Device to process electrical circuits

Abstract: Device to process green-tape type circuits, in which a green-tape foil (12) of alumina in the raw state or of another like or analogous material (green-tape foil) acts as a support for circuits (solar cells, etc.) and contains holes for electrical connection of circuits borne on other green-tape foils positioned above or below, the green-tape foil (12) undergoing a printing operation to fill the electrical connection holes and a possible operation of printing an electrical circuit, these printing operations being performed by associating the green-tape foil (12) with a band of paper or with a mesh or another analogous material (26) positioned between the green-tape foil (12) and a supporting base (29) for the printing, the device comprising in cooperation: a step-by-step conveyor (60) with a shaft (53) able to move step-by-step and stationary lateral surfaces (13) together with rigid supports (20), the step-by-step conveyor (60) comprising at least one loading station (16) and one discharge station (19); a transfer conveyor (58) substantially parallel to the step-by-step conveyor (60); a spongy platform (40) able to move step-by-step on the transfer conveyor (58) between the loading station (16) and the discharge station (19), the spongy platform (40) comprising an upper surface (29) to support the green-tape foil (12), a position identification station (17) and a printing station (18) being included between the loading station (16) and discharge station (19), these stations being single stations or being associated with each other in a number of two or more.

Description: This invention concerns a device to process electrical circuits as set forth in the main claim. To be more exact, the device makes possible the operations of conveying, printing and filling of connecting holes (e.g. screen process printing) and discharge of the foils. The device according to the invention can also be employed to carry out operations for the processing of solar cells, printed circuits and in the so-called green-tape technology. Hybrid circuits in the so-called green-tape technology consist of very thin foils of alumina in the raw state or of another like or analogous material, which have a circuit printed on one or both of their two faces. The green-tape foils are superimposed on each other in numbers amounting even to some tens and are compressed to achieve reciprocal bonding so as to produce a multi-layer product of a slender thickness. The various components of the circuit comprised in the individual foils are possibly set in communication with each other through suitable holes made in the foils and filled with a conductive material. The green-tape foils of the technology of the state of the art are conveyed on belts, for instance, of paper to the various processes so as to prevent, during filling of the connecting holes with a conductive material, that conductive material being split on and/or adhering to the support. Thereafter the green-tape foils are dried, assembled in a pre-set number and compressed to produce a multi-layer electrical circuit. These engagement, positioning and insertion operations are done by hand and entail long times and high costs as well as a great number of rejects owing to the lack of accuracy in the filling and printing operations (screen process printing) and to the damage caused by manual handling. US-A-4 981 074 discloses a device for printing an electronic circuit on a board by screen printing. The device comprises movable carriers wherein vacuum is applied to the carriers to hold the boards. The present applicant have designed, tested and obtained this invention so as to be able to obtain an automatic or semi-automatic working cycle and to achieve further advantages. This invention is set forth and characterized in the main claim, while the dependent claims describe variants of the idea of the embodiment. In a preferred embodiment described hereinafter suitable rigid supports stacked in a suitable container and bearing green-tape foils are taken from that container one by one and are positioned in a continuous sequence on a conveyor able to move step by step. The green-tape foils have standard dimensions, are placed on their specific rigid supports and contain connecting holes and other possible holes and/or marks, reference holes or marks, for instance. The rigid supports contain holes to identify the presence of the green-tape foil and also a plurality of small holes arranged on part of their surface. These small holes have the task of retaining the green-tape foil on the rigid support when a negative pressure is created below the rigid support, or else of lifting the green-tape foil from the rigid support when air under pressure is created below the rigid support. The rigid supports are thus retained on the step-by-step conveyor by negative pressure, and in