阅读说明：本技术 多腔槽ltcc基板与封装盒体焊接结构及方法 (Multi-cavity LTCC substrate and packaging box body welding structure and method ) 是由 卢茜 张剑 董东 陆吟泉 文泽海 季兴桥 徐榕青 向伟玮 于 2021-07-23 设计创作，主要内容包括：本发明公开了多腔槽LTCC基板与封装盒体焊接结构及方法,该结构包括多腔槽LTCC基板、封装盒体和连接多腔槽LTCC基板与封装盒体的过渡金属片,所述过渡金属片设有若干不相连的通孔。本发明通过增加图形化的过渡金属片,有效缓解LTCC基板与金属盒体之间的热失配,提升了整个焊接结构的焊接可靠性。通过过渡金属片不同区域的开孔设计,在提升焊接可靠性的同时,保证整个焊接结构的接地性能与焊接气密性。通过焊接面活化、印刷焊膏焊接过渡金属片、清洗之后再使用焊料片真空焊接的方法解决了AuPtPd焊接层浸润性差,助焊剂难以清洗的问题。(The invention discloses a multi-cavity LTCC (low temperature co-fired ceramic) substrate and packaging box body welding structure and a method. According to the invention, by adding the graphical transition metal sheet, the thermal mismatch between the LTCC substrate and the metal box body is effectively relieved, and the welding reliability of the whole welding structure is improved. Through the trompil design in the different regions of transition metal piece, when promoting welding reliability, guarantee whole welded structure's ground connection performance and welding gas tightness. The problems of poor wettability of an AuPtPd welding layer and difficulty in cleaning of the soldering flux are solved by a method of activating a welding surface, printing soldering paste to weld a transition metal sheet, and cleaning and then using a soldering flux sheet for vacuum welding.)

1. Many chambeies groove LTCC base plate and encapsulation box body welded structure, its characterized in that includes many chambeies groove LTCC base plate, encapsulation box body and connects the transition metal piece of many chambeies groove LTCC base plate and encapsulation box body, the transition metal piece is equipped with a plurality of disconnected through-holes, and the through-hole of the transition metal piece of connecting on the different regions of multi-chambeies groove LTCC base plate accounts for the area difference of transition metal piece, is equipped with one deck stress buffer layer between multi-chambeies groove LTCC base plate and encapsulation box body, and stress buffer layer includes the complete stress release hole of a plurality of structures.

2. The multi-chambered LTCC substrate and package box welding structure of claim 1, wherein said transition metal sheet is welded to the multi-chambered LTCC substrate by an auxiliary material containing a small amount of flux; the transition metal sheet is welded with the packaging box body through auxiliary materials without soldering flux.

3. The multi-chambered LTCC substrate and package box bonding structure of claim 1, wherein the region where said transition metal sheet is bonded to the multi-chambered LTCC substrate comprises a structural weakness region, a ground sensitive region, and a coincidence region, wherein the coincidence region is a portion where the structural weakness region coincides with the ground sensitive region;

in the structural weak area of the multi-cavity LTCC substrate, the area of the through hole of the transition metal sheet accounts for at least 60% of the area of the projection area of the structural weak area of the multi-cavity LTCC substrate;

in the grounding sensitive area of the multi-cavity groove LTCC substrate, the through hole area of the transition metal sheet accounts for 40% at most of the area of the projection area of the grounding sensitive area of the multi-cavity groove LTCC substrate;

in the overlapping area of the multi-cavity groove LTCC substrate, the area of the through hole of the transition metal sheet accounts for 40-50% of the area of the projection area of the grounding sensitive area of the multi-cavity groove LTCC substrate.

4. The bonded structure of a multi-chambered LTCC substrate and package body of claim 3, wherein the through holes are formed in an array or grid of small holes.

5. The multi-chamber LTCC substrate and package box welding structure of claim 1, wherein the bottom of the package box is provided with a through groove, the projection area of the through groove on the bottom surface of the package box is provided with an opening with the same shape as the through groove on the transition metal sheet, and the distance between the outer edge of the opening with the same shape as the through groove and the outer edge of the through hole adjacent to the opening is not less than 0.5 mm.

