Background
The LTCC (low temperature co-fired ceramic) technology is a high-density and multilayer wiring circuit substrate and packaging technology, can integrate passive elements inside the LTCC substrate, realizes the manufacture of a high-density and high-integration component integrated substrate, is favorable for improving the high-frequency performance and transmission speed of components, and is a preferred mode of integration and modularization of future electronic devices.
In the application of high-performance and high-density integrated products such as three-dimensional multi-chip assemblies, system-in-package and the like, designers can embed chips in a substrate by utilizing the unique cavity technology of LTCC (low temperature co-fired ceramic), so that the integration of an interconnection substrate and a package shell is realized, the package density is improved, the volume is reduced, the weight is reduced, the microwave characteristic is improved, and the reliability is improved. The structure of the double-sided cavity further improves the assembly density on the basis of the original single-sided cavity, so that the circuit design is more flexible, a new idea can be provided for the design of a broadband patch antenna, the defect that the dielectric constant of some raw ceramic tapes cannot be lower is overcome, and the crosstalk among different chips is effectively prevented. However, the key point of the manufacturing of the double-sided cavity is the lamination process, and how to ensure that the cavity is not easy to deform in the isostatic pressing process is a difficult point of the process.
At present, two methods are mainly used for laminating the LTCC substrate with the double-sided cavity structure, the top surface of the cavity is filled with a silica gel insert during laminating, the bottom surface of the cavity is filled with a homogeneous filling plug, so that the deformation of the cavity is limited, and the insert and the filling plug are taken out after laminating. In the method, a mold is required to be designed for each circuit and used for manufacturing the silica gel insert, so that the process is complex, the speed is low, and the production efficiency is influenced; and the bottom surface homogeneity is filled the stopper and need fold in advance and press to carry out the hot cutting according to every kind of circuit design, in order to guarantee that the filling stopper does not link with the unburned bricks, need encapsulate it, the technology degree of difficulty is big, and the cost is higher.
The second method is that the top surface of the cavity is filled with a silica gel insert during lamination, the bottom surface of the cavity is filled with a carbon-based material, the insert on the top surface of the cavity is taken out after lamination, and the carbon-based material on the bottom surface of the cavity is removed by a sintering process. In the method, the insert is also required to be manufactured, the process is complex, and the production efficiency is influenced; the filled carbon-based material needs to be completely removed by adjusting a sintering curve, the difficulty of substrate manufacturing is increased, when the cavity depth of the bottom surface of the cavity is large, the filling material is thick, after co-firing is completed, unburned carbon-based material residues can remain on the surface of a conductor in the cavity, and the residues are wrapped by glass in the LTCC green ceramic chip in the co-firing process, so that the residues are difficult to remove after sintering is completed, and the yield of the substrate is influenced.
Disclosure of Invention
In view of the above, aiming at the defects in the prior art, the invention provides a laminating method for a double-sided cavity structure of an LTCC substrate, in order to avoid high process cost and low efficiency in the laminating process of the LTCC substrate with the double-sided cavity structure.
In order to achieve the above object, the present invention provides a laminating method for a double-sided cavity structure of an LTCC substrate, including: designing and manufacturing a lamination table bottom plate and a lamination table cover plate; completing the circuit manufacture of the single-layer green ceramic chip and the manufacture of the open cavity to obtain the single-layer green ceramic chip after the cavity is opened; respectively manufacturing protection plates on the top surface and the bottom surface of the cavity; carrying out a lamination process on the single-layer green ceramic chips with the plurality of cavities, and carrying out tool combination according to a preset lamination process sequence to obtain an LTCC green ceramic stack; and (3) packaging and laminating the LTCC green ceramic stack to obtain the green ceramic blank with a double-sided cavity structure.
According to the embodiment of the invention, the step of performing the lamination process on the plurality of single-layer green ceramic chips after the cavities are opened, and the step of performing the tool combination according to the preset lamination process sequence comprises the following steps: hanging and sleeving the protection plate on the bottom surface on a positioning pin nail of a bottom plate of the lamination table; hanging and sleeving the first polyester film on the positioning pin nails to cover the bottom surface protection plate; sequentially hanging and sleeving the single-layer green ceramic chips with the cavities on positioning pin nails, wherein the bottom green ceramic chips in the single-layer green ceramic chips with the cavities are positioned on the first polyester film; hanging and sleeving a second polyester film on the positioning pin nails to cover the top layer green ceramic sheets of the single-layer green ceramic sheets after the cavity is opened; and sequentially hanging and sleeving the top surface protection plate and the lamination table cover plate on the positioning pin nails.
According to an embodiment of the present invention, wherein the first mylar is used to isolate the bottom protective plate from the bottom green ceramic sheet of the single-layered green ceramic sheet after the cavity is opened; and the second polyester film is used for isolating the top surface protection plate from the top layer green ceramic chip in the single-layer green ceramic chip after the cavity is opened, so that the assembled LTCC green ceramic stack is obtained.
