A double-sided packaging structure of a filter module and a manufacturing method thereof

Abstract

A double-sided packaging structure of a filter module and a manufacturing method thereof, the double-sided packaging structure being a double-sided packaging structure without an inductance passive element; a filter chip is packaged on a front surface of a substrate by a front surface plastic packaging layer, and a switch chip is packaged on a back surface of the substrate by a back surface plastic packaging layer. The double-sided packaging structure solves the conflict between a filter cavity coating and a gap of a copper column of an inverted switch chip, solves the gap filling problem between two poles of an inductance passive element, solves the reliability hidden danger problem caused by the extreme size reduction of a filter packaging body, solves the product deformation and failure hidden danger problem caused by the uneven internal stress of multiple different materials in single-sided packaging of a device, and solves the problem of insufficient filling of epoxy resin in a small gap of a component.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor radio frequency technology, in particular to a signal receiving end filter module integrated device. BACKGROUND

[0002] Current packaging structure one:

[0003] PiP (Package in Package) module device internal filter plastic packaging device

[0004] Common shapes include LGA (Land Grid Array) grid array packaging. The internal planar structure is to mount all components on the substrate (component carrier). The arrangement of components includes: multiple filter packages LGA (Land Grid Array) grid array, a flip-chip switch chip, multiple inductor passive components, etc. The filter package is connected to the module substrate using tin solder. The component gap is filled with epoxy resin, which serves as circuit isolation and protection.

[0005] The common structure of the filter package is to flip a filter chip on the substrate. A layer of isolation film is attached on top of the chip, so that the IDT resonator on the surface of the filter chip is in a cavity environment, ensuring the normal operation of the IDT resonator. Epoxy resin is filled on top of the isolation film to fill the gap and make the surface flat.

[0006] Current packaging structure two:

[0007] Planar integration mounting. Common shapes include LGA (Land Grid Array) grid array packaging. The internal planar structure is mainly arranged on the surface of the substrate (component carrier). There are also a small number of chip-on-chip stacking forms. The arrangement of components includes: multiple filter chips, a flip-chip switch chip, multiple inductor passive components, etc.

[0008] The internal longitudinal structure is to mount all components on the surface of the substrate. A layer of isolation film is attached on top of all components, so that the IDT resonator on the surface of the filter chip is in a cavity environment, ensuring the normal operation of the IDT resonator. Epoxy resin is filled on top of the isolation film to fill the gap and make the surface flat.

[0009] Single-sided PiP (Package in Package) module device internal filter plastic packaging device

[0010] Advantages: After using epoxy resin to fill between the switch chip and the substrate, there is no cavity stress release and good circuit protection effect. After using epoxy resin to fill between the two poles of the inductor passive component, there is no cavity leading to short circuit problem.

[0011] Disadvantages: large number of filter package, high device density, small device spacing gap. Most filter module layout cannot be completed, and even if a few filter modules can be laid out, the epoxy resin filling during the plastic sealing process is insufficient, forming internal cavities in the module device, which is prone to tin short circuit between different line elements, poor sealing causing cracking, cavity water vaporization causing internal explosion of the device, etc. As a balance, the filter package volume will be greatly reduced, which will reduce the distance between the filter chip and the edge of the package, thereby reducing the ability of the filter film to block water vapor immersion, which will further derive secondary reliability problems.

[0012] Planar integrated mounting

[0013] Advantages: compared with the PiP structure, the filter chip is smaller in area and volume than the filter package, and can appropriately move the surface mounting space. Most filter modules are of this structure.

[0014] Disadvantages: high device density, small device spacing gap, and the epoxy resin filling during the plastic sealing process is extremely prone to be insufficient, forming internal cavities in the module device, poor sealing causing cracking, cavity water vaporization causing internal explosion of the device, etc. The more serious problem is that the inductor passive element and the flip-chip switch are in a cavity state between the substrate, and this cavity is an unnecessary structure caused by process limitations. The overall film will form a cavity between the two poles of the passive element, which has a high risk of tin short circuit. It will also form a cavity between the flip-chip switch chip and the substrate, which has a risk of tin short circuit. At the same time, there is no effective epoxy resin filling between the flip-chip switch chip and the substrate, and the uneven stress of the module device in different environments will easily cause the copper column and the substrate, the copper column and the tin, the copper column and the chip, etc. to be disconnected, causing circuit failure.

[0015] Reference Figure 11 and Figure 12 As shown in the figures, they are both products with inductor passive elements in the prior art, and are both single-sided packaging. Summary

[0016] To solve the problems in the prior art, the technical solutions of the present application are as follows:

[0017] The necessary technical means adopted is to provide a double-sided packaging structure of a filter module, comprising a substrate, characterized in that the double-sided packaging structure is a double-sided packaging structure without an inductor passive element; the filter chip is packaged on the front surface of the substrate through a front plastic sealing layer, alone or in the form of a filter package, and the switch chip is packaged on the back surface of the substrate through a back plastic sealing layer.

[0018] Preferably, the filter package is composed of a filter chip with gold pillars, a passivation adhesive layer, a filter substrate, a resonator, and a plastic encapsulation material. The filter chip is placed on the filter substrate, the lower end of the gold pillars is combined with the gold-plated layer on the surface of the filter substrate, the upper end of the gold pillars is connected with the pad terminals of the filter chip, and the tin balls protrude from the lower bottom surface of the filter substrate.

[0019] Further, the filter package is encapsulated on the front surface of the substrate by the front plastic encapsulation layer.

[0020] Further, the filter chip has a cavity between the lower bottom surface of the filter chip and the upper surface of the filter substrate, the resonator is arranged on the lower bottom surface of the filter chip and in the cavity, the filter chip is coated with the passivation adhesive layer except for the bottom surface, the passivation adhesive layer is encapsulated with the plastic encapsulation material on the outside, and the filter substrate is separated from the plastic encapsulation material by the passivation adhesive layer.

[0021] Further, the substrate pads are arranged on the substrate with a spacing, the back plastic encapsulation layer is provided with pad openings at the positions of the substrate pads, the substrate pads are provided with pad tin balls and located in the pad openings, the bottom of the pad tin balls protrudes from the bottom surface of the back plastic encapsulation layer, and the pad tin balls are encapsulated on the back surface of the substrate by the back plastic encapsulation layer.

[0022] Another preferable embodiment is that the filter chip is encapsulated on the substrate by the passivation adhesive layer (coated with the mold plastic encapsulation layer), the filter chip has a cavity between the lower bottom surface of the filter chip and the top surface of the substrate, and the resonator is arranged on the lower bottom surface of the filter chip and in the cavity.

[0023] Further, the filter chip is provided with 4-6 tin balls of different quantities at the bottom, according to the functional logic of the filter module, part of the tin balls are connected with the logic ports of the module substrate circuit, and the other part of the tin balls are connected with other functional circuits of the module substrate.

[0024] Preferably, it also includes a wire inductance arranged on the front surface of the substrate. The substrate wire is designed according to the corresponding inductance value of the input and output of different filter specifications, and the substrate wire realizes the inductance function as follows.

[0025] The wire inductance conversion formula is as follows:

[0026]

[0027]

[0028] L is the inductance value, Ɩ is the length of the substrate wire, w is the width of the substrate wire, and h is the thickness of the substrate wire. It is noted that the substrate wire inductance is independent of the copper thickness.

[0029] As can be seen from the above formula, if the length of the substrate wire is reduced by half, the inductance value is also reduced by half. However, the width of the wire needs to be increased by 10 times to reduce the inductance value by half.

[0030] Preferably, the filter chip has a thickness of 200-250um, the passivation bonding layer has a thickness of 20-50um, the filter substrate has two or more layers of superimposed circuits with a thickness of 110-200um, the interconnect layers between the filter chip and the filter substrate 1-5 are 10-15um gold pillars, and the total thickness of the filter package is 450-550um.

[0031] A method for manufacturing a double-sided packaging structure for a filter module, characterized by comprising the following steps:

[0032] 1. Prepare the filter package or the filter chip after ball mounting, and prepare the switch chip containing copper pillars.

[0033] The center of the copper pillars on the switch chip coincides with the center of the pads, using circular copper pillars as a reference. The spacing between the copper pillars is 100-110µm. A 3µm thick PI organic filler is placed between the copper pillars and the chip. The overall height of the copper pillars is 65-75µm, with the copper pillar height being 35-40µm, the solder cap height being 25-35µm, and the pad opening being 55-60µm. The chip pad spacing is 100-110µm, and the chip pads are evenly distributed within the effective area of ​​the chip.

[0034] After the switch chip completes the advanced copper pillar packaging process, it undergoes intermediate testing to distinguish between good and defective products and produce an electron distribution map; it is then ground and cut into individual chips, with the thickness of the switch chip excluding the copper pillar maintained at 90-100um; the intermediate testing good products are packaged in tape and reel and labeled for use in the SMT packaging process.