6. The welding method of the multi-cavity groove LTCC substrate and the packaging box body is characterized in that the ratio of the total surface area of the cavity grooves on the surface of the multi-cavity groove LTCC substrate to the surface area is more than 40%, and the thermal expansion coefficient of the packaging box body is 1-3 times of that of the LTCC substrate, and the welding method comprises the following steps:

s1: determining a structural weak area of the multi-cavity LTCC substrate through structural analysis, and determining a grounding sensitive area of the multi-cavity LTCC substrate through circuit analysis;

s2: activating the welding surface of the multi-cavity groove LTCC substrate;

s3: printing an auxiliary material containing a small amount of soldering flux on the welding surface of the multi-cavity groove LTCC substrate corresponding to the region where the transition metal sheet is not provided with the hole;

s4: welding a transition metal sheet on the welding surface of the multi-cavity groove LTCC substrate and cleaning residues;

s5: sequentially and sequentially loading a solder sheet, a multi-cavity groove LTCC substrate and a welding tool into the packaging box body, and applying pressure to the multi-cavity groove LTCC substrate through the welding tool;

s6: and welding the multi-cavity groove LTCC substrate welded with the transition metal sheet in the packaging box body.

7. The method of soldering a multi-chambered LTCC substrate to a package tray of claim 6, wherein the areas of the transition metal sheet openings corresponding to the structurally weakened, ground sensitive and overlapped areas of the multi-chambered LTCC substrate are:

in the structural weak area of the multi-cavity LTCC substrate, the area of the through hole of the transition metal sheet accounts for at least 60% of the area of the projection area of the structural weak area of the multi-cavity LTCC substrate;

in the grounding sensitive area of the multi-cavity groove LTCC substrate, the through hole area of the transition metal sheet accounts for 40% at most of the area of the projection area of the grounding sensitive area of the multi-cavity groove LTCC substrate;

in the overlapping area of the multi-cavity groove LTCC substrate, the area of the through hole of the transition metal sheet accounts for 40-50% of the area of the projection area of the grounding sensitive area of the multi-cavity groove LTCC substrate;

the shape and the center position of the opening of the solder sheet are consistent with those of the transition metal sheet.

8. The method of soldering a multi-chambered LTCC substrate to a package tray of claim 6, wherein the bonding side of the activated multi-chambered LTCC substrate is specifically:

s21: heating the multi-cavity groove LTCC substrate to a temperature required by activating the soldering flux;

s22: coating the soldering flux on the welding surface of the multi-cavity groove LTCC substrate;

s23: after the heat preservation is carried out for 30-60 seconds, the liquid is cleaned and dried;

s24: and (5) processing the welding surface to improve subsequent solder wettability.

9. The method of soldering a multichamber trough LTCC substrate to a package housing of claim 6 wherein said minor flux-containing minor adjuvant has a melting point at least 30 ℃ higher than the melting point of said solder tabs.

10. The method of claim 6, wherein the welding assembly comprises a press block, a support body and a backing plate, the backing plate is directly disposed on a surface of the multi-chamber LTCC substrate, the support body is disposed on a surface of the backing plate corresponding to the non-structural weakened area of the multi-chamber LTCC substrate, and the press block is disposed on the support body.

Technical Field

The invention belongs to the technical field of microwave assembly micro-assembly, and particularly relates to a multi-cavity LTCC substrate and packaging box body welding structure and a method.

Background

Electronic information systems are developing towards the direction of multifunction, high performance and miniaturization, the integration level of microwave assemblies is higher and higher, and low temperature co-fired ceramic (LTCC) substrates are widely applied to microwave assemblies due to the fact that the LTCC substrates have multilayer wiring capacity and good radio frequency signal transmission characteristics.

In order to ensure low-loss and high-isolation transmission of radio frequency signals in the microwave component, the chip is generally installed in the cavity. With the increase of the functional density of the components, the number of integrated chips is increased, and the number and the area of the cavity grooves on the surface of the LTCC circuit are increased. The welding of the large-area LTCC substrate with the multi-cavity groove and the packaging box body has the following technical difficulties:

a) severe thermal mismatch (thermal expansion coefficient difference is one to three times) exists between the LTCC substrate and the light packaging box body (materials such as Al, SiAl and the like), and the LTCC substrate is easy to crack in the processes of brazing and subsequent use, so that the assembly fails. Utility model CN206200376U alleviates the thermal mismatch stress between pottery and the metal through set up the release space at the interface of pottery and metal. However, the cavity groove structure for releasing stress is processed on the welding surface of the LTCC, so that the processing difficulty of the multi-cavity groove LTCC circuit piece is further increased, and the circuit piece is warped and deformed; and the cavity groove structure is processed on the welding surface of the packaging box body, so that the strength of the bottom plate of the box body is reduced.

