CN116153871A - Underfill and flip-chip bonding packaging method for chip packaging - Google Patents

Underfill and flip-chip bonding packaging method for chip packaging Download PDF

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Publication number
CN116153871A
CN116153871A CN202211473405.8A CN202211473405A CN116153871A CN 116153871 A CN116153871 A CN 116153871A CN 202211473405 A CN202211473405 A CN 202211473405A CN 116153871 A CN116153871 A CN 116153871A
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China
Prior art keywords
chip
welding
underfill
flip
packaging
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Pending
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CN202211473405.8A
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Chinese (zh)
Inventor
杨雪艳
胡安亚
袁俊
李志华
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Kunming Institute of Physics
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Kunming Institute of Physics
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Priority to CN202211473405.8A priority Critical patent/CN116153871A/en
Publication of CN116153871A publication Critical patent/CN116153871A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/28—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection
    • H01L23/29—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the material, e.g. carbon
    • H01L23/293—Organic, e.g. plastic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/50—Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
    • H01L21/56—Encapsulations, e.g. encapsulation layers, coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/50—Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
    • H01L21/60—Attaching or detaching leads or other conductive members, to be used for carrying current to or from the device in operation
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J179/00—Adhesives based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen, with or without oxygen, or carbon only, not provided for in groups C09J161/00 - C09J177/00
    • C09J179/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • C09J179/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/50—Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
    • H01L21/60—Attaching or detaching leads or other conductive members, to be used for carrying current to or from the device in operation
    • H01L2021/60007—Attaching or detaching leads or other conductive members, to be used for carrying current to or from the device in operation involving a soldering or an alloying process

Abstract

The invention relates to an underfill and flip-chip bonding packaging method for chip packaging, and belongs to the field of advanced electronic packaging. The underfill is photosensitive polyimide, and the method adopts a mode of filling the underfill first and then flip-chip welding. Firstly, uniformly coating photosensitive polyimide serving as underfill on the pixel surface of a focal plane chip to realize filling uniformity, then removing the photosensitive polyimide above a metal electrode by photoetching to form a reverse welding hole by utilizing the photosensitive characteristic of the photosensitive polyimide, exposing the metal electrode, inserting a welding spot of a substrate into the reverse welding hole during flip-chip welding, and realizing tight connection between the welding spot and the underfill through heating, melting, reflow and filling to realize flip-chip welding; the method solves the problems existing in the prior art that the underfill is refilled by welding, realizes the redistribution of thermal stress, improves the reliability of the whole structure, and simplifies the packaging steps.

