Abstract:
The present invention is generally related to devices which place surface-mounted (leadless) electronic components on recipient materials such as printed wiring boards or ceramic substrate and is more particularly concerned with a group of devices whose combined functions result in a systematized method of identifying suitable surface-mounted component location points on recipient material, and then placing the components at these location points en masse, in groups, or one at a time, as positioning requirements dictate.

Description:
This invention relates to a planned coordinate component placement system for electronic circuitry. 
     BACKGROUND OF THE INVENTION 
     At the present time, the methods generally used to assemble electronic curcuitry employing surface-mounted components on a recipient material essentially amount to arbitrary determination of component locations considering only electrical/electronic circuitry requirements and what is most expedient for the electronics draftsperson, with respect to component orientation, then etching or printing conductors on recipient material to support circuitry so determined. This arbitrary method of determining component locations and orientation has the disadvantage of causing difficulty when using automatic component placement devices to place surface-mounted components because the automatic devices must be adjusted to place components at each arbitrarily chosen point. After the recipient material is prepared, the surface-mounted components are placed in their appropriate positions using manual methods or by automatic electromechanical component placement devices. Manual methods have the disadvantage of being labor intensive and result in component placement rates of only 400 to 700 per hour. The relatively slow manual placement rates result from the fact that the assembly person must first deposit a small, metered amount of adhesive material onto the recipient material, one deposit at a time and then manipulate the component into position with tweezers. The tweezers, or in some instances, vacuum-type pickup devices, are required because of the small size of the components. Automatic electromechanicl component placement devices usually consist of several component handling segments, each segment, when properly adjusted, has the capability to deposit adhesive and one component on the recipient material during each cycle of the device. Surface-mounted components mounted on paper tape is the most common way to feed components to these electromechanical surface-mounted component placement devices. Each segment of the device must be fed a tape containing the appropriate component to be placed by that segment. The electromechanical mechanisms in each segment mechanically remove the component from the paper tape, mechanically manipulate it into position, then place the component into the adhesive on the recipient material using various forms of mechanical positioners. Because of the complexity of electromechanical surface-mounted component placement devices, they have the disadvantage of being relatively expensive, with prices ranging from about $50,000.00 for small semi-automatic models, to $750,000 or more for large, computer-controlled models. While the electromechanical surface-mounted component placement devices do significantly increase component placement rates to typically 10,000 to 15,000 per hour, they have another disadvantage in that the maximum length and width dimensions of the recipient material they can handle is about four inches by four inches. 
     To overcome these disadvantages of the existing methods, the present invention is developed as a system to systematize surface-mounted electronic component placement and is comprised of three primary supportive devices, the first of which defines in an identifiable manner, all possible surface-mounted component location points available in the system. The large number of possible component location points available per unit area of recipient material, lends flexibility to the system in that the draftsperson still has considerable latitude as to where a component may be placed, but the system requires that the draftsperson choose a specific point within the system for each component to be placed on the recipient material. The second supportive device is an adhesive dispensing device capable of applying to the recipient, a wide variety of adhesive materials at all component location points or any specific component location point within the system simultaneously with one cycle of the device, rather than one point per cycle as is the case with existing methods. The third supportive device is a component placement device which has no requirement for the mechanical component manipulation mechanisms found in existing surface-mounted component placement devices. The elimination of mechanical mechanisms greatly simplifies construction of the component placement device used in this system and significantly lowers the cost, thereby making the advantages of surface-mounted components as well as the advantages of mechanized component placement devices, more readily available to more electronic equipment manufacturers. Like the adhesive dispensing device, the component placement device in this system is designed to place components at any, or all, of the system&#39;s possible component location points. This is accomplished by precisely positioning the recipient material to the various predetermined component location points about the fixed component placement mechanisms, rather than adjusting each component placement mechanism to place a component at a desired point on the recipient material as is the case with existing component placement devices. Since each possible component location point within the system is identifiable, it can be programmed into a computerized system, and because it can be easily computerized, this system has the added advantage of being able to be readily integrated into existing computer-aided design and computer-aided manufacturing systems. 
     An object of the invention is to overcome disadvantages of existing systems. 
