FR2618020A1 - METHOD FOR MOUNTING SEMICONDUCTOR DEVICES AND DEVICE FOR CARRYING OUT SAID METHOD - Google Patents

Abstract

The invention relates to a method of mounting semiconductor devices. According to the invention, it consists in forming a connection strip in a wire 22 between two contact surfaces 1, 2 of the housing 3 and of the crystal 4 of the semiconductor device, by connecting the wire 22, with a welding tool 6 , at the contact surface 1, by driving the wire 22 through the welding tool 6 and by connecting it to the contact surface 2; the wire is driven along a path defining the shape of the future connection bar 5, forming a section 7 ascending from the contact surface 1, during the movement to meet one another of the tool welding 6 and the four-movement table 11 carrying the semiconductor device, an inflection point 8, at which the wire 22 is retained by the working member 33 of a retaining assembly 32 and a section 9, descending to the contact surface 2, the latter being done by lowering the welding tool 6, the working member 33 remaining stationary relative to the semiconductor device. The invention applies in particular to electronics.

Description

The present invention relates to welding during

  of semiconductor devices, and more specifically

  a method for mounting semiconductor devices and a device for producing it, used to form connection strips between contact surfaces of

  semiconductor devices and integrated microcircuits.

  There is now a range of semiconductor devices and integrated microcircuits, in which the connection strips between the contact surfaces must have a predetermined shape: to have rectilinear sections-and various angles of inclination of the bars relative to the connection plan. Such a shape of the terminal strips is essential to obtain better output characteristics of the devices

  semiconductors, especially for semiconductors

  in ultra-high frequency. To obtain semi-

  particularly reliable conductors, connection strips of guaranteed strength must be made between the contact surfaces. On the other hand, in semiconductor devices with high mounting density and with a large number of connection strips, it is profitable to

  identify welded connections of poor quality immediately

  after the formation of each bar.

  Methods of mounting semi devices

  conductors are known, which consist in forming a wire strip between the contact surfaces of the housing and the semiconductor crystal by connecting this wire by means of a welding tool to the first of these contact surfaces, to pass and train the wire through a welding tool along a path that consists of two ascending sections directed at an obtuse angle with respect to each other, to lower the wire towards the second contact surface without driving it and to connect to it (installation WB-1511, prospectus of the firm Kaiso Denki, Co. Ltd, Japan, 1977;

  author of USSR N 740448, 1978).

  The two ascending sections of the wire drive path are required to bend the wire to give a convex shape to the terminal strip, to avoid contact of the bar with other wiring elements and with the topology around the wires. contact surfaces. However, because of the irregular distribution

  mechanical properties of the wire along its length, in particular

  With regard to its plasticity, the bar may take an arbitrary form, which is why short-circuits may occur. On the other hand, almost every consecutive bar has a shape that differs from the previous one. The presence of two ascending segments of the path of the wire, the first of which lies at a right angle to the contact surface, reveals microcracks where the welded connection passes to the wire. These microcracks are due to the friction of the wire

  against the welding tool when driving the wire.

  On the other hand, the drive of the wire during the formation of the two ascending sections and its lowering to the second contact surface to be welded requires the bending several times of the wire at the mentioned places of passage of the wire to the connection , which becomes the cause, in addition to said disadvantage, of a degradation of the mechanical properties of the bar and, consequently, of the decrease of the

  quality of the assembly of semiconductor devices.

  Devices carrying out the indicated methods of mounting semiconductor devices are known, each having a base, on which a multi-motion table, a welding head with a vertical displacement control, in the welding tool of which is passed a wire from which connection strips are formed between the contact surfaces

  on the housing and on the crystal of semi-

  drivers, and a control and command block

welding head, are provided.

  In the device described in the aforementioned prospectus of the firm Kaiso Denki Co, it is the semiconductor device mounted on the table with several movements that moves according to the coordinates x, y, y (CP being the angle of rotation in the horizontal plane xy), and in the device described in the USSR author's certificate No. 740448, the semiconductor is fixed but the welding head is provided with commands for moving it according to the coordinates x, y, cp. formation of a connection strip by means of said devices is carried out, in both cases, for

  the essential, in the same way. The difference lies only

  the fact that in the first case, the vertical lifting of the welding tool is halfway up the connection strip to be formed, and in the second case,

  about a quarter of the height of the bar.

  The first of these devices, characterized by a greater height of the rise of the welding tool, in comparison with the second device, does not ensure the required quality of the assembly of the semiconductor devices because of the microcracks at the places of passage the wire solder connection, in addition, its efficiency is low because the length of the path of movement of the welding tool greatly exceeds the length of the bar

connection.

  In the second device, the disadvantages indicated are partially eliminated by reducing the height of the vertical rise of the welding tool, as a result, the amount of microcracks decreases and the efficiency of the device is thus improved. However,. the shape of the connection strips created with these devices depends on the uniformity of the distribution of properties

  of the wire along its length and remains arbitrary.