Description

Underfill and flip-chip bonding packaging method for chip packaging
Technical Field
The invention relates to an underfill and flip-chip bonding packaging method for chip packaging, and belongs to the field of advanced electronic packaging.
Background
The focal plane detector needs to connect the discrete photosensitive chips with each element of the readout circuit substrate in a one-to-one correspondence manner through a reverse welding mode. After the chip is subjected to flip-chip bonding, an underfill is filled in a gap between the chip and the readout circuit substrate to protect the solder joints. In the chip packaging process, the chip is connected with the substrate through the convex welding spots by adopting flip-chip welding, and in the flip-chip welding process, because the thermal expansion coefficients between materials are large, great thermal stress can be caused, and in order to ensure the integrity of the welding spots and improve the fatigue life of the welding spots, the underfill is filled around the welding spots to disperse the concentrated stress. In order to prevent fatigue cracking of conventional solder bumps, it is generally required that the underfill have a high glass transition temperature (Tg) and modulus of elasticity, and a coefficient of thermal expansion close to that of solder.
As chip size increases, the thermal mechanical reliability of flip-chip bonding pads becomes a critical issue in flip-chip packaging, and thermal mechanical problems are mainly caused by thermal mismatch between the semiconductor chip and the silicon or ceramic substrate, which puts higher demands on the interconnect medium. Compared with the traditional dielectric layer, the low dielectric constant material can generate great thermal stress between the chip and the dielectric layer as the dielectric layer, so that the underfill protects the welding spots and the chip. The commonly used underfill is epoxy resin, which is doped with a large amount of SiO 2 A liquid encapsulating material formed from particles. Compared with the condition of not filling the underfill, the strain level of the key welding spots can be reduced by 0.10-0.25 after filling, and the fatigue life of the welding spots can be improved by 10-100 times.
In the prior art, the underfill and the packaging process are complicated, and the production cost is increased. The underfill and packaging process typically refills the underfill after the flip-chip interconnect is formed between the chip and the substrate, causing the underfill to flow into the gap between the chip and the substrate by capillary action. However, due to slow flow and incomplete filling of the underfill under the capillary action, the problems of cavity occurrence, uneven filling and the like in the packaging structure can be caused, uneven stress distribution can be caused, and local cracking and warping of the chip can be further caused. In addition, since the soldering flux is used in the soldering process, the residual soldering flux covers the cracks of the solder joints, and the cause of product failure cannot be checked, so that the residual soldering flux needs to be cleaned. However, after die bonding, no thorough removal of the flux is guaranteed. The components in the underfill may react with the flux residue and it may occur that the underfill delays curing or does not cure.
The photosensitive polyimide (PSPI) used in the invention is a high polymer material with heat resistance and photosensitivity, has electrical insulation property, and can protect a semiconductor circuit from physical and chemical conditions. Photosensitive polyimide has two main functions of photoresist and electronic package, and the "polyimide photoresist" can be obtained by adding sensitizer, stabilizer, etc. into photosensitive polyimide. Compared with the traditional photoresist, the polyimide has good dielectric property, so that the polyimide does not need to be coated with a light blocking agent only serving as a working medium when in use, the working procedure can be greatly shortened, and the production efficiency is improved. At present, photosensitive polyimide is mainly used as a purifying layer and an interlayer insulating material in a large-scale integrated circuit, but the photosensitive polyimide is used as an underfill for flip-chip bonding and is realized by a photoetching mode. And in the existing flip chip welding process, the method of filling the underfill after the flip chip is performed. The invention can avoid a series of thermal stress problems caused by uneven flowing of the bottom filling glue and holes in the prior art by filling glue and then welding.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide an underfill and flip-chip bonding packaging method for chip packaging; the bottom filling glue adopts photosensitive polyimide, and the method adopts a mode of filling the bottom filling glue and then welding the bottom filling glue upside down, so that the conditions of non-uniformity, holes and the like in the capillary flow of the bottom filling glue in the prior art are avoided, the filling uniformity of the bottom filling glue is ensured, and therefore, better thermal stress redistribution can be realized and the production efficiency is improved.
In order to achieve the purpose of the invention, the following technical scheme is provided.
An underfill for chip packaging, the underfill being a photosensitive polyimide.
The flip-chip bonding packaging method in chip packaging adopts a mode of filling underfill firstly and then flip-chip bonding, wherein the underfill is photosensitive polyimide; the method comprises the following specific steps:
(1) Uniformly coating photosensitive polyimide on the pixel surface of the focal plane chip to be subjected to flip-chip bonding encapsulation to form an underfill layer, wherein the thickness of the underfill layer is higher than the height of the metal electrode on the pixel surface of the chip; photoetching to remove photosensitive polyimide right above the top of the metal electrode on the pixel surface of the chip to form a reverse welding hole, wherein the bottom of the reverse welding hole is the top of the metal electrode; imidizing the residual photosensitive polyimide on the pixel surface of the focal plane chip to obtain the focal plane chip with the underfill layer and the flip-chip holes.
In step (1):
the focal plane chip is suitable for flip-chip bonding and underfill encapsulation in the prior art.
The photosensitive polyimide is preferably uniformly coated on the pixel surface of the focal plane chip to be flip-chip packaged by adopting a spin coating process.
The height difference between the thickness of the underfill layer and the thickness of the metal electrode on the pixel surface of the chip depends on the height of the welding spot during flip-chip welding, and the inverted welding hole can completely cover the welding spot.
The photoetching is completed by adopting a photoetching method of photosensitive polyimide photoresist in the prior art through pre-baking, masking, exposure and development in sequence.
(2) Preparing welding spots on the substrate to obtain a substrate with the welding spots; the length of the welding spot is equal to that of the reverse welding hole, and the maximum width or diameter of the welding spot is slightly smaller than that of the reverse welding hole.
In the step (2):
preferably, the maximum width or diameter of the welding spot is 5-10 μm smaller than the diameter of the back welding hole.
The method for preparing the welding spots on the substrate is a substrate, a welding spot and a preparation method which are commonly adopted In the prior art, wherein the substrate is a silicon substrate or a ceramic substrate, the welding spots are indium (In), copper (Cu), tin (Sn), gold (Au) and the like, and the preparation method can adopt methods of electroplating, stencil printing, vapor plating, ball placement and the like.
