CN115719710A - Integrated forming method for array metal salient points on surface of LTCC substrate and LTCC substrate - Google Patents
Integrated forming method for array metal salient points on surface of LTCC substrate and LTCC substrate Download PDFInfo
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Abstract
The invention provides an integrated forming method of an array metal salient point on the surface of an LTCC substrate and the LTCC substrate, and relates to the technical field of hybrid integrated circuits. The salient points and the LTCC substrate prepared by the method are combined into a green body through isostatic pressing at the green body stage, synchronous glue discharging and synchronous sintering shrinkage of the substrate and the array salient points can be realized in the co-sintering process, no contraposition deviation occurs, and the contraposition precision of the salient points is high. Meanwhile, the metal bumps are synchronously and integrally formed when the LTCC substrate is directly prepared, so that the process steps of printing soldering paste, ball planting and the like in post-processing are omitted, a large amount of processing time can be saved, extra special equipment is not needed, and the production cost can be greatly reduced.
Description
Technical Field
The invention relates to the technical field of hybrid integrated circuits, in particular to an integrated forming method of an array metal salient point on the surface of an LTCC substrate and the LTCC substrate.
Background
The low temperature co-fired ceramic (LTCC) substrate is an important branch of ceramic packaging substrates, has the advantages of high integration density, excellent high-frequency performance and the like, and is widely applied to the microwave field. Meanwhile, with the rapid development of miniaturization, densification and high integration of electronic equipment, the traditional hybrid integrated module gradually moves to high-density packaging. Among them, the Ball Grid Array (BGA) packaging type has been widely used in electronic packaging and interconnection due to its high interconnection density, small integration area, superior high frequency transmission performance, and the like. Therefore, the Ball Grid Array (BGA) package based on the LTCC substrate can satisfy the requirements of flexible multilayer wiring, hermetic package, low transmission loss, high density interconnection, etc., and has excellent mechanical, thermal and processing properties, so that the more compact package has great application potential in a new generation of rf micro system. In such LTCC-based ball grid array package, how to form reliable and consistent bumps/solder balls on the LTCC substrate is one of the key technologies.
Currently, the metal bumps of the LTCC surface array are usually made by post-processing after the LTCC substrate is fired. Commonly used methods include solder ball placement remelting, metal mask deposition, micro-droplet deposition, and the like. However, such post-processing methods generally have a problem of low post-processing bump alignment accuracy.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides an integrated forming method of an array metal bump on the surface of an LTCC substrate and the LTCC substrate, and solves the technical problem that the existing processing method of the array metal bump on the surface of the LTCC substrate has low alignment precision of a post-processed bump.
(II) technical scheme
In order to achieve the purpose, the invention is realized by the following technical scheme:
in a first aspect, the invention provides an integrated molding method for an array metal bump on a surface of an LTCC substrate, which includes:
s1, preparing a green sheet layer by using a burnout green sheet material, attaching a high polymer film to the surface of the green sheet layer, and carrying out hot pressing by using a hot press to obtain a surface layer green sheet;
s2, the surface of the surface layer green sheet faces upwards, holes are punched on the surface layer green sheet by adopting machinery or laser according to a designed bump pattern to form bump punching holes, and positioning holes for alignment are punched at the positions of four corners of the surface layer green sheet;
the surface green sheet with punched holes faces upwards, metal slurry is filled in the bump punched holes, and the polymer film on the surface is removed to obtain a formed bump layer;
s3, aligning and laminating the bump layer and the LTCC green body with positioning holes at four corners according to the positioning holes at the corners, packaging the stacked laminated body, and then putting the laminated body into an isostatic pressing machine for pressing to form an integrated green body with the bump layer;
s4, placing the integrated green body on a sintering plate in a mode that the convex point layer faces upwards, placing the sintering plate in a muffle furnace for co-sintering, and sintering to remove raw sheet materials.
Preferably, the green sheet material comprises organic matter, in particular comprising polyimide powder, polyvinyl alcohol and graphite powder.