  On the other hand, there is known a method of mounting semiconductor devices, which consists in forming, between contact surfaces of the housing and the crystal of a semiconductor device, a connection strip in a wire which is connected to by means of a welding tool at the first of the contact surfaces, which is passed through the welding tool, and connected to the second contact surface (USSR author's certificate N 821,100,

published on April 15, 1981).

  In the described method, the yarn is driven along a path, which consists of an ascending section, at a sharp angle to the first contact surface, which allows the formation of microcracks to be excluded. place of passage of the welded connection to the wire, which are due to the friction of the wire against the welding tool during the vertical rise of the latter. However, there are microcracks due to the folding of the wire appearing when the wire is lowered towards the

  second contact surface without pulling it.

  In the process indicated, as well as in those indicated above, the shape of the connecting strip obtained, determined by the mechanical properties of the wire, is arbitrary. This leads to the appearance of shortcircuits in the wiring and topology caused by the terminal strip around the contact surfaces. Each consecutive bar, created by the method described, has a shape that differs from the previous one. On the other hand, during the formation of the connection strips between contact surfaces at different levels,

  the probability of occurrence of short circuits increases.

  The device for carrying out the method of mounting semiconductor devices comprises a base on which is mounted a two-movement table receiving semiconductors, on which is installed a carriage connected to a control provided to drive it in a moving movement. -and-comes-from the base, parallel to one of the horizontal axes of the table, and a welding head with a control allowing its vertical movement, through the welding tool which passes a wire to form connection strips between contact surfaces on the housing and crystal of the semiconductor devices, and a control block, whose outputs are electrically connected to the welding head, to its drive control in the vertical plane and to control the movement of the carriage back and forth (certificate

US 821100).

  In the device under consideration, the carriage moves relative to the base at an angle equal to the feed angle of the wire in the welding tool, which defines the angle of inclination of the ascending section of the path of the welding path. yarn training but this becomes the cause of a

  insufficient quality of mounting semi-automatic devices

  conductors. Although, in this device, there is no vertical rise of the welding tool, the length of the path of its displacement still exceeds the length of the terminal strip, the output of the

device remains insufficient.

  A particularly high reliability of the semiconductor devices assumes a quality control of the terminal strips, and in particular their mechanical properties. For this reason, after the formation of all the terminal strips, their quality is checked on a separate control device by applying a traction force to the terminal strip in one

  any point. Each connection strip of a device

  The semi-conductor is then oriented relative to the measuring assembly of the tensile force, and then the tensile force is applied. Such quality control is difficult, especially for high-density semiconductor devices, where the terminal strips

  are arranged close to each other. The applica-

  The stress on any point of a bar results in a change in its shape, and as a result, microcracks appear at the passage points of the wire at the welded connection. On the other hand, each welded connection is subjected to different tensile forces due to the different angles of inclination of the connection strip.

  relative to the contact surfaces of the housing and the crystal.

  Thus, the described control reduces the efficiency of the mounting method and the device for its realization because it is performed after the formation of all the terminal strips of the semiconductor device and,

  on the other hand, reduces the quality of editing.

  The aim of the invention is to create a method for mounting semiconductor devices and a device for producing it, in which the wire is driven along a path that makes it possible to form bars of

predetermined form.

  The problem solved is solved by the fact that, in a semiconductor mounting method which consists of forming, between the contact surfaces of the housing and the crystal of a semiconductor device, a connection strip in a wire, in connecting it by means of a welding tool to the first of these contact surfaces, in

  leading the wire through the welding tool and connecting it

  at the second contact surface, according to the invention, the wire is conducted in a path that defines the shape of the future terminal strip, first forming an ascending section starting from the first contact surface, then a point of inflection, which is formed by fixing the wire provisionally in its position at this point, and, finally, a second section, descending, up to the second contact surface, the descending section being formed with a force ensuring the deformation plastic wire at the point of inflection. It is rational to lead the yarn along a path, the ascending and descending sections of the future bar are at the same angle with respect to the corresponding contact surfaces, after the connection of the wire to the second contact surface. the welding tool is returned to the initial position by simultaneously applying to the connection strip a traction force at the point of inflection, the value of which ensures elastic deformation of the connection strip,

  and then, let that pulling force disappear.

  The problem is also solved by the fact that

  device for carrying out the device mounting method.

  semi-conductors, having a base on which

  mounted a table with several movements receiving

  semiconductor devices, and is installed a carriage, connected to a control of the movement back and forth relative to the base, parallel to one of the horizontal axes of the multi-motion table and a welding head, with a control for moving it vertically, through the welding tool from which a wire is passed to form connection strips between connection surfaces on the semiconductor device housing and on its crystal, as well as a control unit whose outputs are electrically connected to the welding head, to the control of its movement in a vertical plane and to the control of the reciprocating movement of the carriage, according to the invention, comprises a set retaining wire mounted on the base with a possibility to oscillate in a vertical plane parallel to the plane of movement of the welding head and whose working member cooperates with the wire during the formation of the descending section juice at the second contact surface of the terminal strip, and, connected to the wire retainer assembly, a displacement control in a vertical plane, electrically connected to an additional output of the control block, the multi-table movements being provided with controls in a horizontal plane, in a vertical plane, as well as an angular displacement control on a horizontal plane, electrically connected to other additional outputs of the control block. It is advantageous that the welding head is installed on the carriage with a possibility of oscillating in a plane parallel to the oscillation plane of the assembly.

retaining wire.

