Bare chip packaging structure and RF module of the filter

Abstract

The embodiment of the present invention provides a bare chip packaging structure and radio frequency module of a filter, wherein the bare chip packaging structure of the filter includes: a circuit substrate; a substrate; an interdigital transducer spaced apart from the circuit substrate; a substrate solder ball, wherein the substrate solder ball includes a plurality of substrate solder balls, the plurality of substrate solder balls being fixed to a side of the substrate close to the circuit substrate, the substrate solder balls being spaced apart from the interdigital transducer, the substrate being fixed to the circuit substrate via the substrate solder ball support and forming an electrical connection; at least some of the substrate solder balls use different ratios of soldering materials, so that the substrate solder balls at different positions have different sinking degrees under the same reflow soldering temperature conditions, and the substrate is tilted relative to the circuit substrate, so that the substrate and the circuit substrate form an oblique cavity; a cover layer, and a substrate protective layer. The bare chip packaging structure of the filter of the present invention is convenient to package, has high production efficiency, and has good module quality.

Description

Technical Field

[0001] The present invention is applicable to the field of wireless communication technology, and in particular relates to a bare chip packaging structure of a filter and a radio frequency module. Background Art

[0002] An RF module integrates two or more discrete components, such as RF switches, low-noise amplifiers, filters, duplexers, and power amplifiers, into a single module, improving integration and performance while miniaturizing the device. RF modules can be categorized into different types and functions based on their integration method.

[0003] In the prior art, since filters use mechanical vibration for filtering, a cavity that cannot contact the filter's interdigital transducers needs to be created in the package. In the bare die module package (BDMP), a substrate protective layer forms a protective layer around the filter to prevent the mold material from filling the bottom of the filter under pressure of several megapascals, thereby causing the filter to fail. However, in order to form and cover the device, the substrate protective layer is generally made of organic material and has a low Young's modulus. The pressure of the solid resin layer curing is generally relatively fixed, which means that the solder balls of the filter must be precisely proportioned. It is necessary to conduct multiple reflow soldering temperature tests for different module products to ensure that the solder balls collapse a certain amount during C4 (Controlled Collapse Chip Connection) packaging and reach a very precise height after collapse. That is, this height cannot be too small, so that the filter's interdigital transducers contact the circuit substrate, and cannot be too large, so that the mold material overflows excessively, or even breaks through the substrate protective layer, and then the mold material contacts the filter's interdigital transducers.

[0004] However, during the above-mentioned bare chip module packaging process, the mold material contacts the IDT, causing the IDT to fail. At the same time, under a wide range of reflow temperatures, the bare chip packaging effect is poor, the production efficiency of the RF module is low, and the quality is poor. Summary of the Invention

[0005] The embodiments of the present invention provide a bare chip packaging structure of a filter and a radio frequency module, aiming to solve the problems of poor packaging effect of bare chip modules, low production efficiency and poor quality of radio frequency modules in the prior art.

[0006] In a first aspect, an embodiment of the present invention provides a bare chip packaging structure of a filter, wherein the bare chip packaging structure of the filter includes:

[0007] Circuit substrate;

[0008] a substrate, the substrate being spaced apart and arranged on one side of the circuit substrate;

[0009] an interdigital transducer, the interdigital transducer being fixed to a side of the substrate close to the circuit substrate and spaced apart from the circuit substrate;

[0010] Substrate solder balls, comprising a plurality of substrate solder balls, fixed to a side of the substrate close to the circuit substrate, the substrate solder balls being spaced apart from the IDT, the substrate being fixed to the circuit substrate via the substrate solder balls and forming an electrical connection thereto; at least some of the substrate solder balls having different solder material ratios, so that the substrate solder balls at different positions have different sags under the same reflow soldering temperature conditions, and the substrate being tilted relative to the circuit substrate, forming an oblique cavity between the substrate and the circuit substrate; the IDT being located within the oblique cavity;

[0011] a cover layer, the cover layer completely covering the circuit substrate, the cover layer comprising a cover layer body, a mounting groove formed by the cover layer body being recessed away from the circuit substrate, and an overflow bump formed by a groove sidewall protruding on either side of the mounting groove, the substrate being mounted in the mounting groove such that the overflow bump is sandwiched between the substrate and the circuit substrate, with the side of the substrate abutting the overflow bump being further away from the circuit substrate than the other side opposite thereto; and

[0012] The substrate protection layer is sandwiched between the cover layer and the substrate and extends between the cover layer and the circuit substrate, and the overflow bumps are blocked outside the oblique cavity.

