APPARATUS FOR AUTOMATIC SOLDERING

Abstract: An apparatus for automatic soldering of lead pins dis­ tributed on a packaged IC chip in bilateral or quadrilateral parallel rows with corresponding contact pins, which are dis­ tributed on a substrate printed circuit board in rows cor­ responding to said rows of lead pins and have preliminarily been pasted with solder, by the process steps of placing the packaged IC chip on the substrate board, positioning said packaged IC chip so as to align each lead pin in said rows on said packaged IC chip with corresponding contact pin in said rows on the substrate board and exposing the lead pin together with the contact pin aligned therewith to an irradia­ tion of heat ray beam emitted from a heat ray soldering head and focussed thereto as a line focus in a form of a segment of a line corresponding to the soldering line defined so as to encompass one of said parallel rows of lead pins on the pack­ aged IC ship aligned with corresponding row of contact pins on the substrate board, which apparatus comprises, a memory-operation section (A), a control section (B) and an actuation section (C), wherein the control section (B) provides its function under subordination to the commands from the memory-operation section (A) and governs the actuation sec­ tion (C), so as to move the heat ray soldering head along x- and/or y-coordinates on the substrate board to each preset position for the packaged IC chip to be worked by soldering and so as to effect the soldering of each spot, where an elec­ tric junction is to be built up, by said heat ray beam focussed as line focus, under programmed control.

Description: The present invention relates to an apparatus for automatic soldering of, for example, lead pins distributed in bilateral or quadrilateral parallel rows on a semiconductor chip, such as, packaged IC, with correspondingly distributed contact pins on a substrate plate of printed circuit board by heat ray irradiation. More particularly, the invention concerns an automatic soldering apparatus which operates on at least a pair of parallel soldering lines each encompassing each of the bilateral or quadrilateral parallel rows of lead pins on a flat packaged IC by irradiating each of the lead pins and corresponding aligned contact pins with a heat ray beam from a heat ray soldering head. The beam is focussed as a line focus in the form of a segment of a line corresponding to the soldering line, and adjustment and positioning of the irradiating line focus are effected automatically by the programmed control of a mechanical actuator to cause the heat ray soldering head to shift in x- and/or y-coordinate direction and to turn the heat ray soldering head to y- or x-coordinate direction on the substrate plate. Conventional processing apparatus for mounting such packaged IC on a substrate plate employ, for example, heating by soldering iron, heating by pulse heater, so-called infrared heating reflow method, hot-air process (Denshi-Zairyo - Materials for Electronics - (1985), No. 2, p 37) and, as a recent proposal, laser beam heating (Keikinzoku-Yosetsu - Welding of Light Metals - Vol. 17, No. 1 (1979)). These conventional techniques are accompanied by problems: For example, a small IC package may often suffer from soldering failures, such as, faulty alignment of the lead pins with the contact pins, short-circuiting between the pins caused by excessive pasting of solder and so on, in particular when the lead pins of the IC package are densely distributed, e.g. on small size IC packages where the pitch or interval of the lead pins is quite small. Thus, a highly accurate technique for printing of solder paste and mounting and positioning of the IC package on the substrate plate and so on, is required. On the other hand, due to the recent trend of employment of substrate materials of considerably low heat stability, such as, paper, phenol resin etc., the substrate plate may suffer thermal damage, especially when infrared heating reflow technique, hot-air process or laser beam heating is employed. GB-A-1,151,330 (Western Electric) discloses apparatus for soldering leads of integrated circuits to contact areas which uses a vacuum and flexible cover to maintain the IC and circuit board in fixed relation and solders the leads using radiant energy such as IR radiation directed onto the whole circuit or focussed radiation, e.g. from a laser, directed onto the junctions. In case of laser beam heating, in which the laser beam is guided by a flexible light conduction fiber and the beam emitting end thereof is moved to scan or track the soldering line by a beam scanning robot so as to focus the laser beam onto each required soldering point, the beam emission head does not suffer from ageing or time change by, for example, formation of surface oxide layer and so on, and thus, stable soldering is attained, as contrasted with the case of heating by thermal conduction using, such as, soldering iron etc. Here, however, an intensive irradiation of laser occurs also in the vicinity of the contemplated