b) In order to meet the brazing requirement, a sintering slurry system is adopted in the LTCC process, the most common welding layer is a mixture of gold, platinum, palladium and glass, the material is very poor in infiltration with a solder under the condition of no soldering flux, and the welding is difficult to realize; if the soldering flux is used, the wettability is improved, and the residual soldering flux in the welding layer is difficult to clean due to the large welding area, so that the long-term reliability of the welding interface is influenced.

c) With the increase of system integration density, LTCC becomes a part of the package, and the welding with the box body needs to have airtightness and ensure good grounding characteristics. Therefore, how to solve the problems of thermal mismatch and wettability in the welding process of the multi-cavity groove LTCC substrate and the packaging box body, and meanwhile, the welding strength, the air tightness and the grounding characteristic of the microwave circuit are ensured, and no solution is provided in the prior art.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a multi-cavity groove LTCC substrate and packaging box body welding structure and a multi-cavity groove LTCC substrate and packaging box body welding method. Through the trompil design in the different regions of transition metal piece, when promoting welding reliability, guarantee whole welded structure's ground connection performance and welding gas tightness. The problems of poor wettability of an AuPtPd welding layer and difficulty in cleaning of the soldering flux are solved by a method of activating a welding surface, printing soldering paste to weld a transition metal sheet, and cleaning and then using a soldering flux sheet for vacuum welding.

The purpose of the invention is realized by the following technical scheme:

many chambeies groove LTCC base plate and encapsulation box body welded structure, including many chambeies groove LTCC base plate, encapsulation box body and the transition metal piece of connecting many chambeies groove LTCC base plate and encapsulation box body, the transition metal piece is equipped with a plurality of disconnected through-holes, and the through-hole of the transition metal piece of connecting occupies the area difference of transition metal piece on the different regions of many chambeies groove LTCC base plate, is equipped with one deck stress buffer layer between many chambeies groove LTCC base plate and encapsulation box body, and stress buffer layer includes the complete stress release hole of a plurality of structures.

Furthermore, the transition metal sheet is welded with the multi-cavity groove LTCC substrate through an auxiliary material containing a small amount of soldering flux; the transition metal sheet is welded with the packaging box body through auxiliary materials without soldering flux.

Furthermore, the region where the transition metal sheet is connected with the multi-cavity groove LTCC substrate comprises a structural weak region, a grounding sensitive region and a superposed region, wherein the superposed region is a superposed part of the structural weak region and the grounding sensitive region;

in the structural weak area of the multi-cavity LTCC substrate, the area of the through hole of the transition metal sheet accounts for at least 60% of the area of the projection area of the structural weak area of the multi-cavity LTCC substrate;

in the grounding sensitive area of the multi-cavity groove LTCC substrate, the through hole area of the transition metal sheet accounts for 40% at most of the area of the projection area of the grounding sensitive area of the multi-cavity groove LTCC substrate;

in the overlapping area of the multi-cavity groove LTCC substrate, the area of the through hole of the transition metal sheet accounts for 40-50% of the area of the projection area of the grounding sensitive area of the multi-cavity groove LTCC substrate.

Furthermore, the opening mode of the through holes is an aperture array or a grid.

Furthermore, a through groove is formed in the bottom of the packaging box body, an opening with the same shape as the through groove is formed in a projection area of the through groove in the bottom surface of the packaging box body through the transition metal sheet, and the distance between the outer edge of the opening with the same shape as the through groove and the outer edge of the through hole adjacent to the opening is not less than 0.5 mm.

In another aspect, the present invention further provides a method for welding a multi-cavity LTCC substrate to an encapsulation box, wherein a ratio of a total surface area of cavities on a surface of the multi-cavity LTCC substrate to a surface area of the multi-cavity LTCC substrate is greater than 40%, and a thermal expansion coefficient of the encapsulation box is 1 to 3 times of a thermal expansion coefficient of the LTCC substrate, and the method includes:

s1: s1: determining a structural weak area of the multi-cavity LTCC substrate through structural analysis, and determining a grounding sensitive area of the multi-cavity LTCC substrate through circuit analysis;

s2: activating the welding surface of the multi-cavity groove LTCC substrate;

s3: printing an auxiliary material containing a small amount of soldering flux on the welding surface of the multi-cavity groove LTCC substrate corresponding to the region where the transition metal sheet is not provided with the hole;

s4: welding a transition metal sheet on the welding surface of the multi-cavity groove LTCC substrate and cleaning residues;

s5: sequentially and sequentially loading a solder sheet, a multi-cavity groove LTCC substrate and a welding tool into the packaging box body, and applying pressure to the multi-cavity groove LTCC substrate through the welding tool;

s6: and welding the multi-cavity groove LTCC substrate welded with the transition metal sheet in the packaging box body.