Preferably, S1 specifically includes:
stirring and mixing polyimide powder and graphite powder uniformly, and grinding for 15-30 min by using a mortar; adding mixed powder of polyimide powder and graphite powder into 5-8 wt% concentration water solution of PVA, and mixing and stirring;
repeatedly rolling by using a roller press, adjusting the distance between rollers, pressing into green sheets with certain thickness, and cutting the green sheets into squares by using a cutting machine;
attaching a layer of polymer film on the surface of the cut green sheet;
and placing the green sheet and the polyester back film under a uniaxial hot press, wherein the temperature of the hot press is 70-80 ℃, the pressure is 8-12 MPa, and the pressure maintaining time is 5-10 min to obtain the surface green sheet.
Preferably, the aperture of the bump punching hole is 100-500 μm; the distance between the centers of adjacent holes is larger than or equal to the aperture multiplied by 2.
Preferably, the manner of filling the metal paste in the bump punching holes includes:
coating metal slurry on the surface of the surface layer green sheet, scraping the slurry back and forth by using a scraper, and filling the metal slurry into the salient points to punch holes;
or the like, or, alternatively,
and filling the metal slurry into the bump punched hole through the mask.
Preferably, in step S3, the laminate is preheated in an isostatic press for 20-30 min, the isostatic pressure is 3000-3500 PSI, the isostatic temperature is 70-75 ℃, and the dwell time is 15-20 min.
Preferably, the S4 specifically includes:
placing the integrated green body on a burning bearing plate, wherein the convex point layer is upward when the integrated green body is placed; then putting the sintering bearing plate into a muffle furnace for co-sintering; the integrated green body binder removal section is respectively insulated for 2 to 3 hours at the temperature of between 200 and 230 ℃ and between 450 and 470 ℃; after the rubber is discharged, the temperature is raised to 850-870 ℃ and the temperature is kept for 10-20 min;
after the furnace body is cooled, taking out the sintered LTCC sintered ceramic body, and removing residues on the surface of the substrate after sintering by using a soft brush; the raw sheet material of the bump layer is completely burnt out, and metal bumps with specific sizes are formed at the positions of the bumps.
Preferably, the heating rate of the co-sintering of the integrated blank body in the glue discharging section is less than or equal to 2 ℃/min, and the heating rate after glue discharging is 5-8 ℃/min.
Preferably, the diameter of the metal bump is 80-500 μm; the height of the salient point is 50-450 mu m.
In a second aspect, the invention provides an LTCC substrate, which is prepared by the integrated forming method of the array metal bumps on the surface of the LTCC substrate.
(III) advantageous effects
The invention provides an integrated forming method of an array metal salient point on the surface of an LTCC substrate and the LTCC substrate. Compared with the prior art, the method has the following beneficial effects:
the salient points and the LTCC substrate prepared by the method are combined into a green body through isostatic pressing at the green body stage, synchronous glue discharge and synchronous sintering shrinkage can be realized for the substrate and the array salient points in the co-sintering process, no contraposition deviation occurs, and the contraposition precision of the salient points is high. Meanwhile, the metal bumps are integrally formed in a synchronous mode when the LTCC substrate is directly prepared, so that the process steps of printing soldering paste, ball planting and the like in post-processing are omitted, a large amount of processing time can be saved, extra special equipment is not needed, and the production cost can be greatly reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flowchart of an integrated molding method of an array metal bump on a surface of an LTCC substrate according to an embodiment of the present invention;
FIG. 2 is a top view of a bump layer in an embodiment of the invention;
FIG. 3 is a schematic view of a bump layer stacked with an LTCC green body according to an embodiment of the present invention;
FIG. 4 is a cross-sectional view of an integrated green body with a bump layer obtained after completion of isostatic pressing in an embodiment of the invention;
FIG. 5 is a top view of an LTCC substrate obtained after co-sintering in an embodiment of the invention;
FIG. 6 is a cross-sectional view of an LTCC substrate obtained after co-sintering in an embodiment of the invention;
the structure comprises 1-surface green sheet, 2-filled metal slurry, 3-bump layer positioning holes, 4-LTCC green body, 5-LTCC green body positioning holes, 6-printed patterns in the LTCC green body, 7-interlayer interconnection through holes in the LTCC green body, 8-array metal bumps, 9-sintered LTCC ceramic body, 10-sintered surface layer LTCC patterns and 11-sintered LTCC positioning holes.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete description of the technical solutions in the embodiments of the present invention, it is obvious that the described embodiments are some, but not all, embodiments of the present invention. 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.