soldering spot by the diffraction of laser light, resulting in an unexpected damage of the packaged IC and the substrate printed circuit board. In particular, in the case of packaged IC having quadrilateral rows of lead pins, there exists no processing technique in which the soldering works in directions of x- and y-coordinates along the soldering lines are effected automatically in successive procedures. According to the present invention, there is provided an apparatus for automatic soldering of contact pins on items to connection leads on a workpiece, comprising a lamp head carrying one or more heat ray lamps for irradiating with a line-focused heat ray beam the junction of the connection leads and the contact pins aligned therewith, characterized in that it further comprises; an actuator (C) for moving the lamp head along first and/or second directions relative to the workpiece and elong a direction perpendicular to the workpiece; a controller (B) for controlling the actuator (C) to move the lamp head to each of a number of pre-programmed soldering positions and at each position to position the lamp head at such a distance from the junction that the junction is irradiated with a defocused part of said heat ray beam and to illuminate the lamps at a low level to preheat the junction and then to move the lamp head to such a position that the line focus of said heat ray beam is focused on the said junction and to increase the illumination level to solder at the position using said line-focused heat ray beam and then to return the head to the preheat position and reduce the illumination of the lamps and to repeat the head positioning and illumination operation at each position in turn whereby a pre-programmed sequence of soldering operations are performed; and a memory-operation section (A) which can be pre-programmed with data to be provided to the controller (B) and representative of the pre-programmed sequence of soldering operations. With the present invention therefore, packaged IC's etc., may be automatically soldered by the use of a pair of heat ray beams each focussed onto the spot to be soldered, and the heat ray soldering head carrying the heat ray beam sources may shift in the direction of x- and/or y-coordinates and turn to the direction of y- or x-coordinates. The present invention thus attains high efficiency of soldering while reducing the occurrence of faulty connections due to excessive pasting of solder, even for a packaged IC having a dense distribution of lead pins. The invention will further be described by way of non-limitative example with reference to the accompanying drawings in which: Fig.1 depicts packaged IC chips placed on the substrate board for working by the apparatus according to the present invention, in a plan view. Figs.2(a) and 2(b) each show a different embodiment of the heat ray soldering head according to the present invention both in a front view. Fig. 2(c) is a vertical section of an embodiment of the heat ray beam restriction system. Fig.3 is an operation control system block chart for the apparatus according to the present invention. Figs.4(a) to 4(f) are each an explanatory diagram explaining the essential construction of each elementary part of the apparatus according to the present invention. Fig.5 is an operation sequence diagram for the apparatus according to the present invention. In. Fig. 1, three flat packaged IC chips 2, 2′, 2″ each provided with quadrilateral parallel rows of lead pins 2a, 2a′ 2a″ are placed on a substrate plate of printed circuit board 1 in predetermined positions which are displaced with each other in both the directions of x- and y-coordinates. Each lead pin in the rows on each packaged IC chip is soldered with corresponding one of contact pins on the substrate board, which are distributed also in parallel rows correspondingly aligned with said quadrilated rows of lead pins, by a pair of heat ray beams from a pair of heat ray lamp units 3, 3 each having a lamp head 4. Each of the pair of lamp heads 4, 4 is supported pivotingly by a pivot joint 5 and is permitted to slide so as to close to or depart from each other for adjusting the width W1 between the pair of line focuses 6, 6. This width W1 between the pair of line focuses is so adjusted that it coincides with the distance W2 between the pair of parallel rows of lead pins 2a and 2a extending in the direction of x-coordinates on the flat packaged IC chip 2 shown in Fig. 1. When the rows of lead pins extending in the direction of y-coordinates are to be worked by soldering, the soldering head is turned rectangularly to the direction of y-coordinates, so as the pair of line focuses 6, 6 to align with said pair of rows of lead pins extending in y-coordinate direction. This rectangular turning of the soldering head is effected by a rotor 50 supported on a support plate 113 by a bearing means. The rotor 50 has a gear wheel 51 which is held in engagement with another gear wheel 52 driven by a rotary actuator 53 disposed on a support plate 113. The support plate 113 is connected to the piston