[0035] 2. Design and fabrication of substrate for double-sided packaging of filter modules;

[0036] 2.1 The product's external design uses a BGA structure. The large-area grounding is changed to an inner and outer two-layer design. The inner layer features a flip-chip pad layout for the switching chip, while the outer layer maintains grounding through solder balls.

[0037] 2.2 Four-layer or multi-layer circuit board technology is used. The middle two layers of the board are mainly used for interconnection conversion and fan-out layout applications. The outer front layer serves as the bonding carrier layer for filter chips or filter packages, as well as the wire-wound inductor layer. The surface of the exposed back pads of the board is treated with an OSP anti-oxidation organic protective layer.

[0038] 2.3 Substrate fabrication: Use an even-numbered layer-by-layer process with core material, or a single-layer stacking process without core material.

[0039] 2.3.1 Inner layer circuit processing: Circuit and via are made by additive process, according to the design, the core material is drilled through by double-sided laser drilling, 3um copper material is chemically deposited on the whole surface of the hole wall to connect the circuits on both sides of the material, the substrate panel on both sides is covered with dry film in the yellow light room, the non-circuit area and non-drilling area of the dry film is exposed, the dry film in the unexposed area is etched, copper is electroplated to fill the hole and form the circuit layer, the thickness of the circuit layer is 12-25um, the exposed dry film is removed, the seed layer is etched and copper is chemically deposited, the inner layer circuit processing of the panel is completed,

[0040] 2.3.2 Outer layer circuit processing: The panel is pressed with semi-cured material on both sides and baked, according to the design, laser blind holes are drilled on both sides to expose the inner layer copper pads connected to the outer layer circuit, 3um copper material seed layer is chemically deposited on the whole surface, the substrate panel on both sides is covered with dry film in the yellow light room, the non-circuit area and non-drilling area of the dry film is exposed, the dry film in the unexposed area is etched, copper is electroplated to fill the hole and form the circuit layer, the thickness of the circuit layer is 12-25um, the exposed dry film is removed, the seed layer is etched and copper is chemically deposited, the outer layer circuit processing of the panel is completed;

[0041] 2.3.3 Ink and surface treatment: The substrate panel is coated with anti-soldering ink in the yellow light room, the non-soldering area is exposed, the unexposed ink is etched to expose the soldering area on the outer layer circuit of the substrate panel, the substrate panel is punched or milled to separate into single substrate with a size that can be used for packaging, the exposed copper pads on the front and back are protected by OSP anti-soldering layer deposition,

[0042] 3 Filter module double-sided packaging

[0043] 3.1 Substrate back OSP cleaning: Print with oxidizing flux, in the reflow oven from room temperature to 260 degrees Celsius and then cool down to room temperature, during the whole process, the flux reacts with the OSP to generate water, carbon dioxide and small molecules above 100 degrees Celsius, water and carbon dioxide are discharged in gas form in the reflow oven, small molecules adhering to the surface of the substrate are removed by high-pressure water washing; After the substrate passes through the reflow oven and water washing line, it will produce irregular warping and absorb part of the water in the glass fiber core layer and the ink layer, and is pressed flat in a 120 degree oven with a 5-10 kilogram pressure block,

[0044] 3.2 Backside mounting: flip 100um thickness 70-80um copper column height switch chip on the back of the substrate pad, mounting the chip in the flux tank, according to the chip copper column on the tin cap 25-30um height configuration 35-50um depth of flux dipping tank, ensure that the tin cap surface 100% effective coverage of flux, after reflow oven according to the tin cap composition and flux composition of the optimal reflow temperature curve, the substrate with the flip switch chip in the reflow oven from room temperature to 260 degrees Celsius, the highest point, in the reflow to room temperature state, the reflow substrate washing treatment to remove residual in the substrate and chip surface flux, at this time the substrate surface to the chip back height in 150-170um,

[0045] 3.3 Backside plastic package: before plastic package in 120 degrees Celsius oven baking 6-8 hours to remove the previous washing process into the steam, before plastic package in 95% argon and 5% oxygen in the ion state of plasma cleaning, remove the substrate surface contamination or grease and increase the substrate surface binding activity; backside plastic package, plastic package material needs to be adjusted to the maximum 20um diameter particles, select 250-400um height plastic package material cavity in 175 degrees vacuum environment, after plastic package chip back to the plastic package material surface distance 80-250um, plastic package in 175 degrees Celsius oven baking 8-12 hours again solidification,

[0046] 3.4 Backside thinning: the plastic package after the substrate is fixed in the fixture using grinding wheel to grind the plastic package, after grinding the plastic package thickness in 160-200um, mobile phone filter module product application thinning to 160um, polishing to 140um to expose the back of the switch chip,

[0047] 3.5 Substrate front OSP cleaning: as described in 3.1, print with oxidizing flux, in the reflow oven from room temperature to 260 degrees and then cool to room temperature, the whole process of flux and OSP reaction will generate water, carbon dioxide, and small molecules above 100 degrees Celsius, water and carbon dioxide in the form of gas in the reflow oven, small molecules of compounds adhering to the surface of the substrate are removed by high pressure washing, the substrate after the reflow oven and washing line will produce irregular warping and absorb part of the moisture in the glass fiber core layer and ink layer, need to be baked in 120 degrees Celsius oven with 5-10kg pressure block,

[0048] 3.6 Optional Front-End Mounting: The filter module can be packaged using pre-packaged and tested filter units with 100% yield for surface mount secondary packaging, or filter chips with solder balls can be used for flip-chip mounting. The filter package can be a 4G single-band receiver or a 4G dual-band receiver, and any one of the following frequency bands can be selected from 1, 2, 3, 5, 7, 8, 20, 26, 28, 34, 39, 40, 41, and 66 depending on the different terminal platforms.

[0049] 3.7 Front-side molding: Molding is performed according to different surface-mount components.

[0050] 3.8 Laser Etching: After the front-side molding is completed, the TMV process is used to laser-groove the terminal positions on the back of the substrate. The grooving ensures that the bottom copper pad terminals of the substrate are exposed. At this time, the terminals inside the exposed hole are circular pads, and the outer side of the hole is a circular molded material opening. The groove is funnel-shaped, wider at the outside and narrower at the inside. After grooving, the entire substrate is immersed in a descaling solution for 30 minutes to remove the molded material dust after laser etching, exposing the complete bottom copper pad terminals.

[0051] 3.9 Laser Printing: After slotting the back-side plastic-encapsulated terminals, flip the substrate and align it with the front side of the substrate according to the positioning holes. Laser print the positioning points and material text for each module unit.

[0052] 3.10 Solder Ball Formation: After completing the stamp printing on the front side, flip the substrate and fix it in the fixture. Cover it with a stencil and print solder paste. The stencil opening size is consistent with the diameter of the slotted side, which is 300um. After printing the solder paste, heat the substrate in a reflow oven from room temperature to a maximum of 260 degrees Celsius, and then return it to room temperature. Wash the reflowed substrate with water to remove the flux residue on the substrate molding compound surface. Place the substrate containing the solder balls in the fixing fixture, ensuring that the solder balls are not damaged. Bake at 120 degrees Celsius for 6-8 hours to relieve stress and level the substrate.

[0053] 3.11 Single-piece cutting: The entire substrate is cut into individual pieces. After cutting, an optical inspection is performed. Good products are placed on a tray for collection and baked in a 120-degree oven for 4 hours to remove moisture.

[0054] 4. Testing, packaging, and shipping: Good products are tested and sorted into good products and defective products with different electrical properties. Good products are packaged, labeled, and shipped to the application end. Defective products are analyzed and verified to prepare for improvements in subsequent new products.

[0055] Preferably, step 3.6 involves secondary encapsulation using a single-unit filter package, as detailed below:

[0056] According to the design structure corresponding to the frequency band demand filter package, the total height of the filter package is within 400-500um, the filter can be single frequency band system, also can be dual frequency band system, usually dual frequency band system mainly has B1+B3, B8+B26, B2+B66, B20+B28, B34+B39, B39+B41 one of the combinations,

[0057] The filter package structure is that the filter chip circuit pad surface realizes the gold column and the chip through the ultrasonic welding method, the gold column is combined with the filter substrate, the height of the gold column is 10-15um, the chip is inverted and buckled on the substrate, a layer of 20-50um thick semi-cured film is covered on the outer surface of the chip and the substrate to form a cavity between the filter circuit surface and the substrate, and the resonator cavity structure is realized to work normally, and the semi-cured isolation film is plasticized and solidified again,

[0058] The exposed pad and the module alignment pad on the filter package substrate are designed as a circular structure, which is beneficial to the eddy current filling of the epoxy resin plastic sealing material in the plastic sealing process in the secondary packaging of the module,

[0059] Filter package: tin paste is printed on the filter pad alignment point on the module substrate through steel mesh with a thickness of 80um; different filter packages are attached according to the design drawing corresponding to different positions, and the attachment is completed once, and then reflow soldering is carried out, the printed tin paste is liquefied and solidified to realize the circuit connection between the filter package terminal and the module substrate pad. At this time, the filter package is supported on the module substrate by the cylindrical tin columns on the multiple terminals, corridors are formed between the tin columns, the vertical distance between the filter package and the module substrate is 40-60um, and the gap is the smallest gap in the packaging process.