(3) And (3) reversely buckling the substrate with the welding spots on the focal plane chip with the underfill layer and the reverse welding holes, which is manufactured in the step (1), wherein the welding spots are inserted into the reverse welding holes, the tops of the welding spots are contacted with the tops of the metal electrodes, gaps are reserved between the peripheries of the welding spots and the underfill layer around the reverse welding holes, and the welding spots are melted and welded with the metal electrodes through a reflow welding process to fill the gaps, so that the flip-chip welding packaging between the substrate and the chip is realized.
Advantageous effects
(1) The invention provides an underfill for chip packaging, which is photosensitive polyimide, has higher glass transition temperature, lower thermal expansion coefficient and lower viscosity strength, can reduce the strain level of key welding spots after filling, improves the fatigue life of the welding spots, plays a role of conventional underfill, and is suitable for packaging chips and substrates as the underfill for chip packaging; furthermore, the photosensitive polyimide can be conveniently removed through a conventional photoetching process to form a reverse welding hole, the metal electrode is exposed, and then the reverse welding hole is welded with the welding spot of the substrate, so that the photosensitive polyimide can be coated before welding, and the problem of refilling the bottom filling glue by welding in the prior art is avoided.
(2) The invention provides a flip-chip bonding packaging method in chip packaging, which comprises the steps of uniformly coating photosensitive polyimide serving as underfill on a pixel surface of a focal plane chip to realize filling uniformity, removing photosensitive polyimide above a metal electrode by photoetching to form a flip-chip hole by utilizing the photosensitive characteristic of the photosensitive polyimide, exposing the metal electrode, inserting a substrate welding spot into the flip-chip hole during flip-chip bonding, and realizing tight connection between the welding spot and the underfill through heating, melting, reflow and filling to realize flip-chip bonding; holes and uneven filling of the underfill caused by capillary effect can be avoided to a great extent; the method does not need to independently coat soldering flux and clean the soldering flux, simplifies the packaging step, avoids the problems existing in the prior art that the bottom filling glue is refilled by welding, realizes the redistribution of thermal stress, and improves the reliability of the whole structure.
(3) The invention provides a flip-chip bonding packaging method in chip packaging, which is characterized in that a spin coating process is preferably adopted in the method, so that photosensitive polyimide can be coated on the pixel surface of a focal plane chip more uniformly.
(4) The invention provides a flip-chip bonding packaging method in chip packaging, wherein the thickness of an underfill adhesive layer is preferably higher than the height of a chip pixel surface metal electrode.
(5) The invention provides a flip-chip packaging method in chip packaging, wherein the maximum width or diameter of a welding spot is smaller than the diameter of a flip-chip hole.
Drawings
Fig. 1 is a schematic view of a focal plane chip that needs to be flip-chip packaged in embodiment 1.
FIG. 2 is a schematic view of a focal plane chip after uniformly coating the photosensitive polyimide in example 1.
Fig. 3 is a schematic view of a focal plane chip with an underfill layer and a flip-chip hole in embodiment 1.
Fig. 4 is a schematic view of a substrate with solder joints in example 1.
Fig. 5 is a schematic diagram of the flip-chip bonding of the substrate with solder joints on the focal plane chip with the underfill layer and the flip-chip bonding holes in embodiment 1.
Fig. 6 is a schematic diagram of the flip-chip package of the substrate and the focal plane chip after completion.
Wherein, 101 is focal plane chip, 102 is metal electrode, 103 is photosensitive polyimide, 201 is substrate, 202 is welding spot
Detailed Description
The invention will now be described in detail with reference to the drawings and specific examples, but is not intended to limit the scope of the patent.
Example 1
A flip chip bonding packaging method in a chip package, the method comprising the steps of:
(1) Uniformly coating photosensitive polyimide 103 serving as an underfill layer on the pixel surface of the InSb focal plane chip 101 needing flip-chip bonding packaging by adopting a spin coating process, wherein the thickness of the underfill layer is higher than the height of the pixel surface metal electrode 102 of the focal plane chip 101; removing photosensitive polyimide 103 right above the top of the pixel surface metal electrode 102 of the focal plane chip 101 by photoetching through pre-baking, masking, exposing and developing to form cylindrical reverse welding holes, wherein 4 metal electrodes 102 are uniformly distributed on the pixel surface of the focal plane chip 101; the bottom of the reverse welding hole is the top of the metal electrode 102; and heating the residual photosensitive polyimide 103 on the pixel surface of the focal plane chip 101 at 150 ℃ for 45min for imidization curing to obtain the focal plane chip 101 with the underfill layer and the flip-chip holes.
The metal electrode 102 is cylindrical and consists of Ti, pd and Au in sequence from bottom to top.
(2) Electroplating and growing a cylindrical indium column on the Si substrate 201 to serve as a welding spot 202, so as to obtain a substrate 201 with the welding spot 202; the length of the welding spot 202 is equal to that of the reverse welding hole, the diameter of the welding spot is 5 mu m smaller than that of the reverse welding hole, and the reverse welding hole can completely cover the welding spot 202.
(3) And (2) reversely buckling the substrate 201 with the welding spots 202 on the focal plane chip 101 with the underfill layer and the reverse welding holes, which is prepared in the step (1), inserting the welding spots 202 into the reverse welding holes, enabling the tops of the welding spots 202 to be in contact with the tops of the metal electrodes 102, enabling gaps to be reserved between the peripheries of the welding spots 202 and the underfill layer around the reverse welding holes, and heating the substrate 201 until the welding spots 202 are melted, realizing welding between the welding spots 202 and the metal electrodes 102, and reflowing to fill the gaps, so that flip-chip welding packaging between the substrate 201 and the focal plane chip 101 is realized, and a device after flip-chip welding packaging is obtained.
In the method, the underfill is photosensitive polyimide 103, has higher glass transition temperature, lower thermal expansion coefficient and lower viscosity strength, can reduce the strain level of the key welding spots 202 after filling, improves the fatigue life of the welding spots 202, and plays a role of the conventional underfill.
The method comprises the steps of uniformly coating photosensitive polyimide 103 serving as underfill on the pixel surface of a focal plane chip 101 to realize filling uniformity, removing the photosensitive polyimide 103 above a metal electrode 102 by photoetching to form a reverse welding hole by utilizing the photosensitive characteristic of the photosensitive polyimide 103, exposing the metal electrode 102, inserting a welding spot 202 into the reverse welding hole during flip-chip welding, and realizing tight connection between the welding spot 202 and the underfill through heating, melting, reflow and filling to realize flip-chip welding; holes and uneven filling of the underfill caused by capillary effect can be avoided to a great extent; the method does not need to independently coat soldering flux and clean the soldering flux, simplifies the packaging step, avoids the problems existing in the prior art that the bottom filling glue is refilled by welding, realizes the redistribution of thermal stress, and improves the reliability of the whole structure.