rod 45 coupled to an air cylinder 46 of a pneumatic unit for effecting vertical movement. Underneath the gear wheel 51 is arranged fixed thereto a mechanism for effecting adjustment of the width W1 between the pair of line focuses 6, 6, which consists of two ball screw shafts 25 and 26 each guided rotatably in a guide member 116, 116 and threaded in reverse sense with each other, as shown in Fig 4(b). On each of the ball screw shafts 25 and 26 is mounted a slide member 117 under engagement with the screw thread. The opposing inner ends of the ball screw shafts are provided each with a bevel gear 28, 29 fixed thereto and held in engagement with another bevel gear 30 disposed at the lower ends of the rotor 50 and permitted to rotate by a stepping motor, whereby the slide members 117, 117 are slid so as to close to or depart from each other, in order to adjust the width W1 between the line focuses 6 and 6. The length L1 of each line focus 6 is adjusted automatically by sliding a pair of shield members 32, 32; 33, 33 arranged in the heat ray emission opening 7 of the heat ray lamp unit 4, so that it coincides with the length L2 of the row of lead pins 2a. Thus, each of the pairs of shield members 32, 32 and 33, 33 will function to effect adjustment of the length of each line focus 6 by slidingly limiting the width of the heat ray emission opening 7 of the lamp unit 3. As the heat ray lamp 8, a halogen lamp is employed preferably. The infrared ray from the lamp 8 is focussed by the gold-plated concave mirror 9 or elliptic profile onto the soldering line to form the line focus 6, 6, whereby soldering of each lead pin 2a in the lead pin row on the packaged IC chip 2 with the corresponding contact pin in the contact pin row on the substrate board 1 aligned thereto is achieved instantaneously. In order to arrest the packaged IC chip 2 placed on the substrate board 1 under cooling of the chip during the soldering operation, an arrester tube 60 is provided through the bevel gear 30 at its center. The arrester tube 60 plays a role of arresting the IC chip by pressing onto it and guiding and blowing the cooling air onto the IC chip. The vertical movement of the arresting tube 60 is effected by means of a cylinder/piston unit 55/59. The actuation mechanism for adjusting the distance between the pair of shield members 32, 32 or 33, 33 disposed in the heat ray emission opening 7, 7 is similar to that for the pair of lamp heads 4, 4. Thus, as suggested in Fig. 4(c), the pair of ball screw shafts 34, 35 or 36, 37 are provided at their opposing inner ends each with a level gear 38, 39; 38a, 29a both held in engagement with a driving bevel gear 40, 40a which is driven by a stepping motor STM. Alternatively, it is possible also to employ a pneumatic actuation mechanism for effecting the sliding adjustment of the distance between the pair of shield members 32, 32; 33, 33. Thus, as indicated in Fig. 2(b), a pair of heat ray lamp units 3, 3 are fixed each to an arm 100 by connection pins 5, 5. Each arm 100 is fixed to a slide member 101 guided on a pair of guide rods 102, 102 so as to effect sliding movement thereon by means of an air cylinder 103 and a piston rod 104 coupled therewith [in Fig. 2(b), only the left hand half thereof is shown]. The air cylinder 103 is connected to a pneumatic actuation valve means through connection pipes 105, 106 to actuate the cylinder/piston unit 103, 104. The piston rod 104 is connected to a slide member 101 [the left slide member in Fig.2(b)] through a connection plate 108 via a terminal member 107. The other slide member [the right slide member in Fig.2(b)] has the same structure and thus is not shown in this Figure. By sliding the pair of lamp units 3, 3 using this mechanism, the width W between the pair of line focuses 6, 6 is adjusted. This width W is let coincide with the distance "W" between the pair of rows of lead pins 2a, 2a extending both in x-coordinate direction on the flat packaged IC chip 2 shown in Fig. 1. The rectangular turning of the pair of line focuses 6, 6 to the direction of y-coordinates is achieved by turning the pair of lamp heads 4, 4 at right angle using the rotor 50, as explained previously. The rotation of the rotor 50 is carried out by means of a rotary actuator 111 of "High Rotor" (trade mark) via a driving belt 110. The support plate 113 supporting the rotor 50 rotatably by a bearing means is connected to the piston rod 45 coupled with the air cylinder 46 for the vertical movement of the lamp units. Explaining now the manner of adjustment of the length of line focues 6 with reference to Fig. 2(c), the length of line focus 6 becomes small, when the free space or width between the pair of shield members 32, 32 is rendered narrow, and becomes large, on the contrary, when it is rendered wide. The slide movement of the pair of shield members 32, 32; 33, 33 is effected all at once by means of a pair of flexible wire actuation means 117, 117. The pairs of flexible wires 117, 117 are actuated by a pair of shield member adjusting cylinder units 118, 118, whereby