阅读说明：本技术 一种基于cam系统的自动移线移孔的检测与优化方法 (CAM system-based automatic line and hole moving detection and optimization method ) 是由 王克昌 梅炽元 薛敬 吕聪 于 2021-08-10 设计创作，主要内容包括：本发明公开了一种基于CAM系统的自动移线移孔的检测与优化方法,包括：预处理、参数导入与设置、自动监测、优化调整等步骤。通过上述方式,大幅度提升了工作效率以及PCB板走线图优化的成功概率,从而提升了PCB制造业的整体盈利效率,另外,自动化智能化移线移孔方法贯彻了工业制造自动化智能化的发展趋势,以高效的系统操作代替大量人工操作,节约制造前处理生产资料的成本。(The invention discloses a detection and optimization method for automatically moving lines and holes based on a CAM system, which comprises the following steps: preprocessing, parameter importing and setting, automatic monitoring, optimization and adjustment and the like. By the mode, the working efficiency and the success probability of optimizing the wiring diagram of the PCB are greatly improved, so that the overall profit efficiency of the PCB manufacturing industry is improved, in addition, the automatic intelligent line and hole moving method follows the development trend of industrial manufacturing automation intelligence, a large amount of manual operation is replaced by efficient system operation, and the cost of manufacturing pretreatment production data is saved.)

1. A detection and optimization method for automatically moving lines and holes based on a CAM system is characterized by comprising the following specific steps:

(1) the wire-shifting and hole-shifting functional module carries out industrial manufacturing analog simulation pretreatment on the multilayer PCB wiring diagram;

(2) recording the layout prohibiting parameters, and forming a layout prohibiting area on the periphery of each hole, line and pad disc on the PCB according to the layout prohibiting parameters;

(3) detecting the current spacing between all components in the industrial manufacturing simulation structure, and if the current spacing does not meet preset layout prohibition parameters, reporting an error and displaying an error analysis list and error comparison information;

(4) and selecting a manual optimization mode or an automatic optimization mode to optimize error points and generate a hole-shifting and line-shifting optimization file.

2. The method for detecting and optimizing automatic line and hole shifting based on the CAM system as claimed in claim 1, wherein the preprocessing in step (1) comprises:

(1.1) the wire moving and hole moving functional module acquires a lead-in multilayer PCB wiring diagram;

(1.2) carrying out production industrial manufacturing simulation on the components and the wiring lines on the PCB wiring diagram according to preset industrial manufacturing simulation parameters to obtain an industrial manufacturing simulation structure;

(1.3) carrying out shape fine adjustment on all components according to preset shape adjustment parameters so as to match the equipment limit of a production line;

(1.4) synchronous movement of the multilayer holes: combining the same hole on the multilayer circuit layer and a pad disc corresponding to the hole, wherein the hole and the pad disc in each combination are represented on PCBs of different levels by mutually-associated graphs with preset sizes, and performing network analysis on a graph set of the holes according to network relation information of the circuit board so as to integrate the graphs affecting the same hole of multiple levels, so that the same hole synchronously moves on different multilayer circuit layers;

(1.5) moving holes/wires does not change connectivity: and analyzing and acquiring the network communication relation information of the connecting lines and the holes to form and store a network relation set of the lines and the holes.

3. The method of claim 2, wherein the industrial simulation parameters include inner and outer layer compensation parameters and loop optimization parameters.

4. The CAM system-based automatic line-shifting and hole-shifting detection and optimization method of claim 3, wherein the inner and outer layer compensation parameters comprise global line parameters, global large copper surface parameters, optical alignment point position information, global patch parameters, global ball patch parameters, PTH compensation parameters, VIA compensation parameters.

5. The CAM system-based automatic line-shifting and hole-shifting detection and optimization method of claim 3, wherein the hole-ring optimization parameters include a single-sided minimum hole-ring value VIA parameter, a single-sided optimal hole-ring value VIA parameter, a minimum hole-ring value blind hole parameter, a single-sided minimum hole-ring value PTH parameter, and a single-sided optimal hole-ring value PTH parameter.