The embodiment of the application provides an integrated forming method for the array metal bumps on the surface of the LTCC substrate and the LTCC substrate, solves the technical problem that the alignment precision of the post-processed bumps is low in the existing processing method for the array metal bumps on the surface of the LTCC substrate, realizes that the bumps and the LTCC substrate are pressed into a green body through isostatic pressing in the green body stage, and is high in alignment precision of the bumps.
In order to solve the technical problems, the general idea of the embodiment of the application is as follows:
currently, the metal bumps of the LTCC surface array are usually manufactured by post-processing after the LTCC substrate is fired. Commonly used methods include solder ball placement remelting, metal mask deposition, micro droplet deposition, and the like. However, such post-processing methods generally have problems with post-processing alignment accuracy, bump dimensional uniformity, bump strength, and the like. The key of the application of the array salient point in the microwave product is that on the vertical interconnection formed by the array salient point, the size of the salient point is inconsistent or the defects of insufficient solder, position offset and the like cause the microwave performance of the vertical interconnection to be seriously deteriorated, thereby directly influencing the performance of the product. Especially for solder ball placement process, it is necessary to print solder paste first, then assemble solder balls and reflow, and the post-processing process has long flow and many processes, wherein solder paste material, print thickness, reflow process parameters, etc. may have a great influence on the reliability of the finally formed bumps. In addition, the methods of post-processing the bumps all require additional special equipment to complete the corresponding bump forming work, and the cost is relatively high. Therefore, the embodiment of the invention provides an integrated forming method of an array metal bump on the surface of an LTCC substrate.
In order to better understand the technical solution, the technical solution will be described in detail with reference to the drawings and the specific embodiments.
The embodiment of the invention provides an integrated forming method of an array metal bump on the surface of an LTCC substrate, which comprises the following steps as shown in figure 1:
s1, preparing a green sheet layer by using a burnout green sheet material, attaching a layer of high polymer film on the surface of the green sheet layer, and carrying out hot pressing by using a hot press to obtain a surface layer green sheet;
s2, the surface of the surface layer green sheet faces upwards, holes are punched on the surface layer green sheet by adopting machinery or laser according to a designed bump pattern to form bump punching holes, and positioning holes for alignment are punched at the positions of four corners of the surface layer green sheet;
the surface layer green sheet after punching is upward, metal slurry is coated on the surface layer green sheet, and a polymer film on the surface layer is removed to obtain a formed bump layer;
s3, aligning and laminating the bump layer and the LTCC green body with the positioning holes arranged at the four corners according to the positioning holes of the corners, packaging the stacked laminated body, and putting the packaged laminated body into an isostatic pressing machine for pressing to form an integrated green body with the bump layer;
and S4, placing the integrated green body on a sintering plate in a mode that the convex point layer faces upwards, and placing the sintering plate into a muffle furnace for co-sintering.
The salient points and the LTCC substrate prepared by the method are combined into a green body through isostatic pressing at the green body stage, synchronous glue removal and synchronous sintering shrinkage can be realized for the substrate and the array salient points in the co-sintering process, alignment deviation cannot occur, and the salient points are high in alignment precision. Meanwhile, the metal bumps are synchronously and integrally formed when the LTCC substrate is directly prepared, so that the process steps of printing soldering paste, ball planting and the like in post-processing are omitted, a large amount of processing time can be saved, extra special equipment is not needed, and the production cost can be greatly reduced.
It is noted that all methods of forming bumps by burning off the green sheet material are within the scope of the present application. The green sheet material in the embodiment of the present invention takes polyimide powder, polyvinyl alcohol, and graphite powder in organic matters as an example, and the polymer film takes a polyester type film as an example, and the integrated molding method is described in detail.
