WO2008044254A1

WO2008044254A1 - Automatic machine for optical alignment and inductive bonding of the layers of a semi-finished multilayer printed circuit

Info

Publication number: WO2008044254A1
Application number: PCT/IT2006/000834
Authority: WO
Inventors: Bruno Ceraso
Original assignee: Cedal Equipment Srl
Priority date: 2006-10-13
Filing date: 2006-12-04
Publication date: 2008-04-17
Also published as: ITMI20061960A1; TW200817128A

Abstract

A description is given of a machine for making semi-finished products of a printed circuit type of multi-layer comprising two supporting templates (14, 25) and two piles of layers for processing, situated between a station for piling layers (A) or for unloading the semi-finished product (B) and a station where the layers are bonded by electromagnetic induction (D). The two templates are aligned along a common axis of translation and alternate between the piling station and the bonding station, and vice versa. Before exchanging positions between the two stations, the templates are turned over outwards to avoid reciprocal mechanical hindrance A mobile robot, aligned along the common axis of translation, draws up by suction each new layer from a pile of layers placed in the reverse order and aligned by means of a set of video cameras and linear motors for rotation-translation of the layer The robot then moves on to the piling station.

Description

Automatic machine for optical alignment and inductive bonding of the layers of a semi-finished multilayer printed circuit Field of application

The present invention relates to machinery for producing electrical printed circuits, and in particular to an automatic machine .for optical alignment and inductive bonding of the layers to form a printed circuit board still in the form of a semi-finished product. Review of the prior art

For many years the applicant has been actively engaged in designing machinery for manufacturing printed circuit boards, or PCBs, and is the holder of a number of international patents. The most recent innovation consists of a press capable of generating the heat required for bonding the inner layers of these products, exploiting the Joule effect created by induced short-circuit current circulating within metal patterns placed close to the edges of each component layer, produced by corresponding inductors with polar expansions across the multilayer circuit board.

Inductive bonding was obviously used for multilayer boards whose single layers were superimposed in iull respect of the necessary geometrical tolerances. Only if alignment is accurate can electrical continuity be achieved along paths created by metalized through-holes of a small diameter. The conventional alignment systems of a purely mechanical type include holes cut at the same position in each layer, through which pins are passed to fix each new layer in position when it is added to the pile.

When the pile has been completed and compressed the pins are removed. However, the latest types of alignment systems use a video camera to focus a fiducial icon printed .on the layer, and to correct the position of the layer in relation to a value already stored. Optical alignment is much faster and more accurate than the mechanical type and is therefore the

, one most widely used at present. Purpo.se of the invention

As both inter-layer inductive bonding and optical alignment have recently come into use, at the present state of the art the need is felt for a machine that can efficiently combine these two technologies to produce a multi-layer PCB as a semi-finished product easy to transport and store. Irrespective of the present invention, \he semi-finished product would then be subjected to heat and pressure to complete it as a PCB. Preferably, the stages of producing a semi-finished product of the usual size would be automated using a machine of small mechanical parts. Summary of the invention To achieve these purposes, subject of the present invention is a machine for making semi -finished products of the printed circuit multi-layer type, hereinafter indicated solely by the term "multi-layer", said machine comprising: a first plate to carry the single layers forming the multi-layer - a second plate to carry the single layers of the multi-layer, said first and second supporting plates being aligned along a common axis; means for piling and aligning the layers of the multi-layer, one with another; v

- electromagnetic induction means for bonding the aligned layers together, separated from the piling means by a distance greater than the length of said plates; - first means for translating said first supporting plate along said common axis between the piling means and the bonding means, and vice versa;

- second means for translating the second supporting plate along said common axis between the bonding means and the piling means, and vice versa;

- first means for turning the first supporting plate over, and for causing it to make primary rotations in relation to a first axis parallel to the common axis of translation; - second means for turning the second supporting plate over, and for causing it to make secondary rotations in the direction opposite to that of the primary rotations in relation to a second axis parallel to

• said first axis, as described in Claim 1.

Further characteristics of the present invention considered as innovative are described in the dependent claims.

According to one aspect of the' invention, the first and second means' of translation respectively comprise a first and a second linear guide situated, as said first and second axes, at either side of the common axis of translation, and preferably consisting of bars of tempered steel of a circular cross section.

According to another aspect of the invention, the means for piling and reciprocal alignment consist of a robot that- can move backwards and

^• forwards along said common axis of translation between a station, where the single layers are picked up from a pile of layers laid in reverse order, and the first or second supporting plate (the one which at that moment is to be loaded with new layers).

According to another aspect of the invention, said robot comprises means for picking-up the single printed circuit layers, said means preferably consisting of a Venturi tube type of aspirator. According to another aspect of the invention, said robot comprises optical^' means for. focusing fiducial icons present at previously defined .

positions on each layer, preferably consisting of polychromatic video cameras.

According to another aspect of thev invention, said robot comprises mechanical means for rotation-translation of each single layer taken up, the means for doing this preferably consisting of linear electric motors. According to another aspect of the invention, the means fpr piling and reciprocal alignment of said first and second supporting plates comprise mechanical means of adjustment for matching the one with the other, preferably consisting of strongly-built tempered steel pins and bushes. According to another aspect of the invention, said first and said second ■ supporting plate comprise pairs of retractile pincers for compressing the layers- that have been aligned and piled up.