     Other objects and advantages will becomore more apparent from the following detailed description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view of a typical component layout template which illustrates component location points and their identification means; 
     FIG. 2 is a side view of the multipoint adhesive dispenser; 
     FIG. 2A is an isometric drawing of a typical adjustable recipient material support; 
     FIG. 3 is a sectional view of the assemblies disposed in the body of the multipoint adhesive dispenser; 
     FIG. 3A illustrates the needle seating block plugs; 
     FIG. 4 shows a cut-away, simplified view of a component placement device; 
     FIG. 5 is a sectional view of the component dispensing tube assembly; 
     FIG. 5A illustrates a component vial; 
     FIG. 6 shows a top view of a Cartesian positioning mechanism; 
     FIG. 7 is a plan view of the top of the component placement device, and; 
     FIG. 7A is a sectional view of a corner support disposed in the recipient material holder. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1 of the drawing, numeral 1 designates an example of a component layout template based on a major two-dimensional Cartesian coordinate system, having a hole at its center 2 and holes at the centers of all Cartesian coordinate subsystems represented by dots in the centers of the small squares exemplified by 3. Holes also appear at all possible system coordinates in each Cartesian coordinate subsystem as exemplified by 4. The X=0, Y=0 coordinates of each Cartesian coordinate sybsystem 3 are identified by combining a column designation, exemplified by 5, and a row designation exemplified by 6. The Cartesian coordinate subsystem 4 has X=0, Y=0 coordinates identified by the R4 column designator and the number 4 row designator, therefore, the X=0, Y=0 coordinates (or the center) of the Cartesian coordinate subsystem 4 are identified as R44. To identify a specific component location point within the set coordinates in Cartesian coordinate subsystem 4, such as the coordinates of the point indicated by 7, count the number of points to the +X direction (to the right) and the number of points in the -Y direction (or down) in the usual manner. The point 7 is identified on the template then as R44 which designates the specific Cartesian coordinate subsystem, and X=4, Y=-4 designates the specific component location point, or coordinates, within the Cartesian coordinate subsystem R44. 
     Assume for the purpose of this descriptive discussion that the recipient material to be designed is a printed wiring board. The center of the component layout template 2 is to be located directly over the center of the printed wiring board design artwork; both the design artwork and the component are of the same scale, for example 1:1 or 2:1, with the locations of all surface-mounted components being selected from coordinates available on the component layout template. Outlines of the terminations of the surface-mounted components are then placed on the printed wiring board design artwork by superimposing the surface-mounted component centers over the appropriate selected component location coordinates. Traces are then drawn to connect the components in the desired electrical configuation. In addition to using a template, the component location coordinates could be identified on design artwork by optically projecting them onto a suitable drawing material from behind a transparent drafting table or displaying them on the video display unit of a computer-aided design system with print-to-scale capabilities. When a printed wiring board is designed so that each surface-mounted component center is located at a point which coincides with coordinates in any one of the Cartesian coordinate subsystems, then those component location points are functionally coincident with points which may be operated upon by a multipoint adhesive dispensing device which will be discussed presently. 
     In FIG. 2, numeral 1 denotes the printed wiring board, or recipient material, which is placed on an adjustable recipient material support 2. A more detailed view of the adjustable recipient material support is shown in FIG. 2A. At each of the four corner supports 3, of the adjustable recipient material support, is a recipient material locating pin 3A, which is intended to pass through a drilling registration hole that is designed to appear near each of the four corners of the printed wiring board. 