6. The CAM system-based automatic line shifting and hole shifting detection and optimization method according to claim 1, wherein the layout prohibition parameters include a line-to-line pitch threshold, a line-to-SMD-PAD pitch threshold, a line-to-BGA-PAD pitch threshold, a line-to-PTH-PAD pitch threshold, a line-to-VIA-PAD pitch threshold, a SMD-PAD-to-BGA-PAD pitch threshold, a SMD-PAD-to-PTH-PAD pitch threshold, a SMD-PAD-to-VIA-PAD pitch threshold, a BGA-PAD-to-PTH-PAD pitch threshold, a BGA-PAD-to-VIA-PAD pitch threshold, and a PTH-PAD-to-VIA-PAD pitch threshold.

7. The method of claim 2, wherein when the manual optimization mode is selected to optimize the error reporting points:

(4.1.1) selecting holes/lines needing to be moved and moving the positions of the holes/lines, and detecting a network relation set of the connecting lines and the holes and the current distance between a moving object and surrounding components in real time in the moving process;

(4.1.2) if the network relation set of the connecting line and the hole is detected to be changed after the hole is moved and the line is moved, namely the network relation of the connecting line and the hole is changed, judging that the position of the moving object is a wrong position and reporting the wrong position to a user so that illegal operation cannot be finished;

(4.1.3) if the current distance between the moving object and the peripheral components does not meet the preset layout prohibition parameters, displaying a layout prohibition area contacted or entered by the moving object around the components in real time, and meanwhile, judging that the position of the moving object is an error position and sending prompt information;

(4.1.4) when the network relation set of the connecting lines and the holes and the preset layout prohibiting parameters are simultaneously met, judging that the position of the moving object is the correct position;

and (4.1.5) judging whether copper surface adaptation is needed or not according to preset selection information when the hole is moved and the line is moved.

8. The method according to claim 2, wherein when the automatic optimization mode is selected to optimize the error points:

(4.2.1) constructing a multi-dimensional model according to the number of error reporting objects;

and (4.2.2) according to preset or acquired arrangement rules, network relation information among components, industrial manufacturing simulation parameters and layout prohibition parameters, carrying out automatic position arrangement fine adjustment on the error reporting object by adopting a genetic algorithm so as to realize one-key automatic adjustment optimization and copper surface adaptation.

9. The method for detecting and optimizing automatic line shifting and hole shifting based on the CAM system according to claim 7 or 8, wherein the step of copper surface adaptation during line shifting and hole shifting comprises: when the copper surface is selected to be matched, after the hole/line moves, the system automatically selects a local copper surface area to be matched according to the position of the hole/line, and adjusts the range size and the shape of the copper surface area according to the network relation information and the layout prohibition parameters among all components, so that the copper surface is matched with a new hole line arrangement space.

Technical Field

The invention relates to the field of PCB manufacturing industry, in particular to a detection and optimization method for automatic line and hole shifting based on a CAM system.

Background

When a PCB board diagram (production data) is processed at a PCB board factory (production manufacturer), the following ubiquitous problems are found:

1. real-time detection is not provided when a certain figure in a certain layer is moved, and a plant engineer cannot predict the influence of operation on a PCB wiring diagram in the actual operation process.

2. The multi-layer holes cannot be moved in a single operation, and a plate factory engineer needs to repeatedly operate different levels and compare hole coordinate parameters, so that the implementation method is unrealistic.

3. When the hole is moved, the moved hole is disconnected with a connecting wire connected with the moved hole, so that the circuit is opened, and the PCB network connection is disconnected. The board mill engineer needs to manually compensate the connecting wires.

4. The connectivity of a plurality of connecting lines in different board diagram networks cannot be detected, the distance is not considered in the line moving process, and the line interleaving and the parallel connection are caused by the large-amplitude movement; the small-amplitude movement can reduce the thickness of an insulating base material between components, noise signals are generated under the condition of high frequency or high voltage to interfere, even breakdown is caused to form a short circuit, the circuit principle is changed, and the actual using effect of the PCB is deviated.

5. The copper skin area of the moving area is not automatically modified to fit the modified hole line layout after moving the hole, and the board factory engineer needs to manually modify the copper surface shape.

