heat treatment at 500 ° C. for 2 hours. The heat treated coil is cold rolled into a sheet with a thickness of 2.0 mm. This sheet is split to form a 50 mm flat strip

  wide for multi-gauge bands.

  The flat strip is transformed into a multi-gauge strip by Pilger rolling and rolling with a grooved roller and a flat roller. The intermediate strip is annealed continuously at a speed of 13 m / s in an annealing furnace (at a temperature of 725 C and with a heating zone with a length of m). The annealed strip undergoes a final rolling with a grooved roller and a flat roller. Thus, the desired multi-gauge band specified below is obtained. Thickness of the thick part: 1.25 mm Thickness of the thin part: 0.40 mm Width of the thick part: 29 mm Width of the thin part: 28 mm Overall width: 75 mm Angle of the side wall of the part thick: 15 The intermediate multi-gauge strip is laminated under different conditions so the thin part varies in thickness. Annealing is carried out under different conditions so that the softening value varies. A finish rolling is carried out under different conditions so that the amount of work hardening varies and the hardness of the thin part varies. Table 5 shows the thickness of the thick part and the thin part of the intermediate multi-gauge band and the band

multiple calibers completed.

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Table 5

  Multiple gauge strip Intermediate multiple gauge strip terminated Thin part Thick part Thin part Thick part Example 5 9 0.48 mm 1.60 mm 0.40 mm 1.25 mm Example 10 0.80 mm 1.60 mm 0.40 mm 1.25 mm comparative 11 0.43 mm 1.60 mm 0.40 mm 1.25 mm (Hardness measurement) The multi-gauge strip prepared as mentioned above is examined with regard to the hardness (Hv) of the thin part and the hardness of the part

  thick. The results are shown in Table 6.

  In this example, the thin part and the thick part

have the same hardness.

  Sample N 10 of the comparative example is characterized in that the hardness of the thin part is much higher than that of the thick part. This is due to the fact that the thickness reduction is small during the rolling of the intermediate multi-gauge strip, the softening value is low during the annealing, and the thickness reduction during the finishing rolling is important (which leads to a

significant work hardening).

  Sample N 11l of the comparative example is characterized in that the hardness of the thin part is lower than that of the thick part. This is due to the fact that the reduction in thickness is important during the rolling of the intermediate multi-gauge strip, the value of the softening is important during the annealing, and the reduction in thickness during the rolling of finish is weak

  (which leads to less work hardening).

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Table 6

  N Hardness of the thin part Hardness of the thick part H1 / H2

(H1) (H2)

  Example 5 9 120 120 1.0 Example 10 145 120 1.21 comparative 11 104 120 0.87 (Results) The multi-gauge strips of the examples and comparative examples are transformed into connection grids by continuous stamping. The multi-gauge strips of Example 5 do not pose problems with stamping and lead gates

  resulting do not have a transverse curvature.

  On the contrary, the multi-gauge strips of the comparative example obstruct the stamping matrix, and the stamped connection grid (sample N 10) undergoes a transverse curvature and a twist. This can be attributed to a large residual stress. The multi-gauge strip (sample N 11) poses no problem with stamping but the punched connection grids undergo a slight transverse curvature. According to the present invention, it is possible to produce multi-gauge strips having a low residual stress value (deformation). Such multi-gauge strips contribute to the productivity and efficiency of pressing, mounting the transistors, and assembling the terminals, because they do not undergo deformation such as elongation, contraction, camber,

  transverse curvature and torsion.

* The multi-gauge strip of the present invention is laminated so that the stress distribution varies from the thin part to the thick part. Therefore, the thin part has a Hi hardness and the thick part has a H2 hardness so that the H1 / H2 ratio is in the range of 0.9 to 1.5. This value suggests that the multi-gauge strip has an adequately distributed residual stress and this value also makes it possible to evaluate whether or not the residual stress is adequately distributed. In accordance with the present invention, the multi-gauge strip is evaluated by measuring the offset between two points (which appears when cuts are made in the sample as specified) and by measuring the angle of inclination of the thin part. The results of the measurements make it possible to assess whether or not the stress is adequately distributed at the position where a residual stress tends to accumulate. This allows us to assess whether the given multi-gauge band

  may or may not be suitable for another production.

  In accordance with the present invention, the multi-gauge strip receives a tensile stress which produces plastic deformation in the range of 0.05 to 1% in the length direction. The tensile stress thus applied equalizes the multi-gauge strip having a residual stress and therefore minimizes the residual stress which has

accumulated during manufacturing.

Claims (6)

  1. Multiple gauge strip (1) having a cross section which comprises one or more thin parts (2) and thick parts (3) formed by rolling across its width, said cross section being uniformly continuous in the direction of the length, which is characterized in that the thin part (2) has a hardness Hi and the thick part (3) has a hardness H2, the ratio H1 / H2 being from 0.9 to 1.15.   2. Multiple gauge strip (1) according to claim 1, in which the thick part (3) is formed only at the center of the width and the thin parts (2) are formed on both sides of the thick part (3) and the cross section is uniform so that when the multi-gauge strip is cut lengthwise over 1.2 to 5 times its width in five positions, one in the center of the width, one on each side at the limit between the thin part (2) and the thick part (3), and one on each side at the edge of the thin part (2) to be split, the variability in size between the two points which are symmetrical with respect to the center of the width of the cutting surface is less than 0.15 mm at the end where cutting begins. 3. Multiple gauge strip (11) according to claim 1, in which two thick parts (13) are formed symmetrically, a thin part (12b) being formed at the center of the width, and thin parts (12a) being formed at the two outer edges of the thick parts (13), and the cross section is uniform so that when the multi-gauge strip is cut lengthwise over 1.2 to 5 times its width in five positions, one at center of the width, one on each side at the outer limit between the thin part and the thick part, and one on each side at the edge of the thin part to be split, the dimension variability between the two points which are symmetrical with respect to at the center of the width in the cutting surface is less than 0.15 mm at the end where cutting begins. 4. Multi-gauge strip according to claim 1, wherein the thick part is formed only in the center of the width and the thin parts are formed at both edges, and the cross section is uniform so that when the multi-gauge strip is cut lengthwise over 1.2 to 5 times its width in five positions, one in the center of the width, one on each side at the limit between the thin part and the thick part, and one on each side at the edge of the thin part to be split, the angle of inclination of the cut thin part is less than 4 relative to the horizontal line   at the end o begins cutting.   5. Multiple gauge tape according to claim 1, in which two thick parts are formed symmetrically, a thin part being formed in the center of the width, and thin parts are formed at the two outer edges of the thick parts, and the cross section is uniform so that when the multi-gauge strip is cut lengthwise over 1.2 to 5 times its width in five positions, one in the center of the width, one on each side at the outer limit between the thin part and the thick part, and one on each side at the edge of the thin part to be split, the angle of inclination of the thin cut part is less than 4 relative to the line   horizontal base at the end o begins cutting.   6. Multiple gauge strip having a cross section which has one or more thin portions and thick portions formed by rolling across its width, said cross section being uniformly continuous in length, said multiple gauge strip being equalized after rolling by application of a tensile stress which produces a plastic deformation corresponding to 0.05 to 1% of the elongation in the longitudinal direction.