Packaging structure for increasing area of welding gasket by using radiating fin

Abstract

The packaging structure for increasing the area of the welding gasket by using the cooling fin comprises the cooling fin adhered to the surface of a flip chip, and the top surface of the cooling fin penetrates through a packaging material; and the penetrating surface of the radiating fin is used as a welding gasket of an SMT upper plate. A flip chip and a metal cooling fin are bonded through a high-heat-conduction crystal grain bonding film or other viscous heat-conduction interface materials, a die-leakage packaging technology is adopted, the cooling fin serves as an SMT welding gasket, existing processing equipment is utilized, under the condition that the double-face packaging integration degree is not affected, the area of the gasket is enlarged, the double-face packaging heat dissipation performance and the upper plate reliability are improved, and the packaging cost is reduced. And the method has high practicability and wide applicability.

Description

TECHNICAL FIELD

[0001] The application relates to a packaging structure, in particular to a packaging structure using a heat sink to increase the area of a soldering pad, and belongs to the technical field of semiconductor packaging. BACKGROUND

[0002] With the light and thin development of consumer electronics, the integration of the semiconductor packaging field is also improved, and packaging means with high integration such as wafer level packaging, fan-in, fan-out and double-sided packaging are emerging in an endless stream.

[0003] Double-sided packaging is an improvement means with little change to the existing process, but the current double-sided packaging mainly considers the implementation means and signal lead-out of the process, and cannot effectively unify heat dissipation, integration and reliability.

[0004] For example, patent CN117438321A does not consider the heat dissipation of a combination of many components and the reliability of subsequent board mounting.

[0005] For example, patent CN115274578A increases the number of ball planting by increasing the opening, similar to BGA design, to improve reliability, which affects the mounting density of components on the second surface of the substrate, etc. SUMMARY

[0006] To solve the problems of the prior art, the purpose of the application is to provide a packaging structure using a heat sink to increase the area of a soldering pad.

[0007] In order to achieve the above-mentioned target, the application adopts the following technical scheme:

[0008] The packaging structure using a heat sink to increase the area of a soldering pad comprises a heat sink pasted on the surface of a flip chip, and the top surface of the heat sink is exposed to the encapsulating material; and the exposed surface of the heat sink is used as a soldering pad for SMT board mounting.

[0009] The heat sink is pasted on the surface of the flip chip through a heat-conducting die-attaching film, a die-attaching adhesive or a heat-conducting interface material with adhesion.

[0010] Further, the die-attaching film is a heat-curing or thermoplastic die-attaching film sensitive or insensitive to ultraviolet light, with epoxy resin as the main resin and silicon oxide or aluminum oxide as the filler, and the thickness is 20-30 um.

[0011] Further, the die-attaching adhesive is a conductive adhesive with silver powder as the main filler.

[0012] The heat sink is a metal sheet-shaped flat plate heat sink with a thickness of 0.3-0.8 mm.

[0013] The application has the following advantages:

[0014] The application discloses a packaging structure with increased soldering pad area by using a heat sink, which is characterized by the following steps: a flip chip and a metal heat sink are bonded by using a high-thermal-conductivity die-bonding film or other adhesive thermal conductive interface material; a Die-exposed packaging process is adopted; the heat sink is used as an SMT soldering pad; and the existing process equipment is used to expand the pad area, improve the heat dissipation of double-sided packaging and the reliability of board mounting without affecting the integration of double-sided packaging, thereby achieving strong practicability and wide applicability. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 FIG. 1 is a structural schematic diagram of the packaging structure.

[0016] The meanings of the marks in the drawings are as follows: 1, substrate; 2, flip chip; 3, die-bonding film; 4, heat sink; 5, plastic encapsulation resin; 6, conductive column; and 7, electroplated tin. DETAILED DESCRIPTION

[0017] The application will be specifically described below in combination with the drawings and specific embodiments.

[0018] The packaging structure with increased soldering pad area by using a heat sink is mainly characterized by the following steps: a heat sink is pasted on the surface of a flip chip, and the top surface of the heat sink is exposed to the encapsulation material; and the exposed surface of the heat sink is used as a soldering pad for SMT board mounting.

[0019] The specific operation steps are as follows:

[0020] The substrate is a substrate with two or more layers of circuit superposition, has first and second surfaces in opposite directions, and has signal input and output solder pads on both surfaces.

[0021] A, after the substrate is heated and pre-baked, the flip chip and components are mounted on the first surface of the substrate by reflow soldering, then the die-bonding glue or die-bonding film is used to mount the normal chip, the die-bonding glue or die-bonding film is baked and solidified, the plasma is cleaned, the lead bonding is performed, the plasma is cleaned again, the first surface is encapsulated by the plastic encapsulation resin, and the thickness of the plastic encapsulation resin is 0.5-1.0 mm. The product after encapsulation is solidified at 175 DEG C, and a 3kg pressing block is used to ensure the flatness of the substrate after solidification.