Further, the transition metal sheet opening areas of the structural weak area, the grounding sensitive area and the overlapping area which are correspondingly arranged on the multi-cavity LTCC substrate are respectively as follows:

in the structural weak area of the multi-cavity LTCC substrate, the area of the through hole of the transition metal sheet accounts for at least 60% of the area of the projection area of the structural weak area of the multi-cavity LTCC substrate;

in the grounding sensitive area of the multi-cavity groove LTCC substrate, the through hole area of the transition metal sheet accounts for 40% at most of the area of the projection area of the grounding sensitive area of the multi-cavity groove LTCC substrate;

in the overlapping area of the multi-cavity groove LTCC substrate, the area of the through hole of the transition metal sheet accounts for 40-50% of the area of the projection area of the grounding sensitive area of the multi-cavity groove LTCC substrate;

the shape and the center position of the opening of the solder sheet are consistent with those of the transition metal sheet.

Further, the activated multi-cavity groove LTCC substrate welding surface is specifically as follows:

s21: heating the multi-cavity groove LTCC substrate to a temperature required by activating the soldering flux;

s22: coating the soldering flux on the welding surface of the multi-cavity groove LTCC substrate;

s23: after the heat preservation is carried out for 30-60 seconds, the liquid is cleaned and dried;

s24: and (5) processing the welding surface to improve subsequent solder wettability.

Furthermore, the melting point of the auxiliary material containing a small amount of soldering flux is at least 30 ℃ higher than that of the solder sheet.

Further, the welding frock includes briquetting, supporter and backing plate, and the backing plate is directly placed on multicavity groove LTCC base plate surface, and the supporter is placed in the non-structural weak area that the backing plate surface corresponds multicavity groove LTCC base plate, and the briquetting is placed on the supporter.

The invention has the beneficial effects that:

(1) according to the invention, the graphical transition metal sheet is added between the multi-cavity LTCC substrate and the packaging box body, so that the thermal mismatch between the multi-cavity LTCC substrate and the metal box body is effectively relieved, and the welding reliability of the whole welding structure is improved.

(2) According to the invention, through the design of corresponding openings of the transition metal sheet in different welding areas on the multi-cavity LTCC substrate, the welding reliability is improved, and meanwhile, the grounding performance and welding airtightness of the whole welding structure are ensured.

(3) The invention solves the problems of poor wettability of an AuPtPd welding layer and difficult cleaning of the soldering flux by activating the welding surface, printing a welding auxiliary material containing a small amount of the soldering flux to weld a transition metal sheet and cleaning the transition metal sheet and then using a soldering flux sheet without the soldering flux to carry out vacuum welding.

Drawings

Fig. 1 is a cross-sectional view of a multi-cavity LTCC substrate and package box welding structure provided in embodiment 1 of the present invention;

FIG. 2 is an enlarged view at A in FIG. 1;

fig. 3 is a schematic view of a weak area of a multi-cavity LTCC substrate structure in a welding structure of the multi-cavity LTCC substrate and a package box according to embodiment 1 of the present invention;

fig. 4 is a schematic view of a transition metal sheet in a multi-cavity LTCC substrate and package box welding structure provided in embodiment 1 of the present invention;

fig. 5 is a schematic top view of a package box in a multi-cavity LTCC substrate and package box welding structure according to embodiment 1 of the present invention;

fig. 6 is a flowchart of a method for welding a multi-cavity LTCC substrate and a package box according to embodiment 2 of the present invention;

fig. 7 is a schematic diagram of a welding tool in the process method for improving the welding reliability of the multi-cavity LTCC substrate and the package box provided in embodiment 3 of the present invention.

Reference numerals: 1-multi-cavity groove LTCC substrate, 2-packaging box body, 3-transition metal sheet, 4-solder sheet, 5-solder paste, 6-backing plate, 7-support body, 8-pressing block, 9-side wall, 10-bottom surface and 11-through groove.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.