  It is advantageous that the restraint-wire assembly

  has a console, two points arranged horizontally

  fixed on the base, on which said console is mounted, an electromagnet fixed on the console and electrically connected to the corresponding additional output of the control block, two vertically arranged spikes and fixed on the console, an L-shaped lever to two arms, mounted on said vertical points and clamped by a spring against the console and cooperating with one of its arms with the armature of the electromagnet, the working member being connected to the other arm of the lever It is advantageous that the working member of the wire retainer assembly comprises a rod holder and a rod, arranged in a vertical plane, perpendicular to the plane of movement of the welding head, which consists of three sections, one of which is fixed to the support, a second is disposed in a plane parallel to the plane of movement of the welding head, at an obtuse angle relative to the first section, the third section being available at a right angle with respect to the second section and cooperating with the wire during formation of the section of the connecting bar down to the second contact surface, and a recess for receiving the second section of the rod be practiced in the body of

the welding tool.

  It is advantageous to provide the device with a set of measurement of the traction force connected to the yarn retaining assembly and. electrically connected

at the input of the control block.

  It is advantageous to provide the measuring assembly with the tensile force of an elastic element, on which is fixed the working member of the holding assembly of the

  wire, and a displacement sensor of this elastic element.

  The drive of the wire with a force ensuring its plastic deformation while simultaneously moving the welding tool and the semiconductor device after the first welding, as well as the retention of the wire at the point of inflection, allow to obtain bars of the desired shape between the contact surfaces and to exclude

  the appearance of the most frequent defect, which is the short-

  circuiting, by the bar, the topology and conductive tracks around the contact surface. This allows, moreover, to obtain an accurate reproducibility of the shape of the terminal strips, independently of the

  distribution of the mechanical properties of the yarn over its length.

  The position of the point of inflection and the angles of inclination

  The connection of the terminal strip with respect to the contact surfaces can be modified, which allows the assembly of semiconductor devices characterized by a significant difference in height of the contact surfaces of the housing and the crystal, without the bar of

  connection comes into contact with the crystal.

  The displacement of the welding tool on a path defining the shape of the connection strip makes it possible to improve the efficiency of the operation

  mounting of semiconductor devices.

  The formation of terminal strips with identical angles of inclination with respect to the contact surfaces, as well as the application of a traction force at the top of the jib of the connection strip, makes it possible to improve the quality of the devices. semiconductors having a high mounting density, due to the absence of significant changes in the shape of the terminal strip during the onset of tensile stress, which may result in the occurrence of microcracks at the passage locations weld wire, as well as through weld connections obtained, which have guaranteed properties

mechanical resistance.

  The application, to carry out the control, of a traction force on the terminal strip, just before the formation of the next terminal strip, makes it possible to reduce the time and the means necessary for mounting the semiconductor devices having a large number of

connection strips.

  The invention will be better understood, and other purposes, features, details and advantages thereof

  will become clearer during the description

  explanatory text which will follow with reference to the accompanying schematic drawings given solely by way of example illustrating an embodiment of the invention, and in which: - Figure 1 shows a part of a semiconductor device with surfaces of contact and a connection strip between them, formed by a method according to the invention; FIG. 2 shows an overall view of a device for mounting semiconductor devices (in perspective), according to the invention; FIG. 3 shows the block diagram of a device for mounting semiconductor devices, according to the invention; - Figure 4 shows the assembly of Figure 2, on an enlarged scale, according to the invention; and FIG. 5 shows a measuring assembly of the tensile force, on an enlarged scale, according to the invention.

- 2618020

  The method of mounting semi-automatic devices

  drivers consists of the following. Between contact surfaces 1 (FIG. 1) and 2 of the housing 3 and the crystal 4 of a semiconductor device, a connection strip 5 is formed into a wire by connecting the latter to the contact surface I by means of a welding tool 6 driving the wire through the welding tool 6 in a path that defines the shape of the future terminal strip 5, forming an ascending section 7 starting from the contact surface 1, a point of inflection 8, at which the wire is retained,

  and a section 9 going down to the contact surface 2.

  Then, the wire is connected to the contact surface 2 of the

  crystal 4 of the semiconductor device. The section descends

  9 is formed with a force ensuring its deformation at

inflection point 8.