[0013] Preferably, the ratio of the soldering material is tin / copper.

[0014] Preferably, the overflow protrusion is an arc structure.

[0015] Preferably, the cover layer is made of solid resin material.

[0016] Preferably, the distance between the substrate and the circuit substrate gradually decreases along a direction from a side of the substrate close to the overflow bump to a side of the substrate away from the overflow bump.

[0017] Preferably, a plurality of substrate solder balls are fixed to the substrate and spaced apart on opposite sides of the IDT.

[0018] Preferably, the substrate solder ball includes a columnar copper column fixed to the substrate and a semicircular solder ball formed at the end of the copper column, and the arc surface of the solder ball is fixed to the circuit substrate to achieve electrical connection.

[0019] Preferably, of the end of the substrate close to the overflow bump and the other end opposite thereto, the IDT is closer to the other end.

[0020] Preferably, the bare chip packaging structure of the filter further includes a plurality of module solder balls fixed at intervals on a side of the circuit substrate away from the substrate.

[0021] In a second aspect, an embodiment of the present invention provides a radio frequency module, which includes the bare chip packaging structure of the above-mentioned filter.

[0022] The beneficial effect achieved by the present invention is that, due to different soldering material ratios for the solder balls at different positions of the filter, the solder balls at different positions will sink to different degrees at the same reflow soldering temperature; thereby forming an oblique cavity and completing the filter packaging of the oblique cavity; the cover layer forms a larger overflow bump of the mold material at one end of the oblique cavity, which is used to support the fixed substrate; and the filter fingers are arranged at a position away from the end, so that under relatively wide reflow soldering temperature conditions, it can be ensured that the overflow of the mold material will not touch the filter interdigital transducer, and that the filter interdigital transducer will not contact the circuit substrate and cause failure. In this way, by obliquely packaging the filter, the packaging difficulty of the bare chip packaging structure is reduced, and the yield rate of the RF module packaging is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the bare chip packaging structure of the filter provided by an embodiment of the present invention.

[0024] In the figure, 100, the bare chip packaging structure of the filter, 1, the circuit substrate, 2, the substrate, 3, the interdigital transducer, 4, the substrate solder ball, 41, the copper pillar, 42, the solder ball, 5, the substrate protective layer, 6, the cover layer, 61, the cover layer body, 62, the mounting groove, 63, the overflow bump, 7, the oblique cavity, 8, the module solder ball. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] Please refer to Figure 1 An embodiment of the present invention provides a bare chip packaging structure 100 of a filter, and the bare chip packaging structure 100 of the filter includes: a circuit substrate 1, a substrate 2, an interdigital transducer 3, a cover layer 6, a substrate solder ball 4 and a substrate protective layer 5.

[0027] The circuit substrate 1 is used to support and fix the cover layer 6 .

[0028] The substrate 2 is spaced apart and disposed on one side of the circuit substrate 1 .

[0029] The IDT 3 is fixed to a side of the substrate 2 close to the circuit substrate 1 and is spaced apart from the circuit substrate 1 , so that the IDT 3 does not contact the circuit substrate 1 , thereby improving safety.

[0030] The substrate solder balls 4 include multiple substrate solder balls 4, which are fixed to the side of the substrate 2 close to the circuit substrate 1. The substrate solder balls 4 and the interdigital transducer 3 are arranged at intervals. The substrate 2 is supported and fixed to the circuit substrate 1 by the substrate solder balls 4 and forms an electrical connection; at least some of the substrate solder balls 4 use different ratios of solder materials, so that the substrate solder balls 4 at different positions have different sinking degrees under the same reflow temperature conditions, and the substrate 2 is arranged at an angle relative to the circuit substrate 1, and the substrate 2 and the circuit substrate 1 form an oblique cavity 7; the interdigital transducer 3 is located in the oblique cavity 7.