Claims (5)

1. An underfill for chip packaging, characterized in that: the underfill is photosensitive polyimide.
2. A flip-chip bonding packaging method in chip packaging is characterized in that: the method adopts a mode of filling the underfill firstly and then carrying out flip-chip bonding, wherein the underfill is the photosensitive polyimide as claimed in claim 1.
3. A flip-chip bonding method in a chip package according to claim 2, wherein: the method comprises the following steps:
(1) Uniformly coating photosensitive polyimide on the pixel surface of the focal plane chip to be subjected to flip-chip bonding encapsulation to form an underfill layer, wherein the thickness of the underfill layer is higher than the height of the metal electrode on the pixel surface of the chip; photoetching to remove photosensitive polyimide right above the top of the metal electrode on the pixel surface of the chip to form a reverse welding hole, wherein the bottom of the reverse welding hole is the top of the metal electrode; imidizing the residual photosensitive polyimide on the pixel surface of the focal plane chip to obtain the focal plane chip with the underfill layer and the flip-chip holes;
(2) Preparing welding spots on the substrate to obtain a substrate with the welding spots; the length of the welding spot is equal to that of the reverse welding hole, and the maximum width or diameter of the welding spot is slightly smaller than that of the reverse welding hole;
(3) And (3) reversely buckling the substrate with the welding spots on the focal plane chip with the underfill layer and the reverse welding holes, which is manufactured in the step (1), wherein the welding spots are inserted into the reverse welding holes, the tops of the welding spots are contacted with the tops of the metal electrodes, gaps are reserved between the peripheries of the welding spots and the underfill layer around the reverse welding holes, and the welding spots are melted and welded with the metal electrodes through a reflow welding process to fill the gaps, so that the flip-chip welding packaging between the substrate and the chip is realized.
4. A flip-chip bonding method in a chip package according to claim 3, wherein: in the step (1), the photosensitive polyimide is uniformly coated on the pixel surface of the focal plane chip which needs flip-chip packaging by adopting a spin coating process.
5. A flip-chip packaging method in a chip package according to claim 3 or 4, characterized in that: in the step (2), the maximum width or diameter of the welding spot is 5-10 μm smaller than the diameter of the back welding hole.
CN202211473405.8A 2022-11-21 2022-11-21 Underfill and flip-chip bonding packaging method for chip packaging Pending CN116153871A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202211473405.8A CN116153871A (en) 2022-11-21 2022-11-21 Underfill and flip-chip bonding packaging method for chip packaging

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202211473405.8A CN116153871A (en) 2022-11-21 2022-11-21 Underfill and flip-chip bonding packaging method for chip packaging

Publications (1)

Publication Number Publication Date
CN116153871A true CN116153871A (en) 2023-05-23

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CN202211473405.8A Pending CN116153871A (en) 2022-11-21 2022-11-21 Underfill and flip-chip bonding packaging method for chip packaging

Country Status (1)

Country Link
CN (1) CN116153871A (en)

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