  The wire is conducted along a path whose ascending sections 7 and 9 downward are arranged under a

  same angle with respect to the corresponding contact surfaces

  After connecting the wire to the second contact surface 2, the welding tool 6 is brought into the initial position and a pulling force P reaching a value of one to one is applied simultaneously to the point of inflection. elastic deformation of the connecting strip 5, then, the traction force P is suppressed. When the angles oC are equal, the traction force P creates reactions P1 and P2 identical to the connections

corresponding welded joints.

  The device for mounting semiconductor devices comprises a base 10 (FIG. 2) on which is mounted a four-movement table 11, which

  receives a semiconductor device (conventionally

  tionally by a dashed line on the drawing).

  On the base 10 is mounted, on guides 12, 13, a

  cart 14 connected to a command 15 involving him a movement

  back and forth from the base, parallel to one of the horizontal axes of the four-movement table (in the variant described, the y-axis). The control 15 is made with a stepper motor mounted at the base 10 and

  the carriage 14 is connected to the base 10 by a spring 16.

  The carriage 14 is connected to the welding head 17, provided with a control 18 for moving in a vertical plane, which, in the variant described, is perpendicular to the x-axis. The control 18 is made with a stepper motor mounted on the carriage 14, and the welding head 17 is tightened against

this control by a spring 19.

  The welding head 17 comprises an L-shaped bracket 20, connected to the carriage 14 and a welding tool 6, fixed to a tool holder 21 and connected to the carriage 14. The tool holder 21, in the variant described of the device, represents in itself an ultrasonic vibration converter. Through the welding tool 6 passes a wire 22 to form a connection strip 5 between the contact surfaces 1,2 of the housing 3 and the crystal 4 of the semiconductor device, respectively. The wire 22 is fed to the welding tool 6

  from a reel (not shown in the drawing).

  The welding head 17 also comprises a feeding and breaking assembly of the wire which comprises a

  lever 23 connected by a spring 24 to the console L 20.

  On the lever 23 is fixed an electromagnet 25 provided to open jaws 26 mounted on the L-lever 20 with the possibility of pivoting. The jaws 26 are connected to the electromagnets 27, 28 ensuring the advance and rupture of the wire 22 by the jaws 26. On the other hand, on the L-shaped bracket 20 is fixed a contact 29 of a "tool-piece" contact sensor (not shown in the drawing) and an assembly creating the welding force in the described variant of the device, which comprises a stirrup 30, fixed at one end to the L-shaped bracket 20, and a spring 31, connecting the other end of the stirrup 30 to the tool holder 21

of the welding tool 6.

  In the device there is a wire retainer 32 mounted on the base 10 with the possibility of oscillating in a vertical plane parallel to the plane of movement of the welding head 17, i.e. perpendicular to the x axis. The working member 33 of the assembly 32 for retaining the wire cooperates with the wire 22 during the formation of the section 9 of the terminal strip 5

  down to the contact surface 2 of the crystal 4.

  The wire retention assembly 32 is provided with a control 34 of the displacement in a vertical plane, perpendicular to the x axis. The control 34 is made with a stepper motor installed on the base 10, the assembly 32 retaining the wire

  being connected to this motor via a spring 35.

  The four-movement table 11 is equipped with

  commands 36, 37 for traveling in a horizontal plane

  in the direction of the x and y axes and moreover, a control 38 for the rotation in the horizontal plane with respect to the z-axis and a control 39 for moving in a vertical plane, in the direction of the z axis. The device also comprises a control block 40 (FIG. 3), of which an input 41 is connected.

  electrically to the contact 29 of the contact sensor "tool-

  "while its outlets 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 are respectively electrically connected to the control 15 of the movement of the carriage back and forth, to the control 18 of displacement of the welding head, to the electromagnets 25, 27, 28, to the control 34 for moving the assembly 32 for retaining the wire and to the controls 36, 37,

  38, 39 moving the four-movement table 11.

  As indicated above, the tool holder 21

  (Figure 2) the welding tool consists of a

  wirer of infrasonic oscillations, connected to the output of a generator 52 (FIG. 3), the input of which is connected

  at an output 53 of the control block 40.

  The welding head 17 (FIG. 2) is mounted on the carriage 14 with the possibility of oscillating in a plane parallel to the plane of oscillation of the assembly 32 for retaining the wire, that is to say, perpendicular to the x axis. In the variant described of the device, the possibility of oscillating is conferred on the head 17 thanks to

  its mounting at points 54, 55 fixed to the carriage 14.

  In the variant described of the device, the assembly 32 retaining the wire has two tips 56, 57 arranged horizontally, fixed on the base 10, between which is mounted a bracket 58. On the console 58 is fixed an electromagnet 59 with 60. On the other hand, vertically arranged tips 61, 62 are mounted on the console 58, on which is mounted, with the possibility of oscillating in a horizontal plane, perpendicular to the z-axis, an L-shaped lever. two arms 63, connected by a spring 64 to the console 58. On one arm of the lever with two arms 63 is mounted the working member 33 of the assembly 32 retaining the wire, while the other arm of this lever 63 cooperates with the armature 60 of the electromagnet 59 electrically connected to an output 65 (FIG.

order 40.