Example 1:
s1, preparing a surface layer green sheet:
stirring and mixing polyimide powder and graphite powder uniformly, and grinding for 15-30 min by using a mortar; preparing polyvinyl alcohol (PVA) aqueous solution with the concentration of 5-8 wt%.
Adding the mixed powder into a PVA solution, and uniformly mixing and stirring; then repeatedly rolling by using a roller press, adjusting the distance between rollers, and pressing into a green sheet with a certain thickness; and finally, cutting the green sheets into squares for later use by using a cutting machine.
Adhering a layer of polyester type film on the surface of the green sheet, and then placing the green sheet and the polyester type film under a uniaxial hot press, wherein the temperature of the hot press is 70-80 ℃, the pressure is 8-12 MPa, and the pressure maintaining time is 5-10 min, so as to obtain a complete surface layer green sheet;
s2, forming a bump layer:
the surface layer green sheet is upward, and punching is carried out on the corresponding position of the green sheet by adopting machinery or laser according to the designed bump pattern to form bump punching holes; and punching positioning holes for alignment at the four corners of the green sheet. The aperture of the bump punching hole is 100-500 mu m; the distance between the centers of adjacent holes is larger than or equal to the aperture multiplied by 2.
The film surface of the green sheet after the holes are punched faces upwards, a piece of air-permeable filter paper is padded below the green sheet, and then the green sheet and the filter paper are placed on an adsorption table together for firmly absorbing; and coating metal slurry on the back film of the green sheet, scraping the slurry back and forth for 2-3 times by using a scraper, recovering the slurry on the film surface, and removing the polyester film on the film surface to obtain the formed bump layer. It should be noted that, in the specific implementation process, the metal paste can be directly filled into the bump punching holes through the mask.
S3, multilayer laminating:
and preparing an LTCC green body containing a printed pattern and interlayer interconnection through holes according to a conventional LTCC process, and preparing positioning holes at four corners of the green body.
Aligning and laminating the bump layer in the step S2 and the LTCC green body according to the positioning holes of the corners; and packaging the stacked laminated body, and then putting the laminated body into a hot isostatic pressing machine for pressing, thereby forming an integrated green body with a bump layer.
S4, co-sintering:
placing the integrated green body on a burning bearing plate, wherein the convex point layer is upward when the integrated green body is placed; and then putting the sintering bearing plate into a muffle furnace for co-sintering. The integrated blank rubber discharge section is respectively insulated for 2 to 3 hours at the temperature of between 200 and 230 ℃ and between 450 and 470 ℃; after the rubber is discharged, the temperature is raised to 850-870 ℃ and the temperature is kept for 10-20 min.
After the furnace body is naturally cooled, taking out the sintered LTCC sintered ceramic body, and removing residues on the surface of the substrate after sintering by using a soft brush; and completely burning off organic matters in the bump layer, and forming a metal bump with a specific size at the position of the bump. In the embodiment of the invention, the diameter of the metal bump is 80-500 μm; the height of the salient point is 50-450 mu m.
Example 2:
s1, preparing a surface layer green sheet:
100g of polyimide powder and 150g of graphite powder are weighed, stirred and mixed uniformly, and ground for 20min by using a mortar. 50g of prepared polyvinyl alcohol (PVA 1799) is weighed into 900ml of deionized water, heated and stirred to prepare PVA aqueous solution.
Adding 20g of the prepared PVA solution into the mixed powder, mixing, stirring, grinding uniformly, taking out, repeatedly rolling by using a roller press, adjusting the distance between rollers to be 200 mu m, and pressing into a green sheet; and finally, cutting the green sheets into 40mm/40mm square sheets by using a cutting machine for later use.
And attaching a layer of polyester film on the surface of the green sheet, and then placing the green sheet and the polyester film under a uniaxial hot press, wherein the temperature of the hot press is 75 ℃, the pressure is 10MPa, and the pressure holding time is 10min, so that the complete surface layer green sheet is obtained.
S2, forming a bump layer:
the surface layer green sheet prepared in the step S1 is upward in film surface, punching is carried out on the center of the green sheet by adopting laser, a protruding point punching hole is formed, the aperture size is 150 mu m, the circle center distance of adjacent holes is 400 mu m, and the array design is 12 x 12; and positioning holes for alignment were punched at the four corners of the green sheet, the hole diameter of the positioning hole being 200 μm.