According to another aspect of the invention said means of induction bonding comprise opposing polar expansions that can be situated along an axis perpendicular to the common axis of translation, respectively aligned to a metalized grid present oϊj each layer composing the multilayer. ^{' • ■}

Another subject of the invention is a method for making semi-finished multi-layer printed circuits realizable using the machine subject of the invention, as described in an independent claim on method. Advantages of the invention

The form of the above machine is entirely, linear and symmetrical in relation to a longitudinal axis, a fact that greatly simplifies its construction. Tt is also extremely compact making possible a continuous operative cycle due to the presence of two templates placed to support the multi-layer, said templates simultaneously executing different stages of production at work stations aligned one with another, then returning to ^■ the starting point to unload the semi-finished product and begin a fresh cycle, this being done without interfering with each other during movement in the two directions^" of translation. The system of optical alignment makes it entirely unnecessary to cut holes in the single layers or use pins to adjust the position of the layers, in this way reducing production costs.

The use of numerous layer compressing pincers on either side of the pile of layers ensures their alignment prior to bonding.

Thermo-bonding by magnetic induction is quick, sure and reliable and makes it possible to bond the multi-layer up to a thickness of 10 mm. Extensive use is made of actuators that operate by compressed air to control the various mechanical movements, a further factor that makes possible a reduction in production costs.

Taken as a whole the invention is capable of satisfactorily combining different techniques of optical alignment and inductive thermo-bonding (means already known when considered separately) in a single machine that offers innovative and advantageous aspects compared with the present technical knowledge available in this field. Brief description of the drawings

Further purposes and advantages of the present invention will be clarified by the following detailed description of an example of its realization and by the attached drawings provided of a purely explanatory and in no way restrictive nature, wherein: figure 1 shows the upper face of a layer used in the present invention showing the targets for optical alignment (figure IA) and the metalized grid for inductive bonding (figure IB);

- figure 2 shows a plan view of an automatic machine for layer alignment and bonding as in figure . 1, realized according to the present invention; figure 3 shows an axonometric projection of the machine in figure 2; -^■ figure 4 shows an axonometric view of a robot used for picking up layers, and aligning them, marked 10, at the same station indicated by A in figure 2, superimposed onto a template 14 at the piling station indicated by B in figure 2; " - figure 5 shows an axonometric view of an inductive bonding station marked by a D in figure 2, when a multi-layer board, supported by u second template marked 25 in figure 2, is in the bonding stage;

- figure 6A shows a simplified view of part of a longitudinal section c f the machine seen in figure 2, to make clear how the mechanism works when the template 14 is to be turned over;

- figure 6B is the same as the previous view but applied to the second template 25;

- figures 6C, 6E and 6F illustrate a cross section of the machine in figure 2 to clarify the mechanism for turning the template 14 over to assume the horizontal, inclined and approximately vertical positions respectively; figure 6D shows a mobile joint forming part of the mechanism seen in the preceding figures 6C, 6E₅ 6F; - figure 6G shows a side view of the template 14 complete with the mechanism for fixing it to a conveyor belt visible in an exchange station marked with D in figure 2;. figure 6 H is a cross section along the plane drawn through AA in figure 6G; - figures 7 to 14 give perspective views of the machine subject of the invention with the shapes it assumes in the stages of manufacture from start to completion of the semi-finished product. Detailed description of a preferred realization of the invention The same parts appearing in different figures are given the same numbei 5 throughout the description.

Figure 1 shows the upper face of a layer 1 , utilizable in any position for ,a multi-layer formed of a variable number of similar layers suitably aligned one on top of another. For the sake of simplicity the circuit! il metalization present on the layer is not shown; this metalization can comprise paths, contact areas, any holes for extending the paths taken by the signal or else for providing electric contacts between the different layers of the multi-layer; these holes will be internally metalized after completion of the multi-layer. Although not shown, the layer in the figure presents other references such as, ^■ for example, a product code; the number in the piling sequence; initial references for finding the correct position for the upper and under side of the layer; secondary references for finding the correct left-right, upper-lower positions of the layer. Figure 1 also shows two circular metalized points, 2 and 3, opposite each other placed close to the edges along a midway line, and four identical metalized grids 4, 5, 6 and 7 (or entirely of copper) placed close to the four corners of the layer 1. Points 2 and 3 are respectively surrounded by metal-free areas 2a and 3 a.

As explained in the introductory description, points 2 and 3 are used for optical alignment of the layer according to the respective axes x and y, marked on the figure. The grids 4 to 7 are used for inductive bonding of the layers as stated in the introduction. Characteristics of the product are given in the following table. ^' •

N.B.: 1 inch = 2.54 cm; 1 mil. = 1/1000 of an inch; 1 mm. = 39.4 mils The following table shows the dimensions of a, b, c, d, e, f, g in figure 1.