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.

Example 1

As shown in fig. 1, the sectional view of the multi-cavity LTCC substrate and package box welding structure provided in this embodiment specifically includes a multi-cavity LTCC substrate 1, a package box 2, and a transition metal sheet 3 connecting the multi-cavity LTCC substrate 1 and the package box 2. The transition metal sheet 3 is welded with the multi-cavity groove LTCC substrate 1 through a soldering paste 5, and the transition metal sheet 3 is welded with the packaging box body 2 through a soldering paste 4. The through-hole of the transition metal piece 3 that connects on the different regions of multicavity groove LTCC base plate 1 accounts for the area difference of transition metal piece 3, is equipped with one deck stress buffer layer between multicavity groove LTCC base plate 1 and encapsulation box body 2, and stress buffer layer includes the complete stress release hole of a plurality of structures.

The ratio of the total surface area of the surface cavity of the multi-cavity LTCC substrate 1 to the surface area is more than 40%, and the metal of the LTCC welding layer is preferably a gold-platinum-palladium layer; the thermal expansion coefficient of the light packaging box body 2 is 1-3 times of that of the LTCC substrate.

Fig. 4 is a schematic view of a transition metal sheet 3 in a soldering structure of a multi-chamber LTCC substrate 1 and a package case 2 according to this embodiment. The transition metal sheet 3 is provided with a plurality of unconnected through holes occupying different areas in different areas of the multi-cavity LTCC substrate 1. The thickness of the transition metal sheet 3 is 0.1mm-0.5mm, and the surface is plated with Ni, NiAu or NiPdAu. The transition metal sheet 3 is provided with a through hole with a round shape, an oval shape, a rectangular shape or an irregular shape; the minimum diameter or side length is not less than 0.5 mm.

Specifically, in the structural weak area of the multi-cavity groove LTCC substrate 1, the through hole area of the transition metal sheet 3 occupies at least 60% of the projection area of the structural weak area of the multi-cavity groove LTCC substrate 1. Wherein Q is the structural weakness of the structure as shown in fig. 3.

In the grounding sensitive area of the multi-cavity groove LTCC substrate 1, the through hole area of the transition metal sheet 3 accounts for at most 40% of the area of the projection area of the grounding sensitive area of the multi-cavity groove LTCC substrate 1.

In the overlapping area of the multi-cavity LTCC substrate 1, the through hole area of the transition metal sheet 3 accounts for 40-50% of the area of the projection area of the grounding sensitive area of the multi-cavity LTCC substrate 1. The overlap region refers to the portion of the structural weakness that overlaps the ground sensitive region.

The through holes of the transition metal sheet 3 are opened in a small hole array or grid mode. As shown in fig. 5, the periphery is a side wall 9 of the enclosure body, and in the projection area of the through groove 11 on the bottom surface 10 of the enclosure body 2, the transition metal sheet 3 is provided with an opening with the same shape as the through groove. In order to ensure the welding air tightness of the multi-cavity groove LTCC substrate 1 and the packaging box body 2, the distance between the edge of the opening with the same appearance as the through groove and the edge of the adjacent through hole is not less than 0.5 mm. If the distance is less than 0.5mm, air leakage may occur.

The multi-cavity groove LTCC base plate and encapsulation box body welded structure that this embodiment provided can effectively alleviate the thermal mismatch problem between multi-cavity groove LTCC base plate and the metal box body through the transition sheetmetal that increases the graphics between multi-cavity groove LTCC base plate and the encapsulation box body, has promoted whole welded structure's welding reliability. In addition, this structure passes through the different welding area's of transition metal piece on multicavity groove LTCC base plate corresponding trompil, when having promoted welding reliability, guarantees whole welded structure's ground connection performance and welding gas tightness.

Example 2

As shown in fig. 6, a flow chart of a method for welding a multi-cavity LTCC substrate and a package box provided in this embodiment includes:

the method comprises the following steps: the structural weak area and the ground sensitive area of the multi-chamber LTCC substrate 1 are determined by circuit analysis. The weak positions of the structure of the multi-cavity LTCC substrate 1 are determined to be side thin-wall structures of four long cavities through structural simulation analysis, and the grounding sensitive position is determined to be a cavity bottom area through circuit analysis.