the sliding adjustment of the pairs of shield members 32, 32 and 33, 33 are attained simultaneously. The operation control system of the apparatus according to the present invention is as shown in Fig. 3. This comprises a memory-operation section (A), a control section (B) and an actuation section (C). The memory-operation section (A) includes an operation change-over part 10, a digital control memory part 11 and a digital control input system part 12. The operation change-over part 10 represents a means for changing over the mode of operation of the apparatus from automatic to manual and vice versa. The digital control memory part 11 represents the function of positioning of the pair of heat ray lamp units 3, 3, adjustment of the length of line focus of heat ray beam and the control of the heating conditions. The digital control input system part 12 represents input units for, such as, the x-y-plotter for the pair of heat ray lamp units 3, 3, for example, an x-y-positioning mechanism; a means for effecting turning of the heat ray lamp units; a means for adjusting the length of the line focus; and all other actuation means for realizing the positioning, adjustment and so on of different sized IC chips under programmed control. It is of course possible to construct the digitial control input system part 12 as a partial unit in an automation line under cooperation with a mechanism for automatic transporting of IC chips, a device for positioning the IC chips and so on. The operation change-over part 10 is connected with the digital control memory part 11 which is connected to the digital/sequence control part 14 in the control section (B). The control section (B) includes a digital control circuit part 13, a digital/sequence control circuit part 14 and a sequence control circuit part 15. The digital control part 13 represents the function of controlling of positioning of the pair of heat ray lamp units 3, 3 under shifting them in the direction of x- and/or y-coordinates by the pulse train input control as well as effecting control of adjustment of distance between the pair of heat ray lamp units 3, 3 and of the width between the pair of shield members 32, 32; 33, 33. The digital/sequence control part 14 represents the function of controlling the output power of the heat ray lamp, the adjustment of heating duration and so on by a timing program. The sequence control part 15 represents the function of the rectangular turning of the pair of lamp units 3, 3, vertical movement of the arrester tube 59 and actuation of the solenoid valve for controlling the coolng air supply to the tube 59. The digital control part 13, the digital/sequence control part 14 and the sequence control paret 15 are connected with each other. the actuation section (C) includes a lamp positioning part 16, a heat ray regulation part 17, a heat ray operation control part 18, a lamp support shaft operation part 19 and a chip arresting and cooling part 20. The lamp positioning part 16 and the heat ray regulation part 17 receive commands from the digital control part 13. The lamp positioning part 16 controls the DC servomotors for x- and y-coordinates. The heat ray regulation part 17 governs the stepping motors STM for the lamp distance adjustment and for the shield member distance adjustment. The heat ray operation control part 18 receives output signals of the digital/sequence control part 14, in order to effect control of adjustment of the output power of the lamp, heating duration and so on. The lamp support shaft operation part 19 and the chip arresting and cooling part 20 receive commands from the sequence control part 15. The lamp support shaft operation part 19 represents the function of controlling the air cylinder 46 for vertical movement of the lamp head and controllling the actuator 53 for rectangular turning of the lamp head pair. The chip arresting and cooling part 20 represents the function of controlling the air cylinder for vertical movement of the arresting tube and controlling the blowing of the cooling air. Now, the explanation is directed to each function of the control parts in the actuation section (C) with reference to Figs. 4 (a) to 4 (e). Fig. 4(a) shows the essential functions and mechanism of the lamp positioning part 16. The lamp positioning part 16 controls the shifting of the pair of heat ray lamp units 3, 3 as a whole in the directions of x- and/or y-coordinates, as shown in Fig. 1, by means of a ball screw 21 for the x-coordinates and a ball screw 22 for y-coordinates. The ball screw shaft 21 is driven by a servomotor M1 for x-coordinates, which is connected to the pulse train input control circuit for x-coordinates in the digital control part 13 via a torque generator TG and a pulse encoder PE. This input control circuit is connected to said servomotor M1 via a servo-amplifier 23. The pulse train input control circuit for x-coordinates receives the command pulses for x-coordinates, such as, commands for the stroke and for the direction of shifting and so on, from a personal computer pulse generator 24 in the