Disclosure of Invention
The invention provides a packaging method and a packaging structure of a radio frequency module aiming at the defects existing in the prior art.
In order to achieve the above object, the technical scheme of the present invention is as follows:
a packaging method of a radio frequency module comprises the following steps:
1) Providing a carrier plate, assembling a chip module on the carrier plate, wherein the chip module comprises a filter chip and other chips, the filter chip is provided with a functional surface facing the carrier plate, a first gap is arranged between the functional surface and the carrier plate, the other chips at least comprise chips to be filled, the chips to be filled are provided with a lower surface facing the carrier plate, and a second gap is arranged between the lower surface and the carrier plate;
2) Providing an isolating film, and covering the isolating film on the carrier plate and the chip module;
3) Cutting the isolation film on the chip to be filled by adopting a cutting technology;
4) Attaching the isolation film to the surfaces of the carrier plate and the chip module by adopting a vacuum film coating process, wherein the isolation film seals the first gap to form a cavity, and the cutting part of the isolation film enables the second gap to be communicated with the outside;
5) And carrying out plastic packaging on one side of the carrier plate with the chip module to form a plastic packaging layer, wherein the second gap is filled with plastic packaging materials.
Optionally, the carrier plate is provided with a connection circuit, the filter chip is connected with the connection circuit of the carrier plate through a first bump at the bottom and forms the first gap, the bottom of the filter chip is provided with a functional area, and the chip to be filled is connected with the connection circuit of the carrier plate through a second bump at the bottom and forms the second gap.
Alternatively, the cutting technique is a laser cutting technique or an ion cutting technique.
Optionally, the laser cutting technology is to adjust the focal length of the laser to a preset height position, and cutting is performed by horizontal linear movement of the light spot.
Optionally, in the step 4), the pressure of the vacuum coating is 0.9-1.0 MPa, the temperature is 100-110 ℃, and the pressurizing time is 45-60 s.
Optionally, the laser cutting technology is to cut the isolating film around the chip to be filled by using a laser spot cutting technology to form a plurality of gaps, wherein the gaps are separately and alternately arranged, and the gaps form a hollowed-out structure after vacuum film coating.
Optionally, in step 3), cutting is performed on the outer side of the chip to be filled to form at least two notches, the at least two notches are located on two adjacent sides, two opposite sides or multiple sides of the chip to be filled, and the at least two notches form a hollow structure after vacuum film coating.
Optionally, in step 3), wire cutting of the isolation film is performed around the chip to be filled, where the wire cutting position is located in a range of a first length of the isolation film extending from the edge of the top surface of the chip to be filled to the inner side of the top surface and a second length of the isolation film extending to the outer side of the top surface, and the isolation film is cut to form a first portion and a second portion which are separated, where the first portion is located on the chip to be filled.
Optionally, the first length is designed such that the cutting edge of the second portion is located on the surface of the carrier plate between the chip to be filled and the adjacent chip after the vacuum film is covered, and the first portion is located on the top surface of the chip to be filled.
Optionally, the second length is designed such that the cutting edge of the first portion is located on the side wall of the chip to be filled after vacuum film coating, and the cutting edge of the second portion is located on the surface of the carrier plate between the chip to be filled and the adjacent chip.
Optionally, the isolating film is an epoxy resin, polyimide, thermoplastic resin or thermosetting resin film, and the thickness is 10-50 μm.
Optionally, the other chips include other functional chips and/or passive devices.
The packaging structure of the radio frequency module comprises a carrier plate, a chip module, an isolating film and a plastic sealing layer, wherein the chip module is arranged on the carrier plate, the isolating film is arranged on the surfaces of the carrier plate and the chip module, the plastic sealing layer is arranged on the isolating film and coats the carrier plate and the chip module, the chip module comprises a filter chip and a chip to be filled, the filter chip is arranged adjacently, the filter chip is provided with a functional surface facing the carrier plate, a first gap is arranged between the functional surface and the carrier plate, the chip to be filled is provided with a lower surface facing the carrier plate, a second gap is arranged between the lower surface and the carrier plate, the isolating film comprises a first part and a second part which are separated, the first part is arranged on the chip to be filled, the second part encloses the first gap to form a closed cavity, the plastic sealing layer fills the second gap through the separation of the first part and the second part, the distance between the top of the chip to be filled and the carrier plate is H 1, the distance between the top of the filter chip and the carrier plate is H 2, and the distance between the filter chip to be filled and the filter chip to be filled is D 1,D1:(D1+H1+H2, and the distance between the filter chip to be 1,D1:(D1+H1+H2 is equal to or greater than 1.