It is well known that a multi-layer type of PCB consists of layers of printed circuits alternating with layers of prepreg later subjected to heat and pressure to obtain the finished product. The single layers of the printed circuit consist of glass fabric and polymerised epoxy resin (FR4 for example) to whose faces the copper electric circuit has been applied by the normal procedure of chemical deposition of copper, photo-resist masking, removal of excess copper and hardened photo-resist, or one of the many possible alternatives. The through-holes can already be present but this is .not usual. Before being piled up the printed circuit layers are blackened by immersion in an oxidizing chemical bath. This is done to improve adherence and assist bonding. The prepreg is produced by a process of impregnating glass fabric with epoxy resin. The induction heating used in the machine, that will shortly be described, polymerises the prepreg limited to the bonding area .at the polar expansions sufficient for creating layer adhesion due to formation of polymeric chains between adjacent layers. This is the semi-finished product made by the machine subject of the invention. It is easy to move and store without causing misalignment of the metalized parts on the faces of the inner layers. Irrespective of what the present invention accomplishes, the semi-finished product will have to be completed by application of varying degrees of heat and pressure according to the manufacturing cycles, in order to extend polymerization to the remaining areas beyond where they are bonded:

Figure 2 shows the plan view of a machine 8 for alignment and adhesion of the layers of a multi-layer (not shown). The machine consists of four work stations marked A, B, C, D that operate as. follows: A Station for picking up, aligning and moving the single layers. B Station for piling/unloading the aligned/bonded layers. C Exchange station.

D Station for electromagnetic induction bonding. A strongly-built framework 9 supports these stations which are aligned as described along an axis of longitudinal symmetry LL. In station A is^' an aligning robot enclosed in a mobile frame 10 held by two linear guides 11 and 12 placed on either side of the, LL axis close to the sides of the framework 9. A motor-driven belt 13 allows the frame 10 to translate along the linear guides 11 and 12. These guides^ consisting of two round bars of tempered steel, extend along the whole length of station B. Visible in the piling and unloading station B is a template 14 consisting of a substantially rectangular plate, of specific dimensions for each type of panel, placed horizontally to support the layers when the multi-layer is being formed. The template 14 is fitted with a set of eight layer compressing pincers 15-22 disposed in pairs along the two external sides close to the corners. Each pair of pincers is so placed on the template that when they compress a layer, a respective metal grid 4-7 (Figure 1) lies between the two pincers without coming in contact with them. The template 14 is fixed to a more internal linear guide 23, along an axis LLl, parallel to axis LL and close to it, consisting of a round bar of tempered steel that extends along the whole length of stations B, C and D. A motor-driven belt 24 translates the template 14 between piling station B and bonding station D, and vice versa, passing through the exchange station C. The frame 10 and template 14 also comprise a mechanically precise coupling system consisting of two tempered steel pegs Al and A2 present at opposite sides of the frame 10, and of two tempered steel bushes 14a and 14b at corresponding positions on the template 14. The bonding station D comprises four electromagnetic induction bonding heads, Dl, D2, D3 and D4 connected to the framework 9 at positions corresponding to those of the metal grids 4-7 on the layer in Figure 1. The positions of the four bonding heads along the x axis are precision adjusted by four screws and four knobs D5, D6, D7 and D8. The positions along the y axis of the bonding heads Dl and D7 only, are precision adjusted by two screws and two knobs D9 and DlO. Visible in the bonding station D is a second template 25, identical in every way to the template 14, held in place by a second linear guide 26, identical to guide 23, placed along an axis LL2 parallel to axis LLl and at the same distance from axis LL. A second motor-driven belt 27, separate from the other belt 24, translates the template 25 between^' the bonding station D and the piling station B, and vice versa, passing through the exchange station C. The template 25 has its own set of eight layer-compressing pincers 28-35 placed in the same way as. the pincers 15-22, and comprises two tempered steel bushes 25a and 25b occupying positions on template 25 corresponding to those on the similar bushes 14a and 14b on the template 14. Unlike template 14, however, template 25 carries an already completed multi-layer ready. foV bonding (or else already bonded and ready for expulsion). Opposite template 14 there is a sketched-in figure of an operator, engaged in manual preparation of a multi-layer, his work consisting of laying a sheet of prepreg over each new layer after alignment. Apart from the aspect of mechanical configuration, the machine is also symmetrical on account of the role of the two templates, alternating at the end of each operative cycle, a point that will be clarified when its function is fully described, to explain why connection of template 14 to the sliding bar 23, and of template 25 to bar 26 is entirely arbitrary and can be reversed.

Figure 3 gives a perspective view of .the machine 8 in Figure 2 which shows a brushless motor 36 for translating the frame 10. round the pickup and alignment robot, and a support 37 that emerges through a central aperture in the upper face of said franite. The motor 36 sets the drive belt 13 in motion around a tensioning means 38 mounted on the framework 9. The frame 10 is fixed to the belt 13 by two plates 39, one at each end, screwed up to clamp the belt 13. The support 37 sustains the mechanical parts in the frame 10, this latter. being more clearly visible in the next figure. Looking at Figure 4, this shows the inside of the pick-up and alignment robot with the outer frame 10 removed. The robot comprises a heavy upper rectangular plate 40 anchored to the support 37 (Figure 3) so that it can slide. The plate 40 carries three polychromatic video-cameras of which a mobile one 41 and a fixed one 42^' are visible, placed so that the lenses are approximately above the fiducial icons 2 and 3 (Figure. 1) on the layer 1. The two tempered steel pegs Al and A2 are rigidly fixed to the plate 2 for adjusting the layer oή. the template, each peg having an extended cylindrical body, 49 and 50 respectively, emerging uppermost. Parallel to plate 40 and at a certain distance from its lower face, an adjustment plate 43 can be seen, connected to the plate 40 by three assemblies of hardened steel with sliding couplings, of which only two, 44 and 45, are visible. The plate 43 carries the mobile component of three linear single-phase motors 46, 47 and 48, the frame of which is anchored to the upper plate 40. These three motors serve for a movement consisting of rotation-translation of plate 43 and of layer 1 that adheres to its lower face due to the effect of a depression created by a suction pump of the Venturi tube type (not shown in the figure) whose purpose is to remove the air between plate 43 and layer 1.