digital/sequence control part 14. The ball screw shaft 22 for y-coordintes is driven by a DC servomotor M2 which is connected to the pulse train input control circuit for y-coordinates in the digital control part 13 via a torque generator TG and a pulse encoder PE. The pulser train input control circuit for y-coordinates is connected through a servo-amplifier 24 to the servomotor M2 and the torque generator TG mentioned above. The pulse train input control circuit for y-coordinates receives from the personal computer pulse generator 24 in the digital/sequence control part 14 command pulses for y-coordinates, such as, command for shifting stroke and command for shifting direction. The pulse generator 24 receives commands for lamp head positioning (program memory for x- and y-coordinates) of the digital control memory part 11. Fig. 4(b) depicts the fundamental function and construction of the heat ray regulation part 17. The left side lamp head 4 of the pair of heat ray lamp units 3, 3 and the right side lamp head 4 thereof are moved by means of a ball screw 25 for the left side lamp head and a ball screw 26 for the right side lamp head respectively, so as to close to or depart from each other. The ball screw shafts 25 and 26 are driven by a bevel gear arrangement 27 in such a manner, that the ball screw 25 and the ball screw 26 are driven by the bevel gears 28 and 29 respectively, which are held in engagement with a bevel gear 30 driven by a stepping motor STM. The stepping motor STM receives commands from the pulse input driver control circuit for controlling the lamp distance and the shield member distance in the control part 13. The pulse input driver control circuit receives command pulses from the personal computer pulse generator 31 of the digital/sequence control part 14, for example, for the stroke and direction of slidding of the slide members. The personal computer pulse generator 31 receives the outputs of the digital control memory part 11. In Fig. 4(c), the heat ray regulation part 17 for automatically regulating the length L1 of the line focus 6 is explained. As is seen from this Figure, each heat ray emission opening 7 for the pair of heat ray lamp heads 4, 4 is provided with a pair of shield members 32, 32 or 33, 33, each siladably. By sliding adjustment of the distance between the pair of shield members 32, 32 or 33, 33, the width P of the heat ray emission opening is determined, so as to focus each heat ray beam into a desired length of line focus 6. The shield members 32, 32 and 33, 33 are slid by means of a pair of ball screw shafts 34, 35 and 36, 37. The ball screw shafts 34 and 35 are driven each through a bevel gear 38 or 39 both driven by a bevel gea 40. The bevel gear 40 is driven by a stepping motor STM which is controlled by the output command pulse of the pulse input driver control circuit which receives command pulses, such as, commands for stroke and for direction etc., from the personal computer pulse generator 41 in the digital/sequence control part 14. The personal computer 41 receives the outputs of the digital control memory part 11. The other lamp head has the same construction as above. By supplying the same output from the digital control memory part 11 to the personal computers 41 and 42, the two pairs of shield members 32, 32 and 33, 33 are slide in the same amount simultaneously so as to buid up a pair of congruent line focuses 6, 6 as shown in Fig. 2. In Fig. 4(d), the heat ray operation control part 18 for governing the halogen lamp 8 is explained. The operation of the halogen lamp 8 is controlled by an output power regulator 43 connected to the power source. The power regulator receives from a personal computer pulse generator 44 in the digital/sequence control part 14 control pulses, such as, for the output voltage, heating duration and so on. The personal computer 44 receives commands from the digital control memory part 11. Fig. 4(e) explains the lamp support shaft operation part 19 for operating the lamp heads 4, 4 for vertical movement and for rectangular turning. The piston rod 45 moves the lamp heads 4, 4 towards or away from the work piece by actuation of an air cylinder 46 of a pneumatic actuator unit. The air cylinder 46 is operated by a solenoid valve 49 of which two operation pipes 47 and 48 are connected to the upper and lower ends of the cylinder 46. The solenoid valve 49 is connected to a source of compressed air (not shown) and is governed by valve operation command signals from the sequence control part 14, whereby the vertical movement of the piston rod 45 is controlled by the pneumatic control of the air cylinder 46. For realizing rectangular turning of the pair of lamp heads 4, 4 around the axis of the piston rod 45, there is provided a rotor 50 supported by bearing means. The piston rod 45 is arranged piercing the rotor 50 freely rotatably. The rotor 50 is provided at its lower end with a spur gear 51 fixed thereto which is connected with the lamp heads 4, 4 integrally therewith and is held in engagement with a driving gear wheel 52 driven