the station for engagement of the green-tape foil suitable jets of air cooperate with the small holes in the rigid support so as to keep the green-tape foils raised and to assist their engagement and removal. The green-tape foil is taken from the rigid support and positioned on a flat plate having a spongy supporting body, hereinafter called "spongy platform". A sheet of transpirable material, which is advantageously paper of the type used for cigarettes, is placed between the spongy platform and the green-tape foil. The sheet of transpirable material supported on the spongy platform is able to bear the green-tape foil during the printing and screen process printing steps. The green-tape foil is handled by suitable engagement and positioning means, which consist advantageously of movable arms that support suction means terminally. The device according to the preferred embodiment of the invention is equipped with conveyor means which can convey the spongy platform bearing the green-tape foil to successive stations along the processing line. In these successive stations are performed respectively the operations of engaging the green-tape foil and placing it on the spongy platform, identifying the exact position of the green-tape foil, filling the connecting holes in the green-tape foil with a conductive material and/or printing the circuit. The device according to the preferred embodiment of the invention comprises a discharge station in which the printed green-tape foil is re-positioned on the rigid support and is sent to the successive processes. The device of this embodiment enables the green-tape foil to be handled semi-automatically or automatically without using machine operators but very accurately in very short cycle times and with an excellent finished result. According to this embodiment the sheet of transpirable paper is provided to assist the operations of removing and aspirating the green-tape foil and also to prevent the conductive material dirtying the spongy platform and the circuit. The spongy platform is borne on a container, within which a negative pressure of a desired value is created so as to keep the green-tape foil and the transpirable sheet always adhering closely to the upper surface of the spongy platform. That upper surface is smooth and flat and is conformed in such a way that it does not create even the smallest misalignments of the green-tape foil placed thereupon. The sheet of transpirable material placed between the upper surface of the spongy platform and the green-tape foil is replaced automatically whenever the green-tape foil is changed. As we said above, the transpirable material consists, for instance of paper used for cigarettes or another analogous material, or may consist of a mesh with very thin weft elements (a mesh for screen process printing, for instance) The spongy platform assembly according to this preferred embodiment of the invention includes winding/unwinding rollers which enable the transpirable material to run in the form of a band. The winding/unwinding rollers are capable of an intermittent motion, which is actuated at the moment of removal of the screen-printed foil for the required period of time, thus enabling the transpirable material to be moved forwards by a required value so as to replace the transpirable material for the next green-tape foil. The band of transpirable material hinders the passage of the substances such as the paste of conductive material used to fill the connecting holes in the green-tape foil. In this way, during the filling of the holes in the green-tape foil with the screen process printing the conductive filling material is prevented from reaching the porous spongy platform and obstructing the holes therein and damaging the platform. In the meantime the band of transpirable material does not hinder the passage of the air due to the negative pressure in the container, so that the work of filling the connecting holes in the green-tape foil is assisted. During the operation of discharging the green-tape foil from the spongy platform onto the rigid support the band of transpirable material is caused to advance, thus taking with it the green-tape foil and discharging the finished piece of green-tape foil. By using a direction-switching edge of the container and/or the spongy platform it is possible to detach the green-tape foil from the transpirable band while the green-tape foil continues advancing in a substantially straight direction. Thus the next green-tape foil placed on the spongy platform comes into contact with a clean segment of the band of transpirable material without any residues of the conductive material. The attached figures are given as a non-restrictive example and show a preferred lay-out of the invention as follows: Fig.1 is a plan view of a device to produce hybrid circuits of the green-tape type; Fig.2 shows a partial block diagram