Disclosure of Invention

The invention mainly solves the technical problem of providing a detection and optimization method for automatically moving lines and holes based on a CAM system, has the advantages of high reliability, accurate positioning, high detection precision and the like, and has wide market prospect in the application and popularization of PCB manufacturing.

In order to solve the technical problems, the invention adopts a technical scheme that:

the method for detecting and optimizing the automatic line and hole shifting based on the CAM system comprises the following specific steps:

(1) the wire-shifting and hole-shifting functional module carries out industrial manufacturing analog simulation pretreatment on the multilayer PCB wiring diagram;

(2) recording the layout prohibiting parameters, and forming a layout prohibiting area on the periphery of each hole and line on the PCB according to the layout prohibiting parameters;

(3) and detecting the current spacing between all components in the industrial manufacturing simulation structure, and if the current spacing does not meet the preset layout prohibition parameters, reporting errors and displaying an error analysis list and error comparison information.

(4) And selecting a manual optimization mode or an automatic optimization mode to optimize error points and generate a hole-shifting and line-shifting optimization file.

In a preferred embodiment of the present invention, the pretreatment in step (1) comprises the following specific steps:

(1.1) the wire moving and hole moving functional module acquires a lead-in multilayer PCB wiring diagram;

(1.2) carrying out production industrial manufacturing simulation on the components and the wiring lines on the PCB wiring diagram according to preset industrial manufacturing simulation parameters to obtain an industrial manufacturing simulation structure;

(1.3) carrying out shape fine adjustment on all components according to preset shape adjustment parameters so as to match the equipment limit of a production line;

(1.4) synchronous movement of the multilayer holes: combining the same hole on the multilayer circuit layer and the pad disc corresponding to the hole, wherein the hole and the pad disc in each combination are represented on PCBs of different levels by mutually-associated graphs with preset sizes, and performing network analysis on the graph sets of the holes according to the network relation information of the circuit board so as to integrate the graphs affecting the same hole of multiple levels, so that the same hole can synchronously move on different multilayer circuit layers;

(1.5) moving holes/wires does not change connectivity: and analyzing and acquiring the network communication relation information of the connecting lines and the holes to form and store a network relation set of the lines and the holes.

In a preferred embodiment of the present invention, the industrial manufacturing simulation parameters include inner and outer layer compensation parameters and an annular ring optimization parameter.

In a preferred embodiment of the present invention, the inner and outer layer compensation parameters include global line parameters, global large copper surface parameters, optical alignment point position information, global paste parameters, global ball paste parameters, PTH compensation parameters, VIA compensation parameters.

In a preferred embodiment of the present invention, the ring optimization parameters include a single-sided minimum ring value VIA parameter, a single-sided optimal ring value VIA parameter, a minimum ring value blind VIA parameter, a single-sided minimum ring value PTH parameter, and a single-sided optimal ring value PTH parameter.

In a preferred embodiment of the present invention, the forbidden arrangement parameters include a line-to-line pitch threshold, a line-to-SMD-PAD pitch threshold, a line-to-BGA-PAD pitch threshold, a line-to-PTH-PAD pitch threshold, a line-to-VIA-PAD pitch threshold, an SMD-PAD-to-BGA-PAD pitch threshold, an SMD-PAD-to-PTH-PAD pitch threshold, an SMD-PAD-to-VIA-PAD pitch threshold, a BGA-PAD-to-VIA-PAD pitch threshold, a PTH-PAD-to-VIA-PAD pitch threshold.

In a preferred embodiment of the present invention, when the manual optimization mode is selected to optimize the error reporting point:

(4.1.1) selecting holes/lines needing to be moved and moving the positions of the holes/lines, and detecting a network relation set of the connecting lines and the holes and the current distance between a moving object and surrounding components in real time in the moving process;

(4.1.2) if the network relation set of the connecting lines and the holes is changed after the hole moving and the line shifting are detected, namely the network relation of the connecting lines and the holes is changed, judging that the position of the moving object is a wrong position and reporting the wrong position to a user so that the user cannot finish illegal operation;

(4.1.3) if the current distance between the moving object and the peripheral components does not meet the preset layout prohibition parameters, displaying a layout prohibition area contacted or entered by the moving object around the components in real time, and meanwhile, judging that the position of the moving object is an error position and sending prompt information;

(4.1.4) when the network relation set of the connecting lines and the holes and the preset layout prohibiting parameters are simultaneously met, judging that the position of the moving object is the correct position.