by a rotary actuator 53 which is connected to a solenoid valve 54 and is subjected to the valve operation signal from the sequence control part 15, whereby the rotary actuator 53 is put in operation so as to rotate the spur gear 51 via the driving gear wheel 52 to effect rectangular turning of the pair of lamp heads 4, 4. Fig. 4(f) explains the fundamental construction and function of the chip arresting and cooling part 20. The chip arresting and cooling part 20 has a pneumatic actuation air cylinder 55 connected to the solenoid valve 58 through two operation pipes 56, 57. The solenoid valve 58 is connected to a compressed air source (not shown) and is subject to the command pulses for controlling the valve operation from the sequence control part 15. By the pneumatic actuation of the air cylinder 55 by the solenoid valve 28, the piston rod 59 is operated to effect vertical movement, in order thus to arrest or release the work piece by or from the arrester tube 60 disposed at the front end of the piston rod. The arrester tube 60 is connected to a cooling air source (not shown) via a controlling solenoid valve 62 and has also a role of guiding and blowing the cooling air onto the chip being soldered for cooling it, under the control by actuation signals for the valve operation coming from the sequence control part 15. Fig. 5 is fundamental operation timing chart of the apparatus according to the present invention. In the following, the time sequence of each operation of the apparatus according to the present invention is described for the case of successive soldering of packaged IC chips 2, 2′, 2″ having each two pairs of parallel rows of lead pins 2a, 2a′, 2a″ arranged quadrilaterally on each IC chip placed on a substrate board 1 as shown in Fig. 1. On starting the apparatus according to the present invention by switching on of the power source, the soldering head of the apparatus is first moved to the soldering position of the first packaged IC chip 2 on the substrate board 1 by a programmed choice of the x- and y-coordinates thereof and is settled there. The movement of the soldering head in the direction of x-coordinates on the substrate board 1 is effected by a servomotor M1 under government by the command signals from the lamp positioning control circuit in the digital control memory 11 through the digital/sequence control part 14 via the pulse train input control circuit for x-coordinates in the digital control part 13 and via the servo-amplifier 23. Thus, the ball screw shaft 21 is rotated by the servomotor M1 and te soldering head, and thus, the pair of heat ray lamp units 3, 3 are moved in the direction of x-coordinates for a distance corresponding to the number of pulses of the command. In the same way, the shifting of the soldering head in the direction of y-coordinates is caused by the servomotor M2 under government by the command from the lamp positioning control circuit in the digital control memory 11 through the digital/sequence control part 14 via pulse train input control circuit for y-coordinates in the digital control part 13 and via servo-amplifier 24. Thus, the ball screw shaft 22 for y-coordinates is rotated by the servomotor M2 and the soldering head is shifted together with the pair of heat ray lamp units 3, 3 in the direction of y-coordinates by a stroke corresponding to the number of pulses of the command. In this manner, the pair of lamp heads 4, 4 will be set at the proper soldering position of the first IC package 2 on the substrate board 1. The adjustment of the with W between the pair of rows of lead pins 2a, 2a for coinciding with the distance between the pair of line focuses 6, 6 is effected by the actuation system shown in Fig. 4(b). Thus, the stepping motor STM for adjusting the lamp head distance in the heat ray regulation part 17 is controlled by the command pulses from the pulse input driver control circuit for the lamp distance in the digital control part 13. Thereby the rotation of the screw shafts 25, 26 by the bevel gear arrangement 27 is controlled so as to let the width "W" between the pair of lamp heads 4, 4 coincide with the distance between the pair of parallel rows of lead pins on the IC chip. For the control to let the distance between the pair of line focuses 6, 6 of the heat rays from the pair of lamp heads 4, 4 and the length thereof coincide with those of the pair of parallel rows of lead pins 2a, 2a on the IC chip, the system as shown in Fig 4(c) is used. Thus, the stepping motors STM in the heat ray regulation part 17 are operated simultaneously on receipt of the command pulses from the pulse input driver control circuit in the digital control part 13 for controlling, such as, the sliding stroke and the silding direction, whereby the bevel gears 40 and 40a are driven simultaneously to rotate the pairs of bevel gears 38, 39 and 38a, 39a so as to slide the pairs of the shield members 32, 32 and 33, 33 simultaneously via the ball screws 34, 35; 36,37 to restrict the width of each irradiation opening 7 to a proper value. Both the heat ray lamps 8, 8 