Optionally, the second portion extends to a length D 2,D2 -20 μm or more and D 2<D1 near the surface of the carrier plate of the chip to be filled.
The beneficial effects of the invention are as follows:
1) The isolation film is pre-coated on the carrier plate and the chip, then the isolation film on the chip to be filled is cut, the isolation film is attached to the surfaces of the chip and the carrier plate through a vacuum film coating process, a gap at the bottom of the filter chip is sealed through the isolation film to form a cavity which is completely isolated from a subsequent plastic sealing layer, and the gap at the bottom of the chip to be filled is communicated with the outside through the cutting part so as to facilitate the subsequent plastic sealing layer to enter filling, thereby meeting the requirements of integrated packaging of the filter chip and other chips and improving the reliability;
2) The laser focal length is not required to be adjusted, the same horizontal plane can be cut, the operation is convenient, and the carrier plate is not damaged.
Detailed Description
The invention is further explained below with reference to the drawings and specific embodiments. The drawings of the present invention are merely schematic to facilitate understanding of the present invention, and specific proportions thereof may be adjusted according to design requirements. The definition of the context of the relative elements and the front/back of the figures described herein should be understood by those skilled in the art to refer to the relative positions of the elements and thus all the elements may be reversed to represent the same elements, which are all within the scope of the present disclosure.
Example 1
The following describes the packaging method of the rf module of embodiment 1 with reference to fig. 1 to 9.
Referring to fig. 1, a carrier plate 1 is provided. The carrier board 1 has connection lines for achieving line connection, rerouting and line extraction, and may be, for example, a multilayer PCB board, a glass-based, ceramic-based package substrate, or the like. According to the layout of the chip module, a solder mask layer 12 is arranged in a non-layout area of the surface of the carrier plate 1.
Referring to fig. 2, the combination of a chip module including a saw filter chip 2 and other chips with a carrier board 1 is realized using a surface mount technology. Other chips include other functional chips such as switch chips, low Noise Amplifier (LNA) chips, etc., and/or passive devices such as capacitors, resistors, inductors, etc. The other chips include chips to be filled, and in this embodiment, a chip to be filled 3A is taken as an example. The acoustic surface filter chip 2 and the chip to be filled 3A are arranged on the carrier plate 1 and are respectively connected with the carrier plate 1 in a bonding way through the first lug 21/the second lug 31 at the bottom, and the functional area of the acoustic surface filter chip 2 is coplanar with the first lug 21. The surface of the carrier plate 1 and the chip 3A to be filled are provided with a first gap 2a with the height of the first bump 21, which first gap 2a is not in contact with the surface of the carrier plate and the functional area of the surface of the carrier plate 2, and a second gap 3A with the height of the second bump 31. Due to the difference of the size and the structure of the chips, the heights of the bumps of different chips are the same, partially the same or different.
Referring to fig. 3, a pre-coating is performed. The dry film 4 is used as an isolating film to cover the carrier plate 1, namely the acoustic surface filter chip 2 and the chip 3A to be filled, which cover the surface of the carrier plate 1. The dry film 4 is a film of epoxy resin, polyimide, thermoplastic resin or thermosetting resin, and has a thickness in the range of 10 to 50 μm, for example, 20 μm, 30 μm, 40 μm or any value therebetween. The surface of the dry film facing away from the chip is provided with a protective layer 41 before pre-lamination. After the two are pre-coated together, the dry film 4 is lapped on the top surface of each chip, and a natural falling state under gravity is presented between adjacent chips or between the chips and the surface of the carrier plate.
Referring to fig. 4, the protective layer 41 is peeled off.