And (4.1.5) judging whether copper surface adaptation is needed or not according to preset selection information when the hole is moved and the line is moved.

In a preferred embodiment of the present invention, when the automatic optimization mode is selected to optimize the error reporting points:

(4.2.1) constructing a multi-dimensional model according to the number of error reporting objects;

and (4.2.2) according to preset or acquired arrangement rules, network relation information among components, industrial manufacturing simulation parameters and layout prohibition parameters, carrying out automatic position arrangement fine adjustment on the error reporting object by adopting a genetic algorithm so as to realize one-key automatic adjustment optimization and copper surface adaptation.

In a preferred embodiment of the present invention, the step of copper surface adaptation during hole and line shifting comprises: when the copper surface is selected to be matched, after the hole/line moves, the system automatically selects a local copper surface area to be matched according to the position of the hole/line, and adjusts the range size and the shape of the copper surface area according to the network relation information and the layout prohibition parameters among all components, so that the copper surface is matched with a new hole line arrangement space.

The invention has the beneficial effects that: the work efficiency and the success probability of the optimization of the PCB wiring diagram are greatly improved, so that the overall profit efficiency of the PCB manufacturing industry is improved, in addition, the automatic intelligent line and hole moving method follows the development trend of the industrial manufacturing automation intelligence, a large amount of manual operation is replaced by efficient system operation, and the cost of manufacturing pretreatment production data is saved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without inventive efforts, wherein:

FIG. 1 is a flowchart illustrating a preferred embodiment of a method for detecting and optimizing automatic line and hole shifting according to the present invention;

FIG. 2 is a schematic diagram of a pre-hole-shifting structure of an embodiment of an automatic line-shifting and hole-shifting detection and optimization method based on a CAM system of the present invention;

FIG. 3 is a schematic diagram of a hole-shifting structure of an embodiment of a method for detecting and optimizing automatic line-shifting and hole-shifting of a CAM system according to the present invention;

FIG. 4 is a schematic diagram of a post-hole-shifting structure of an embodiment of a method for detecting and optimizing automatic line-shifting and hole-shifting of a CAM system according to the present invention;

FIG. 5 is a schematic diagram of a copper surface structure before hole shifting according to a preferred embodiment of the method for detecting and optimizing automatic line and hole shifting of the CAM system of the present invention;

fig. 6 is a schematic diagram of a copper surface avoiding structure after hole shifting according to a preferred embodiment of an automatic line-shifting and hole-shifting detection and optimization method based on a CAM system of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-6, an embodiment of the present invention includes:

a detection and optimization method for automatic line and hole shifting based on a CAM system is characterized in that a unique line and hole shifting function module is provided in the CAM system, and design principle detection of holes/lines is carried out while hole and line shifting is carried out, so that the connectivity between networks or components is not changed by hole shifting operation, each operation of a board factory engineer in the system can be ensured to be within a rule according with the design principle, and single hole shifting operation can simultaneously act on multiple layers, thereby improving the convenience of operation in the line and hole shifting process. In addition, the copper sheet is automatically modified to adapt to the new hole line arrangement after the hole and line moving operation.

A detection and optimization method for automatic line and hole shifting based on a CAM system comprises the following specific steps:

(1) and the wire moving and hole moving functional module is used for preprocessing the multilayer PCB wiring diagram.

And (1.1) the wire shifting and hole shifting functional module acquires a lead-in multilayer PCB wiring diagram.

And (1.2) carrying out production industrial manufacturing simulation on the components and the wiring lines on the PCB wiring diagram according to preset industrial manufacturing simulation parameters to obtain a production industrial manufacturing simulation file.

The industrial manufacturing simulation parameters comprise inner and outer layer compensation parameters and pore ring optimization parameters.

The inner and outer layer compensation parameters comprise a whole Line (Line & Arc TD) parameter, a whole large copper Surface (Surface) parameter, a whole optical point (Mark) parameter, a whole Surface Mount (SMD) parameter, a whole ball mount (BGA) parameter, a single-side hole PAD (PTH) parameter, a single-side hole PAD (VIA) parameter and the like.