  The working member 33 (FIG. 2) of the wire retainer assembly 32 comprises a rod holder 66 (FIG. 4).

  and a rod 67 arranged in a vertical plane, perpendicular

  on the plane of movement of the welding head 17 (FIG. 2). The rod 67 (FIG. 4) consists of three parts: a first part 68, fixed to the rod holder 66, a second part 69, arranged on a plane parallel to the plane of movement of the welding head 17 (FIG. 2), at an obtuse angle I '(FIG. 4) with respect to the first portion 68, and a third portion 70 at a right angle) relative to the second portion 69. This portion 70 of the rod 67 cooperates with the wire 22 during the formation of the second stretch 9 going down to the

  second contact surface 2, - of the terminal strip 5.

  In the body of the welding tool 6 is arranged a recess 71 to receive the second part 69 of the

stem 67.

  The device also comprises a set 72 for measuring the tensile force, connected to the assembly 32 retaining the wire. The measuring assembly72 comprises an elastic element 73 (FIG. 5) on which is fixed the working member 33 (FIG. 2) of the assembly 32 which is

  wire or rod holder 66 (FIG. 5), and a sensor 74 of the displacement

  cement of the elastic element, sensor whose output is electrically connected to an input 75 (Figure 3) of the control block 40. The elastic element 73 (Figure 5) has the shape of a blade, fixed by its ends between two pairs of sconces 76, one of which is fixed to the L-shaped lever 63 (FIG. 2). In the variant described of the device, a tensometric sensor mounted on the element is used.

elastic 73.

  The device for carrying out the method of mounting semiconductor devices operates in the same way

  next. After the installation of a semi-

  4, the latter, under the action of the controls 36, 37, 38, moves the semiconductor device according to the x, y, CP coordinates until the center of the first contact surface 1 of the housing 3 of the semiconductor device coincides with the vertical axis of the welding tool 6. Under these conditions, the working member 33 of the assembly 32 retaining the wire is under the the working end of the welding tool 6. After stopping the four-movement table 11, on orders from the control block 40 (FIG. 3) provided by its outputs 43, 47, the controls 18 and 34 of moving in a vertical plane, respectively, of the welding head 17 (Figure 2) and the assembly 32 retaining the wire, lower the tool holder 21 of the welding tool with the wire 22 to its entrance in contact with the first contact surface 1, when an electrical signal from the contact 29 of the contact sensor "tool-p "is applied to the input 41 (Figure 3) of the control block 40. Simultaneously, the working member 33 (Figure 2) of the assembly 32 retaining the wire is brought into the working position (the position of work is somewhat above the level of training height of the bar of

  connection 5). Simultaneously with the beginning of the movement

  commands 18, 34, on orders from the control block 40 (FIG. 3) provided by its outputs 45, 46, 65, the electromagnets 27, 28, which supply and break the wire 22. ( 2), are actuated, as well as the electromagnet 59 which pulls the working member 33 out of the wire retainer 32 from beneath the welding tool 6. When the welding tool 6 comes into contact with the contact surface 1, the tool holder 21 stops, while the L-shaped console 20 continues to descend and consequently the contact 29 of the sensor of the "tool-workpiece" contact opens. Then, on an order from the control block 40 (FIG. 3), the control 18 (FIG. 2) of vertical displacement of the welding head stops and the welding tool 6 connects the wire 22 to the contact surface 1 by sending an ultrasonic pulse from

  generator 52 (FIG. 3) via the carrier

  21 (Figure 2) of the welding tool on an order from the output 53 (Figure 3) of the control block 40 and thanks to the welding force created by the spring 31

(Figure 2).

  During welding, the speeds and the discrete values of displacement of the stepper motors of the movement control 37 of the four-movement table (movement of the four-movement table 11 according to the y-coordinate) are calculated. the control 15 of the reciprocating movement of the carriage (displacement of the welding head 17 according to the coordinate y), of the control 18 of the displacement of the welding head in the vertical plane (displacement of the welding head 17 according to the coordinate

  z), the control 39 of the four-movement table 11.

  (displacement according to the z coordinate). The calculation indicated is carried out starting from the following condition: during the mutual displacement of the welding tool 6 and the semiconductor device, the wire 22 must be led through the welding tool 6 in a straight line and under a

  assigned angle relative to a horizontal plane.