Movement of the linear motors 46, 47., 48 for focusing the fiducial icons v 2 and 3 is governed by a processor whose memory has stored the ideal position to be given to each fiducial icon and its respective video-camera. The processor commands small movements in orthogonal directions (x, y) of the layer to be aligned, and any small horizontal rotations needed to obtain a perfect focus, this being indicated by a sensor provided for the purpose in the video-camera (this might be a CCD device, for example). The Δx and Δy in relation to the ideal fiducial positions Xo, Yo, on account of working tolerances and of .their position against the plate 43, represent corrections introduced by the system of alignment, The movement of rotation-translation of the lower plate 43 is guided by the sliding couplings 44 and 45. Plate 40 translates along the z axis (raising and lowering) by means of a pneumatic sliding cylinder (not shown) anchored inside the frame 10, with its shank fixed to the upper face of plate 40. The vertical sliding movement made by the two cylindrical rods 49 and 50 fixed to plate 40, is guided by axial bearings mounted on the plate that carries the pneumatic cylinder. Referring to the template 14, Figure 4 shows the presence of a support 14c placed below its layer-carrying plate, • the function of which is to engage the parts that cause the template to turn over outwards, as will later be explained. The pneumatic compressing pincers 19-22 are visible in their closed position. These pincers are fitted to their respective rails, such as 19a, onto which they can withdraw to allow each new layer to be added to the pile, and then advance to compress it. Figure 5 shows details of the bonding heads D1-D4 and of the conclusive part of movement of the two templates 14 and 25. It will be seen in Figure 5 that each bonding head consists of several parts: head Dl comprising parts DIa - DIf; head D2 comprising parts D2a - D2f; head D3 comprising parts D3a - D3f and head D4 comprising parts D4a - D4f (though not all these parts appear in the figure). The four heads are all the same so that a description of Dl covers them all. In Dl the central part DIa is a strongly-built C-shaped steel container that encloses a core of ferromagnetic material (ferrite), also C-shaped, around whose central part are wound the turns of an inductor winding that functions as the secondary of a transformer calculated so that the current circulating through it produces sufficient magnetic flow_. for inductive bonding. The inductor DIa presents two hollow seats at the two ends of a substantially square section to allow for introduction of two polar expansions DIb, Die orthogonally to the two parallel arms of the C. The polar expansions DIb, Die are enclosed in two Ertalon shells for connection to the sliding means in the terminal seats of the central inductor DIa placed across the template 25, and therefore across the ^•muiti-layer. The two shells DIb, Die are joined to two rods Did, Dig moved vertically by two pneumatic cylinders Die, DIf, respectively aligned above and below the polar expansions. Actuators Die, DIf control the distance between the polar expansions DIb, Die and the two faces of the multi-layer independently one from another. Precise centering of the copper grids with the axis of the polar expansions is adjusted separately by the adjustment knobs seen in Figure 2. When centering and distances are correctly adjusted, the polar expansions DIb,- Die permit maximum inductive bonding between the core DIa and the copper grids on the layers. Figure 5 also shows two brushless motors 51,. 53, anchored to the framework 9 beyond the terminal supports of the sliding bars 23 and 26; each shaft carries a serrated pulley 52 and 54. The two pulleys in turn engage the serrated belts 24 and 27 stretched by two other opposing serrated pulleys (not shown) placed before the starting point of station B. The belts 24, 27 rotating round their pulleys make a prevailingly rectilinear movement for translating the templates 14 and 25 anchored to them. As will become clearer when the way the machine functions is explained, the control system stops the motors 51 and 53 before they can continue beyond the stop placed at the bonding station A and at the piling/unloading station B, in the opposite direction of movement. After stopping, on reaching the stopping point their direction of rotation is reversed, together_. with their direction of translation. At one point in the process, the two templates, whose positions will alternate between stations A and B, are both obliged to pass through station C, this being , obtained by a mechanism for turning them over to be described later in Figures 6A and 6D, while their linear movement is made possible by means shown in Figures 6E and 6F. Figure 6A shows a section along a longitudinal plane that passes midway through the machine in Figure 2; to simplify the drawing only two central stations, B and C, are shown (these being the only two concerned with overturning). Referring to Figure 6a, the template 14 is seen when it has fully entered station B with, on top of it, a multi-layer ready to be taken to the bonding station D, passing through station C. The lower face of the thick supporting plate 14c of the template 14 is firmly fixed to two supports 70 and 70', spaced one from the other and extending right i inside the machine. The supports 70, 70' are drilled lower down to allow the template to slide along the translation guide 23, sustained by two terminal blocks fixed to the framework 9; of these only block 64 can be seen in the figure. A dotted line between supports 70- and 70' indicates, the TR mechanism that draws the template. 14 along. Supports 70 and 70' each end in a component joining them to their respective tabs 71 and .