[0060] Another preferred scheme, the step 3.6 is to use a filter chip package with tin balls

[0061] According to the design structure corresponding to the frequency band demand filter chip, the total height of the tin ball filter chip is within 210-270um, the filter can be single frequency band system, also can be dual frequency band system, usually dual frequency band system mainly has B1+B3, B8+B26, B2+B66, B20+B28, B34+B39, B39+B41 one of the combinations

[0062] Preparation of tin ball filter chip: advanced packaging tin ball implantation processing is carried out on 4-inch or 6-inch filter wafer, the thickness of 4-inch filter wafer is 250um, the thickness of 6-inch filter wafer is 350um, the opening of the chip pad on the filter wafer is 80um, the diameter of the tin ball after implantation is 80um, and the height of the tin ball is 50um,

[0063] Filter wafer measurement: each chip on the completed tin ball implantation wafer is tested, and a good product and a defective product electronic distribution map is generated in the system, and the filter module packaging process is as follows:

[0064] 3.6.2.1 Grinding and dicing of tin-containing ball filter wafer

[0065] 4-inch wafers do not need to be ground and thinned, 6-inch wafers need to be thinned to a thickness of 200-250 um, and after dicing, the single filter chip is in a separated state,

[0066] 3.6.2.2 Good filter chip ribbon

[0067] According to the good and bad electronic distribution map, the separated filter good chip is placed in the ribbon carrier and covered, and each type of filter chip is placed in one ribbon, different filter chips are distinguished in different ribbons, and label processing is done,

[0068] 3.6.2.3 Paste filter chip

[0069] Before pasting, a steel mesh is printed with tin paste according to the solder pad design of the filter corresponding module substrate, and after completing the tin paste printing, all selected filters are pasted, this process will paste multiple types of filters required in the module at the corresponding position of the embedded component substrate, after completing the pasting, tin ball reflow soldering is performed, the filter chip and the module substrate complete the electrical performance signal line connection, the filter chip line surface and the module substrate surface are spaced apart by 20-30 um,

[0070] 3.6.2.4 Covering isolation film

[0071] A 20-50 um thick isolation film is pasted and vacuum baked in a constant temperature oven at 130 degrees for 2-4 hours to ensure that the isolation film is effectively combined with the filter chip and the module substrate, a cavity structure is formed between the filter chip line surface and the module substrate to ensure normal operation of the resonator between the filter chip lines.

[0072] Further, the front plastic process of step 3.7 is a secondary plastic process of the module pasted with the filter package:

[0073] After reflow baking and water vapor removal, epoxy resin plastic is performed, the plastic material selects silica or aluminum nitride ceramic spheres with a maximum diameter of 20 um as fillers, when the minimum gap of the plastic encapsulated components is greater than twice the diameter of the fillers, plastic filling can achieve complete and effective filling, adjust the mold cavity thickness to 400 um and plastic at 175 degrees Celsius, the encapsulation process is a crosslinking reaction process of thermosetting epoxy resin small molecules, and after plastic encapsulation, constant temperature baking and curing at 175 degrees Celsius for 8-12 hours are required to ensure complete crosslinking reaction.

[0074] Another preferably, the front plastic process of step 3.7 is a module plastic process of pasting filter chips and pressing isolation film:

[0075] The module substrate is plastic encapsulated on a die forming plastic encapsulation device, the die pressure of single die cavity plastic encapsulation device is controlled at 2.3-2.8 Ton, the die pressure of double die cavity plastic encapsulation device is controlled at 5-6 Ton, the isolation film is not broken by high pressure of plastic encapsulation material, and after plastic encapsulation, 175 degree 8-12 hour constant temperature baking solidification is carried out, so as to ensure complete crosslinking reaction.

[0076] The scheme effectively strengthens the module design and structure building.

[0077] Firstly, the switch chip with copper pillar is placed on the back of the substrate, and the epoxy resin is effectively filled, covered and protected.

[0078] Secondly, the inductor passive element is removed, and the function of the inductor passive element is realized by substrate winding.

[0079] Thirdly, the filter package or the tin ball implanted filter chip is placed on the front of the substrate (inside the module) in the first method, and the gap between the filter package and the substrate is effectively filled and protected by the epoxy resin, and the isolation film is pasted on the tin ball implanted filter chip in the second method, and then the epoxy resin is effectively filled.

[0080] Fourthly, the module LGA (Land Grid Array) grid array packaging structure is changed into BGA (Ball Grid Array) ball grid array packaging structure.

[0081] The present application has the following beneficial effects:

[0082] The removal of the switch chip cavity structure improves the reliability, and the removal of the copper pillar processing saves the cost. The built-in switch flip chip without the cavity effect in the filter module device saves the copper pillar reprocessing procedure, the bare chip is embedded in the substrate, and the high-risk problems of tin bridge connection between copper pillars and copper pillar structure fracture in the flip switch structure are abandoned. The surface of the embedded chip is isolated from the outside world to prevent impurities in the air from corroding the chip circuit and causing electrical performance degradation, protect the chip surface and connection leads, so that the chip is free from external force damage and external environmental influence in electrical or thermal physical aspects.

[0083] Through complete filling of the epoxy resin in the substrate, the thermal expansion coefficient of the chip is matched with the thermal expansion coefficient of the substrate, the stress caused by the change of external environment such as heat and the internal stress caused by chip heating is effectively relieved, and the chip damage or copper pillar and tin ball fracture failure can be prevented. At the same time, it is also convenient for installation and transportation.

[0084] Complete and effective filling, can provide firm and reliable mechanical support for chips and other components, and can adapt to various working environments and changes in conditions, and the accumulated heat during long-term operation of the device is dissipated, ensuring that the system works normally within the required temperature range, which is very convenient for packaging users, circuit board manufacturers and semiconductor manufacturers, and is also convenient for standardization

[0085] The removal of the switch chip cavity structure improves the reliability. The built-in switch SOI flip chip that does not need the cavity effect in the filter module device is attached to the front surface of the substrate, and the cavity left after the film is changed to the back surface of the substrate. The gap between the surface of the chip and the substrate material is filled with plastic encapsulant. It effectively prevents the device from being bridged by tin during application due to incomplete or incomplete filling of the gap. The surface of the SOI chip is isolated from the outside to prevent the corrosion of the chip circuit by impurities in the air, which can cause a decrease in electrical performance. The chip surface and the connecting lead are protected, so that the chip is protected from external damage and external environmental influences in terms of electrical or thermal physics. By completely filling the plastic encapsulant, the thermal expansion coefficient of the chip and the thermal expansion coefficient of the substrate are matched, which can alleviate the stress caused by changes in the external environment and the stress caused by the heating of the chip. It can prevent SOI chip damage or copper column and tin ball fracture failure. At the same time, it is also convenient for installation and transportation. Complete and effective filling can provide firm and reliable mechanical support for SOI chips and other components, and can adapt to various working environments and changes in conditions. The accumulated heat during long-term operation of the device is dissipated, ensuring that the system works normally within the required temperature range, which is very convenient for packaging users, circuit board manufacturers and semiconductor manufacturers, and is also convenient for standardization.

[0086] Release the filter mounting space, and the process is rich. The present application changes the single-sided packaging of the filter module to double-sided packaging, changes the crowded mounting structure of the original single-sided components to double-sided mounting, effectively releases the space on the front surface of the substrate, changes the inductance component mounted on the front surface of the substrate to a substrate front surface coil winding method to replace the passive component, and makes the selection process of the filter cavity formed on the front surface more diversified.