The ring optimization parameters include a single-sided minimum ring Value (VIA) parameter, a single-sided optimum ring Value (VIA) parameter, a minimum ring value (blind hole) parameter, a single-sided minimum ring value (PTH) parameter, a single-sided optimum ring value (PTH) parameter, and the like.

And (1.3) carrying out shape fine adjustment on all components (holes, lines, bonding pads and the like) according to preset shape and size adjustment parameters so as to match the equipment limit of the production line.

(1.4) synchronous movement of the multilayer holes: in the CAM system, the same hole on the multilayer circuit layer and the pad corresponding to the hole are combined, and the combined hole and pad are represented on PCBs of different levels by mutually associated circular figures with the same size (or scaled); the method comprises the steps of carrying out network analysis on a graph set of holes/lines according to pre-acquired network relation information of a circuit board, integrating graphs affecting the same holes/lines of multiple levels, enabling the same holes to move synchronously on different multilayer circuit layers, giving abstraction of an original graph to components as attribute data, and enabling the users to operate the components instead of the graphs when the holes are moved, so that complexity and difficulty of the hole moving operation are reduced.

The network relation information is the connection and conduction relation of the circuit structure on each circuit board and the connection and conduction relation of the circuit structures on two adjacent circuit boards, namely the network refers to the whole circuit design on the plane design drawing.

(1.5) connectivity is not changed for hole shifting: in the process of automatic network analysis of the CAM system, network relation (network communication relation) information of connecting lines and holes is obtained, and a network relation set of the connecting lines and the holes, which is composed of the communication information, is stored in the bottom layer of the CAM system as a special data structure so as to ensure that the communication relation of the holes and the lines cannot be changed in hole shifting and line shifting. After the holes are moved and the lines are shifted, if the network communication relation between the connecting lines and the holes is changed, the network relation set between the connecting lines and the holes is also changed.

(2) A prohibited arrangement region is formed at the periphery of each hole and line on the PCB according to prohibited arrangement parameters previously entered by mrc (manufacture Rule check). And generating real-time error prompt when the arrangement forbidden area collides with the real object. The layout forbidden area of the object which can not be moved is accurately calculated to visualize the space of the layout forbidden area, so that the operation of a user in the layout forbidden area space can not violate the design rule, and the convenience and the accuracy of the operation of moving the line and the hole are greatly improved.

The inhibit placement parameter may be set via the RobotCAM interface in the main program of the EPCAM. In the wire shifting and hole shifting module, the parameters can be directly introduced or used only, and the operating user is not given the authority of modifying the forbidden parameter.

The forbidden placement parameters include a line-to-line pitch threshold, a line-to-SMD-PAD pitch threshold, a line-to-BGA-PAD pitch threshold, a line-to-PTH-PAD pitch threshold, a line-to-VIA-PAD pitch threshold, an SMD-PAD-to-BGA-PAD pitch threshold, an SMD-PAD-to-PTH-PAD pitch threshold, an SMD-PAD-to-VIA-PAD pitch threshold, a BGA-PAD-to-PTH-PAD pitch threshold, a BGA-PAD-to-VIA-PAD pitch threshold, a PTH-PAD-to-VIA-PAD pitch threshold, and so forth.

Among them, four kinds of pitches, i.e., line-to-line pitch, line-to-VIA-PAD pitch-to-VIA (i.e., line-to-VIA-PAD pitch), line-to-PAD pitch (i.e., line-to-SMD-PAD/BGA-PAD/PTH-PAD pitch), and VIA-to-PAD pitch, are key detection objects, and the other pitches will be used as warning terms (warnings) rather than error terms (errors).

In the main program of the EPCAM and the functional block for hole and line shifting, the parameters used by the two MRCs are identical (refer to), and the rule purpose of the two MRCs is to check whether the various types of pitches on the PCB trace diagram are within the threshold, but the emphasis is slightly different. The rule in the EPCAM main program is more important to whether a production manufacturer can actually produce the PCB according to the PCB routing diagram; the rule in the hole and line shifting module is more focused on whether the operation of hole and line shifting causes errors in circuit principle on a PCB routing diagram or not, and the actual error positions are kept consistent.