Referring to fig. 5 and 6, a laser spot-cutting process is used to spot-cut the dry film 4 around the periphery of the chip 3A to be filled to form a plurality of discrete gaps 4a. The cutting position is designed on the premise that the notch 4a is communicated with the second gap 3a after the vacuum coating is stretched. The notches 4a are preferably arranged at equal intervals around the top surface of the chip 3A to be filled, so as to form a hollowed-out structure on the integrated dry film. For example, for a dry film thickness of 20 μm, an ultraviolet 355 nanosecond laser with a power of 15-30W is used, the focal length of the laser is adjusted to a preset height position for spot cutting and the laser is moved around the periphery of the chip 3A to be filled by the level of the light spot.
Referring to fig. 7-8, a vacuum film coating process is adopted to carry out secondary film coating, the pressure adopted by the film coating is 0.9-1.0 MPa, the temperature is 100-110 ℃, and the pressurizing time is 45-60 s. In the film coating process, under the action of vacuumizing and pressure, the dry film 4 is stretched and attached to the surfaces of the acoustic surface filter chip 2, the chip 3A to be filled and the carrier plate 1, so that a closed cavity V is formed at the first gap 2a of the first bump 21, and for the chip 3A to be filled, the gap 4a is positioned at the second gap 3A of the second bump 31 after adsorption to form a hollowed-out structure, so that a window which is communicated with the space outside the dry film 4 is formed between the second gap 3A between the chip 3A to be filled and the surface of the substrate 1, wherein the width d1 of the gap 4a is about 20-40um, and the interval d2 is about 40-60um. Specifically, the thickness of the chip 3A to be filled is h 1, the height of the second bump 31 is h 2, and the notch is located at a distance L 1 where the dry film 4 extends outward from the edge of the top surface of the chip 3A to be filled, then h 1<L1<(h1+h2).
Referring to fig. 9, the molding is performed to form a molding layer 5. In the plastic packaging process, the second gap 3A between the chip 3A to be filled and the surface of the substrate 1 is filled with the plastic packaging material through the notch 4a, so that the reliability of the device is improved. The sealed cavity V is reserved due to the sealing and blocking effects of the dry film 4, and the bottom surface of the acoustic surface filter chip 2 has a functional area, which is located in the sealed cavity V to ensure the normal operation thereof.
The obtained packaging structure of the radio frequency module comprises a carrier plate 1, one or more acoustic surface filter chips 2, one or more other chips (exemplified by a chip to be filled 3A), a dry film 4 and a plastic sealing layer 5. The non-layout area on the surface of the carrier plate 1 is provided with a solder mask layer 12, the sound meter filter chip 2 and other chips comprising the chip 3A to be filled are arranged on the carrier plate 1, and the sound meter filter chip 2 and the other chips comprising the chip 3A to be filled are respectively connected with the carrier plate 1 through the first bump 21/the second bump 31 at the bottom, wherein the surface of the sound meter filter chip 2 and the surface of the carrier plate 1 are provided with a first gap 2a with the height of the first bump 21, and the surface of the chip 3A to be filled and the surface of the carrier plate 1 are provided with a second gap 3A with the height of the second bump 31. The dry film 4 covers the surface of the sound surface filter chip 2, other chips including the chip 3A to be filled and the surface of the carrier plate 1, a closed cavity V corresponding to the first gap 2a is formed between the dry film 4 and the sound surface filter chip 2 and between the dry film 4 and the carrier plate 1, a plurality of gaps 4a are formed at the positions, corresponding to the second gaps 3A, of the dry film 4, the carrier plate 1, the sound surface filter chip 2 and other chips including the chip 3A to be filled are covered by the plastic layer 5, the cavity V is isolated from the plastic layer 5 by the dry film 4, and plastic sealing materials are filled into the second gaps 3A of the chip 3A to be filled and the surface of the carrier plate 1 through the gaps 4 a.
For a plurality of other chips which have gaps with the surface of the carrier plate 1 and need to be subjected to plastic packaging cladding, the mode can be adopted, and a hollowed-out structure is formed on the periphery of the required chips so as to realize the filling of the subsequent plastic packaging layers.
In the embodiment, on one hand, the film is pre-coated and then laser cutting is carried out, the laser position is regulated to the preset height position of the film, and as the film is not attached to the surface of the carrier plate and the side wall of the chip between adjacent chips or between the chip and the surface of the carrier plate, the damage of the laser cutting to the surface of the carrier plate and the side wall of the chip is avoided, on the other hand, the heat affected area of the spot cutting on the dry film is smaller by adopting a laser spot cutting mode, smaller chip spacing, higher product density and integration level can be realized, no requirement is provided for the arrangement of the chips, the applicable range is wide, the production efficiency is improved, the product cost is reduced, and on the other hand, the filling of the plastic packaging material in the required area is carried out through the notch of the hollowed-out structure, the dry film is still in an integrated structure, the stable combination is realized, and the sealing effect of the cavity and the coating effect of the chip are ensured.