     Referring to FIG. 2A, the thumbscrews 4A, are used to loosen clamping mechanisms, exemplified by 5A, which are located in the fixed support rails 6A, and the adjustable support rails 7A. Loosening the thumbscrews on the adjustable support rails and corner supports 3, releases the clamping mechanisms and permits adjustment of the adjustable support rails and the corner supports. The corner supports and the adjustable side rails are maneuvered to allow fitting of all four recipient material locating pins into the drilling registration holes of the recipient material. The recipient material is then properly positioned in the multipoint adhesive dispensing device and then the thumbscrews are tightened to clamp the corner supports and the adjustable side rails firmly in place. With the recipient material properly positioned, the operator of the multipoint adhesive dispensing device depresses both actuators 4, FIG. 2, of a two-hand, no tie-down switching system to start the multipoint adhesive dispenser operating cycle. The operating cycle begins by control valve 5 opening allowing pressurization of a pneumatic spring-return cylinder 6 which in turn, causes the recipient material support with recipient material properly positioned thereon, to be raised upward to a suitable distance from the adhesive dispensing needles, exemplified by 7. When the recipient material has been raised to the proper position, it&#39;s presence is detected by a proximity sensor or switch 8, which provides a signal to valve 9. Valve 9 is supplied with a metered amount of pneumatic or hydraulic pressure through pressure inlet fitting 10 and pressure hose 11. The metered pressure is admitted by valve 9 and through pressure hose 12, to the inlet of a double-acting cylinder 13, which causes the rod 13A of the cylinder to force the pressure plate 14 in the body 15 of the adhesive dispensing device, downwardly. This positive downward pressure on the reservoir of adhesive 16 disposed in the body of the adhesive dispensing device, causes the adhesive to be forced through the adhesive dispensing needles and then onto the recipient material. The pressure on the adhesive reservoir is maintained for a period of time sufficient to force the desired amount of adhesive onto the recipient material. The pressure is then relieved by the relief mechanism in valve 9. At the same time that valve 9 begins to relieve the pressure in cylinder 13, valve 5, because of timing, begins to relieve the pressure in the spring-return cylinder 6. Relieving the pressure on cylinder 6 allows the recipient material to begin descending to its initial starting position. This descent is detected by a second proximity sensor 17 or switch which sends a signal via appropriate conductors to valve 18, causing it to activate momentarily when the recipient material is approximately one-sixteenth of an inch from the tips of the dispensing needles. Valve 18 is supplied with pneumatic pressure through pressure inlet 19 and pressure hose 20. The momentary burst of pressure from valve 18 passes through pressure hose 20 to the inlet side of cylinder 13 via pressure hose 21 which will cause the pressure plate to be lifted upward momentarily causing a negative pressure of brief duration to develop in the adhesive reservoir. This negative pressure will cause the adhesive material appearing at the tips of the adhesive dispensing needles to be drawn a short distance up into the dispensing needles. The negative pressure portion of the operating cycle is necessary to eliminate the formation of threads of adhesive material which form when the deposits of adhesive material on the recipient material are drawn away from the tops of the dispensing needles. The threads of adhesive tend to form due to the high viscosity and elasticity of uncured component staking adhesives. 
     FIG. 3, numeral 22 designates an adhesive dispensing needle seating block molded of neoprene or other similar flexible, solvent-resistant material. Molded inside the adhesive dispensing needle seating block is a one-eighth inch thick steel support plate 23, which has numerous holes through it. The steel support plate is also drawn to form a uniform, shallow dome. Each hole in the steel support plate corresponds to a set of component location coordinates on the component layout template, therefore, a typical steel support plate would have one hole in it for each component location point in the system of component location points. The holes in the steel support plate are functionally coincident with the component location points. During, or after the process of molding the perforated steel support plate inside the neoprene block, small passages are created through the neoprene block which also pass through centers of the holes in the steel support plate. These passages will allow adhesive dispensing needles 7 to be pressed into the needle seating block in a manner that will result in the adhesive dispensing needle being pressed into the needle seating block from one side, pass through the corresponding hole in the steel support plate, and protrude out of the opposite side of the needle seating block by a minute amount. The size of the passages through the needle seating block are small, therefore, a liquid-tight seal is formed between the body of the dispensing needle and the neoprene needle seating block. To prepare the multipoint adhesive dispensing device for use, all adhesive dispensing needle passages are initially plugged in a manner exemplified by 24, using molded plastic plugs, FIG. 3A, 35, molded into strips 26, with tear-away retaining strips 27. The molded plastic plugs are molded in strips and spaced at a distance on the strips that is equal to the spacing between the dispensing needle passages in the needle seating