The film surface of the green sheet after the hole punching is upward, a piece of breathable filter paper is padded below the green sheet, and then the green sheet and the filter paper are placed on an adsorption table together for firmly absorbing; coating Ag slurry on the back film of the green sheet, scraping the slurry back and forth for 3 times by using a scraper, leaking the slurry into the punched bump punched holes, then recovering the slurry on the film surface, and removing the polyester type film on the film surface to obtain a formed bump layer.
S3, multilayer laminating:
and (3) preparing an LTCC green body with the thickness of 1.27mm according to the conventional LTCC punching, hole filling, screen printing, laminating and hot cutting processes, wherein the size of the green body after hot cutting is 30mm-30mm consistent with the size of the bump layer, a three-dimensional circuit is distributed in the green body, and positioning holes with the thickness of 200 mu m are also prepared at four corners of the green body.
And aligning and positioning the bump layer in the S2 with the LTCC green body by using the positioning holes of the corners, and then laminating the bump layer and the LTCC green body together. And (3) plastically packaging the stacked laminated body by using a sealing bag, and then putting the laminated body into a hot isostatic pressing machine for pressing, wherein the preheating time in the isostatic pressing machine is 25min, the isostatic pressing pressure is 3200PSI, the isostatic pressing temperature is 75 ℃, and the pressure maintaining time is 20min, so that the integrated green body with the bump layer is formed.
S4, co-sintering:
placing the integrated green body on a quartz burning bearing plate, wherein the convex point layer is upward when the integrated green body is placed; the setter plates were then placed in a muffle furnace. Firstly, performing glue discharging treatment: firstly, keeping the temperature for 2h from room temperature to 200 ℃ according to the heating rate of 1.5 ℃/min; and then preserving the heat for 2 hours from 200 ℃ to 470 ℃ according to the heating rate of 1.5 ℃/min, thereby finishing the rubber discharge. Then sintering is carried out: keeping the temperature for 15min according to the temperature rising rate of 6 ℃/min from 470 ℃ to 870 ℃, and then naturally cooling. After the furnace body is naturally cooled, taking out the sintered LTCC sintered ceramic body, and removing residues on the surface of the substrate after sintering by using a soft brush; metal bumps with the diameter of 120 μm, the height of 150 μm and the pitch of 340 μm are formed at the bump positions.
Example 3:
s1, preparing a surface layer green sheet:
100g of polyimide powder and 200g of graphite powder are weighed, stirred and mixed uniformly, and ground for 30min by using a mortar. 80g of prepared polyvinyl alcohol (PVA 1799) is weighed and added into 1000ml of deionized water, and the mixture is heated and stirred to prepare PVA water solution.
Adding 15g of the prepared PVA solution into the mixed powder for mixing and stirring, taking out after grinding uniformly, repeatedly rolling by using a roller press, adjusting the distance between rollers to be 150 mu m, and pressing into green sheets; finally, the green sheet is cut into 30mm square pieces by a cutting machine for standby.
And attaching a layer of polyester film on the surface of the green sheet, and then placing the green sheet and the polyester film under a uniaxial hot press, wherein the temperature of the hot press is 70 ℃, the pressure is 9MPa, and the pressure holding time is 8min, so that the complete surface layer green sheet is obtained.
S2, forming a bump layer:
the surface layer green sheet prepared in the step (1) faces upwards, holes are punched in the center of the green sheet by laser, protruding points are formed, holes are punched, the aperture size is 200 microns, the circle center distance of adjacent holes is 500 microns, and the array design is 10 x 10; and positioning holes for alignment were punched at the four corners of the green sheet, the hole diameter of the positioning hole being 200 μm.
The film surface of the green sheet after the hole punching is upward, a piece of breathable filter paper is padded below the green sheet, and then the green sheet and the filter paper are placed on an adsorption table together for firmly absorbing; and coating Au slurry on the back film of the green sheet, scraping the slurry back and forth for 3 times by using a scraper, leaking the slurry into the punched bump punched holes, recovering the slurry on the film surface, and removing the polyester film on the film surface to obtain the molded bump layer.
