The present invention relates to a process to compensate for the positioning tolerance introduced when positioning electronic components (e.g. dies) on a substrate used in an e.g. fan-out panel level package (FOPLP) or fan-out wafer level package (FOWPL) process. When the electronic components are positioned by e.g. a pick and place machine with an offset or rotation compared to the nominal position, the artwork describing the electrical connections to the electronic components must go through an error-correction accordingly to provide proper electrical connection. This process is preferably performed in real time in order not to limit the throughput in a production line of electronic modules each containing one or multiple electronic components. The invention will contribute to increasing the yield during the manufacturing process as less of the electronic components have to be rejected due to bad positioning and hence lack of electrical connection without the drawback of having to generate a new rasterized artwork.
The electronic components industry uses different technologies to achieve electrical connection between electronic components or modules of electronic components. In one embodiment, a substrate is used as a temporary carrier on which the components are placed in predefined positions using an adhesive tape. Each electronic component can for example be positioned with a “pick and place”-machine and this process will give some position and rotation error due to the accuracy limitations of such pick and place equipment where high speed and throughput are required. The electronic components are now over-molded with a compound, and in such molding process the electronic components might slightly move or rotate. Then the substrate and the adhesive tape are removed in a special process. The result is a compound layer with the electronic components and their electrical connections/pads visible from one side.
The electric connections between the components are then achieved by imposing a predefined artwork by e.g. light exposure on to a photosensitive material on top of the electronic components on the carrier substrate. If the positioning of the electronic components does not match the predefined artwork of electronic interconnection due to tolerances in the component placement process, the actual positions of the components need to be measured and the artwork needs to be error-corrected at some positions around the electronic components before imposing the artwork on to the components on the substrate to provide proper electric connection.
Several techniques have been identified to perform rearrangements of artwork. U.S. Pat. Nos. 8,799,845 and 4,835,704 describe a process where a completely new pattern is created for each substrate assembled with electronic components, based on the measurement of the actual electronic components position. U.S. Pat. No. 8,799,845 describe a process allowing routing of the tracks of electric connections in a totally new order, while U.S. Pat. No. 4,835,704 describe a process where parts of the tracks are rerouted. Both techniques will be time consuming as it requires a rerouting of the artwork and subsequent rasterization process of the artwork before the data is transferred to the recording device, e.g. a direct imaging machine that impose the pattern on to the substrate where the components will be mounted in a later stage of the process. Rerouting and rasterization process is time consuming, limiting the overall production process throughput. If the positioning of the electronic components is reasonable and within certain limits, rerouting is not required, and only error-correction of the rasterized artwork will be sufficient.
As it is desired to avoid any limitation in production time consumption due to the artwork error-correction, the predefined artwork needs to be preprocessed during an offline process in such a way so that the original artwork can be error corrected in real time when imposing the artwork, rather than creating a new artwork for each substrate to be produced.
In the following description, the term “artwork” refers to a design in the form of a database which describes interconnect structure and via hole structure for providing interconnects between electronic components. The term “rasterization” refers to the task of taking an image described in a vector graphics format (shapes) and converting it into a raster image, i.e. a series of pixels, dots or lines, which, when displayed together, create the image which was represented via shapes.
The object of the invention is to provide a system and a method where a predefined artwork can be error corrected in real time during the process of recording the predefined artwork on to a substrate by means of a substrate recording machine on to a substrate. The substrate recording machine comprises a recording device unit comprising optical elements, for example photo heads or projectors that projects the artwork onto the substrate. In the following description, the term “photo head” will sometimes be used as a collective term comprising the optical elements of the exposure system and may be used interchangeably with the term recording device unit or recording unit.
In order to achieve the real time requirement, the predefined artwork needs to undergo certain offline preprocessing steps and online real time processing steps as illustrated in
After rasterization, the preprocess includes division of the modules further into one or more submodules in one or multiple levels (
In order to prepare for minimum delay during transfer of the tiles to the substrate recording machine, a lossless compression (e.g. Run Length Encoding) of the tiles can be performed before intermediate storage. At this stage, the configuration of the substrate recording machine parameters, such as initializing motion drives and recording parameters is performed.
The online process provides real time error correction and recording of the rasterized predefined artwork divided into tiles. The error correction is performed based on the input of measured position coordinates of multiple reference objects, such as local fiducial points for each module on a substrate, provided by e.g an external measurement machine. These position coordinates provide information on how the electronic components that are to be electrically interconnected are actually positioned on the substrate relative to each other. Also, the measured position coordinates providing information regarding the substrate's position inside the substrate recording machine, often called global fiducials, are used in the error correction. This can be done by means of an algorithm that calculates the required scaling and positioning of each Tile to provide correct error correction of the predefined artwork.
Based on the available machine configuration (e.g. number of recording heads in actual substrate recording machine and their internal distance) and the size of the actual substrate and artwork, the information required to perform recording of the error corrected artwork on to the substrate is requested by the recording device (e.g. one or multiple recording head(s)) from a Tile server. The tile server is where the Tiles are stored intermediately during the offline process. Also, the data containing information regarding the calculated scaling and positioning of each Tile is provided from the online warping calculation in order to provide error correction of the predefined artwork. When all Tiles are received by the recording device together with the position of each Tile and the scaling and positioning for each Tile, the recording of the complete error corrected artwork is enabled. Both global and local error correction can be performed simultaneously. An example of the resulting error corrected artwork is described in
The invention will now be described in more detail by means of examples and with reference to the accompanying figures.