According to the embodiment of the invention, the first polyester film and the second polyester film are used for reducing the adhesion degree of the protection plate and the single-layer green ceramic chip after the cavity is opened.
According to an embodiment of the present invention, the step of performing a wrapping and laminating process on the combined LTCC green ceramic stack to obtain a green ceramic blank with a double-sided cavity structure includes: wrapping the combined LTCC green ceramic stack by using a mixing silica gel pad to obtain a wrapped LTCC green ceramic stack; carrying out a laminating process on the wrapped LTCC green ceramic stack to finish the laminating process of the double-sided cavity structure; and deblocking the laminated wrapped LTCC green ceramic stack to obtain a green ceramic blank with a double-sided cavity structure.
According to the embodiment of the invention, the circuit manufacturing of the single-layer green ceramic chip comprises the processes of punching, hole filling and printing.
According to an embodiment of the invention, wherein the lamination table base plate is a hollow stone plate with a plurality of pins in a shape like a Chinese character 'hui'; the lamination platform cover plate is a hollow steel plate which is shaped like a Chinese character 'hui' and is provided with a plurality of solid holes.
According to the embodiment of the invention, the protection plate on the top and bottom surfaces of the cavity is provided with an opening, and the position of the opening of the protection plate comprises: and punching according to the cavity position of the product.
According to the embodiment of the invention, the protection plate with the opening is made of stainless steel and has a thickness of 1-2 mm.
According to the embodiment of the invention, the mixed silica gel is used for supporting and protecting the cavity structure of the LTCC substrate during the lamination process, so that the cavity structure is not easy to deform.
According to the technical scheme, the laminating method of the LTCC substrate double-sided cavity structure has the following beneficial effects:
according to the invention, through designing a new lamination mode, the combined action of the lamination table, the top surface and bottom surface protection plate and the wrapping process is utilized, the green ceramic sheets in the lamination process are supported, the side wall of the cavity is protected, the deformation of the side wall of the cavity in the lamination process is avoided, the double-sided cavity structure is formed at one step, the process method is simple and feasible, the filling plug does not need to be manufactured according to the size of the cavity, the carbon-based material does not need to be filled, the operability is strong, the process difficulty and the production cost are reduced, the process production efficiency is improved, and the method is suitable for preparing cavities with more numbers and sizes and types.
Detailed Description
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
Fig. 1 schematically shows a flow chart of a laminating method of a double-sided cavity structure of an LTCC substrate according to an embodiment of the present invention.
As shown in fig. 1, the method includes operations S101 to S105.
In operation S101, a lamination stage base plate and a lamination stage cover plate are designed and manufactured.
According to the embodiment of the invention, the lamination table bottom plate and the lamination table cover plate are both rectangular steel plates.
For example, FIG. 2 schematically illustrates a schematic view of a lamination station base plate of an embodiment of the present invention; and FIG. 3 is a cross-sectional view taken along plane A-A of FIG. 2.
As can be seen from fig. 2 and 3, the lamination platform base plate is in a novel square-shaped shape, the square-shaped lamination base plate is a hollow steel plate, and a plurality of positioning pins are arranged at solid positions of the square-shaped lamination base plate and used for hanging and sleeving an LTCC substrate assembly workpiece and a plurality of single-layer green ceramic chips.
FIG. 4 schematically illustrates a schematic view of a lamination station cover plate of an embodiment of the present invention; and FIG. 5 is a cross-sectional view taken along plane B-B of FIG. 4.
It can be seen from fig. 4 and 5 that the lamination table cover plate is a novel hollow steel plate shaped like a Chinese character 'hui', a plurality of solid holes are formed in the solid part of the lamination table cover plate shaped like a Chinese character 'hui', and the positions of the solid holes in the lamination table cover plate correspond to the positions of a plurality of positioning pins arranged on the lamination base plate and are used for inserting the positioning pins into the solid holes to fix the cavity structure of the LTCC base plate.
According to the embodiment of the invention, the sizes of the hollow parts of the square-clip-shaped lamination bottom plate and the square-clip-shaped lamination cover plate are set according to the cavity design requirement of the double-sided cavity.
In operation S102, the circuit manufacturing of the single-layer green ceramic chip and the manufacturing of the open cavity are completed, and the single-layer green ceramic chip after the open cavity is obtained.
According to the embodiment of the invention, the circuit manufacturing of the single-layer green ceramic chip comprises the following steps: and supporting a plurality of single-layer green ceramic chips by using backing paper, and completing the procedures of punching, steel mesh hole filling, silk screen printing and the like of the green ceramic chips according to the punching, hole filling and printing processes of the LTCC green ceramic chips so as to realize the circuit manufacturing of the single-layer green ceramic chips.
According to the embodiment of the invention, the manufacturing of the open cavity of the single-layer green ceramic chips comprises the steps of arranging openings on the plurality of single-layer green ceramic chips according to the design requirement of the cavity, wherein the shape of the openings of the single-layer green ceramic chips comprises at least one of the following shapes according to the design requirement of the product cavity: triangular, square, circular, polygonal.