  After welding, the jaws 26 loosen under the action of the electromagnet 25, the electromagnet 27 is de-energized, bringing the jaws 26 to the neutral position by means of the spring lever 23, the control block 40 (FIG. 3) delivers, by its outputs 49, 42, 43, 51, commands for displacements applied to the controls 37, 15, 18, 39. The four-movement table II (FIG. 2) and the welding tool 6 are then move to meet each other. Thus, the wire 22 is driven during the reciprocal movement of the welding tool 6 and the semiconductor device, to form the section 7, rising from the first contact surface 1, of the connection strip. 5. When the wire is pulled to the required height, corresponding to the height of the terminal strip 5, the body of. Work 33 of the retaining assembly 32 having descended to the same height on an incoming order from the control block 40 (FIG. 3) and coming from its output 65, the electromagnet 59 of the assembly 32 (FIG. 2) retaining plate is de-energized and, under the action of the spring 64, the two-arm L-lever 63 pivots on the tips 61, 62, and the working member, the rod 67 (FIG. 4), in particular its part 70, is fed under the wire 22 by forming a point of inflection 8, to which the wire 22 is retained. On orders arriving from the control block 40 (FIG. 3), coming from its outlets 43, 42, the welding head 17 (FIG. 2) with the welding tool 6 is lowered by the action of the control 18 and simultaneously the carriage 14 moves in the

  same meaning, indicated above, by the action of the command 15.

  The working member 33 of the assembly 32 retaining the wire is then stationary relative to the semiconductor device. During the movement of the welding tool 6 down towards the second contact surface 2, that of the crystal 4, when the descending section 9 of the terminal strip 5 is formed, the wire 22 is driven with a force determined by the friction of the wire against the welding tool 6, which ensures a plastic deformation of the wire 22

at inflection point 8.

  When the welding tool 6 touches the contact surface 2 of the crystal 4, the tool holder 21 stops, while the L-shaped console 20 continues to lower and, consequently,

  the contact 29 of the "tool-workpiece" contact sensor opens.

  On the orders arriving from the control block 40 (FIG. 3) provided by its outputs 42, 43, the commands 15, 18 stop. Then, the welding is carried out as described

above.

  After completion of the welding on orders of the

  control block 40 provided by its outputs 44, 46, the elec-

  the magnet 30 (FIG. 2) for clamping the jaws 26 and the electromagnet 28 'for breaking the wire are actuated. Under the action of the spring 24, the lever 23 rotates the jaws 26 to thereby break the wire 22 after the second weld. During the formation of the connection strip 5, the wire 22 is driven through the welding tool 6 along a path defining the shape of the connection strip 5, forming the ascending section 7 from the first surface of the contact 1, then the

  point of inflection 8, and finally the second section 9, descending

  to the second contact surface 2. The driving of the wire 22 by simultaneously moving the welding tool 6 and the semiconductor device, after the first welding, makes it possible to exclude the appearance of cracks where the wire 22 passes first welded connection, that is to say to exclude the most common defect arising during the assembly of semiconductor devices, which is caused by multiple bends of the wire 22 at this location. On the other hand, the driving of the wire 22 with a force ensuring its plastic deformation makes it possible to obtain the strict reproducibility and the necessary shape of the connecting strips 5. The position of the inflection point 8 can be modified as well as the angles of inclination of the sections 7 and 9 with respect to the horizontal plane, which

  is very important during the assembly of semi-automatic

  drivers, in which there is a significant difference

  between the heights of the contact surfaces 1 and 2,

  of the case 3 and crystal 4. This possibility

  makes it possible to increase the quality of assembly of semi-

  drivers by reducing the number of defects such

  that short-circuits wire 22 - conductive tracks and wire 22 -

  topology close to the contact surfaces 2 of the crystal 4.

  The fact that during the formation of the connection strip 5, the welding tool 6 follows a trajectory totally corresponding to the shape of the future terminal strip 5 is also very advantageous since it allows to significantly reduce the duration of the formation of all the terminal strips between the contact surfaces

of the semiconductor device.

  Most types of semiconductor devices

  They are subject to stringent requirements concerning the reliability of assembly, in particular, they must necessarily undergo a control - not destructive of the solidity of the connections. For this purpose, for the wire 22, when it is connected by the welding tool 6 to the second contact surface 2, on an order of the control block 40 (FIG. 3) delivered by its output 43, the control 18 the movement of the welding head moves the welding tool 6 (FIG. 2) and returns it to the starting position. Simultaneously, from the output 51 (FIG. 3) of the control block 40 comes an order to the control 39 (FIG. 2) of displacement along the z axis of the four-movement table 11 which lowers the latter, carrying the semi-automatic device. -driver. Then because the working member 33 of the assembly 32 retaining the wire, and in particular, the third portion 70 (Figure 4) of the rod 67, is at point 8 of inflection, it is in this point B that a traction force P is applied to the connection strip 5. During the descent of the connection strip together with the semiconductor device, the elastic element 73 (Figure 5) of the set of measurement of the tensile force is bent. According to the displacement value of the elastic element 73, the value of the tensile force applied to the connection strip 5 (FIG. 4) is evaluated by means of the sensor 74 of the displacement of the elastic element. The tensile force can also be applied by moving the work member 33 (FIG. 2) upwardly from the thread retainer assembly 32,

  the four-movement table 11 remaining stationary.

