Search

CN-115694389-B - Wafer level packaging method of filter

CN115694389BCN 115694389 BCN115694389 BCN 115694389BCN-115694389-B

Abstract

The invention discloses a wafer level packaging method of a filter, which comprises the steps of forming a through hole and a groove by adopting a positive photoresist dry film through a secondary exposure one-time developing process, then attaching the through hole and the groove to a wafer to enable the groove and a chip functional area to be enclosed in a one-to-one correspondence manner to form a cavity, depositing metal on wiring connection of the through hole and the chip for leading out a circuit, and then cutting to form a single filter packaging structure. The invention adopts the single-layer positive photoresist dry film for packaging, the cavity is formed in the single-layer dry film, the layering problem of the wall layer and the top layer is avoided, and the reliability of the device is improved. Meanwhile, the process is simplified, the process cycle time is shortened, multiple layers of materials are not needed, and the cost is saved.

Inventors

  • WEI XIN
  • LI XIAOJUN
  • LI PEIKUN

Assignees

  • 泉州市三安集成电路有限公司

Dates

Publication Date
20260505
Application Date
20221031

Claims (10)

  1. 1. A wafer level packaging method of a filter, comprising the steps of: 1) Providing a positive photoresist dry film with the thickness of more than 20um, performing first exposure on the positive photoresist dry film through a first photomask, wherein the exposure dose is less than 250mj, and the exposure depth is the thickness of the positive photoresist dry film; 2) Developing, wherein a through hole is formed after the first exposure area is developed, and a groove is formed after the second exposure area is developed; 3) Attaching a positive photoresist dry film to the surface of a wafer, wherein the wafer is provided with a plurality of filter chips, the filter chips are provided with functional areas and wiring, wherein the grooves and the functional areas are enclosed to form cavities, and part of the wiring corresponds to the through holes and is exposed; 4) Baking at 80-250 ℃ for 0.5-1.5 h; 5) Depositing metal inside the through hole and connecting with the wiring; 6) And cutting the packaged wafer to form a single filter packaging structure.
  2. 2. The method of wafer level packaging of a filter of claim 1, wherein the positive photoresist dry film is a photosensitive epoxy, and the first and second exposures are I-line light.
  3. 3. The method of wafer level packaging of a filter of claim 1, wherein the exposure gap between the first exposure and the second exposure is 10-30um.
  4. 4. The method of packaging a filter according to claim 1, wherein in step 2), the number of developing steps is 2, each for 30 to 60 seconds, and the number of rinsing steps is 2, each for 4 to 8 seconds.
  5. 5. The method of packaging a filter according to claim 1, wherein in step 3), the positive photoresist dry film is bonded on the surface of the wafer by a film lamination process at a temperature of 25-60 ℃.
  6. 6. The method of claim 1, wherein in step 5) the metal is deposited by electroless plating or electroplating, and further comprising forming solder balls on top of the metal by solder paste printing and high temperature reflow soldering.
  7. 7. The method of claim 1, wherein in step 1), a protective film is further provided on one side of the positive photoresist dry film, and a predetermined scribe line region is exposed at the same time when the first exposure is performed, and scribe lines are formed after the development in step 2).
  8. 8. The method of wafer level packaging of a filter of claim 7, wherein in step 3), a surface of the positive photoresist dry film facing away from the protective film is bonded to the wafer surface, and the protective film is peeled off after bonding.
  9. 9. The method of claim 8, wherein in step 6), a dicing process is performed along the dicing streets by laser dicing or mechanical dicing.
  10. 10. The method of packaging a filter according to claim 7, wherein the protective film is a PET film having a thickness of 30-60 μm.

Description

Wafer level packaging method of filter Technical Field The invention belongs to the technical field of semiconductor packaging, and particularly relates to a wafer level packaging method of a filter. Background The Surface Acoustic Wave (SAW) filter integrates low insertion loss and good inhibition performance, can realize wide bandwidth and small volume, and is widely applied to the front end of a signal receiver, a duplexer and a receiving filter. The surface acoustic wave filter product needs to ensure the cavity structure design during packaging, namely the chip functional area cannot contact any substance, otherwise, the transmission of the surface wave is influenced, and the product performance is further influenced. When the existing surface acoustic wave filter is packaged, in order to form a cavity structure and an interconnection line, multiple packaging layers are sequentially stacked on a chip and are etched for multiple times. For example, a first packaging layer is overlapped on a chip, a through hole is formed by etching, the first packaging layer is used as a wall part of a cavity, then a second packaging layer is overlapped to cover the top of the through hole, the second packaging layer is used as the top of the cavity, so that the cavity is formed in a closed mode, and then processes such as etching of vertical through holes of interconnection lines are performed. On one hand, interfaces for contact adhesion exist between the multi-layer packaging layers, when the interface bonding strength of the two layers of materials is smaller than the born stress, interface stripping can be generated, delamination occurs between the two layers of materials, so that the reliability of a packaging product is invalid, and on the other hand, the etching process of the packaging layers is carried out on the surface of a chip, so that the device is easily damaged, and the performance of the device is influenced. Disclosure of Invention The invention provides a wafer level packaging method of a filter aiming at the defects in the prior art. In order to achieve the above object, the technical scheme of the present invention is as follows: A wafer level packaging method of a filter, comprising the steps of: 1) Providing a positive photoresist dry film with the thickness of more than 20um, performing first exposure on the positive photoresist dry film through a first photomask, wherein the exposure dose is less than 250mj, and the exposure depth is the thickness of the positive photoresist dry film; 2) Developing, wherein a through hole is formed after the first exposure area is developed, and a groove is formed after the second exposure area is developed; 3) Attaching a positive photoresist dry film to the surface of a wafer, wherein the wafer is provided with a plurality of filter chips, the filter chips are provided with functional areas and wiring, wherein the grooves and the functional areas are enclosed to form cavities, and part of the wiring corresponds to the through holes and is exposed; 4) Baking at 80-250 ℃ for 0.5-1.5 h; 5) Depositing metal inside the through hole and connecting with the wiring; 6) And cutting the packaged wafer to form a single filter packaging structure. Optionally, the second exposure time is <20s. Optionally, the positive photoresist dry film is photosensitive epoxy resin, and the first exposure and the second exposure adopt I-line light. Optionally, the exposure gap between the first exposure and the second exposure is 10-30um. Optionally, in the step 2), the developing time is 2 times, each time is 30-60 s, and the flushing time is 2 times, each time is 4-8 s. Optionally, in step 3), a film laminating process is adopted to laminate the positive photoresist dry film on the surface of the wafer, and the temperature is 25-60 ℃. Optionally, in step 5), the metal is deposited using a electroless or electroplating process. Optionally, in step 5), solder paste printing and high temperature reflow soldering processes are further used to form solder balls on the top of the metal. Optionally, in step 1), a protective film is further disposed on one surface of the positive photoresist dry film, and when the first exposure is performed, a preset dicing channel area is exposed at the same time, and dicing channels are formed after the development in step 2). Optionally, in step 3), one surface of the positive photoresist dry film, which faces away from the protective film, is attached to the surface of the wafer, and the protective film is peeled off after the attachment. Optionally, in step 6), a cutting procedure is performed along the cutting path by using a laser cutting or mechanical cutting method. Optionally, the protective film is a PET film, and the thickness is 30-60 um. The beneficial effects of the invention are as follows: (1) The single-layer positive photoresist dry film is adopted for packaging, the cavity is formed in the single-layer dry film, the layering problem of t