block. The plugs are pressed into the needle seating block, then the retaining strips are torn away leaving the plugs in place. The needle seating block is then inverted and the upper needle retaining plate, FIG. 3, 28, is placed over guide pins 29, and then positioned against the needle seating block. The upper needle retaining plate is perforated in a manner identical to the steel support plate 2. Adhesive dispensing needles are then inserted through the holes in the upper needle retaining plate that correspond with the component location points (coordinates) previously selected from the component layout template and transferred to the recipient material. The dispensing needles are pressed through the upper retaining plate and the needle seating block is exemplified by 7. As the dispensing needles are pressed through the needle seating block, they displace the plastic plugs 24 previously inserted. When dispensing needles have been inserted at all desired locations, the lower dispensing needle retaining plate 30 is placed over the guide pins exemplified by 29, and over the dispensing needles since it too is perforated in a manner identical to that of the steel support plate and the upper needle retaining plate. Once the lower needle retaining plate is in place, slide fasteners, exemplified by 31, mounted on the lower needle retaining plate, are used to engage and hold the locating pins 29, which results in the needle seating block, upper needle retaining plate, dispensing needles, and the lower needle retaining plate being fastened together in an integral unit which is then placed into the body 15 of the adhesive dispensing device. Around the perimeters of the needle seating block and upper and lower needle retaining plates, are flexible seals, exemplified by 32. The fit of these three components relative to the inner walls of the body of the adhesive dispensing device is such that a liquid-tight seal is formed between the seals and the inner walls of the body of the adhesive dispensing device. The next component fitted into the body of the adhesive dispensing device is a fine mesh adhesive filter 33 which is attached to a metal frame having locating pins exemplified by 34, connected to it. These locating pins are inserted through passages provided in the needle seating block, upper and lower needle retaining plates, and the lower body support flange, exemplified by 35, on the body of the adhesive dispensing device; then they are secured by fastening means exemplified by 36. The inner assemblies of the adhesive dispensing device fastened together as described above, will keep all components in their proper places during both the positive and negative pressure portions of the adhesive dispensing cycle. Next, the adhesive material is placed into the adhesive reservior 16 in the body of the adhesive dispensing device, then the pressure plate 14, having a flexible seal 32, affixed to its perimeter, is inserted into the body of the adhesive dispensing device. The fit of the pressure plate is such that the seal about its perimeter forms a liquid-tight seal between the inner walls of the body of the adhesive dispensing device and the seal. A manually operated pressure relief valve 37 is opened to allow the air that would otherwise be trapped to escape. The pressure plate is lowered into the body of the adhesive dispensing device to the level of the adhesive, then the pressure relief valve is closed. The rod from the pneumatic cylinder 13 mounted on the adhesive reservior cover 38, is attached to the pressure plate, then the cover is placed over the adhesive dispensing device body and securely clamped in place by clamps emplified by 39. The pressure hoses 21 and 12 are then connected to the pneumatic cylinder 13 and the adhesive dispensing device is ready for use. 
     After adhesive material has been deposited on the recipient material, the recipient material is transferred to a surface-mounted electronic component placement device. 
     Referring to FIG. 4, numeral 3 is a second adjustable recipient material holder. Recipient material 1 with adhesive material applied, is placed on the recipient material holder with the side having adhesive applied facing downward. The recipient material holder is connected to an X-Y or Cartesian positioning mechanism 40 which can be actuated by manual or computer-controlled means. Also, connected to the Cartesian positioning mechanism by means of a supportive structure 41, is an openwork recipient material holddown platen 42 which has integrated into it a mechanism 43 for grasping the recipient material at its edges. The recipient material holddown platen is lowered manually by a lever 44, or by computer-controlled means, onto the recipient material after the recipient material has been properly positioned on the recipient material holder to clamp the recipient material firmly in place during the component placement cycle. Components are placed on the recipient material by first providing, for example, pneumatic pressure at the pressure inlet connection 45. The air under pressure passes through a pressure regulator and filter unit 46, to control valves 47. When the control valves are opened, the regulated pneumatic pressure is released into pressure hoses 48, leading to distribution manifold 49. Pressure hoses, exemplified by 50, from the distribution manifolds are connected to component dispensing tube assemblies 51, each of which contains surface-mounted types of electronic components stacked into a column. The pressure supplied to the component dispensing tube assemblies causes the columns of components to be forced upward and through the open ends, exemplified by 52, of the component dispensing tube assemblies. The open ends of the component dispensing tube assemblies are functionally