Step two: and activating the welding surface of the multi-cavity groove LTCC substrate 1. Activating the welding surface of the LTCC substrate by using the soldering flux, then cleaning and drying by using liquid, and then using Ar/H₂The welding surface of the LTCC substrate is treated by the plasma, so that the wettability of subsequent solder is improved.

Step three: and printing the soldering paste 5 on the welding surface of the multi-cavity groove LTCC substrate 1 corresponding to the non-perforated area of the transition metal sheet 3.

Step four: and welding a transition metal sheet 3 on the welding surface of the multi-cavity LTCC substrate 1 and cleaning residues. The welding method is vacuum reflow welding. Wherein, the transition metal sheet 3 trompil area that corresponds the structure weak area, the ground connection sensitive area that sets up at multicavity groove LTCC base plate 1 and overlap region respectively is:

in the structural weak area of the multi-cavity LTCC substrate 1, the area of the through hole of the transition metal sheet 3 accounts for at least 60% of the area of the projection area of the structural weak area of the multi-cavity LTCC substrate 1.

In the grounding sensitive area of the multi-cavity groove LTCC substrate 1, the through hole area of the transition metal sheet 3 accounts for at most 40% of the area of the projection area of the grounding sensitive area of the multi-cavity groove LTCC substrate 1.

In the overlapping area of the multi-cavity LTCC substrate 1, the through hole area of the transition metal sheet 3 accounts for 40-50% of the area of the projection area of the grounding sensitive area of the multi-cavity LTCC substrate 1.

The outer shape and the center position of the opening of the solder sheet 4 are in conformity with those of the transition metal sheet 3. The overall dimension is 0.05mm-0.2mm larger than that of the transition metal sheet 3, and the diameter/side length of a single hole is 0.02-0.1mm smaller than that of the corresponding hole/diameter on the transition metal sheet 3. The material of the solder sheet 4 is: in60Pb40, Sn63Pb37 or Sn96.5Ag3Cu0.5, and the thickness is 0.05-0.1 mm.

Step five: and sequentially loading the solder sheets 4, the multi-cavity groove LTCC substrate 1 and the welding tool into the packaging box body 2, and applying pressure to the multi-cavity groove LTCC substrate 1 through the welding tool. The welding frock exerts pressure to multicavity groove LTCC base plate 1 through the gravity of briquetting, fixes the position of multicavity groove LTCC base plate 1 in welding process, and the pressure of exerting is 1000 and gives other 10000 Pa.

Step six: and welding the multi-cavity groove LTCC substrate 1 welded with the transition metal sheet 3 in the packaging box body 2. The soldering method is vacuum soldering and no flux is applied.

According to the method for welding the multi-cavity LTCC substrate and the packaging box body, the problems that a welding layer is poor in wettability and scaling powder is difficult to clean are solved by activating a welding surface, printing soldering paste to weld a transition metal sheet and then using a soldering flux sheet to perform vacuum welding after cleaning. Meanwhile, the corresponding hole opening design of the transition metal sheet in different welding areas on the multi-cavity groove LTCC substrate is adopted, so that the welding reliability is improved, and meanwhile, the grounding performance and welding airtightness of the whole welding structure are guaranteed. In addition, the graphical transition metal sheet is additionally arranged between the multi-cavity groove LTCC substrate and the packaging box body, so that the thermal mismatch between the multi-cavity groove LTCC substrate and the metal box body is effectively relieved, and the welding reliability of the whole welding structure is improved.

Example 3

The embodiment provides a specific technological method for improving the welding reliability of a multi-cavity groove LTCC substrate and a packaging box body. The specific method comprises the following steps:

in the first step, a multi-cavity LTCC substrate 1 and a package box body 2 are provided. In this embodiment, the multi-cell LTCC substrate 1 has a surface cell total area to surface area ratio of 47%, a size of 200mm x 150mm, and the LTCC bonding layer metal is AuPtPd. The thermal expansion coefficient of the packaging box body 2 is 1 time of that of the LTCC substrate 1.

And secondly, determining that the weak positions of the structure of the multi-cavity LTCC substrate 1 are side thin-wall structures of four long cavities through structural simulation analysis, and determining that the grounding sensitive position of the multi-cavity LTCC substrate 1 is a cavity bottom area through circuit analysis. The bottom surface of the packaging box body 2 is provided with a through hole, and the LTCC circuit chip and the packaging box body 2 are required to be welded to have air tightness.