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71', these in turn being fixed to a narrow bar 69 of a length substantially

. equal to that of the template 14, or slightly longer, parallel to the guide bar 23 but lower down and further inside. A pneumatic cylinder 66 can be seen close to the boundary between stations B and C, placed lower down than the bar 69. The pneumatic cylinder 66 is sustained by a support 65 anchored to the framework 9. The shank 61 of cylinder 66 terminates in a bronze joint 68 mou'rited on the tip. In joint 68 is a partially open hole into which the bar 69 can be fitted and slide if required. This is possible because, when the actuator 67 is idle, the axis of the hole in the bronze joint 68 is in perfectly aligned with the longitudinal axis of the bar 69.

Section B shows the template 14 just before it is made to rotate outward by the pneumatic cylinder 66 whose shank 67 is therefore fully retracted, but with the joint 68 already engaging one end of the rotating bar 69. ■ The bar 69 does not engage the joint 68 when the template 14 is in station A and before it is fully inside station B. When in station B the template 14 is made to rotate outwards by pneumatic cylinder 66 and, still in that position, is translated towards station C. This station in fact shows the template 14, as a dotted line, completely rotated outwards just before the pneumatic cylinder 66 turns it to a hqrizontaϊ position, which means that the shank 67 of cylinder 66 is elongated to maximum while the joint^' 68 still engages the other end of the rotating bar 69 but is higher up compared with the previous position. When it has resumed its horizontal position, the template 14 continues its movement towards station D while the rotating bar is no longer engaged with the bronze joint 68.

Figure 6B shows a view of the longitudinal section opposite to that in Figure 6A. In this figure the template 25 can be seen lying horizontally inside station C with an already bonded multi-layer laid on it ready to be overturned and then moved towards the unloading station B. Station B in fact shows the template 14, as a dotted line, still completely turned outwards just before reaching a horizontal position from where it can unload the multi-layer. The description given for trie preceding figure . _,

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also applies in this case where the ^equivalent parts are indicated by addition of the letter b. It is clear that the process controller commands actuators 66 and 66b in rotating their respective templates 14 and 15 in

^' opposite directions outwards, and in their subsequent translation through the exchange station C, both turned over.

In its upper part Figure 6C shows a cross section of the machine in

^■ Figure 2, along a plane that passes through the stations B and C turned towards the template 14 in station B. Lower down, the figure illustrates how a cross section view would look if template 25 were present instead of template 14. Referring to the figure, it will be seen that the framework 9 sustains two lateral supports, 61 and 62, for the sliding bars 11 and 12 of the pick-up and alignment robot 10. Visible in the central part of framework 9 is a mechanical support 65 anchored to which are two supports 63, 64 of the sliding bars 26 and 23. Further inwards and lower down than support 65, pneumatic cylinder 66 can be seen standing vertically with its shank 67 idle and almost completely retracted. Inside the hole in the bronze joint 68 at the end of the shank 67, the rotation bar 69 can be seen rigidly joined to a tab 71. Said tab is screwed against the connection to support 70, anchored to the plate 14c that sustains the template 14. The tab 71 and the connection to the support 70 form a square component one arm of which is rigidly joined to the bar 69 and the^' other arm connected to the support 70. Being pivotable, the pneumatic cylinder 66 can partially rotate around a pin 75 fixed to a mechanical support 74 anchored to the framework 9. The pin 75, parallel to the bar 69, partially passes through the cylinder 66 approximately at its centre. The figure shows template 14 in its horizontal position, as seen on the- right hand side of Figure 6A. Translation of template 14 is assisted by a bearing 73 sustained by a short arm 72 orthogonally connected to the plate 14c. The bearing 73 rolls on the cylindrical bar 26 that guides translation of the other template 25 providing another supporting surface. On looking at the lower part of Figure 6C where the same elements as those in the upper part are indicated by addition of the letter b, it will be seen that the tλvo figures are exactly the same in relation to the longitudinal axis of symmetry LL; this means that the two pneumatic cylinders 66 and 66b are placed at the two sides of axis LL, as are also the parts that fix the shanks 67 and 67b to the axes of rotation of templates 14 and 25 placed centrally on the translation guides 23 and 26. The configuration of templates 14 and 25 and of their respective means of rotation here described, explain how the upward thrust of shanks 67 and 67b causes the two templates to rotate in opposite directions, both as regards the way they turn over and as regards their return to a horizontal position.