[0022] The components are active or passive components, such as inductors, resistors, capacitors and the like.

[0023] Preferably, the die-bonding film is a UV-sensitive or non-sensitive thermosetting or thermoplastic die-bonding film with epoxy resin as the main resin and silicon oxide or aluminum oxide as the filler, and the thickness is 20-30 um.

[0024] Preferably, the die-bonding glue is a conductive glue with silver powder as the main filler.

[0025] The preferred plastic sealing resin is a conventional or high-thermal-conductivity plastic sealing resin with bisphenyl, phenolic resin, multifunctional epoxy resin as the main resin and silicon oxide or aluminum oxide as the filler.

[0026] B. Subsequently, the components are mounted on the second surface of the substrate by reflow soldering, and the flip-chip operation is performed; the flip-chip bumping area is filled and reinforced by using a underfill adhesive, and the metal heat sink is fixed on the surface of the flip-chip by using a heat-conducting die-attaching film or a conductive thermal interface material.

[0027] The preferred underfill adhesive is an organic polymer mixture of epoxy resin, acrylic resin, silica or aluminum oxide microspheres.

[0028] C. The through-hole is filled and reinforced by using a die-attaching adhesive or a die-attaching film, and the flip-chip is mounted on the substrate by baking and curing, plasma cleaning, wire bonding, and plasma cleaning of the substrate. The second surface is encapsulated by a plastic sealing resin with a thickness of 1.0-1.5 mm, and the encapsulated product is post-cured at 175°C and subjected to a 5kg pressing process to ensure the flatness of the substrate after post-curing.

[0029] The preferred heat sink is a metal sheet-shaped flat heat sink, such as copper, stainless steel, etc., with a thickness of 0.3-0.8 mm.

[0030] D. The second surface of the substrate is mechanically drilled, laser slotted or chemically etched to open a circular through-hole of a specific size (diameter 0.1-0.3 mm), so that the solder pad on the second surface of the substrate is exposed. The through-hole is cleaned with pure water and anhydrous alcohol, and baked at 50°C for 20 minutes to remove mechanical stress.

[0031] E. The second surface of the substrate is plasma cleaned, the through-hole is filled with conductive pillars and tin paste or conductive silver adhesive, and the solder pad signal on the second surface of the substrate is led out to the surface of the plastic sealing resin by reflow soldering or high-temperature oven curing.

[0032] The preferred tin paste is a mixture of tin-silver-copper or tin-silver-lead.

[0033] The preferred conductive pillar is a columnar conductive material made of metal, such as copper, tin, silver, etc.

[0034] F. The plastic sealing resin on the second surface of the substrate is polished to remove the excess plastic sealing resin on the surface of the metal heat sink, the conductive pillars and conductive silver adhesive that protrude from the through-hole, and to ensure the flatness of the surface of the plastic sealing resin.

[0035] G. The surface of the metal heat sink and the surface of the conductive pillar are electroplated with tin to protect the metal surface for subsequent SMT.

[0036] The preferred tin is an electroplated tin ingot with a purity of 99.9%.

[0037] H, laser mark on the first surface plastic sealing resin, then cut into single, electrical signal test, tray.

[0038] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the above examples do not limit the present application in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of the present application.

Claims

1. A package structure for increasing the area of a solder pad by using a heat sink, characterized by, The heat sink is pasted on the surface of the flip chip, and the top surface of the heat sink is exposed to the encapsulation material; the exposed surface of the heat sink is used as a solder pad of the SMT upper plate; The heat sink is pasted on the surface of the flip chip by a heat-conducting die-attaching film, die-attaching glue or adhesive heat-conducting interface material.

2. The package structure of claim 1, wherein, The thickness of the die-attaching film is 20-30 um.

3. The package structure of claim 1, wherein, The heat sink is a metal sheet-shaped flat heat sink with a thickness of 0.3-0.8 mm.

4. The package structure of claim 1, wherein, The flip chip is mounted on the first surface and the second surface of the substrate.

5. The package structure of claim 4, wherein, The second surface of the substrate is encapsulated with resin and a through hole is formed, and the through hole is filled with conductive columns matched with tin paste or conductive silver glue.

6. The package structure of claim 5, wherein, The diameter of the through hole is 0.1-0.3 mm.

7. The package structure of claim 5, wherein, The conductive column is a columnar conductive material made of metal, such as copper, tin or silver.

8. The package structure of claim 1, wherein, The surface of the heat sink is electroplated with tin.

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