[0087] The present application solves the conflict problem of filter cavity film and flip switch chip copper column gap filling, solves the gap filling problem between the two poles of the inductance passive component, solves the reliability problem caused by the extreme miniaturization of the filter packaging body, solves the product deformation and failure problem caused by the uneven internal stress of the single-sided packaging of the components of different materials, and solves the problem of insufficient filling of the epoxy resin in the dense gap of the components. BRIEF DESCRIPTION OF DRAWINGS

[0088] Figure 1 is a structural schematic diagram of the filter module of the present application example 1;

[0089] Figure 2 is a structural schematic diagram of the filter packaging body;

[0090] Figure 3 is a structural schematic diagram of the filter module of the embodiment 2 of the present application;

[0091] Figure 4 is a structural schematic diagram of the filter chip of the present application;

[0092] Figure 5 is a structural schematic diagram of the switch chip;

[0093] Figure 6 is a top structural schematic diagram of the double-sided packaging structure of the present application;

[0094] Figure 7 is a side structural schematic diagram of Figure 6 ;

[0095] Figure 8 is a process flow chart of the present application;

[0096] Figure 9 is a top structural schematic diagram of the existing packaging structure;

[0097] Figure 10 is a side structural schematic diagram of Figure 9 ;

[0098] Figure 11 is a structural schematic diagram of the filter module of the prior art with inductive passive components;

[0099] Figure 12 is a structural schematic diagram of another filter module of the prior art with inductive passive components. DETAILED DESCRIPTION

[0100] The specific embodiments of the present application will be described in more detail below with reference to the accompanying drawings. The advantages and features of the present application will be more apparent according to the following description and the patent claims. It should be noted that the drawings are very simplified and use non-precise proportions, only to facilitate and clarify the purpose of assisting the description of the embodiments of the present application.

[0101] Please refer to Figure 1 , the filter module of the embodiment 1 of the present application has a substrate 6, the front surface of the substrate 6 is a PiP structure, and a plurality of packaged post-filter packaging bodies 1 are attached to the front surface of the substrate 6 and are packaged by a front surface plastic packaging layer 2-1. The filter packaging bodies 1 are separate and not directly connected to each other.

[0102] The substrate 6 is a four-layer board structure, as shown in the attached Figure 1 and the attached Figure 2The total thickness of the substrate is 300-400 um, the thickness of the substrate ink 6-1 is 25-30 um, the thickness of the non-chip layer copper column is 30-40 um, the height of the chip layer copper column 4-2 is 125-150 um, the thickness of the circuit layer is 20-25 um, the width of the substrate circuit is more than 15 um, and the circuit spacing is more than 15 um.

[0103] The wire inductance 13 is wound on the substrate 6 and covered with a passivation adhesive layer 1-3 on the substrate. In this way, the inductance passive element is replaced. According to different filter specifications, the substrate wire is designed to match the inductance value at the input and output ends. The substrate wire realizes the inductance function as follows.

[0104] The wire inductance conversion formula is:

[0105]

[0106]

[0107] L is the inductance value, Ɩ is the length of the substrate wire, w is the width of the substrate wire, and h is the thickness of the substrate wire. Note that the substrate wire inductance is independent of the copper thickness.

[0108] From the above formula, if the length of the substrate wire is reduced by half, the inductance value is also reduced by half. However, the wire width needs to be increased by 10 times to reduce the inductance value by half.

[0109] The switch chip 8 is placed on the back of the substrate 6 and encapsulated with a back encapsulation layer 2-2. The substrate 6 is provided with a substrate pad 11, the back encapsulation layer 2-2 is provided with a pad opening 11-1 at the position of the substrate pad 11, the substrate pad 11 is provided with a pad tin ball 11 and located in the pad opening 11-1, and the bottom of the pad tin ball 11 protrudes from the bottom surface of the back encapsulation layer 2-2. The front encapsulation layer 2-1 and the back encapsulation layer 2-2 are made of the same encapsulation material.

[0110] The structure of the filter package 1 is shown in FIG. 1. Figure 2 and Figure 4As shown, the filter package 1 is composed of a filter chip 1-1 with gold pillars 1-4, a passivation adhesive layer 1-3, a filter substrate 1-5, a resonator 1-2, and a plastic encapsulation material 1-7. The filter chip 1-1 is placed on the filter substrate 1-5, the lower ends of the gold pillars 1-4 are combined with the gold-plated layer on the surface of the filter substrate, and the upper ends of the gold pillars are connected with the pad terminals of the filter chip. The tin balls 1-6 protrude from the lower bottom surface of the filter substrate 1-5. The lower bottom surface of the filter chip 1-1 and the upper surface of the filter substrate 1-5 have a cavity 1-8, and the resonator 1-2 is arranged on the lower bottom surface of the filter chip 1-1 and in the cavity 1-8. Except for the bottom surface, the periphery of the filter chip 1-1 is covered with the passivation adhesive layer 1-3, and the outer side of the passivation adhesive layer 1-3 is encapsulated with the plastic encapsulation material 1-7. The filter substrate 1-5 is separated from the plastic encapsulation material 1-7 by the passivation adhesive layer 1-3. The thickness of the filter chip is 200-250 um, the thickness of the passivation adhesive layer 1-3 is 20-50 um, the filter substrate 1-5 is two or more layers of circuit superposition, and the thickness is 110-200 um. The interconnection layer between the filter chip 1-1 and the filter substrate 1-5 is mainly composed of gold pillars 1-4 with a thickness of 10-15 um, and the total thickness of the filter package 1 is 450-550 um.

[0111] The distance between the filter chip 1-1 and the outermost edge of the plastic encapsulation material 1-7 is greater than 50 um, preferably 75 um or more. The greater the distance, the stronger the reliability in preventing water absorption. In this embodiment, the distance is 80 um.

[0112] The filter chip has 4-6 tin balls at the bottom, which are connected with the upper end of the switch chip 8 according to the function logic of the filter module, and the other tin balls are connected with other functional lines of the module substrate.

[0113] Reference Figure 3 The filter module of this embodiment 2 has the same substrate 6 as that of embodiment 1, and the filter chip 1-1 is encapsulated on the substrate by the passivation adhesive layer 1-3 and the front plastic encapsulation layer 2-1. The lower bottom surface of the filter chip 1-1 and the top surface of the substrate 6 have a cavity 1-8, and the resonator 1-2 is arranged on the lower bottom surface of the filter chip 1-1 and in the cavity 1-8. Except for the bottom surface, the periphery of the filter chip 1-1 is covered with the passivation adhesive layer 1-3, and the outer side of the passivation adhesive layer 1-3 is encapsulated with the front plastic encapsulation layer 2-1. The filter chip has 4-6 tin balls at the bottom, which are connected with the upper end of the switch chip 8 according to the function logic of the filter module, and the other tin balls are connected with other functional lines of the module substrate.

[0114] The substrate 6 is provided with a substrate pad 11, and the back plastic encapsulation layer 2-2 is provided with a pad opening 11-1 at the position of the substrate pad 11. The substrate pad 11 is provided with a pad tin ball 11 and located in the pad opening 11-1, and the bottom of the pad tin ball 11 protrudes from the bottom surface of the back plastic encapsulation layer 2-2.

[0115] Combining Figure 8 The filter module manufacturing method of the present application is shown as follows:

[0116] 1. Device preparation. Prepare the filter package or the filter chip after ball mounting, and prepare the switch chip containing copper columns.

[0117] 1.1 Prepare the switch chip.

[0118] This method uses a switch chip with copper columns in a reasonable cost control and area effectiveness, and combines Figure 5 As shown in the figure, the upper end surface of the switch chip 8 is provided with multiple rows of copper columns 8-2 in parallel, and the end of the copper column 8-2 is provided with a tin cap 8-1. In other embodiments, a 2-4um nickel layer can also be added between the copper column 8-2 and the tin cap 8-1, the pad opening is 55-60um, the chip pad spacing is 100-110um, and the chip pad layout is balanced within the effective area of the chip. The center of the copper column on the switch chip 8 coincides with the center of the pad, and the copper column is taken as the standard, the copper column 8-2 spacing is 100-110um, the copper column is filled with 3um thick PI organic matter (polyimide) between the copper column and the chip, and the overall height of the copper column is 65-75um, of which the copper column height is 35-40um and the tin cap height is 25-35um.

[0119] After the switch chip completes the advanced packaging process of the copper column, the intermediate test distinguishes between good and bad products and outputs an electronic distribution map. Grind and cut a single grain, and the thickness of the switch chip without copper columns is kept at 90-100um. The intermediate test good product is packaged in a ribbon, and a label is attached for use in the SMT packaging process.

[0120] 1.2 Prepare the filter package or the filter chip after tin ball mounting.

[0121] This method can support two different filter packaging processes of the packaging structure.

[0122] One structure is shown in the figure Figure 1 The front surface is a PiP structure, multiple packaged filter packages 1 are attached to the front surface of the substrate of the present application, and the switch chip is placed on the back surface of the substrate. The filter package structure is shown in the figure

[0123] Another structure is shown in the figure Figure 3 The front surface of the substrate is composed of a filter chip with tin balls, a passivation adhesive layer film, and a plastic packaging material. The switch chip is placed on the back surface of the substrate, and the functional circuit between devices is connected by using the substrate redistribution connector. The filter chip is shown in the figure Figure 4 , which is a tin ball-containing filter chip.