[0031] The cover layer 6 is completely covered on the circuit substrate 1, and the cover layer 6 includes a cover layer body 61, a mounting groove 62 formed by the cover layer body 61 being recessed away from the circuit substrate 1, and an overflow protrusion 63 formed by the groove side wall protruding on any side of the mounting groove 62. The substrate 2 is installed in the mounting groove 62, and the overflow protrusion 63 is clamped between the substrate 2 and the circuit substrate 1. The side of the substrate 2 abutting the overflow protrusion 63 is farther away from the circuit substrate 1 than the other side opposite to it; by covering the cover layer body 61 on the circuit substrate 1, the substrate 2 is installed in the mounting groove 62, and the substrate 2 and the circuit substrate 1 are separated by the overflow protrusion 63 on one side of the mounting groove 62. At the same time, the substrate 2 can also be supported so that the substrate 2 is installed and fixed in the mounting groove 62, and the fixing effect is good.

[0032] The substrate protection layer 5 is sandwiched between the cover layer 6 and the substrate 2 and extends between the cover layer 6 and the circuit substrate 1, with the overflow bumps blocked outside the oblique cavity, thereby providing protection for the cover layer 6, the substrate 2, and the circuit substrate 1.

[0033] Specifically, since different soldering material ratios are applied to the solder balls at different positions of the filter, the solder balls at different positions will sink to different degrees at the same reflow soldering temperature; thus, an oblique cavity 7 is formed, completing the filter packaging of the oblique cavity 7; the cover layer 6 forms a larger overflow bump 63 of the mold material at one end of the oblique cavity 7, which is used to support and fix the substrate 2; the filter's interdigital transducer 3 is arranged at a position away from this end, so that under relatively wide reflow soldering temperature conditions, it can be ensured that the overflow of the mold material will not touch the filter's interdigital transducer 3, and that the filter's interdigital transducer 3 will not contact the circuit substrate 1 and cause failure. In this way, by obliquely packaging the filter, the packaging difficulty of the bare chip packaging structure 100 is reduced, and the yield rate of the RF module packaging is improved.

[0034] In this embodiment, the solder material ratio is tin / copper. Different tin / copper ratios are set for solder balls at different locations on the filter, resulting in different degrees of sag at the same reflow temperature. This in turn forms an oblique cavity 7, completing the filter packaging of the oblique cavity 7.

[0035] In this embodiment, the overflow bumps 63 are arc structures, so that the substrate protection layer 5 will not be squeezed and damaged by the substrate 2 and the overflow bumps 63, and the safety is high.

[0036] In this embodiment, the cover layer 6 is made of a solid resin material. The solid resin material is filled onto the side of the substrate protection layer 5 facing away from the substrate 2 and then solidified, resulting in a high structural strength. Furthermore, the overflow bumps 63 are formed by overflowing the mold material during the solid resin filling process, effectively securing the substrate 2.

[0037] In this embodiment, the distance between the substrate 2 and the circuit substrate 1 gradually decreases from the side of the substrate 2 close to the overflow bump 63 to the side away from the overflow bump 63. This facilitates the formation of the oblique cavity 7 and improves the bare chip packaging efficiency.

[0038] In this embodiment, a plurality of substrate solder balls 4 are fixed to the substrate 2 and spaced apart on opposite sides of the IDT 3. This facilitates installation of the IDT 3, while also providing electrical connection to the circuit substrate 1 via the substrate solder balls 45. This effectively forms a support substrate 2, thereby isolating the IDT 3 from the circuit substrate 1 and preventing contact between the IDT 3 and the circuit substrate 1, which could cause filter failure.