Figure 6D shows an enlarged detail of the bronze joint 68 when it engages the bar 69. The tab 71 is rigidly fixed to the cylindrical bar 69 by any suitable means, such as screwing, welding, dap milling, etc., so long as it is lies parallel to said bar. ^' The line of contact between the edge of tab 71 and the cylindrical surface of bar 69 may vary within an angle of roughly a quadrant (90°). There is a hole 68' through the bronze joint 68 into which the end of the cylindrical bar -69 is inserted. In the wall of the hole 68' is an aperture along its whole length, amplitude of which is preferably less than a quadrant, such as will enable the tab 71 to translate even in the most restrictive conditions required by mechanical tolerances. Any slight reduction in the aperture increases the grip exerted by the joint 68 on the bar 69_. while the shank 67 is being lowered to return the template 14 to its horizontal position. One advantage is that the bronze material assists a sliding movement between the bar 69 and the tab 71. The figure shows a connection 76 between the tab 71 and the axial support 70. •

Figure 6E differs from figure 6C in that the template 14 is rotated round the centre of the circular section of guide 23 at a position of about 45° in relation to the horizontal plane. This position is maintained only for an instant along the trajectory that takes template 14 to a practically vertical position. Rotation of template 14 upwards is caused by the fact that actuator 67 rises and pulls along with it, bar 69 engaged in the hole 68' in the bronze joint 68. On account of mechanical constraints, the longitudinal axis of the shank 67, -and with it the whole pneumatic cylinder 66, rotates around the pin 75 at an angle of φ in relation to vertical. Rotation of the cylinder 66 is caused by elongation of the end of tab 71 towards the LL axis caused by an upward movement of the shank 67. Having once reached maximum elongation, the continued upward movement of the shank 67 returns the cylinder 66 to its initial position. Between the support 65 and the cylinder 66 is a small block (not shown) comprising a rubber end part inside which is a spring/ The block serves to hold the pneumatic cylinder 66 vertical even if it is not engaged by the bar 69. When the template 14 is being turned over, the body of the cylinder 66 rotates pressing against the rubber end and compressing the internal spring. When the shank 67 is recalled, the spring inside the block returns to its idle position so pressing on the cylinder 66 and favouring its vertical position. Rotation of the cylinder 66 in the opposite direction is prevented by contact against a tube in the framework 9. Figure 6F differs from figure 6E because the template 14 has been rotated to an almost vertical position and the cylinder 66 together with its shank- 67 are aligned along the vertical axis. The shank 67 reaches maximum elongation outside the cylinder 66. In this position the two templates 14 and 25 can translate without interfering with one another. In figure 6G the template 14 is seen from the side in a horizontal position with the supports 70 and 70 "engaged in the translation bar 23 whose cross section is cicular. 'Between supports 70 and 70' is a length of tube 80 in which the bar 23 is inserted by means of an Iasco coupling. The two cylindrical ends of the .length of tube 80 penetrate inside the supports 70 and 70' within two respective circular seats having an Iasco coupling. Between the supports 70 and- 70'^' the length of tube 80 outwardly appears as a parallelepiped, screwed into whose central part is a small block 81 that extends downwards and is then fixed to the drive belt 24. ^•

Figure 6H gives a section view along plane A-A of the preceding figure, showing parts 80 and 81, the drive belt 24 and a small plate 82 fixed to the serrated belt 24 by being screwed to the block 81. To obtain a better grip, the inner face of plate 82 presents teeth that are. complementary with those on the belt 24. The mechanism for pulling the template, described in relation to figures 6G and 6H₅ makes possible translation of the template 14 both when it is horizontal and when it is turned over since i the vertical direction of the belt 24 remains unaltered. When template 14 is turned to assume its almost vertical position, while rotating around the bar 23 together with the axial supports 70 and 70', it does not in fact involve the tubular component 80 that rolls in its own seat compensating rotation of the axial supports that sustain it. The only effect is a slightly outward movement of the belt 24 which increases tension and is therefore beneficial.

As regards overturning and translating the second template 25, the same applies as what has been said above for template 14. With the visual help of the following figures a description will now be given of the sequence of stages of production carried out by the machine subject of the invention. Though not explicitly shown in the figures, the

^■ complex movements of the machine are- electronically operated by a processor fitted with the necessary circuits for controlling the bus of the system and with a rewritable memory containing the firmware of the operational program. For positional control of the various mobile parts, sense-points of a type already known are provided for transducing information on positions, distances and angles into digital electric signals supplied to the processor by the bus of the system. In the same way the control points elaborated by the processor reach the various actuators connected to said bus. The actuators comprise: brushless motors 51 and 53 that operate horizontal translation of the templates 14 and 25; the brushless motor 36 for horizontal translation of the robot 10, the W

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pneumatic cylinder for vertically sliding the robot 10; the two pneumatic cylinders 66, 66b for turning over the templates 14 ^'and 25; the four pairs of actuators (Die, DIf , etc.) for vertically sliding the four welding heads D1-D4; the rotation-translation linear motors 46, 47, 48 for 5 aligning the layers inside the robot 10, the mobile video-camera 41 and the aspirator on the Venturi unit.

Stage 0: First of all, the various printed circuit layers that will form the inner layers, blackened and without adjustment holes, must be placed one above another in a reverse order compared with how they are piled for

10 the finished product stage. Respecting this sequence, several sets of

. inner layers can be placed one above another till a thickness compatible with the permitted maximum is reached. This stage can be executed externally to the machine, for example, preparation ,of a series of packages separately that will then be used to feed the machine.