[0124] Filter chip thickness 200-250um, passivation adhesive layer thickness 20-50um, filter substrate is two or more layers of circuit superimposed, thickness 110-200um, filter chip and substrate interconnection layer is mainly 10-15um gold column, filter plastic package total thickness 450-550um.

[0125] Filter chip to plastic package edge needs to be greater than 50um, 75um or more preferably, the greater the spacing, the stronger the reliability of preventing water absorption.

[0126] 2 Filter module two-sided packaging substrate design and processing;

[0127] 2.1 Compared with the traditional substrate, the main process and material of this scheme are consistent, and the key improvement is in the layout and surface treatment of the back of the outer layer circuit of the substrate. As shown in the attached Figure 6 、 Figure 7 、 Figure 9 and Figure 10 , this scheme changes the large-area ground terminal in the middle of the LGA exposed pad of the original product design to BGA structure, and changes the large-area ground to the inner and outer two layers. The inner layer is designed to flip-chip pad layout of the switch chip, and the periphery is kept grounded to realize it in the form of solder ball. The terminal around the original LGA is also changed to pad design shape to prepare for the later packaging of solder ball.

[0128] 2.2 Compared with the traditional substrate, this scheme still uses four or more layers of circuit substrate process, and the total thickness of the substrate is 200um. The two layers of circuit in the middle of the substrate are mainly used for interconnection conversion and fan-out layout. The outer layer of the front surface is used as a solder bearing layer for filter chips or filter packages, as well as a winding inductor layer. The farther the winding inductor is from the ground, the better the performance control. At the same time, winding inductors on the front surface also facilitate early performance debugging and confirmation and finalization. The surface treatment of the back of the exposed surface of the original LGA substrate is usually chemical drug deposition to deposit nickel, palladium and gold three-layer metal as a substrate circuit protection layer and electrical signal combination layer. This method will be changed to OSP oxidation-resistant organic protection layer treatment, which can effectively reduce the cost of substrate manufacturing, and at the same time prepare for the later packaging process.

[0129] 2.3 Substrate processing. This scheme has no restrictions on the process of substrate processing. It can use even-numbered circuit layer incremental mode process with core material, or single-layer circuit stacking mode process without core material. This scheme uses substrate process with core material to illustrate processing.

[0130] 2.3.1 Panel inner layer circuit processing. Circuit and via are made by additive process, core material is drilled through by laser drilling on both sides according to the design, 3um copper material is deposited on the whole surface by electroless plating to connect the circuit on both sides, dry film is covered on both sides of the substrate panel in the photoresist room, the non-circuit area and non-drilling area of the dry film are exposed, the dry film in the unexposed area is etched, copper is plated to fill the hole and form the circuit layer at the drilling position, the thickness of the circuit layer is 12-25um, the exposed dry film is removed, the seed layer is etched and copper is deposited by electroless plating, and the inner layer circuit processing of the panel is completed.

[0131] 2.3.2 Panel outer layer circuit processing. The semi-cured material is pressed on both sides of the panel and baked, laser blind holes are drilled on both sides according to the design to expose the inner layer copper pads connected to the outer layer circuit, 3um copper material seed layer is deposited on the whole surface by electroless plating, dry film is covered on both sides of the substrate panel in the photoresist room, the non-circuit area and non-drilling area of the dry film are exposed, the dry film in the unexposed area is etched, copper is plated to fill the hole and form the circuit layer at the drilling position, the thickness of the circuit layer is 12-25um, the exposed dry film is removed, the seed layer is etched and copper is deposited by electroless plating, and the outer layer circuit processing of the panel is completed. At this time, the front side of the substrate outer layer circuit is shaped according to the design requirements to form a filter package alignment pad, or a filter ball mounting flip-chip alignment pad, and an inductor coil circuit structure. At this time, the back side of the substrate outer layer circuit is shaped according to the design requirements to form a 300um diameter circular pad with a 550um pitch, a ground area is designed to be back-shaped, a line width is 300um, and a back-shaped area is a 1300um x 1100um switch chip pad layout area. A switch chip with a length of 1000um or less and a width of 800um or less can be placed in the back-shaped area, an actual chip with a size of 800um x 700um can support a 12T or less tuning switch, and the area has sufficient margin. The substrate pad in the switch chip area is a 70um diameter circle, and the minimum pad pitch is consistent with the switch chip pad design, which is 110-130um.

[0132] 2.3.3 Covering ink and surface treatment. The substrate panel is coated with a solder mask ink on both sides in the photoresist room, the non-soldering area is exposed, and the unexposed ink is etched to expose the soldering area on the front and back of the substrate outer layer circuit. The substrate panel is punched or milled to separate into single substrate of a size that can be used for packaging. The copper pads exposed on the front and back are protected by OSP solder mask deposition. Appearance inspection and defect marking are performed before packaging and shipment.

[0133] 3 Filter module double-sided packaging

[0134] Referring again to Figure 8, the filter module double-sided packaging needs A substrate back OSP cleaning, B back surface mounting, C back surface plastic packaging, D back surface thinning, E substrate front OSP cleaning, F front surface optional mounting, G front surface plastic packaging, H laser ablation, I laser printing, J tin ball, K film, L single cutting and molding 12 large stations such as molding. The application is adapted to the terminal upper plate scheme, and the structure and process characteristics are optimized. The switch back surface mounting and the front surface filter can select different process modes, which ensures the structural stability and releases the layout space. Specifically:

[0135] 3.1 Substrate back OSP cleaning. OSP protection can maintain the substrate life cycle for 6 months or more, but the covalent bond mode of OSP chelate molecules is also not conducive to the combination of substrate pads and solder material, and needs to be removed during packaging operation. The commonly used method is to print an oxidizing flux, and the temperature in the reflow oven is from room temperature to 260 degrees Celsius and then cooled to room temperature. During the whole process, the flux reacts with the OSP to generate water, carbon dioxide, and small molecule compounds above 100 degrees Celsius. Water and carbon dioxide are discharged in gas form from the reflow oven, and small molecule compounds adhering to the surface of the substrate are removed by high-pressure water washing. After the substrate passes through the reflow oven and the water washing line, it will produce irregular warping and absorb part of the water in the glass fiber core layer and the ink layer, and needs to be baked and flattened in a 120-degree oven with a 5-10 kg pressure block.

[0136] 3.2 Back surface mounting. Flip 100um thickness 70-80um copper column (containing tin cap) height switch chip on the substrate back surface pad, when mounting, the chip needs to be dipped in the flux tank to take the flux, according to the 25-30um height of the tin cap on the copper column, configure 35-50um depth flux dipping tank, ensure 100% effective coverage of the tin cap surface with flux, which is beneficial to wet coverage in the reflow process. After flipping, the reflow oven is used to optimize the reflow temperature curve according to the composition of the tin cap and the composition of the flux, so that the substrate with the flip switch chip is heated from room temperature to 260 degrees Celsius in the reflow oven, and then cooled to room temperature. The reflowed substrate is washed to remove the residual flux on the surface of the substrate and the chip. At this time, the height from the substrate surface to the back surface of the chip is 150-170um.

[0137] 3.3 Backside Plastic Encapsulation. Before plastic encapsulation, bake in 120 degree Celsius oven for 6-8 hours to remove moisture from previous water washing process. Before plastic encapsulation, plasma clean with 95% argon and 5% oxygen in ion state to remove surface contamination or grease and increase surface bonding activity. Plastic encapsulate the backside of the substrate, the plastic needs to fill the gap between the switch chip and the substrate with maximum 20um diameter particles, and other gaps. Use 250-400um height plastic encapsulation mold cavity to encapsulate in 175 degree vacuum environment. After plastic encapsulation, the distance between the backside of the chip and the surface of the plastic is 80-250um. After plastic encapsulation, bake in 175 degree Celsius oven for 8-12 hours to solidify the plastic and make the cross-linking reaction complete.

[0138] 3.4 Backside Thinning. After plastic encapsulation, fix the substrate in a jig and use a grinding wheel to grind the plastic. After grinding, the thickness of the plastic is 160-200um. For mobile phone filter module products, thin to 160um and polish to 140um to expose the backside of the switch chip. This thickness is beneficial for laser drilling and slotting in the later process.

[0139] 3.5 Frontside OSP Cleaning. As described in 3.1, print with oxidizing flux, and in the reflow oven, from room temperature to 260 degrees and then back to room temperature. During this process, the reaction between the flux and the OSP will generate water, carbon dioxide, and small molecules above 100 degrees Celsius. Water and carbon dioxide are discharged in gas form from the reflow oven, and small molecules adhering to the surface of the substrate are removed by high-pressure washing. After passing through the reflow oven and washing line, the substrate will produce irregular warping and absorb some moisture in the glass fiber core layer and the ink layer, which needs to be pressed flat in a 120 degree Celsius oven with a 5-10 kilogram pressure block.