[0039] In this embodiment, the substrate solder ball 4 includes a cylindrical copper pillar 41 fixed to the substrate 2 and a semicircular solder ball 42 formed at the end of the copper pillar 41. The arc surface of the solder ball 42 is fixed to the circuit substrate 1 to achieve electrical connection. This facilitates electrical connection between the substrate 2 and the circuit substrate 1.

[0040] In this embodiment, the bare chip packaging structure 100 of the filter further includes a plurality of module solder balls 8 fixed at intervals to a side of the circuit substrate 1 away from the substrate 2. This facilitates electrical connection between the module solder balls 8 and the chip, thereby achieving overall assembly of the RF module.

[0041] An embodiment of the present invention provides a radio frequency module, which includes the bare chip packaging structure 100 of the filter described above.

[0042] The embodiments of the present invention have been described above with reference to the accompanying drawings. What has been disclosed are only preferred embodiments of the present invention. However, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Under the guidance of the present invention, those skilled in the art may make various equivalent changes without departing from the spirit of the present invention and the scope of protection of the claims, and all of these changes shall fall within the protection of the present invention.

Claims

1. A bare chip packaging structure of a filter, characterized in that: The bare chip packaging structure of the filter includes: Circuit substrate; a substrate, the substrate being spaced apart and arranged on one side of the circuit substrate; an interdigital transducer, the interdigital transducer being fixed to a side of the substrate close to the circuit substrate and spaced apart from the circuit substrate; Substrate solder balls, comprising a plurality of substrate solder balls, fixed to a side of the substrate close to the circuit substrate, the substrate solder balls being spaced apart from the IDT, the substrate being fixed to the circuit substrate via the substrate solder balls and forming an electrical connection thereto; at least some of the substrate solder balls having different solder material ratios, so that the substrate solder balls at different positions have different sags under the same reflow soldering temperature conditions, and the substrate being tilted relative to the circuit substrate, forming an oblique cavity between the substrate and the circuit substrate; the IDT being located within the oblique cavity; a cover layer, the cover layer completely covering the circuit substrate, the cover layer comprising a cover layer body, a mounting groove formed by the cover layer body being recessed away from the circuit substrate, and an overflow bump formed by a groove sidewall protruding on either side of the mounting groove, the substrate being mounted in the mounting groove such that the overflow bump is sandwiched between the substrate and the circuit substrate, with the side of the substrate abutting the overflow bump being further away from the circuit substrate than the other side opposite thereto; and The substrate protection layer is sandwiched between the cover layer and the substrate and extends between the cover layer and the circuit substrate, and the overflow bumps are blocked outside the oblique cavity.

2. The bare chip packaging structure of the filter according to claim 1, wherein: The ratio of the soldering material is tin / copper.

3. The bare chip packaging structure of the filter according to claim 1, wherein: The overflow convex point is an arc structure.

4. The bare chip packaging structure of the filter according to claim 1, wherein: The cover plate layer is made of solid resin material.

5. The bare chip packaging structure of the filter according to claim 1, wherein: The distance between the substrate and the circuit substrate gradually decreases along a direction from a side of the substrate close to the overflow bump to a side of the substrate away from the overflow bump.

6. The bare chip packaging structure of the filter according to claim 1, wherein: A plurality of substrate solder balls are fixed to the substrate and spaced apart on two opposite sides of the IDT.

7. The bare chip packaging structure of the filter according to claim 2, wherein: The substrate solder ball includes a columnar copper column fixed to the substrate and a semicircular solder ball formed at the end of the copper column. The arc surface of the solder ball is fixed to the circuit substrate to achieve electrical connection.

8. The bare chip packaging structure of the filter according to claim 5, wherein: Of the end of the substrate close to the overflow bump and the other end opposite thereto, the IDT is closer to the other end.

9. The bare chip packaging structure of the filter according to claim 1, wherein: The bare chip packaging structure of the filter further includes a plurality of module solder balls fixed at intervals on a side of the circuit substrate away from the substrate.

10. A radio frequency module, characterized in that: The radio frequency module includes a bare chip packaging structure of the filter according to any one of claims 1 to 9.

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