In operation S103, protection plates for the top and bottom surfaces of the cavity are respectively manufactured.
According to the embodiment of the invention, the protection plates on the top surface and the bottom surface of the cavity are made of stainless steel materials, and the thicknesses of the protection plates are 0.1-0.2 mm.
According to the embodiment of the present invention, the manufacturing of the protection plates of the top and bottom surfaces of the cavity includes setting the opening positions of the top protection plate and the bottom protection plate according to the cavity position of the product. The opening shapes of the top surface protection plate and the bottom surface protection plate comprise at least one of the following shapes according to the design requirement of a product cavity: triangular, square, circular, polygonal.
According to the embodiment of the invention, the top surface protection plate and the bottom surface protection plate of the cavity can be used for supporting and protecting the side walls of the cavity from deformation.
In operation S104, a lamination process is performed on the plurality of single-layer green ceramic sheets with the cavities opened, and tool assembly is performed according to a preset lamination process sequence, so as to obtain an LTCC green ceramic stack.
According to the embodiment of the invention, the laminating process of the single-layer green ceramic chips after the cavities are opened is completed according to the LTCC laminating process specification.
According to the embodiment of the invention, the tool combination according to the preset lamination process sequence comprises the following steps: the operation step of S104 is specifically described below, based on the stacking table bottom plate as a reference direction, and combining the product and the tool into a whole in the order of "stacking table bottom plate, bottom surface protection plate, first polyester film, LTCC green ceramic sheet, second polyester film, top surface protection plate, and stacking table cover plate" from bottom to top.
The operation S104 specifically includes: hanging and sleeving the protection plate on the bottom surface on a positioning pin nail of a bottom plate of the lamination table; hanging and sleeving the first polyester film on the positioning pin nails to cover the bottom surface protection plate; sequentially hanging and sleeving the single-layer green ceramic chips with the cavities on positioning pin nails, wherein the bottom green ceramic chips in the single-layer green ceramic chips with the cavities are positioned on the first polyester film; hanging and sleeving a second polyester film on the positioning pin nails to cover the top layer green ceramic sheets of the single-layer green ceramic sheets after the cavity is opened; and sequentially hanging and sleeving the top surface protection plate and the lamination table cover plate on the positioning pin nails to obtain the assembled LTCC green ceramic stack.
According to an embodiment of the invention, the first mylar is used to isolate the bottom protective plate from the bottom green ceramic sheet of the single-layered green ceramic sheet after the cavity is opened; the second polyester film is used for isolating the top surface protection plate from the top layer green ceramic chip in the single-layer green ceramic chip after the cavity is opened.
According to the embodiment of the invention, the first polyester film and the second polyester film are used for reducing the adhesion degree of the protection plate and the single-layer green ceramic chip after the cavity is opened.
In operation S105, the LTCC green ceramic stack is subjected to a wrapping and laminating process to obtain a green ceramic blank with a double-sided cavity structure.
According to an embodiment of the invention, wrapping the stack of LTCC green ware comprises wrapping the entire stack of LTCC green ware with a mixed silica gel mat. Specifically, the operation S105 includes: wrapping the combined LTCC green ceramic stack by using a mixing silica gel pad to obtain a wrapped LTCC green ceramic stack; carrying out a laminating process on the wrapped LTCC green ceramic stack to finish the laminating process of the double-sided cavity structure; and deblocking the laminated wrapped LTCC green ceramic stack to obtain a green ceramic blank with a double-sided cavity structure.
According to the embodiment of the invention, the assembled LTCC green ceramic stack is wrapped by the mixing silica gel pad, and the mixing silica gel pad can fill the opening in the cavity structure in the laminating process, so that the openings in the double-sided cavity of the whole LTCC green ceramic stack are completely filled, and the cavity for supporting the double-sided cavity of the LTCC green ceramic stack is realized.
According to the embodiment of the invention, the lamination process is carried out on the wrapped LTCC green ceramic piles according to the lamination process rule, the isostatic pressing lamination process of the LTCC green ceramic piles is completed, and the mixed silica gel pad wrapping the LTCC green ceramic piles is deblocked to obtain the laminated green ceramic blank with the double-sided cavity structure.
According to the embodiment of the invention, the collapse of the LTCC green body with a double-sided cavity structure can be avoided, the green body with the structure can not be simply operated by using laminating equipment or a conventional laminating table, so that the green ceramic sheets in the laminating process can be supported by designing a new laminating mode and utilizing the combined action of the zigzag laminating table, the top surface protection plate, the bottom surface protection plate and the mixed silica gel, the side wall of the cavity is protected, the deformation of the side wall of the cavity in the laminating process is avoided, the process method is simple and easy to implement, the double-sided cavity is formed at one time, the operability is strong, and the process production efficiency is high.
The above embodiments are provided to further explain the objects, technical solutions and advantages of the present invention in detail, and it should be understood that the above embodiments are only examples of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.