An embodiment of the method according to the invention is illustrated in
The overall offline process is set out in
The offline process is normally performed as preprocessing steps before the online process steps illustrated in
The offline preprocessing steps includes in step (1) receiving data representing the artwork, for example as a CAD file, and in step (2) dividing the predefined artwork into a number of modules before the artwork is rasterized in step (3). The division of the predefined artwork 31 into modules 32, 33 is based on analyzing the artwork to identify sections that are similar and sections that are unique and to identify locations of the components in the artwork. The identification of similar or equal modules 33 provides modules that can be represented by one unique module and a list comprising the position of each of the equal, redundant modules in the predefined artwork 31. Non-redundant parts 33 of the predefined artwork, ie. unique modules of which there is only one, are also represented by a module with a list of their position in the predefined artwork 31. As the unique modules are rasterized only once instead of rasterizing all the redundant modules in the complete predefined artwork, the rasterization process will be reduced in time with a factor of 100-10000, as there can be 100-10000 equal modules in a predefined artwork. Another advantage when splitting the predefined artwork into modules, is that the open areas between the modules do not need to be rasterized, only the areas that contains artwork. Thus, the process of creating modules out of the predefined artwork saves processing time during rasterization. This is desired even if it is an offline process, especially when recording the artwork on small prototype batches or groups of recording substrates.
After rasterization of the non-redundant modules 32, 33 the modules are divided into submodules in one or multiple levels. Different levels means that one submodule can be inside another submodule and a part of the other submodule. The size of a submodule may vary and can in some instances be wider than the width of the working area of the recording device unit/photo head in a substrate recording machine.
This is illustrated in
To limit data transfer to each recording unit inside the substrate recording machine, the submodules may be represented in a flexible format that allows for efficient transfer and minimum processing in the recording device unit. This is solved by splitting each of the submodules into a set of submodules at a lower level, where the submodules at the lower level are smaller than the submodules at a level above.
The submodules are illustrated in
In this case, a Tile can be defined as a limited area of the overall predefined artwork of a module where all or some of the electrical components are interconnected or routed to another ReDistribution Layer (RDL) of electrical connections through electrical vias 85. The electrical component, e.g. a die 83 can then be electrical connected to the substrate 82 using solder balls 84 towards the upper RDL. This stack of RDLs allows that all electrical signals from the die are connected to the substrate while still keeping the size of the total package small. In such a structure, the internal relative distance and positioning of the electrical connections on each RDL is normally only offset and/or rotated and if so, only slightly scaled or distorted to fit to other RDLs.
The size of a Tile 44, 411 is square or rectangular depending on what is optimal to cover the area of the submodule at the higher level. There may also be other suitable shapes for the Tiles, to optimize the adaption to the area to be covered. Also, the size and shape will depend on what is allowed in the defined data protocol for image data transfer to the recording device. In addition, the Tiles inherits information from the submodule at a higher level on how they are allowed to be reshaped in the output on the recording device, ie. during recording.
When the Tiles have been defined, the offline preprocessing step (5) of
The last step (6) of the offline process illustrated in
The online process illustrated in
By using these position measurement data, the artwork can be corrected both locally and globally at the same time. This is performed as the global measured position coordinates from the recording machine will be used to recalculate the local corrections with respect to the substrate recording machine coordinate system. Such correction calculations are typically performed with a bi-linear, spline or similar suitable interpolation method. The recalculated local corrections are then used to calculate the offset and distortion of each Tile in their respective sub-module. When the Tiles and the corresponding list 52 describing the warping of each Tile is transferred to each recording device unit of a substrate recording machine, the internal relative position of the respective recording unit is also compensated to create an overall artwork with no overlaps or gaps between the recorded results of each recording unit inside the substrate recording machine.
In step (4) of the online process, there is generated an order of Tiles to be recorded and distributed to the recording units. The order is generated based on the available machine configuration such as number of recording heads in actual substrate recording machine and their internal distance, and the size of the actual substrate and artwork. The order comprises:
When the complete order of Tiles is prepared, the Tiles and the list of Tile warping information are transferred to the substrate recording machine. In order to obtain the real time requirement with minimum delay before recording in the online process, the Tiles are transferred in step (5) in the same order as they are recorded. This is often referred to as a streaming process. As each Tile is compressed during the offline process (
During the calculation of the warping set in step (3), a control can be performed in step (8) with respect to a predefined set of design rules, set by the user. (Design Rule Check). Examples of items for such design rules are illustrated in
After the recording process step (7), the recorded substrate can undergo a visual inspection in e.g. an external Automatic Optical Inspection (AOI) machine. Such inspection may utilize reference data from the recording machine, and hence the recording machine must prepare the data used for recording in step (10) in such a way so that it can be utilized by the AOI machine in a step (11).
Number | Date | Country | Kind |
---|---|---|---|
21163296.3 | Mar 2021 | EP | regional |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/EP2022/056292 | 3/11/2022 | WO |