of the device of Fig.1; Fig.3 is a three-dimensional view of a spongy platform for processing green-tape type circuits; Fig.4 shows a diagrammatic cross-section of the means which transfers the green-tape foil from the spongy platform of Fig.3 to a rigid support; Fig.5 shows a partial section of the spongy platform and rigid support; Fig.6 shows a section along the line A-A of Fig.4; Figs.7 show a cycle of the discharge and delivery of a green-tape foil; Fig.8 shows a possible form of embodiment of the rigid support; Fig.9 is a three-dimensional view of a part of a device according to the invention; Fig.10 is a diagram of a working step of the device according to the invention; Fig.11 is a diagram of a possible means to move the spongy platform. The number 10 in the figures indicates a device to process hybrid circuits of the green-tape type. The device 10 is connected to an automatic line 46 feeding rigid supports 20 that bear green-tape foils 12 to be printed and also an automatic line 47 that removes printed green-tape foils 12. Fig.2 shows in a block diagram the main processing steps which are accomplished by the device 10. Specific rigid supports 20, each of which bears its own green-tape foil 12 and is placed on a step-by-step conveyor 60, are taken one by one from a suitable container 11 which runs along the feeder line 46. The rigid supports 20 are held and stacked in appropriate grooves within the container 11; the grooves are spaced apart enough to enable a rigid support 20 to be taken automatically without coming into contact with the neighbouring rigid support 20. In this case the step-by-step conveyor 60 consists of two stationary lateral surfaces 13 and a movable shaft 53 capable of an intermittent movement in steps. The withdrawal of the rigid supports 20 from the container 11 is carried out in this case by the movable shaft 53, which is positioned between the two stationary lateral surfaces 13. The movable shaft 53 protrudes lengthwise beyond the stationary lateral surfaces 13 and passes beneath the lowest rigid support 20 held in the container 11. Then the movable shaft 53 with an ascending, retreating and then descending movement takes the rigid support 20 and deposits it on the stationary lateral surfaces 13. During this movement the container 11 descends by one step orthogonally to the feeder line 46, thus making available for removal the next higher rigid support 20. The step-by-step movable shaft 53 is then again caused to protrude and is brought into cooperation with the next rigid support 20 positioned in the container 11. The removal operation is performed in such a way that the movable shaft 53, by one single movement, takes the second rigid support 20 from the container 11 and at the same time causes the first rigid support 20 already taken to advance by one step on the stationary surfaces 13. The removal cycle is repeated until the container 11 has been emptied, and the empty container 11 is then removed along the feeder line 46. According to an advantageous form of the invention the empty container 11 is brought automatically to the removal line 47 to receive rigid supports 20 together with printed green-tape foils 12 leaving a drying oven 49 (Fig.1). The rigid supports 20 (Fig.8) contain holes 54 for identification of the presence of the green-tape foils 12 and contain also a plurality of small holes 55 arranged on a part of their surface. These small holes 55 assist separation of the green-tape foil 12 from the rigid support 20 when air under pressure is blown from below the support 20 and, passing through the small holes 55 in the support 20, lifts and distances the green-tape foil 12 from the rigid support 20. The green-tape foil 12 is sent to a removal station and is taken from its respective rigid support 20. In this removal station each single rigid support 20 is held on the stationary surfaces 13, for instance by suction means applying negative pressure, while suitable jets of air passing through the small holes 55 appropriately contained in the rigid support 20 lift the green-tape foil 12 and keep it lifted. In the removal station the green-tape foil 12 is taken from the rigid support 20, is possibly overturned in an overturning station 30 and is then transferred and positioned on a spongy platform 40 lying in a loading station 16. In this example the green-tape foil 12 is taken from the rigid support 20 by a movable arm 45, which supports suction means 56 (Fig.10) at its end. The movable arm 45 can move perpendicularly to the direction of forward movement of the movable shaft 53 so as to bring the suction means 56 above the rigid supports 20 passing by on the shaft 53 able to move step-by-step. Thereafter the suction means 56 are lowered onto the rigid support 20. During this step two effects of negative pressure are created, of which the first is a greater intensity and is applied from below