  During the formation of the connection strip 5, at the passage places of the welded connection to the wire 22 and near the point of inflection 8, thanks to the elastic properties of the wire 22, radial inflections occur. Therefore, when the traction force increases, at the initial moment, the traction of the wire 22 occurs in the field of elastic deformations, and when the tensile force continues to grow, there is an inflection of the wire 22 relative to the welded connections near the contact surfaces 1 and 2 and with respect to the third portion 70 (Figure 4) of the rod 67, which fixes the inflection of the wire 22 at the point of inflection 8, that is to say that is, there is a plastic deformation of the connection strip 5, and as a result, the ascending and descending sections 7 and 9 of the connection strip become rectilinear. When the solicitation of the connection strip 5 continues, secondary elastic defibrillation occurs. If a

  such value of the tensile stress, causing the deformation

  secondary plastic of the terminal strip 5, is reached, it can cause its rupture. Therefore, it seems reasonable to apply to the terminal strip a tensile stress not exceeding the value at

  which produces a secondary plastic deformation.

  However, this effort must be sufficient to detect the

  welded connections whose strength is insufficient.

  Thus, the proposed device allows to simultaneously achieve the formation of the connection strips 5 and non-destructive control of their strength by applying the required traction force. For this purpose, after the connection of the wire 22 to the first contact surface i (FIG. 2), the wire 22 is driven at such speeds that the segment 7 ascending from the first contact surface 1 and the descending section 9 towards the second contact surface 2 of the wire drive path 22 and, consequently, the path of the displacement of the welding tool 6, form JC angles (FIG. 1)

  identical, with the horizontal plane.

  At the moment when the assigned traction force P is reached, at the inlet 75 (FIG. 3) of the control block 40 arrives, from the measuring assembly of the traction force 72 (FIG. 5). in particular, the sensor 74 of the displacement of the elastic element, a suitable information, after which the control block 40 (FIG. 3) delivers, by its output 51, an order to stop the movement of the control 39 (FIG. ) of the movement of the four-movement table 11 and for the maintenance of the connection strip 5 under the action of a tensile force equal to P for 5 to 10 ms. During this solicitation, through the input 75 in the control block 40 (Figure 3), arrives information on the value of the tensile force from the sensor 74 of the displacement of the elastic member. If a sudden change (a decrease) in the tensile force is recorded, this means that the connection bar 5 (FIG. 2) has not withstood the tensile force, that is to say that it broke. If no information comes from the sensor 74 to the control block 40 (Figure 3), indicating a sudden decrease in the tensile force, it means that the terminal strip 5 (Figure 2) is sufficiently solid. Therefore, if the terminal strip 5 has not supported the rated traction force, the control block 40 (Figure 3) delivers, through its output 47, an order to the control 34 for the displacement of the assembly 32 (FIG. 2) holding the wire up to the working position and through the outlet 51 (FIG. 3), at the control 39, for bringing the four-movement table 11 into the initial position (FIG. ). Simultaneously, the control block 40 (FIG. 3) delivers, via its output 65, an order for the engagement of the electromagnet 59, the armature 60 (FIG. 2) of which pivots the lever with two arms in L-shape. 63 on the tips 61, 62. The portion 70 (Figure 4) of the rod 67 then out from below the terminal strip 5. Then, the semiconductor device is removed from the four-movement table

  11 (Figure 2) and place a semi-moving device

  driver. The work cycle starts again.

  If the bar 5 has withstood the tensile force, the semiconductor device is removed on an order from the control block 40 (FIG. 3) coming from its output 51 and going to the control 39 of the four-movement table 11 (FIG. figure 2) which moves the latter and brings it back to the initial position. After that, the electromagnet 59 is de-energized, the armature 60 rotates the two-arm lever L 63-on the tips 61, 62 and the third part 70 (Figure 4) of the rod 67 of the organ 33 at the same time, the control block 40 (FIG. 3) delivers commands through its outputs 47, 42 to the control 34 to bring the set 32 (FIG. 2) for retaining the wire. in the working position and the control 15 to bring the carriage 14 to the initial position. On the orders of the control block 40 (FIG. 3) delivered by its outputs 48, 49, 50, the four-movement table 11 (FIG. 2), under the action of the controls 36, 37, 38, moves the semi-automatic device conductor according to the coordinates x, y, çp by aligning the vertical axis of the welding tool 6 with the center of the other contact surface of the housing of the same semiconductor device. Then, the formation cycle of wire connection and control strips

their solidity is repeated ,.

  Thus, the formation of the connection strips

  between the contact surfaces of a semi-

  conductor forming identical angles with a horizontal plane and the application of a tensile force at the point of inflection of the terminal strip immediately after its formation improves the quality of the assembly of semiconductors through the manufacture of connecting strips having guaranteed mechanical strength characteristics, each welded connection on the case and on the crystal being tested with the same effort of

  solicitation, and also, thanks to the absence of any changes

  the shape of the terminal strip when applying the tensile force, excluding the occurrence of microcracks at the

wire in soldered connections.