(3) And detecting the current spacing between all components in the industrial manufacturing simulation structure, and if the current spacing does not meet the preset layout prohibition parameters, reporting errors and displaying an error analysis list and error comparison information. The error information includes error point name, location, error reason, etc., which is convenient for the user to modify and adjust.

(4) And selecting a manual optimization mode or an automatic optimization mode to optimize error points and generate a hole-shifting and line-shifting optimization file. Wherein, the user can freely select to use the automatic one-key optimization method or manual operation.

(4.1) when the manual optimization mode is selected to optimize the error reporting point:

and (4.1.1) selecting an object (hole/line) to be moved and moving the position of the object, and detecting the network relation set of the connecting lines and the holes and the current distance between the moving object and surrounding components in real time in the moving process.

(4.1.2) if the network relation set of the connecting lines and the holes is changed (relative to the network relation set acquired in the step 1.5) after the hole is moved and the line is moved, namely the network connection relation of the connecting lines and the holes is changed, judging that the position of the moving object is a wrong position and reporting the wrong position to a user so that the user cannot finish illegal operation.

(4.1.3) if the current distance between the moving object and the peripheral components does not meet the preset layout prohibition parameters, displaying a layout prohibition area contacted or entered by the moving object around the components in real time, judging the position of the moving object to be an error position and sending prompt information.

(4.1.4) when the network relation set of the connecting lines and the holes and the preset layout prohibiting parameters are simultaneously met, judging that the position of the moving object is the correct position.

As shown in fig. 2-4, 30 and 155 represent network numbers assigned to different types of components after network analysis, in the process of moving the position of the moving object 1 with a circular hole structure, if the moving object 1 approaches holes and lines of different networks, an error notification is triggered, an error notification object interacting with the moving object 1 is highlighted as bright green and displays a dark gray arrangement-prohibited area 2 of the object in real time around the moving object, and the moving object 1 must be placed outside the arrangement-prohibited area.

(4.1.5) as shown in fig. 5-6, judge whether need carry on the copper surface adaptation (can move the line and move the hole function module in and choose or cancel this function), when needing the copper surface adaptation, after the hole line moves, choose the area (local) 3 of copper surface needing adaptation automatically according to the position of the hole line, and adjust the scope and shape of the area of copper surface according to shape and size of the hole line, form and dodge the district 4, make the copper surface adapt to the new hole line and arrange the space, this avoids the complexity of the copper operation greatly. During automatic matching, the copper surface is locally recalculated, the global calculation is not performed, the calculation efficiency is improved, only the copper surface of the automatic/manual moving hole line area is modified, the network analysis and the layout prohibition parameters are used, and the network is ensured to be correct after copper is coated and the manufacturing is not influenced.

(4.2) when the automatic optimization mode is selected to optimize the error reporting points:

and (4.2.1) constructing a multi-dimensional model according to the number of error reporting objects.

For example: in fig. 2-4, the hole with the error report analyzed as number 30 has a network error, and regardless of the network with number 155, the number of holes at the position in the 30 network is 6, and a six-dimensional model is constructed.

And (4.2.2) carrying out position arrangement fine adjustment on error reporting objects (holes/lines) by adopting a genetic algorithm according to preset or acquired arrangement rules (which can be a preset hole and line moving rule file), network relation information among components, industrial manufacturing simulation parameters, arrangement prohibition parameters and other arrangement information, thereby realizing one-key automatic adjustment optimization and copper surface adaptation. Wherein the step of copper surface adaptation is the same as in (4.1.5).

The invention discloses a detection and optimization method for automatically moving lines and holes based on a CAM system, which has the beneficial effects that: the work efficiency and the success probability of the optimization of the PCB wiring diagram are greatly improved, so that the overall profit efficiency of the PCB manufacturing industry is improved, in addition, the automatic intelligent line and hole moving method follows the development trend of the industrial manufacturing automation intelligence, a large amount of manual operation is replaced by efficient system operation, and the cost of manufacturing pretreatment production data is saved.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.