15 Stage 1. Figure 7 The robot 10 is translated into station B freeing the work surface underneath. A pack of layers, formed as explained above, is transferred to the loading station A. ^lThe machine appears as shown in the figure with template 14 in the piling station B and template 25 in the bonding station D, both empty. This¹ obviously represents the initial

20 stage only because, after completion of the first working cycle, the two templates are never both empty but alternate between loading the single layers and unloading the semi-finished product. In the forthcoming stages a description will be given of the machine's normal running condition. Stage Z Figure 8 The template 25 arriving from the bonding station,

25 with the multi-layer fixed on top of it at its bonding points, is moved on to the exchange station C.

Stage 3. Figure 9 The robot 10 with the video-cameras 41, 42, takes up a position on the package of inner layers in station A and locates on the first of these the points for alignment mentioned in Figure 1. The

30 processor checks the correct position ©f the layer on the plate (to make sure it is not rotated), the correct position of the faces, (to make sure they are not turned over), and the correct number in the piling sequence. After these -preliminary checks, the robot 10 picks up, by suction, the upper inner layer and transfers it to the piling station B. During translation the position of the layer is adjusted by means of the video-cameras with fiducial icons and the linear rotation-translation motors and is then properly adjusted to the template 14 arid to any layers already laid.

When the robot 10 is entirely inside the piling station B, a command is given for descent towards the template 14, descent ceasing when the two pegs Al and A2 on the robot 10 have coupled with the bushes 14a and 14b at the sides of template 14.^' In this way the inner layer is laid onto the template 14 in perfect alignment w_vith any other layers already placed, but is still held against the plate 43 of the pick-up and alignment device.

Simultaneously the eight pincers 15-22 are caused to recede and open

■ after which they advance once more and close onto the pile of layers in formation including the new layer. At this point, when the pincers compress the new pile of layers against the template 14, the vacuum is released from the Venturi unit and the robot TO, left empty, is returned to the pick-up station A. The operator manually places a sheet of prepreg in the correct position on top of the last layer laid. This stage too could be automated by simply adding^'a robot integrated into the working cycle. The next inner layers are laid and the operations in stage 3 repeated until construction of the multi-layer is completed. •

Stage 4, Figure 10 The template 25, at that stage under the bonding station D, is translated into the exchange station C and the command given for turning it over. Stage 5. Figure 11 The robot 10 is translated into the pick-up station A. The command is given to overturn template 14, at that moment in station B with the pile of completed layers.

Stage 6, Figure 12 The overturned template 14 is translated from the piling station B towards the exchange station C. Simultaneously the overturned template 25 is made to translate from the exchange station C towards the unloading station B. Stage 7, Figure 13 The two templates 14 and 25 are rotated from the turned over position to horizontal. Referring to template 25 in station B, the pincers 28-35 are opened and the bonded multi-layer is manually unloaded by the operator. The robet 10 translates from station A to station B, thus freeing access to the loading station A for introduction of a new package of layers, following which the robot 10 is returned to station A.

Stage 8. Figure 14 Simultaneously with the operations described in the preceding stage, the template 14, carrying a pile of layers, is translated from exchange station C to bonding station D. The four pairs- of actuators (Die, DIf, etc.) are then vertically moved to bring the bonding heads D1-D4 to the metallized grids 4-7 formed on the pile of layers. The electric_, circuit from the current generator that feeds the inductors is closed for a set time for partially fusing the layers on said grids 4-7. Current is then switched off and the bonding heads D1-D4 withdrawn from- the pile of layers which are left to cool off and complete bonding. The cycle is resumed from Stage 1 ;but .with templates 14 and 25 in opposite positions compared with those they occupied in Figure 7.

From the description here given ,of a preferred form of execution, it is clear that changes can be made to the invention by an expert in the field without thereby departing from its sphere, as will appear from the following claims.

Claims

CLAIMS . . .

1. Machine for making semi-finished products of the printed circuit multi-layer type, hereinafter termed multi-layer, wherein are comprised: - a first supporting plate (14) for the single layers (1) composing the multi-layer;

- a second supporting plate (25) for the single layers (1) composing the multi-layer, said first and second supporting plate being aligned along a common axis (LL); - means for piling and reciprocal alignment (-10) of the layers composing the multi-layer;

- means (D1-D4) for electromagnetically bonding the aligned layers composing the multi-layer, separated from the piling means by a distance greater than the length of said plates; - first means (23, 24, 51, 52) able to cause translation of the first supporting plate (14) along said common axis between the piling means (10) and the bonding means (D1-D4), and vice versa;

- second means (26, 27, 53, 54) able to cause translation of the second supporting plate (25) along said common axis between the bonding means (D1-D4) and the piling means (10); and vice versa;

- first means (66, 67, 68, 69, 71, 70, 71', 70') for overturning the ■ first supporting means (14) able to produce first rotations in relation to a first axis (LLl) parallel to the common axis of translation (LL);

- second means (66b, 67b, 68b, /69b, 71b, 70b, 71 'b 70'b) for overturning the second supporting plate (.25) able to produce second rotations in the opposite direction to that of said first rotations in relation to a second axis (LL2) parallel to said first axis (LLl).

2. The machine as in claim 1, wherein said first means of translation comprise a first linear guide (23) of a circular cross section placed along said first axis (LLl) at a distance from the common -axis of translation.

3. The machine as in claim 2, wherein said second means of translation comprise a second linear guide (26) of a circular cross section placed along said second axis (LL2) at a distance from the common axis of translation and on the side opposite to the first axis (LLl).