[0140] 3.6 Optional Frontside Mounting. Filter module packaging can choose to use 100% yield filter packaging units that have completed packaging and testing for secondary packaging, or use filter chips with tin balls for flip-chip packaging. Filter packaging can be 4G single-band receive end format or 4G dual-band receive end format. According to different terminal platforms, select and use in frequency bands 1, 2, 3, 5, 7, 8, 20, 26, 28, 34, 39, 40, 41, 66. The processing and manufacturing methods of the two schemes are as follows:

[0141] 3.6.1 Secondary packaging using single filter packaging unit.

[0142] According to the design structure corresponding to the frequency band demand filter package, the total height of the filter package is within 400-500um, the filter can be single frequency band system, or can be dual frequency band system, usually dual frequency band system mainly has B1+B3, B8+B26, B2+B66, B20+B28, B34+B39, B39+B41 and other combinations. The dual frequency filter integration mode production cost and material use is relatively ideal, which will improve the space release, as the preferred solution.

[0143] The filter package structure is that the filter chip circuit pad surface realizes gold column and chip through ultrasonic welding, the gold column is combined with the filter substrate, the height of the gold column is 10-15um, the chip is inverted and buckled on the substrate, the chip and the substrate are covered with a layer of 20-50um thick semi-cured film to form a cavity between the filter circuit surface and the substrate, to realize the normal work of the resonator cavity structure, and the semi-cured isolation film is plastic encapsulated and solidified again, to effectively protect the internal components and realize the surface flatness standard structure.

[0144] The exposed pad and module alignment pad on the filter package substrate are designed as a circular structure, which is beneficial to the eddy current filling of the epoxy resin plastic encapsulation material in the plastic encapsulation process in the secondary encapsulation of the module, to prevent the gap between the filter substrate and the module substrate from being not filled with plastic encapsulation material, resulting in different terminal tin material bridging short circuit.

[0145] The filter package is pasted. The steel mesh printed tin paste on the module substrate is at the filter pad alignment point, and the thickness of the steel mesh is 80um; different filter packages are pasted according to the design drawing corresponding to different positions, and the pasting is completed at one time. After pasting, reflow soldering is carried out, the printed tin paste is liquefied and solidified to realize the circuit connection between the filter package terminal and the module substrate pad, at this time the filter package is supported on the module substrate by the cylindrical tin columns on the multiple terminals, corridors are formed between the tin columns, the vertical distance between the filter package and the module substrate is 40-60um, and this gap is the smallest gap in the packaging process.

[0146] 3.6.2 Use of filter chip package with tin balls.

[0147] According to the design structure corresponding to the frequency band demand filter chip, the total height of the filter chip containing tin balls is within 210-270um, the filter can be single frequency band system, or can be dual frequency band system, usually dual frequency band system mainly has B1+B3, B8+B26, B2+B66, B20+B28, B34+B39, B39+B41 and other combinations. The dual frequency filter integration mode production cost and material use is relatively ideal, which will improve the space release, as the preferred solution.

[0148] Preparation of tin ball filter chip. Advanced packaging tin ball processing is carried out using 4-inch or 6-inch filter wafer, the thickness of 4-inch filter wafer is 250um, the thickness of 6-inch filter wafer is 350um, the filter wafer pad opening is 80um, the tin ball diameter after balling is 80um, and the tin ball height is 50um.

[0149] Filter wafer measurement. Each chip on the completed tin ball wafer is tested, and a good and bad electronic distribution map is generated in the system. The filter module packaging process is as follows.

[0150] 3.6.2.1 Tin ball filter wafer grinding and dicing.

[0151] 4-inch wafers do not need to be thinned, 6-inch wafers need to be thinned to within 200-250um to facilitate the covering of the isolation film in the later process and the overall thickness control of the module. After dicing, the single filter chip is in a separated state.

[0152] 3.6.2.2 Good filter chip ribbon.

[0153] According to the good and bad electronic distribution map, the separated filter good chips are placed in the ribbon carrier and covered. This process places each type of filter chip in one ribbon, and different filter chips are distinguished in different ribbons, and the label is handled.

[0154] 3.6.2.3 Paste filter chip.

[0155] Before mounting, tin paste steel mesh is printed according to the filter corresponding module substrate pad design. After completing the tin paste printing, all selected filters are mounted. This process mounts multiple types of filters required in the module at the corresponding position of the embedded component substrate at one time. After mounting, tin ball reflow soldering is performed. At this time, the filter chip and the module substrate complete the electrical performance signal line connection, and the distance between the filter chip line surface and the module substrate surface is 20-30um.

[0156] 3.6.2.4 Covering isolation film.

[0157] A 20-50um thick isolation film is vacuum pasted, and after pasting, it is baked in a vacuum oven at 130 degrees Celsius for 2-4 hours to ensure that the isolation film is effectively combined with the filter chip and the module substrate. After this process is completed, a cavity structure is formed between the filter chip line surface and the module substrate, which can ensure the normal operation of the filter chip line resonator.

[0158] 3.7 Front side plastic packaging: there are differences in different mounting element plastic packaging processes.

[0159] 3.7.1 Secondary plastic packaging of filter packaging mounted module.

[0160] After reflow baking and removing moisture, the epoxy resin is molded, and the molding material is selected to use silica or aluminum nitride ceramic spheres with a maximum diameter of 20 um as fillers. When the minimum gap of the molded component is greater than twice the diameter of the fillers, the molding filling can be completely and effectively filled, which not only ensures the flowability of the molding material during molding but also plays a supporting role in gap filling. Adjust the mold cavity thickness to 400 um and mold at 175 degrees Celsius. The packaging process is a cross-linking reaction process of small molecules of thermosetting epoxy resin, and post-molding requires constant temperature baking at 175 degrees Celsius for 8-12 hours to ensure complete cross-linking reaction. At this time, the total thickness of the filter module is 0.74 mm, i.e. the substrate thickness is 200 um, the back molding thickness is 140 um, and the front molding thickness is 400 um.

[0161] 3.7.2 Molding of filter chip and isolation film.

[0162] The module substrate molding is completed on a mold forming molding device. The mold clamping pressure of a single mold cavity molding device is controlled at 2.3-2.8 Ton, and the mold clamping pressure of a double mold cavity molding device is controlled at 5-6 Ton. This device effectively controls the mold clamping pressure to ensure that the isolation film is not broken by high pressure of the molding material. The mold cavity thickness of the molding material is 400 um, and post-molding requires constant temperature baking at 175 degrees for 8-12 hours to ensure complete cross-linking reaction. At this time, the total thickness of the filter module is 0.74 mm, i.e. the substrate thickness is 200 um, the back molding thickness is 140 um, and the front molding thickness is 400 um.

[0163] 3.8 Laser ablation. After the front molding is completed, the TMV process is used to laser groove the terminal position on the back of the substrate. The groove depth is 150 um to ensure that the bottom layer copper pad terminal is exposed. At this time, the inside terminal of the exposed hole is a 250 um diameter circular pad, and the outside is a 300 um diameter molding material opening. The slot body is funnel-shaped with a wide outside and a narrow inside. After grooving, the entire substrate is soaked in degreasing chemicals for 30 minutes to remove the laser molding material dust in the slot and expose the complete copper pad terminal at the bottom.

[0164] 3.9 Laser printing. After the back molding terminal is grooved, the substrate is turned over, and the front of the substrate is aligned according to the positioning hole. Laser printing is performed on each module unit to ensure traceability of each module device.

[0165] 3.10 Solder balling. After the front side is printed with the stamp, the substrate is flipped and fixed in the fixture, and the steel screen is used to print the solder paste. The opening size of the steel screen is 300 um, which is the same as the diameter of the slotted side, and the thickness of the steel screen is 80 um. After printing the solder paste, the substrate is heated in the reflow oven from room temperature to 260 degrees, and then cooled to room temperature. The reflowed substrate is then washed with water to remove the flux residue on the surface of the plastic package. At this time, the height of the solder balls on the surface of the plastic package is 100 um. At this time, the total thickness of the product is 0.84 mm, which meets the space application of the mobile phone end product. The substrate containing the solder balls is placed in a fixed clamp to ensure that the solder balls are not damaged, and then 120 degree baking is performed for 6-8 hours to remove stress and flatten.

[0166] 3.11 Singulation and molding. The entire substrate is singulated, and after cutting, optical inspection is performed to check the appearance. Good products are placed in a tray for storage, and then 120 degree baking is performed for 4 hours to remove water vapor.

[0167] 4. Test packaging and delivery. Good products and different electrical performance of the next product are tested and sorted. Good products are packaged, labeled, and delivered to the application end. The bad products are analyzed and verified to prepare for improvement of the subsequent new product.

[0168] Through the above detailed description of the preferred embodiments, the features and spirits of the present application can be described more clearly, and the scope of the present application is not limited by the above disclosed preferred embodiments. On the contrary, the purpose is to cover various changes and equivalent arrangements within the scope of the claims of the present application.