Example 2
The following describes the packaging method of the rf module of embodiment 2 with reference to fig. 10 to 15.
Referring to fig. 10, a carrier board 1 is provided, a non-layout area of the surface of the carrier board 1 is provided with a solder mask layer 12, and the combination of the saw filter chip 2 and other chips with the carrier board 1 is realized by using a surface mounting technology. The other chips of the present embodiment are exemplified by LNA chips or switch chips as the chip to be filled 3B and the passive device 3C. The sound meter filter chip 2 is connected with the carrier plate 1 through a first bump 21 at the bottom in a bonding way and is provided with a first gap 2B, the chip 3B to be filled is connected with the surface of the carrier plate 1 through a second bump 32 and is provided with a second gap 3B, and the chip 3B to be filled is arranged between the passive device 3C and the sound meter filter chip 2.
Step 3, referring to fig. 11, pre-coating is performed. The dry film 4 is coated on the carrier plate 1, namely the acoustic surface filter chip 2, the chip to be filled 3B and the passive device 3C, which are coated on the surface of the carrier plate 1. The surface of the dry film 4 facing away from the chip is provided with a protective layer 41. After pre-coating, the dry film 4 is lapped on the top surface of each chip, and a natural falling state under gravity is presented between adjacent chips.
Step 4, referring to fig. 12, the protective layer 41 is peeled off.
And 5, referring to fig. 13, cutting the dry film 4 covering the chip 3B to be filled by adopting a laser cutting process, wherein the cutting position meets the following two conditions of 1, enabling the second gap 3B to be communicated with the outside after the vacuum coating is stretched, and 2, enabling the first gap 2B of the adjacent acoustic surface filter chip 2 to form a closed cavity after the vacuum coating is stretched. Considering the chip structure, the distance between chips, and the like, the dicing position may be based on the edge of the top surface of the chip 3B to be filled, and the first length of the isolation film may be moved toward the inside of the top surface or the second length of the isolation film may be moved toward the outside to satisfy the above conditions. In this embodiment, the first length of the isolation film is moved inward of the top surface, i.e., the cutting position is located on the top surface of the chip 3B to be filled.
In this embodiment, a laser wire cutting method is adopted to cut the dry film 4 around the chip 3B to be filled, for example, for a dry film with a thickness of 20 μm, an ultraviolet 355 nanosecond laser with a power of 15-30W is adopted, and the laser is adjusted to a preset height position to perform horizontal moving wire cutting, so that the dry film covered on the top surface of the chip 3B to be filled is separated from other parts at the second gap 3B.
Referring to fig. 14, a vacuum film coating process is adopted to carry out secondary film coating, wherein the pressure adopted by the film coating is 0.9-1.0 MPa, the temperature is 100-110 ℃, and the pressurizing time is 45-60 s. In the film coating process, under the action of vacuumizing and pressure, the dry film 4 stretches and is closely attached to the surface of each structure, the second gap 3b is communicated with the outside due to the disconnection of the dry film, and the first gap 2b forms a closed cavity V. A top view thereof is shown in fig. 15. The above-mentioned cut isolation film 4 is separated to form a first portion 4a and a second portion 4B, the cut edge of the first portion 4a is located on the top surface of the chip 3B to be filled, and the above-mentioned first length is designed such that the cut edge of the second portion 4B is located on the surface of the carrier plate between the chip 3B to be filled and the adjacent chip after vacuum lamination. The embodiment is particularly suitable for the situation that the chip to be filled has a smaller distance or a smaller height difference from the adjacent chip, so that the adjacent devices have a smaller length of dry film after pre-coating, and when the adjacent chip is the acoustic surface filter chip 2, the cavity formation of the adjacent chip can be ensured.