5 4. The machine as in claim 3, wherein each of said first and second

V means of translation (23, 26) also comprise:

- two axial supports (70, 70'; 70b, 70'b) fixed to the supporting plate (14, 25) said supports pivoting on the linear guide (23, 26);

- means for transmitting the translating movement (24, 27); 0 - means (TR, TRb) for connecting the axial supports (70, 70'; 70b, 70'b) to the means for transmitting the translating movement (24, ^{' •} 27).

5. The machine as in claim 4, where in said connecting means comprise: 5 - a tubular component (80) for insertion of said translation guide (23), whose ends revoivingly pivot within two seats of said axial supports (70, 70'); a connecting component (81, 82) one^" end of which is joined to said tubular component (80) and the other end is engaged against a 0 serrated belt (24, 27) that transmits the translating movement.

6. The machine as in claim 4 or 5, wherein each of said first and second overturning means comprises:

- a bar (69) the length of which is about equal to that of the supporting . plate (14, 25); 5 - means (71, 71b, 76) for connecting said bar to the two axial supports (70, 70'; 70b; 70'b), said two connecting means extending towards the common axis of translation (LL) somewhat similar to a square one arm of which is connected to said bar (69, 69b);

- pivotable actuator means (66, 67; ■ 66b, 67b, 68, 68b) placed in a 0 Fixed position and so arranged as to exert a force on said bar (69, 69b) along an axis perpendicular to the translating guide (23, 26).

7. The machine as in claim 6, wherein said actuator means include: - a pneumatic cylinder (66, 66b),

- a joint engaged on the shank (67, 67b) of the pneumatic cylinder in which there is a through-hole (68') for insertion of said bar (69, 69b);

- an lateral opening (68") along the wall bounding the through-hole (68') having an angular opening less than, or equal to a quadrant.

8. The machine as in any one of claims from 1 to 7, wherein further means (11, 12, 13, 36, 38,. 39) are included able to produce translation movements on said means for piling and on said means for reciprocal alignment (10) in both directions along a common axis of ^• translation (LL) between a station (A), for picking up the single printed circuit layers from a pile of layers arranged in the reverse order, and said first or said second supporting plate (14, 25).

9. The machine as in claim 8, wherein the piling means and the means for reciprocal alignment (10) also include means for picking up by suction each single printed circuit layer (1).

10. The machine as in claim 9, wherein the means for piling and for reciprocal alignment (10) comprise optical means (41, 42) for focusing fiducial icons (2, 3) placed at previously established positions on each layer (1).

11. The machine as in claim 10, wherein the means for piling and for reciprocal alignment (10) comprise motor-driven means for rotation- translation (46, 47, 48) of the individual layers (1) previously picked up.

12. The machine as in claim 11, wherein the means for piling and for reciprocal alignment (10) and said first and second supporting plate

(14, 25) comprise mechanical means for adjustment coupled one to another (Al, 14a; A2, 14b).

13. The machine as in claim 12, wherein said first and second supporting plate (14, 25) comprise pairs of retractile .pincers (15-22; 28-35) for compressing the aligned and piled up layers.

14. The machine as in any one of the claims from 1 to 13, wherein said means (D1-D4) for induced bonding comprise opposing polar expansions (DIb, Die; D3b, D3e) that can be placed in position

• along an axis perpendicular to the common axis of translation (LL) and aligned with its respective metallized grid (4-7) present on each printed circuit layer (1) forming the multi-layer,

15. The machine as in any one 'of the claims from 1 to 14, wherein said common axis of translation (LL) is horizontal.

16. Method for making semi-finished products for multi-layer type printed circuits realizable by a machine that can be subdivided into work stations (A, B, C, D) placed along a linear path (LL) on a horizontal plane wherein, during normal running, the following steps are comprised: a) picking up a new layer (1) from a pile of layers for printed circuits, placed in reverse order, at a pick-up point (A); b) alignment of the new layer (1) by means of focusing an icon (2, 3) occupying a previously established position on the layers; c) translation of the aligned layer (1) to a first piling plate (14), placing said layer onto the pile then being formed, compression with the preceding layers and repetition of steps (a) to (c) until the pile of layers is complete; d) simultaneously with execution of the operations described in the preceding steps, bonding by electromagnetic induction of a completed pile of layers and anchorage to a second plate (25); e) translation of the second plate (25) from the bonding station

(D) to a free station (C) lying between said bonding station and the piling station (B), after which the second plate (25) together with its semi-finished multi-layer is then turned over outwards; ■ f) the first plate (14) is also turned over outwards together with the completed pile of layers anchored to it; i g) translation of the first plate (14) to the bonding station (D) and of the second plate (25) to the piling station (B) for unloading the semi-finished product; repetition of steps (a) to (g) with the plates in reversed positions.

17. The method described in claim 16, wherein the step of alignment by focusing is completed during translation.

18. The method described in claim 16 or 17, wherein bonding by electromagnetic induction is limited to circumscribed areas around short-circuiting metalized areas situated at previously established positions on each printed circuit layer.

19. The method described in any one of the claims from 16 to 18 wherein a layer of prepeg is added to the pile before a new printed circuit layer (1) is placed.