Claims

1. A double-sided package structure of a filter module having a substrate (6), characterized by, The double-sided packaging structure is a double-sided packaging structure without inductance passive elements; the filter chip (1-1) is packaged on the front surface of the substrate by the front surface plastic encapsulation layer (2-1) alone or in the form of a filter package; and the switch chip (8) is packaged on the back surface of the substrate by the back surface plastic encapsulation layer (2-2); The filter package is composed of the filter chip (1-1) containing a gold column (1-4), a passivation adhesive layer (1-3), a filter substrate (1-5), a resonator and a plastic encapsulation material (1-7), the filter chip is arranged on the filter substrate; a cavity (1-8) is formed between the lower bottom surface of the filter chip and the upper surface of the filter substrate, the resonator is arranged on the lower bottom surface of the filter chip and in the cavity, the filter chip is covered with the passivation adhesive layer except the bottom surface, the filter chip is encapsulated with the plastic encapsulation material outside the passivation adhesive layer, and the filter substrate is separated from the plastic encapsulation material by the passivation adhesive layer. The double-sided packaging structure further comprises a winding inductor (13) arranged on the front surface of the substrate, and the winding inductor is covered with the passivation adhesive layer (1-3) on the substrate.

2. The dual-side package structure of a filter module according to claim 1, wherein, The filter chip is packaged on the front surface of the substrate by the front surface plastic encapsulation layer in the form of a filter package, the lower end of the gold column is combined with the gold plating layer on the surface of the filter substrate, the upper end of the gold column is connected with the pad terminal of the filter chip, and the solder balls (1-6) protrude from the lower bottom surface of the filter substrate (1-5), The filter package is packaged on the front surface of the substrate by the front surface plastic encapsulation layer (2-1).

3. The dual-side package structure of a filter module according to claim 1, wherein, The substrate is provided with substrate pads (11) at intervals, the back surface plastic encapsulation layer (2-2) is provided with pad openings (11-1) at the positions of the substrate pads (11), the substrate pads are provided with pad solder balls and located in the pad openings, the bottom of the pad solder ball protrudes from the bottom surface of the back surface plastic encapsulation layer, and the pad solder ball is encapsulated on the back surface of the substrate by the back surface plastic encapsulation layer.

4. The dual-side package structure of a filter module according to claim 3, wherein, The filter chip is packaged on the front surface of the substrate by the front surface plastic encapsulation layer alone, the filter chip is encapsulated on the substrate by the mold plastic encapsulation layer after being covered with the passivation adhesive layer (1-3), and the lower bottom surface of the filter chip and the top surface of the substrate have a cavity (1-8), and the resonator is arranged on the lower bottom surface of the filter chip and in the cavity.

5. The dual-side package structure of a filter module according to claim 3 or 4, wherein The filter chip is provided with 4-6 solder balls of different quantities at the bottom, according to the function logic of the filter module, part of the solder balls are connected with the module substrate circuit logic port of the switch chip (8), and the other part of the solder balls are connected with other function circuits of the module substrate.

6. The dual-side package structure of a filter module according to claim 1, wherein, The thickness of the filter chip is 200-250 um, the thickness of the passivation adhesive layer is 20-50 um, the filter substrate is two or more layers of circuit superposition, and the thickness is 110-200 um, the interconnection layer between the filter chip and the filter substrate (1-5) is a 10-15 um gold column, and the total thickness of the filter package is 450-550 um.

7. A method of manufacturing a double-sided package structure of a filter module, characterized by, The method comprises the steps of:

1. preparing a filter package or a ball-implanted filter chip, and preparing a switch chip containing a copper column The center of the copper column on the switch chip coincides with the center of the pad, and the copper column is circular. The copper column spacing is 100-110um, the copper column is filled with 3um thick PI organic matter between the copper column and the chip, and the overall height of the copper column is 65-75um, of which the copper column height is 35-40um, the tin cap height is 25-35um, the pad opening is 55-60um, the chip pad spacing is 100-110um, and the chip pad is balanced in the effective area of the chip, After the switch chip completes the advanced packaging processing of the copper column, the middle test distinguishes between good and bad products and outputs an electronic distribution map; grind and cut a single grain. The thickness of the switch chip without a copper column is kept at 90-100um. The middle test good product is packaged in a ribbon and labeled for use in the SMT process.

2. Filter module two-side packaging substrate design and processing 2.1 The product shape is designed as a BGA structure, and the large-area ground is changed to the inner and outer two layers. The inner layer is designed as a switch chip flip-chip pad layout, and the periphery is kept as a ground to realize it in the form of a tin ball, 2.2 Use a four-layer or multi-layer circuit substrate process. The two-layer circuit in the substrate is mainly used for interconnection conversion and fan-out layout application. The outer layer front surface is used as a filter chip or filter packaging body welding bearing layer, and a winding inductor layer. The substrate exposed surface back surface pad surface is treated by OSP anti-oxidation organic protection layer, 2.3 Substrate processing: use an even number of circuit layer incremental mode process with core material, or use a single-layer circuit stacking mode process without core material 2.3.1 Panel inner layer circuit processing: make the circuit and via in a circuit additive way. According to the design, drill holes through the core material by double-sided laser. Chemically deposit 3um of copper material on the hole wall to connect the circuit on both sides of the material. Cover the dry film on both sides of the substrate panel in the yellow light room. Expose the dry film in the non-circuit area and non-drilling area. Etch the dry film in the unexposed area. Fill the copper plug in the drilling position and form the circuit layer by electroplating copper. The circuit layer thickness is 12-25um. Remove the exposed dry film. Etch the seed layer and chemically deposit copper. The panel inner layer circuit processing is completed. 2.3.2 Panel outer layer circuit processing: press the semi-cured material on both sides of the panel and bake. According to the design, expose the inner layer copper pad connected to the outer layer circuit by laser drilling blind holes on both sides. Chemically deposit 3um of copper material seed layer on the whole surface. Cover the dry film on both sides of the substrate panel in the yellow light room. Expose the dry film in the non-circuit area and non-drilling area. Etch the dry film in the unexposed area. Fill the copper plug in the drilling position and form the circuit layer by electroplating copper. The circuit layer thickness is 12-25um. Remove the exposed dry film. Etch the seed layer and chemically deposit copper. The panel outer layer circuit processing is completed. 2.3.3 Ink covering and surface treatment: cover the anti-welding ink on both sides of the substrate panel in the yellow light room. Expose the non-welding area. Etch the unexposed ink to expose the substrate outer layer circuit front and back welding area. The substrate panel is punched or milled to separate into single substrate of packaging size. The copper pad on the exposed area is protected by OSP anti-welding layer chemical deposition, 3. Filter module two-side packaging 3.1 Backside OSP cleaning: Print with oxidizing flux, from room temperature to 260 degrees Celsius in the reflow oven, and then cool down to room temperature. During the whole process, the reaction between the flux and the OSP will generate water, carbon dioxide, and small molecules above 100 degrees Celsius. Water and carbon dioxide are discharged in gas form from the reflow oven. Small molecules adhering to the surface of the substrate are removed by high-pressure water washing. After the substrate passes through the reflow oven and water washing line, it will produce irregular warping and absorb some moisture in the glass fiber core layer and ink layer. It needs to be baked and flattened in a 120-degree oven with 5-10 kg pressure blocks, 3.2 Backside mounting: Flip 100um thickness 70-80um copper column height switch chip on the backside of the substrate. When mounting, the chip needs to be dipped in the flux tank to take the flux. According to the 25-30um height of the tin cap on the copper column, configure a 35-50um deep flux dipping tank to ensure that the tin cap surface is 100% effectively covered with flux. After flipping, the optimal reflow temperature curve is determined according to the composition of the tin cap and the flux in the reflow oven. The substrate with the flipped switch chip is heated from room temperature to 260 degrees Celsius in the reflow oven, and then cooled to room temperature. The reflowed substrate is washed with water to remove the residual flux on the surface of the substrate and chip. At this time, the height from the substrate surface to the back of the chip is 150-170um, 3.3 Backside plastic packaging: Before plastic packaging, bake in a 120-degree oven for 6-8 hours to remove the moisture from the previous water washing process. Perform plasma cleaning with 95% argon and 5% oxygen in an ion state before plastic packaging to remove contaminants or grease on the surface of the substrate and increase the surface bonding activity. Perform backside plastic packaging of the substrate. The plastic packaging material needs to use a maximum of 20um diameter adjusting material particles. Select a 250-400um height plastic packaging material mold cavity for plastic packaging in a 175-degree vacuum environment. The distance from the back of the chip to the surface of the plastic packaging material after plastic packaging is 80-250um. After plastic packaging, bake in a 175-degree oven for 8-12 hours for solidification, 3.4 Backside thinning: Fix the plastic-packaged substrate in a jig and use a grinding wheel to grind the plastic packaging material. After grinding, the thickness of the plastic packaging material is 160-200um. After thinning to 160um, polish to 140um to expose the back of the switch chip for mobile phone filter module products, 3.5 Front side OSP cleaning: As described in 3.1, print with oxidizing flux, from room temperature to 260 degrees Celsius in the reflow oven, and then cool down to room temperature. During the whole process, the reaction between the flux and the OSP will generate water, carbon dioxide, and small molecules above 100 degrees Celsius. Water and carbon dioxide are discharged in gas form from the reflow oven. Small molecules adhering to the surface of the substrate are removed by high-pressure water washing. After the substrate passes through the reflow oven and water washing line, it will produce irregular warping and absorb some moisture in the glass fiber core layer and ink layer. It needs to be baked and flattened in a 120-degree oven with 5-10 kg pressure blocks, 3.6 Front optional mounting: filter module package can choose 100% yield filter package monomer that has completed packaging and testing for secondary packaging, or choose filter chip with tin ball for flip chip packaging. Filter package can be 4G single frequency band receiving terminal standard, or 4G dual frequency band receiving terminal standard. According to different terminal platforms, any one of the frequency bands 1, 2, 3, 5, 7, 8, 20, 26, 28, 34, 39, 40, 41 and 66 can be selected for use. 3.7 Front plastic packaging: according to different mounting elements, 3.8 Laser ablation: after front plastic packaging, TMV process is used to laser groove on the terminal position of the back of the substrate. The groove ensures that the copper pad terminals on the bottom layer of the substrate are exposed. At this time, the inside terminals of the exposed holes are round pads, and the outside is a circular plastic material opening. The groove is funnel-shaped with a wide outside and a narrow inside. After grooving, the entire substrate is soaked in degreasing chemical solution for 30 minutes. The dust of the plastic material in the groove after laser ablation is removed, and the complete copper pad terminals at the bottom are exposed. 3.9 Laser printing: after grooving the back plastic packaging terminals, the substrate is turned over, the front of the substrate is aligned according to the positioning hole, and the laser printing positioning points and material printing content of each module unit are printed. 3.10 Solder balling: after completing the seal printing on the front, the substrate is fixed in the clamp, the steel mesh is covered with solder paste, and the opening size of the steel mesh is consistent with the diameter of the grooved side, which is 300um. After printing the solder paste, it is heated in a reflow oven from room temperature to 260 degrees, and then back to room temperature. The reflowed substrate is washed to remove the flux remaining on the surface of the plastic material on the substrate. The substrate with tin balls is placed in a fixed clamp to ensure that the tin balls are not damaged. It is baked at 120 degrees for 6-8 hours to remove stress and flatten. 3.11 Single cutting and forming: the entire substrate is cut into single units, and after cutting, optical inspection is performed. Good products are placed in a carrier tray for storage, and are baked in a 120 degree oven for 4 hours to remove moisture.