the rigid support 20 to keep the supports 20 on the stationary surfaces 13, whereas the second is of less intensity and is applied by an aspiration chamber 57 below the movable arm 45 so as to remove the green-tape foil 12 from the rigid support 20; this removal is assisted by air blown through the small holes 55 . The green-tape foil 12 is then released by the suction means 56 onto the spongy platform 40 after withdrawal of the movable arm 45 or is brought into cooperation with the overturning station 30 by a further forward movement of the movable arm 45 if the green-tape foil 12 has to be printed on its reverse face. The green-tape foil 12, after being overturned, is reengaged by the suction means 56 and placed on the spongy platform 40. The spongy platform 40 is equipped with linear displacement means 14 (Fig.11), which in this non-restrictive example consist of linear guides 15 cooperating with a suitable drive means, which is not shown here. In this case the drive means consists of a D.C. motor with a ball-bearing screw 43, the motor being controlled electronically. The displacement means 14 enable the spongy platform 40 to be moved to various processing stations with the greatest possible accuracy in view of the necessity to ensure correct positioning of the green-tape foil 12 during the printing step. In this example the processing stations are positioned on a transfer conveyor 58 parallel to the stations of the step-by-step conveyor 60. The spongy platform 40 is moved from loading station 16 to a position identification station 17, in which the exact position of the green-tape foil 12 and therefore of the micro-holes or reference marks contained on the green-tape foil 12 is detected, by telecameras 50 for instance. This identification, which can be performed by one or more telecameras 50, detects accurately the position of two or more reference marks or holes on the green-tape foil 12. The identification determines on a horizontal plane the exact position of the green-tape foil 12 on the spongy platform 40; this position is detected according to an axis lengthwise to the path of the foil 12, according to an axis crosswise to the path of the foil 12 and according to the orientation of the foil 12 on its plane. Thereafter the spongy platform 40 reaches a printing station 18 in which are carried out the operations of printing a circuit and/or filling the connecting holes in the green-tape foil 12 with conductive material by means of a screen process printing system. The spongy platform 40 and the printing means in the printing station 18 are correctly positioned reciprocally by traversing and rotation movements on a plane parallel to the plane of the green-tape foil 12 being processed; these movements may affect the spongy platform 40 or the printing means or both of them. After the printing operation the spongy platform 40 is transferred to a discharge station 19, in which the finished green-tape foil 12 is repositioned on its relative rigid support 20, which has arrived at the discharge station 19 in the meantime and is firmly secured to its element on the movable shaft 53. In the discharge station 19 the spongy platform 40 cooperates with an engagement and delivery assembly 59 in the re-positioning of the rigid support 20 on the movable shaft 53 and stationary lateral surfaces 13. In this example the discharge station 19 is positioned upstream of the printing station 18. According to a variant the discharge station 19′ and the relative engagement and delivery assembly 59′ are positioned downstream of the printing station 18. Next, the green-tape foil 12 together with the rigid support 20 on which it is positioned is sent to a visual checking station 48 and thence to an oven 48 for a drying step. Upon leaving the drying step the rigid supports 20 bearing the finished green-tape foils 12 are stacked in a container 11 positioned on the removal line 47 by means of a process which is the reverse of the process of removal from the container 11. The spongy platform 40 comprises a transpirable cushion 21 of a spongy material, such as sintered bronze for instance or another material able to retain a perfectly flat upper surface 29 while allowing an aspiration action to pass through. A sheet of transpirable material 26, on which is positioned the green-tape foil 12 to be processed (Fig.3), is moved on the upper surface 29. The transpirable cushion 21 is upheld on a container 22, which forms therewith an inner chamber 23 (Fig.4). A negative pressure of a desired value is created within the inner chamber 23 by aspiration means of a known type, which are not shown here and are unimportant for the purposes of the invention. This negative pressure enables the green-tape foil 12 to stay always immovable in the exact position where it has been placed. A sheet 26 in the form of a band is located between the green-tape foil 12 and the upper