coincident with the center or X=0, Y=0 coord inates of the Cartesian coordinate subsystems shown in FIG. 1, numeral 3, when the Cartesian positioning mechanism is set to its X=0, Y=0 position. However, the open end(s) of one or more of the component dispensing tube assemblies can be made functionally coincident with any set of coordinates in any of the Cartesian coordinate subsystems by properly repositioning the Cartesian positioning mechanism. During the actual component placement operation, the recipient material is positioned in very close proximity to the open ends of the component dispensing tube assemblies. As the columns of components are forced upward, the top component in each column is forced into the adhesive material which was previously deposited on the recipient material. The component dispensing tube assemblies are supported by upper 53, and lower 54, support grids which are suitably mounted on the framework of the component placement device. When the pressure in each distribution manifold reaches sufficient (preset) magnitude to force the electronic components upward and into the adhesive material, the condition is sensed by pressure sensors 55 which send a signal to the associated control valve causing the control valve to close and subsequently relieve the pressure in the associated distribution manifold. When all manifolds have been properly pressurized, and then relieved, a vacuum transducer 56 is activated briefly to cause a brief and gentle vacuum in all distribution manifolds and, consequently, in all component dispensing tube assemblies. The vacuum causes the columns of components remaining in the dispensing tubes to be drawn a short distance back into the dispensing tubes, keeping them securely in position. The components at the tops of the component columns having been forced into the adhesive material adhere to the recipient material. The remainder of the components are drawn back into the dispensing tubes. 
     In FIG. 5, numeral 51 is a component dispensing tube assembly which is provided with clips 57 which firmly hold the component dispensing tube assembly in its position in the upper and lower support grids; 58 provides a means to connect a small pressure hose to the base of the component dispensing tube. A metal pin 59, coated with neoprene or similar flexible material, is sized so a reasonably pressure tight seal is formed between the pin and the periphery of the holes in the component dispensing tube through which it is inserted. 
     A component vial 60, containing surface-mounted types of electronic components which are stacked into a column, is exemplified by FIG. 5A, 61, on top of a moveable or floating seal 62. The moveable seal fills and seals a small segment of the interior space of the component vial. The component vial is the same shape as the component dispensing tube and is dimensioned to telescope into the component dispensing tube. After the component vial is inserted into the component dispensing tube, it is pinned into position by aligning the holes 63 in the component vial with corresponding holes in the component dispensing tube, then the neoprene coated metal pin is inserted through the aligned holes, thus securing the component vial inside the component dispensing tube. The space between the outer walls of the component vial and the inner walls of the component dispensing tube is sealed by means of ring-type seals 64 partially recessed in grooves in the outer perimeter of the component vial. These seals seal the space between the outer walls of the component vial and the inner walls of the component dispensing tube; the neoprene coated metal pin seals the holes in the component dispensing tube. When pneumatic pressure is admitted to the component dispensing tube assembly, it causes the moveable seal 62, and the components placed upon it, to be forced upward. The component vial is molded of a suitable plastic and has the strength to withstand the pressures to which it is subjected. The component vial would also serve as a shipping container for the electronic components. The component dispensing tube would be made of extruded or molded metal or plastic material capable of withstanding operating pressures. 
     Referring to FIG. 6, numeral 65 indicates the points on the Cartesian positioning mechanism at which the adjustable recipient material holder is connected. The Cartesian positioning mechanism is suitably supported by the frame work of the component placement device shown in FIG. 4. 66 (Y-axis), and 67 (X-axis) are ball-detent mechanisms which are actuated manually using levers 68 and 69 respectively. Motion of the Cartesian positioning mechanism along the X-axis is permitted by precision slide mechanisms 70 and 71, and along the Y-axis by precision slide mechanisms 70A and 71A. The ball detent mechanisms are used for manual operation and provide a means to incrementally position the recipient material 1 with precision to any specified coordinates in the Cartesian subsystems. These ball detent mechanisms are replaced with computer-controlled actuators when the system is computerized. The Cartesian positioning mechanism provides the means to move the recipient material to a quantity of component location points above the component dispensing tube assemblies that equals the quantity of component location points or coordinates existing in one Cartesian coordinate subsystem. By moving the recipient material to predetermined locations above the component dispensing tube assemblies, exemplified by 51, while they are supported in the support grid(s) 53, any one of thousands of possible component location points at which a component may be placed is accessible to at least one and, in most cases, more than one of the component dispensing tube assemblies. 