S3, multilayer laminating:
and (3) preparing an LTCC green body with the thickness of 1.27mm according to the conventional LTCC punching, hole filling, silk-screen printing, laminating and hot cutting processes, wherein the size of the green body after hot cutting is 40mm + 40mm consistent with that of the bump layer, a three-dimensional circuit is distributed in the green body, and positioning holes of 200 mu m are also prepared at four corners of the green body.
And (3) aligning and positioning the bump layer in the step (2) with the LTCC green body by using the positioning holes of the corners, and then stacking the bump layer and the LTCC green body together. And (3) plastically packaging the stacked laminated body by using a sealing bag, then putting the laminated body into a hot isostatic pressing machine for pressing, and preheating for 20min in the isostatic pressing machine, wherein the isostatic pressing pressure is 3000PSI, the isostatic pressing temperature is 75 ℃, and the pressure maintaining time is 15min, so that an integrated green body with a bump layer is formed.
S4, co-sintering:
placing the integrated green body on a quartz burning bearing plate, wherein the convex point layer is upward when the integrated green body is placed; the setter plates were then placed in a muffle furnace. Firstly, carrying out glue discharging treatment: firstly, keeping the temperature for 2h from room temperature to 230 ℃ according to the heating rate of 1 ℃/min; and then preserving heat for 2 hours from 230 ℃ to 450 ℃ according to the heating rate of 1 ℃/min, thereby finishing the rubber discharge. Then sintering is carried out: keeping the temperature for 16min according to the temperature rising rate of 5 ℃/min from 450 ℃ to 860 ℃, and then naturally cooling. After the furnace body is naturally cooled, taking out the sintered LTCC sintered ceramic body, and removing residues on the surface of the substrate after sintering by using a soft brush; metal bumps with the diameter of 170 μm, the height of 110 μm and the pitch of 420 μm are formed at the bump positions.
The respective structures involved in the integral molding method are shown in fig. 2 to 6.
The embodiment of the invention also provides the LTCC substrate which is prepared by the integrated forming method of the array metal salient points on the surface of the LTCC substrate.
In summary, compared with the prior art, the method has the following beneficial effects:
1. the salient points and the LTCC substrate prepared by the embodiment of the invention are combined into a green body through isostatic pressing at the green body stage, synchronous glue discharging and synchronous sintering shrinkage of the substrate and the array salient points can be realized in the co-sintering process, no contraposition deviation occurs, and the contraposition precision of the salient points is high.
2. The embodiment of the invention directly and integrally forms the metal salient points synchronously when the LTCC substrate is prepared, omits the process steps of printing soldering paste, ball planting and the like in post-processing, not only can save a large amount of processing time, but also does not need additional special equipment, and can greatly reduce the production cost.
3. The salient points prepared by the embodiment of the invention have good shape and size consistency, and the metal salient points have low resistivity, thereby being particularly beneficial to the transmission of radio frequency signals.
4. The bumps prepared by the embodiment of the invention are connected with the LTCC bottom bonding pads and the through holes through high-temperature sintering in a co-firing stage, and the shear strength is high.
5. The array bump prepared by the embodiment of the invention has the advantages that the key sizes such as diameter, height, pitch and the like can be randomly customized according to the product requirements, the limitation of raw materials, processes and equipment is avoided, and the operation is flexible and convenient.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
The above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. An integrated forming method for an array metal bump on the surface of an LTCC substrate is characterized by comprising the following steps:
s1, preparing a green sheet layer by using a burnable green sheet material, attaching a high polymer film to the surface of the green sheet layer, and carrying out hot pressing by using a hot press to obtain a surface green sheet;
s2, the surface of the surface layer green sheet faces upwards, holes are punched on the surface layer green sheet by adopting machinery or laser according to a designed bump pattern to form bump punching holes, and positioning holes for alignment are punched at the positions of four corners of the surface layer green sheet;
the surface green sheet with punched holes faces upwards, metal slurry is filled in the bump punched holes, and the polymer film on the surface is removed to obtain a formed bump layer;
s3, aligning and laminating the bump layer and the LTCC green body with positioning holes at four corners according to the positioning holes at the corners, packaging the stacked laminated body, and then putting the laminated body into an isostatic pressing machine for pressing to form an integrated green body with the bump layer;
and S4, placing the integrated green body on a sintering plate in a mode that the convex point layer faces upwards, placing the sintering plate in a muffle furnace for co-sintering, and sintering the raw sheet material.