surface 29 of the spongy platform 40. The spongy platform 40 cooperates with winding/unwinding rollers 24 driven by a suitable known motor 25, which is unimportant for the purposes of the invention (Fig.3). The winding/unwinding rollers 24 make possible the intermittent movement of the band 26 of transpirable material by a desired length, the band 26 consisting advantageously of transpirable paper or steel mesh with very thin weft elements or another material suitable for the purpose. The length of this movement is equal to the segment of material required to have a new clean segment of band 26 under the next green-tape foil 12. The band 26 cooperates with lateral guides 27 which divert its path. These lateral guides 27 are intended to detach the green-tape foil 12 from the band 26 when the green-tape foil 12, having undergone the printing action, is transferred onto its rigid support 20 in the discharge station 19. During this step the rigid support 20 cooperates with an engagement and delivery assembly 59, which in this case consists of a movable plate 31 that cooperates with the band 26 in the discharge of the green-tape foil 12 from the spongy platform 40. The movable plate 31 cooperates also with a stationary abutment 32, which comprises abutment ribs 33 that mesh with lengthwise grooves 34 made in the movable plate 31 and oriented in the direction of movement of the plate 31. The movable plate 31 comprises horizontal guides 35 and is moved lengthwise by suitable motor means 52 including for instance, a gearwheel with a rack 51 (Fig.6) or another analogous system. The movable plate 31 contains a manifold 36, which is fed with compressed air through a duct 37 and feeds inclined holes 38. The inclined holes 38 (Fig.5) are tilted in the same direction as the direction of movement of the green-tape foil 12 from the band 26 and have the purpose of creating a fluid bed to support and convey the green-tape foil 12. The stationary abutment 32 is positioned vertically in the vicinity of the position which the front edge 39 of the green-tape foil 12 has to take up on the rigid support 20. The movable plate 31 can be moved (Fig.7a) from a position very near an inversion edge 27 of the band 26 to a fully retracted position (Fig.7d) cooperating with the stationary abutment 32. The band 26 delivers the green-tape foil 12 to the plate 31 either as soon as the foil 12 has been printed or after the foil 12 has been dried. The band 26 includes the inversion edge 27, which diverts the path of the band 26 quickly and sharply. The inversion edge 27 cooperates with an upstream edge 44 of the movable plate 31 in the delivery and detaching of the green-tape foil 12 (Fig.7a). When the green-tape foil 12 has been detached from the band 26, to which it may have adhered owing to the printing paste, and when a great part of the foil 12 is on the movable plate 31, the jets of air or fluid under pressure coming from the inclined holes 38 carry the foil 12 forwards on the movable fluid bed until the front edge 39 of the green-tape foil 12 abuts against the stationary abutment 32 (Fig.7b). When the green-tape foil 12 abuts against the stationary abutment 32, the movable plate 31 starts its retraction movement (Fig.7c) and the rear edge 42 of the green-tape foil 12 slides onto the rigid conveying support 20. This rear edge 42 cooperates with micro-holes 55 (Fig.5) contained in that zone of the rigid support 20; these micro-holes 55 are kept under negative pressure by the action exerted in this example by a negative pressure chamber 41 cooperating with the stationary surfaces 13. This action of negative pressure applied through the micro-holes 55 retains the rear edge 42 of the green-tape foil 12, while the movable plate 31 moves away (Fig.7d) and leaves the green-tape foil 12 positioned flat on the rigid support 20 without mechanical damage and without any risk of the spreading of any conductive material which may still be wet. It should be noted that the delivery motion of the movable plate 31 can be perpendicular to the direction of receipt of the green-tape foil 12. In this case it may be necessary to include an auxiliary stationary abutment 32 and auxiliary inclined holes 38. The band 26 of transpirable material allows the air to pass through but obstructs the passage of substances such as the conductive material used to fill the holes in the green-tape foil 12. In this way that conductive material cannot reach or soil the transpirable cushion 21. The spongy platform 40 according to the invention, when it has transferred the green-tape foil 12 to the rigid support 20, re-positions itself in the loading station 16 to process another green-tape foil 12. The discharge station 19 may also coincide with one of the other processing stations, and the position identification station 17 too may coincide with any one of the other stations or be a station by itself.