  The tensile force is applied by means of the wire retainer cooperating with the wire during the formation of the terminal strip, which allows the use of the proposed method and the device for the connection. mounting semiconductor devices with high mounting density, in which the tool for applying the tensile force can not be brought because of neighboring connection strips being very close. On the other hand, the tensile force is applied to the terminal strip to control its mechanical properties when the welding tool is returned to the initial position, which allows

  to improve the efficiency of the assembly of semi-

conductors.

Claims (8)

- CLAIMS -   1. Method for mounting semi-automatic devices   conductors, of the type consisting of forming between surfaces   contact of the housing and the crystal of a semi-   conductor, a wire connecting bar by connecting it, with a welding tool, to the first of said contact surfaces, bringing the wire through the welding tool and connecting it to the second contact surface, characterized in that the wire (22) is brought along a path which defines the shape of the future connecting strip (5), forming a section (7) rising from the first contact surface (1), a point of inflection (8), to which the wire (22) is retained, and a descending section (9), up to the second contact surface (2), the descending section (9) being formed with a force ensuring plastic deformation of the wire (22) inflection point (8).   2. Method of mounting semi-devices   conductors according to claim 1, characterized in that   that the driving of the wire (22) is carried out along a path   the upward and downward sections (7, 8) of the terminal strip are arranged at equal angles with respect to the corresponding contact surfaces (1, 2) after connection of the wire (22) to the second contact surface ( 2), the welding tool (6) is returned to the initial position by simultaneously applying to the connection strip (5) a traction force at the point (8) of inflection up to the value at which the * elastic deformation of the terminal strip (5) and   the traction force is removed.   3. Device for carrying out the semiconductor mounting method according to claim 1, of the type comprising a base, on which is mounted a table to   four movements to install semi-   drivers and a carriage, connected to a motion control   back and forth from the base, is placed parallel-   one of the horizontal axes of the four-movement table, and has a welding head with a control for moving it on a vertical plane, in the welding tool from which a wire passes to form the connecting strips between the contact surfaces on the housing and on the crystal of the semiconductor device, and   a control block, the outputs of which are electrically connected   the welding head, the control of its movement   vertical cement and the control of the reciprocating motion of the carriage, characterized in that it comprises a set (32) of wire retainer, mounted on the base (10) with a possibility to oscillate in a plane vertical, parallel to the plane of movement of the welding head (17), whose working member (33) cooperates with the wire (22) during formation of the section (9) of the terminal strip (5) down to the second contact surface (2), and a control (34) of displacement in a vertical plane, connected to the wire retainer assembly (32) and electrically connected to an additional output (47) of the block control device (40), the four-movement table (11) being further provided with controls (36, 37, 39) for horizontal and vertical displacements and a control (38) for the rotation in the horizontal plane, electrically connected to other additional outputs   (48, 49, 51, 50) of the control block (40).   4. Device according to claim 3, characterized in that the welding head (17) is mounted on the carriage (14) with the possibility of oscillating in a parallel plane   to the oscillation plane of the wire retainer assembly (32).   5. Device according to any one of   Claims 3 or 4, characterized in that the assembly (32)   retaining means comprises a bracket (58), two horizontally disposed spikes (56, 57) fixed to the base (10), on which the bracket (58) is   magnet (59) attached to the console (58) and electrically connected   at the corresponding additional output (65) of the control unit (40), two vertically arranged spikes (61, 62) mounted on the bracket (58), a two-lever   L-shaped arm (63) mounted at the vertically disposed points (61, 62)   connected by a spring to the console (58) and   cooperating with one arm with the armature (60) of the electro-   magnet (59), the working member (33) being connected to   the other arm of the two-arm L-lever (63).   6. Device according to claim 5, characterized in that the working member (33) of the assembly (32) for retaining the wire comprises a rod holder (66) and a rod (67) disposed in a plane vertical, perpendicular to the plane of movement of the welding head (17), said rod consisting of three parts (68, 69, 70), the first of which is fixed in the portetige (66), the second is arranged in a plane parallel to the plane of movement of the welding head (17), at an obtuse angle with respect to the first portion, and the third is disposed at a right angle to the second portion (69) and cooperates with the wire (22). ) during the formation of the descending section (9) of the connecting strip (5) up to the second contact surface (2), a recess (71) being arranged in the body of the welding tool ( 6), by   which passes the second portion (69) of the rod (67).   7. Device according to any one of the   cations 3 to 6, characterized in that it comprises a set (72) for measuring the tensile force connected to the assembly (32) retaining the wire and electrically connected to an input (75) of the control block (40).   8. Device according to claim 7, characterized in that the measuring assembly of the tensile force (72) comprises an elastic element (73) to which is fixed the working member (33) of the assembly ( 32) and a sensor (74) for moving the elastic member.