are subject to the command pulses supplied to the heat ray operation control part 18 from the digital/sequence control part 14 and the lamps are lit up for preheating, in order to let the IC chip be ready for proper soldering. Then, the lamp head supporting shaft 45 is let descend so as to cause the pair of line focuses 6, 6 to coincide with the pair of parallel rows of lead pins 2a, 2a by operating the lamp support shaft operation part 19, as shown in Fig. 4(e). The piston rod (lamp head supporting shaft) 45 is let descend by the actuation of the air cylinder 46 by the command for the operation of solenoid valve from the sequence control part 15 until the pair of line focuses 6, 6 of the heat ray from the lamps 8, 8 come to coincide with the pair of parallel rows of lead pins 2a, 2a extending in the direction of y-coordinates. At the same time, the piston rod coupled to the air cylinder 55 is lowered by the actuation of the air cylinder 55 under the control by command pulses for the operation of solenoid valve 58 supplied from the sequence control part 15, until the arrester tube 60 connected thereto will press onto the packaged IC chip 2. Subsequently, the voltage of the heat ray lamps 8, 8 is raised sharply so as to effect the soldering in the direction of y-coordinates instantaneously. After termination of the soldering, the heat ray lamps 8, 8 are turned back again to the state of preheating and the arrester tube 60 is let ascend. During the soldering, cooling air is supplied through the arrester tube 60 under the control by the command for the operation of solenoid valve 62 from the sequence control part 15, in order to cool the packaged IC chip 2 by blasting the cooling air onto it. In this manner, soldering in the direction of y-coordinates is effected instantaneously in high accuracy. For carrying out the soldering in the direction of x-coordinates, the pair of lamp heads 4, 4 are turned at right angle per se at the position of said soldering in the direction of y-coordinates by means of the operation system shown in Fig. 4(e). Upon the command from the pulse train input positioning control circuit for x-coordinates in the control section (B), the solenoid valve 54 is actuated so as to effect rotation of the gear wheel 52 by means of the rotary actuator 53 to cause turning of the rotor 50 at right angle by the spur gear 51, in order thus to set the pair of heat ray lamp heads 4, 4 at said position. Thus, the pair of heat ray lamp heads 4, 4 are turned rectangularly so as to align the pair of line focuses 6, 6 with the parallel rows of lead pins extending in the direction of x-coordinates. Other operations are the same as explained previously, except that said turning movement is performed while the package IC chip 2 is held arrested by the arrester tube 60. After the soldering in the direction of x-coordinates has been effected as above and the packaged IC chip 2 has been cooled by the cooling air, the air cylinder 55 is actuated so as to let the piston rod, and thus, the arrester tube 60 ascend to finish 1 cycle of soldering operations. Then, the soldering head is shifted to the second soldering position by shifting the soldering head along x- and y-coordinates as explained previously. In this manner, the pair of soldering heads are further moved to the subsequent soldering positions in succession to perform similar soldering operations in x- and/or y-coordinate direction. While the description has been directed to the processing of packaged IC chips having quadrilateral parallel rows of lead pins, IC chips having bilateral parallel rows of lead pins can be soldered in the same amnner by omitting the rectangular turning of the lamp heads. The soldering sequence can be reversed, namely, for example, by soldering first in x-direction followed by the soldering in y-direction and vice versa. Also, the order of operations in the operation cycle can be varied voluntarily so as to select the optimum work conditions. By the apparatus according to the present invention, which is characterized by the employment of a memory-operation section (A), a control section (B) and an actuation section (C), wherein the control section (B) provides its function under subordination to the command from the memory-operation section (A) and the control section (B) governs the actuation section (C), so as to move the heat ray soldering head in the direction of x- and/or y-coordinates on the substrate board to each preset position for the packaged IC to be worked and so as to effect the soldering of each spot for establishing electric junction by said heat ray beam focussed as line focus, it is made possible that the soldering works for soldering packaged IC chips having bilateral or quadrilateral parallel rows of lead pins on a substrate printed circuit board can be achieved instantaneously in a high efficiency even for a packaged IC chip with highly dense distribution of the lead pins without suffering from junction failures under prevention of short-circuiting due to bridge formation by a spilling out of the solder.