Claims: Device to process a foil (12) which acts as a support for electrical circuits and contains holes for electrical connection of circuits borne on other foils positioned above or below, the foil (12) undergoing a printing operation to fill the electrical connection holes and a possible operation of printing an electrical circuit, the device comprising in cooperation: a step-by-step conveyor (60) with a shaft (53) able to move step-by-step and stationary lateral surfaces (13) together with rigid supports (20) for supporting individual foils; a transfer conveyor (58) substantially parallel to the step-by-step conveyor (60); the step-by-step conveyor (60) being connected with the transfer conveyor (58) by at least one loading station (16) and one discharge station (19); a spongy platform (40) able to move step-by-step on the transfer conveyor (58) between the loading station (16) and the discharge station (19), the spongy platform (40) comprising a sheet of transpirable material (26) positioned between the foil (12) and an upper surface (29) of the platform to support the foil (12) during the printing operation, a negative pressure being created so as to keep the foil and the sheet of transpirable material adhering closely to upper surface of the spongy platform, the sheet of transpirable material being replaced automatically whenever the foil is changed, a position identification station (17) and a printing station (18) being included between the loading station (16) and discharge station (19), these stations being single stations or being associated with each other in a number of two or more. Device as in Claim 1, in which the position identification station (17) includes telecameras (50) to identify the position of the foil (12) on the spongy platform (40). Device as in Claim 1 or 2, in which the printing station (18) includes aligment means working on the spongy platform (40) and/or on the printing system, the aligment means acting on the two axes of the plane on which the foil (12) lies, and in a circular direction on that plane. Device as in any claim hereinbefore, which includes a station (30) for overturning the foil (12). Device as in any claim hereinbefore, in which the spongy platform (40) comprises a transpirable cushion (21) with an upper surface (29) and with an inner chamber (23) under negative pressure. Device as in any claim hereinbefore, in which the spongy platform (40) bears a band (26) of transpirable material with winding/unwinding rollers (24) and a motor (25) for intermittent movement of the band (26), the band (26) being able to move in a direction perpendicular to the shaft (53) which can move step-by-step. Device as in any claim hereinbefore, in which the spongy platform (40) includes lateral guides (27) to divert the band (26) and to detach the foil (12), the guides (27) being substantially parallel to the step-by-step conveyor (60). Device as in any claim hereinbefore, in which a plate (31) positioned above the rigid support (20) and able to move from an engagement position (Figs.7a-7b) to a position of full delivery (Fig.7d) to the rigid support (20) is included in the discharge station (19) opposite the mating lateral guides (27). Device as in any claim hereinbefore, in which the plate (31) cooperates with a stationary abutment (32) that positions the leading end (39) of the foil (12). Device as in any claim hereinbefore, in which the plate (31) contains inclined holes (38) on its surface that positions the foil (12), these holes (38) being inclined in the direction of forward movement of the foil (12) during the transfer of the latter (12) to the plate (31) and being fed with a fluid under pressure. Device as in any claim hereinbefore, in which the stationary abutment (32) cooperates vertically with the position taken up by the leading end (39) of the foil (12) on the rigid support (20). Device as in any claim hereinbefore, in which the rigid support (20) comprises retaining means cooperating with the trailing end (42) of the foil (12). Device as in any claim hereinbefore, in which the retaining means consist of micro-holes (55) kept under negative pressure during the step of transfer of the foil (12). Device as in any claim hereinbefore, in which the rigid supports (20) contain holes (54) to identify the presence of the foil (12) and also small holes (55) for retention/ removal of the foil (12).

Inventors: BACCINI GISULFO, BACCINI, GISULFO
Applicants: BACCINI GISULFO, BACCINI, GISULFO
Application year: 1992
Main classification: H05K3
IPC codes: H05K3, H05K1