And thirdly, designing and processing a metal plate 3 and a solder plate 4, wherein the thickness of the transition metal plate is 0.2mm, and the surface of the transition metal plate is plated with Ni, NiAu or NiPdAu.

Round and rectangular through holes are formed in the transition metal sheet 3, the diameter of an opening in a weak structure area is 8-10mm, and the ratio of the area of the opening to the total area of the area is 75% -80%; the diameter of an opening of the grounding sensitive area is 2-3mm, and the ratio of the area of the opening to the total area of the area is 15% -20%; the transition metal sheet 3 at the projection position of the through groove on the bottom surface of the packaging box body 2 is provided with through holes with the same shape, and the distance between the edge of the transition metal sheet and the edge of the adjacent through hole is not less than 1 mm.

According to the design of the transition metal sheet 3, the solder sheet 4 is designed, the shape and the center position of the opening are consistent with those of the transition metal sheet 3, the shape size is 0.1mm larger than that of the transition metal sheet 3, and the diameter of a single hole is 0.05mm smaller than that of the corresponding hole in the transition metal sheet. The solder sheet is made of the following materials: in60Pb40 with a thickness of 0.05-0.1 mm.

And fourthly, activating the welding surface of the multi-cavity groove LTCC substrate 1. Heating the multi-cavity groove LTCC substrate 1 to the activation temperature of the soldering flux, coating the soldering flux on the welding surface of the multi-cavity groove LTCC substrate 1, keeping the temperature for 30-60 s, then cleaning and drying the liquid, and then using Ar/H₂And (3) processing the welding surface of the multi-cavity groove LTCC substrate 1 by using plasma.

The fifth step: the soldering paste 5 is printed on the welding surface of the multi-cavity groove LTCC substrate 1, the soldering paste 5 is distributed in the area where the transition metal sheet 3 is not provided with the hole, and the side length of the soldering paste 5 graph is not more than 5 mm. The melting point of the solder paste 5 is higher than that of the solder sheet 4 by 30 ℃. The welded interface of the soldering paste 5 is prevented from melting and flowing to generate larger holes in the welding process of the solder sheet 4.

And a sixth step: and welding the transition metal sheet 3 on the welding surface of the multi-cavity LTCC substrate 1 and cleaning. The welding method comprises the steps of attaching the transition metal sheet 3 to the welding surface of the multi-cavity LTCC substrate 1, welding the transition metal sheet and the multi-cavity LTCC substrate together by adopting vacuum reflow welding, removing welding cavities and redundant scaling powder through the vacuum action, and soaking and cleaning after welding.

And seventhly, sequentially loading the solder sheets 4, the multi-cavity groove LTCC substrate 1 and the welding tool into the packaging box body 2. Fig. 7 is a schematic diagram illustrating a placement of a welding tool in the method for welding the multi-cavity LTCC substrate and the package box according to this embodiment. Welding frock includes briquetting 8, supporter 7 and backing plate 6, and backing plate 6 directly places on multicavity groove LTCC base plate 1 surface, and supporter 7 is placed in the backing plate 6 non-structural weak area that corresponds multicavity groove LTCC base plate 1 in surface, and briquetting 6 is placed on supporter 7, and the distance between briquetting 6 and multicavity groove LTCC base plate 1 is 10mm-20 mm. The pressure applied by the welding tool to the multi-cavity LTCC substrate 1 is 1000-10000 Pa.

And step eight, welding the multi-cavity groove LTCC substrate 1 welded with the transition metal sheet 3 in the packaging box body 2. The welding method is vacuum welding, when the solder is in a molten state, the vacuum is pumped and kept for 5-10s, and no soldering flux is applied in the whole welding process.

As shown in fig. 2, the thickness of the transition metal sheet and the via design ensure that the capillary action of the solder does not seal the via during the soldering process.

The multi-cavity groove LTCC substrate and packaging box body welding method provided by the embodiment utilizes the characteristic of poor wettability of a gold platinum palladium layer when no fluxing agent exists, the thickness and through hole design of a transition metal sheet are combined, the welding process is ensured, the capillary action of a welding flux can not seal the through hole, thus after welding is completed, a stress buffer layer with the thickness of 0.2-0.7mm is formed on a welding interface of the LTCC substrate and the box body, and in the buffer layer, stress release holes with complete structure are reserved, so that the thermal mismatch between the LTCC substrate and the box body is effectively relieved, and meanwhile, the problems of air tightness and grounding property are considered.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.