The distance between the top surface of the chip 3B to be filled and the carrier plate is H 1, the distance between the top surface of the filter chip 2 and the carrier plate is H 2, and the distance between the chip 3B to be filled and the filter chip 2 is D 1, so that the requirement of D 1:(D1+H1+H2) is more than or equal to 1:5. The second part 4B extends to a length D 2,D2 which is more than or equal to 20 mu m and D 2<D1 on the surface of the carrier plate 1 close to the chip 3B to be filled.
Referring to fig. 16, plastic sealing is performed to form a plastic sealing layer 5. In the plastic packaging process, the second gap 3b is filled with the plastic packaging material, and the sealed cavity V is reserved due to the sealing and blocking effects of the dry film 4.
In the obtained packaging structure of the radio frequency module, the dry film covered on the top surface of the chip 3B to be filled is separated from the dry films of other parts at the second gap 3B, and the plastic packaging material is filled in the second gap 3B. The dry film covering the top surface of the chip 3B to be filled may cover a part of the area, the whole area, or extend from the top surface down to cover the side wall of the chip 3B to be filled.
In this embodiment, adjust the laser position and cut to the preset high position that the membrane is located, laser focus need not to adjust, and is lower to the precision requirement, easier operation. When a plurality of other devices needing to be filled with plastic packaging materials are arranged in the module, the dry films covered by the other devices can be cut by referring to the process, and after the cutting is finished, vacuum plastic packaging is performed.
Example 3
Referring to fig. 17, embodiment 3 is different from embodiment 2 in that, when the laser dicing is performed, the dicing site is designed such that the edge of the top surface of the chip 3B to be filled is moved to the outside by the second length of the spacer film, that is, the dicing site is located at the side surface of the chip 3B to be filled. Referring to fig. 18, the above-mentioned cut isolation film 4 is separated to form a first portion 4c and a second portion 4d, and the above-mentioned second length is designed such that the cut edge of the first portion 4c is located on the side wall of the chip 3B to be filled after vacuum coating to avoid the influence on the second gap 3B. The embodiment is particularly suitable for the situation that the chip to be filled has a larger distance or a larger height difference from the adjacent chip, so that the dry film 4 with a larger length between the adjacent devices after pre-coating.
Also, the relationship described in example 2 is satisfied between the chip height and the distance.
Example 4
In the method for packaging a radio frequency module of embodiment 4, the steps in the earlier stage refer to the steps in fig. 1 to 4 in embodiment 1.
Referring to fig. 19, at the time of the laser cutting process, the dry film 4 to be filled in the periphery of the chip 3A is cut to form two notches 4b. In this embodiment, the chip 3A to be filled has a square structure, and two adjacent sides of the chip are provided with the filter chip 2, so that the two notches 4b may be located on the other two sides where no filter chip is provided to avoid the influence on the package of the filter chip. Referring to fig. 20, in another embodiment, the distances between two adjacent filter chips 2 at two sides and the chip 3A to be filled are the first distance D 3 and the second distance D 4,D4>D3, respectively, and then two notches 4b are disposed at opposite sides and one of the notches 4b is disposed at the side with the second distance D4, and the two opposite sides of the notch are disposed to obtain a more ideal underfill effect of the molding compound, and the notch is far away from the filter chip as far as possible in the structural design to avoid the influence on the package of the filter chip. The subsequent vacuum lamination and plastic encapsulation process is described in example 1.
The laser cutting process used in this embodiment may be point cutting or wire cutting, and the length of the single notch does not exceed, for example, a side length of the square chip structure. More than two notches can be arranged according to the requirement, so that the notch is in a hollow structure after vacuum film coating.
The above embodiments are described by taking a laser cutting process as an example, and other precise cutting techniques such as ion cutting techniques may be employed.
The packaging method and the packaging structure can be applied to the packaging of the radio frequency module of the acoustic surface filter and finally applied to communication equipment. Along with the development of the rf front-end module and the demand of the application terminal for the light and thin application, the corresponding package integration level is higher and higher. The radio frequency front end module with high integration level needs to put different chips/components in the same package body, solves the problems of large size and high cost of the existing CSP, WLP and other device packaging modes, and promotes the application of the radio frequency module.
The above embodiments are only used to further illustrate a method and a structure for packaging a radio frequency module according to the present invention, but the present invention is not limited to the embodiments, and any simple modification, equivalent variation and modification made to the above embodiments according to the technical substance of the present invention falls within the scope of the technical solution of the present invention.