4. Test packaging and delivery: test and sort good products and different electrical performance of defective products. Good products are packaged, labeled and delivered to the application end. Defective products are analyzed and verified to prepare for improvement of subsequent new products.

8. The method of claim 7, wherein the method further comprises: forming a first dielectric layer on the first surface of the first substrate; forming a second dielectric layer on the second surface of the second substrate; and forming a plurality of vias in the first dielectric layer and the second dielectric layer. In step 3.6, monomer filter package is used for secondary packaging, which is as follows: According to the design structure, the filter package is mounted according to the frequency band requirement. The total height of the filter package is within 400-500um. The filter is a single frequency band standard or a dual frequency band standard. The dual frequency band standard is one of the following combinations: B1+B3, B8+B26, B2+B66, B20+B28, B34+B39 and B39+B41. The structure of the filter package is that the filter chip circuit pad surface is combined with the chip through ultrasonic welding. The gold column is combined with the filter substrate. The height of the gold column is 10-15um. The chip is inverted and placed on the substrate. A layer of 20-50um thick semi-cured film is coated on the outer surface of the chip and the substrate to form an air cavity between the filter circuit surface and the substrate, so that the resonator cavity structure works normally. The semi-cured isolation film is plasticized and solidified again. The filter package substrate exposed pad and module alignment pad are designed as a circular structure, and the plastic encapsulation process is beneficial to the epoxy resin plastic encapsulation material eddy current filling in the secondary encapsulation of the module, The filter package patch: tin paste is printed on the filter pad alignment point on the module substrate by steel mesh with a thickness of 80 um; different filter package is attached according to the design drawing corresponding to different positions, and after attachment, reflow soldering is performed to liquefy and solidify the printed tin paste, thereby realizing the circuit connection between the filter package terminal and the module substrate pad; at this time, the filter package is supported on the module substrate by the cylindrical tin column on the multiple terminals, a corridor gap is formed between the tin columns, the vertical distance between the filter package and the module substrate is 40-60 um, and the gap is the smallest gap in the encapsulation process.

9. The method of claim 7, wherein the method further comprises: forming a first dielectric layer on the first surface of the first substrate; forming a second dielectric layer on the second surface of the second substrate; and forming a plurality of vias in the first dielectric layer and the second dielectric layer. The step 3.6 is to use a filter chip package with tin balls According to the design structure, the filter chip is attached according to the frequency band requirement, the total height of the filter chip containing tin balls is within 210-270 um, the filter is a single frequency band standard or a dual frequency band standard, and the dual frequency band standard is one of the following combinations: B1+B3, B8+B26, B2+B66, B20+B28, B34+B39 and B39+B41, Preparation of tin ball filter chip planting: advanced encapsulation tin ball planting process is performed on a 4-inch or 6-inch filter wafer, the thickness of the 4-inch filter wafer is 250 um, the thickness of the 6-inch filter wafer is 350 um, the chip pad opening on the filter wafer is 80 um, the tin ball diameter is 80 um after ball planting, and the tin ball height is 50 um, Filter wafer testing: each chip on the completed tin ball wafer is tested, and a good and bad electronic distribution map is generated in the system, and the filter module encapsulation process is as follows: 3.6.2.1 Tin ball filter wafer grinding and dicing The 4-inch wafer does not need to be thinned, and the 6-inch wafer needs to be thinned to a thickness of 200-250 um; after dicing, the single filter chip is in a separated state, 3.6.2.2 Good filter chip ribbon According to the good and bad electronic distribution map, the separated state filter good chip is placed in the ribbon carrier and covered, and each type of filter chip is placed in one ribbon, different filter chips are distinguished in different ribbons, and a label is provided, 3.6.2.3 Attach filter chip Before attachment, tin paste steel mesh is printed according to the filter corresponding module substrate pad design, all selected filter is attached after tin paste printing is completed, this process will be required in the module multiple model filter is attached in the embedded component substrate corresponding position at one time, after completion of attachment, tin ball reflow soldering is performed, filter chip and module substrate complete electrical performance signal line connection, filter chip line surface and module substrate surface distance in 20-30 um, 3.6.2.4 Cover isolation film Vacuum paste 20-50 um thickness isolation film, after pasting, bake in a vacuum oven at 130 degrees Celsius for 2-4 hours to ensure that the isolation film is effectively combined with the filter chip and the module substrate, a cavity structure is formed between each filter chip line surface and the module substrate to ensure that the filter chip line resonator works normally.

10. The method of claim 8, wherein the method further comprises: The step 3.7 is a front plastic encapsulation process for attaching the filter package module secondary plastic encapsulation: ​ After the backflow baking dehydrates, the epoxy resin plastic package is carried out, the plastic package material selects the silica or aluminum nitride ceramic ball with the maximum 20um diameter as the filler, the minimum gap of the plastic packaged component is greater than twice the diameter of the filler, the plastic package filling can be realized complete and effective filling, the mold cavity thickness is adjusted to 400um, the plastic package is carried out under the condition of 175 degrees Celsius, the packaging process is the crosslinking reaction process of the thermosetting epoxy resin small molecule, the constant temperature baking curing of 175 degrees Celsius for 8-12 hours is needed after the plastic package, and the crosslinking reaction is ensured to be complete.

11. The method of claim 9, wherein the method further comprises: The positive plastic package process of step 3.7 is the module plastic package of attaching the filter chip and pressing the isolation film: ​ The module substrate plastic package is completed on the die forming plastic package equipment, the mold clamping pressure of the single mold cavity plastic package equipment is controlled to be 2.3-2.8Ton, the mold clamping pressure of the double mold cavity plastic package equipment is controlled to be 5-6Ton, the isolation film is ensured not to be broken by the high pressure of the plastic package material, the constant temperature baking curing of 175 degrees for 8-12 hours is carried out after the plastic package, and the crosslinking reaction is ensured to be complete.

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