2. The method for integrally forming the array metal bumps on the surface of the LTCC substrate as claimed in claim 1, wherein the green sheet material comprises organic materials, in particular polyimide powder, polyvinyl alcohol and graphite powder.
3. The integrated forming method of the array metal bumps on the surface of the LTCC substrate of claim 2, wherein the S1 specifically comprises:
stirring and mixing polyimide powder and graphite powder uniformly, and grinding for 15-30 min by using a mortar; adding mixed powder of polyimide powder and graphite powder into 5-8 wt% concentration water solution of polyvinyl alcohol, mixing and stirring;
repeatedly rolling by using a roller press, adjusting the distance between rollers, pressing into green sheets with certain thickness, and cutting the green sheets into squares by using a cutting machine;
attaching a layer of polymer film on the surface of the cut green sheet;
and placing the green sheet and the polyester back film under a uniaxial hot press, wherein the temperature of the hot press is 70-80 ℃, the pressure is 8-12 MPa, and the pressure maintaining time is 5-10 min to obtain the surface green sheet.
4. The integrated molding method of the array metal bumps on the surface of the LTCC substrate as claimed in claim 1, wherein the aperture of the bump punching hole is 100-500 μm; the distance between the centers of adjacent holes is larger than or equal to the aperture multiplied by 2.
5. The integrated forming method of the array metal bumps on the surface of the LTCC substrate as claimed in claim 1, wherein the manner of filling the metal paste in the bump punching holes comprises:
coating metal slurry on the surface of the surface layer green sheet, scraping the slurry back and forth by using a scraper, and filling the metal slurry into the salient points to punch holes;
or the like, or a combination thereof,
and filling the metal slurry into the bump punched holes through the mask.
6. The integrated molding method of metal bumps on the surface of LTCC substrate according to claim 1, wherein in step S3, the laminate is preheated in an isostatic press for 20-30 min, the isostatic pressure is 3000-3500 PSI, the isostatic temperature is 70-75 ℃, and the dwell time is 15-20 min.
7. The integrated forming method of the array metal bumps on the surface of the LTCC substrate of claim 1, wherein the S4 specifically comprises:
placing the integrated green body on a burning bearing plate, wherein the convex point layer is upward when the integrated green body is placed; then putting the sintering bearing plate into a muffle furnace for co-sintering; the integrated green body binder removal section is respectively insulated for 2 to 3 hours at the temperature of between 200 and 230 ℃ and between 450 and 470 ℃; after the rubber is discharged, the temperature is raised to 850-870 ℃ and the temperature is kept for 10-20 min;
after the furnace body is cooled, taking out the sintered LTCC sintered ceramic body, and removing residues on the surface of the substrate after sintering by using a soft brush; the raw sheet material of the bump layer is completely burnt out, and metal bumps with specific sizes are formed at the positions of the bumps.
8. The integrated molding method of the array metal bumps on the surface of the LTCC substrate as claimed in claim 7, wherein the temperature rise rate of the co-sintering of the integrated green body at the glue discharging stage is less than or equal to 2 ℃/min, and the temperature rise rate after the glue discharging is 5-8 ℃/min.
9. The integrated molding method of the array metal bumps on the surface of the LTCC substrate as claimed in claim 7, wherein the diameter of the metal bumps is 80-500 μm; the height of the salient point is 50-450 mu m.
10. An LTCC substrate, characterized in that the LTCC substrate is prepared by the integrated molding method of the array metal bumps on the surface of the LTCC substrate as claimed in any one of claims 1 to 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211279345.6A CN115719710A (en) | 2022-10-19 | 2022-10-19 | Integrated forming method for array metal salient points on surface of LTCC substrate and LTCC substrate |
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