Claims: 1. An apparatus for automatic soldering of contact pins on items to connection leads on a workpiece, comprising a lamp head carrying one or more heat ray lamps (3) for irradiating with a line-focused heat ray beam (6) the junction of the connection leads and the contact pins aligned therewith, characterized in that it further comprises; an actuator (C) for moving the lamp head along first and/or second directions relative to the workpiece and along a direction perpendicular to the workpiece; a controller (B) for controlling the actuator (C) to move the lamp head to each of a number of pre-programmed soldering positions and at each position to position the lamp head at such a distance from the junction that the junction is irradiated with a defocused part of said heat ray beam and to illuminate the lamps at a low level to preheat the junction and then to move the lamp head to such a position that the line focus of said heat ray beam is focused on the said junction and to increase the illumination level to solder at the position using said line-focused heat ray beam and then to return the head to the preheat position and reduce the illumination of the lamps and to repeat the head positioning and illumination operation at each position in turn whereby a pre-programmed sequence of soldering operations are performed; and a memory-operation section (A) which can be pre-programmed with data to be provided to the controller (B) and representative of the pre-programmed sequence of soldering operations. 2. An apparatus according to claim 1, characterised in that the memory-operation section (A) comprises an operation change-over part (10) for governing a change-over between an automatic and a manual mode of operation and a digital control memory part (11) for storing data for controlling the positioning of the lamp head, the shape of the heat ray beam and the power output of the heat ray lamps. 3. An apparatus according to claim 2, characterised in that the controller (B) comprises: a digital control part (13), which controls the positioning of the lamp head in the first and second directions and of means (32,33) for defining the shape of the beam; a digital/sequence control part (14) for timing and for digital/sequence control of the output power of the one or more heat ray lamps (2); and a sequence control part (15) for controlling the vertical and rotational position of the lamp head. 4. An apparatus according to claim 3 characterised in that it further comprises, under control of the sequence control part, means (60) for positioning and holding the items on the workpiece and for cooling the items (2, 2′, 2″) during and/or after the soldering operation. 5. An apparatus according to claim 4 characterised in that the actuator (C) includes a lamp head positioner (16) for controlling DC servomotors to adjust the position in the first and second directions of the lamp head, a heat ray regulator (17) for actuating stepper motors for controlling the means (32, 33) for defining the shape of the heat ray beam, and where there is a plurality of lamps the inter-lamp distance, a heat ray operation controller (18) for controlling the output power of the lamp or lamps (3) and the irradiation duration, a lamp support shaft operator (19) for controlling an air cylinder for moving the lamp head vertically and a lamp actuator for rotating the lamp head and arresting/cooling means (20) for controlling an air cylinder for vertical movement of the means (60) for holding in position and cooling the items on the workpiece. 6. An apparatus according to claim 15, characterised in that the digital control memory part (11) is connected to the memory-operation part (10) to receive commands therefrom and is connected to the digital/sequence control part (14) to give commands thereto and that the digital/sequence control part (14), the digital control part (13) and the sequence control part (15) are connected together to exchange outputs with each other, and in that the digital control part (13) is connected to the lamp head positioner (16) and to the heat ray regulator (17) to give commands thereto, the digital/sequence control part (14) is connected to the heat ray operation controller (18) to give commands thereto and the sequence control part (15) is connected to the lamp support shaft operator (19) and to the arresting/cooling means (20) to give commands thereto.

Inventors: HAYAKAWA, FUTOMI, ONODA, KAZUO
Applicants: HY-BEC CORPORATION
Application year: 1987
Main classification: B23K1
IPC codes: B23K3, H05K13, H05K3, H01R43, B23K1