     To prepare the component placement device for use, FIG. 7, numeral 72, indicates two spring-loaded centering pins which are manually pulled out far enough to allow the recipient material holddown platen 42, and that portion of the recipient material hold-down platen support 41 which extends over the support grid 53, to be rotated toward the rear of the component placement device to free the area over the support grids of obstructions. The operator is informed in writing as to which components get inserted into specific component dispensing tubes. The component dispensing tubes are identified by consecutive numbers and by which side of the support grid centerline 73 they are on. The operator is also informed where to place each component dispensing tube assembly in the support grid. As the columns in the support grid are filled vertical 74 and lateral 75 support members are assembled into the support grid. As each component dispensing tube is taken from its storage position 76, a component vial is inserted into the component dispensing tube and the vial pinned into place as previously described to create the component dispensing tube assemblies. When all required component dispensing tube assemblies have been placed in the support grid, the recipient material is fitted onto the adjustable recipient material holder and centered over the support grid in a manner similar to that described for FIG. 2. The recipient material holddown platen is then returned to its centered position using the centering pins. The component placement device is now ready for use. 
     Assume that a recipient material with adhesive applied at 80 component location points and that it has been properly positioned on the recipient material holder with the adhesive side facing downward toward 40 component dispensing tube assemblies exemplified in FIG. 7 by numeral 51. The recipient material holddown platen is then lowered onto the recipient material, firmly clamping the recipient material into place. The operating cycle is started manually by depressing a two-hand, no tie-down switch pair 77, or by computer-actuated means. Each of the 40 component dispensing tube assemblies is pressurized as described earlier, resulting in 40 components being deposited in the adhesive on the recipient material. However, adhesive was applied to 80 component location points on the recipient material. The remaining 40 components will be deposited during a second operating cycle of the component placement device. Before starting the second operating cycle, the recipient material must be moved to a set of coordinates in the Cartesian subsystem of coordinates, for example, X=4, Y=-4.  The manually operated system operator would raise the recipient material holdown platen, which also results in the recipient material being raised about one inch above the openings of the component dispensing tube openings. 
     Referring to FIG. 7A, numeral 3 shows one of the four corner supports on the recipient material holder and recipient material 1 as it is supported on the recipient material locating pin 3A disposed in the corner support. The spring 78 is sufficiently strong to raise the recipient material and the locating pin to the upper limit of travel determined by a shoulder 79, on the recipient material locating pin. These springs raise the recipient material well above the openings of the component dispensing tube assemblies between operating cycles of the component placement device to avoid interference between the component dispensing tube assemblies and the previously deposited components. To reposition the recipient material from the present X=0, Y=0 coordinates to the next position, X=4, Y=-4, the X-axis lever FIG. 7, 69, is moved four positions to the right or to the (+4) position. The distance the recipient material is moved is controlled by the previously described ball detent mechanisms connected to the Cartesian positioning mechanism disposed in the component placement device. The Y-axis lever 68, is moved four positions toward the front of the component placement device or to the (-4) position. The recipient material holdown platen is lowered again onto the recipient material and the component placement device is cycled a second time to deposit the remaining 40 components at 40 locations different from the initial 40 locations. Since the recipient material holdown platen is connected to the same Cartesian positioning mechanism as the recipient material holder, both are moved simultaneously, hence, no readjustment of the recipient holddown platen is necessary. The recipient material is repositioned as described above to as many coordinates as necessary and the component placement device recycled as many times as required to deposit surface-mounted components on the recipient material. 
     External electrical power at 115 or 230 volts and 50 or 60 Hertz would be provided through an electrical power cord to the component placement device from a standard source of such electrical power in the event electrical power is required for controls functions. The controls functions can also be performed by pneumatically actuated controls. 
     Thus it can be seen from the preceeding description that surface mounted electronic components can be place on recipient mateial rapidly and accurately using the devices herewith described. 
     While I have illustrated and described several embodiments of my invention, it will be understood that these are by way of illustration only and that various changes and modifications may be contemplated in my invention and within the scope of the following claims: