阅读说明：本技术 一种芯片刷胶方法 (Chip glue brushing method ) 是由 刘剑 唐涛 于 2021-03-05 设计创作，主要内容包括：本发明涉及半导体制造技术领域,具体涉及一种芯片刷胶方法,芯片的背金面涂刷两至三层高导电银胶,每次涂刷后对所述芯片进行加热,使最内层所述高导电银胶完全固化、最外层所述高导电银胶半固化。采用本发明芯片刷胶方法,既解决了胶层容易从芯片上脱落的问题,又不影响芯片与所述引线框架的粘接性能和溢出量,提高了芯片制造的加工质量。(The invention relates to the technical field of semiconductor manufacturing, in particular to a chip glue brushing method. The chip glue brushing method solves the problem that a glue layer is easy to fall off from a chip, does not influence the bonding performance and the overflow quantity of the chip and the lead frame, and improves the processing quality of chip manufacturing.)

1. The method for brushing the adhesive on the chip is characterized in that two to three layers of high-conductivity silver adhesive are brushed on the back gold surface of the chip, and the chip is heated after each brushing so that the high-conductivity silver adhesive on the innermost layer is completely cured and the high-conductivity silver adhesive on the outermost layer is semi-cured.

2. The method for brushing the adhesive on the chip as claimed in claim 1, wherein when three layers of the highly conductive silver adhesive are coated on the back gold surface of the chip, the curing state of the highly conductive silver adhesive in the middle layer is between the curing states of the innermost layer and the outermost layer.

3. The method for brushing the adhesive on the chip as claimed in claim 1, wherein the back gold surface of the chip is subjected to plasma cleaning before the back gold surface of the chip is brushed with the innermost layer of the highly conductive silver adhesive.

4. The method for brushing the glue on the chip as claimed in claim 1, wherein two layers of the highly conductive silver glue are coated on the back gold surface of the chip, comprising the steps of:

m1, coating the innermost layer of the high-conductivity silver adhesive on the back gold surface of the chip, and heating the chip for A1 time, wherein A1 represents the time for the innermost layer of the high-conductivity silver adhesive to be completely cured at a preset temperature;

m2, coating the outermost layer of the high-conductivity silver adhesive on the surface of the innermost layer of the high-conductivity silver adhesive in M1, and heating the chip for A2 time, wherein A2 represents the time for semi-curing the outermost layer of the high-conductivity silver adhesive at a preset temperature.

5. The method for brushing the chip with the glue according to claim 4, wherein the thickness of the high-conductivity silver glue brushed on the outermost layer in M2 is 10-20 microns.

6. The method for brushing the glue on the chip as claimed in any one of claims 1 to 5, wherein the thickness of the high-conductivity silver glue brushed each time is the same.

7. The method of claim 6, wherein the heating temperature of the chip is the same after each brushing.

Technical Field

The invention relates to the technical field of semiconductor manufacturing, in particular to a chip glue brushing method.

Background

In the technical field of semiconductor manufacturing, a layer of highly conductive silver adhesive of 10-20 microns needs to be coated on the back gold surface of a chip, as shown in fig. 1, a layer of template 3 is tightly attached to the periphery of the chip 4, the highly conductive silver adhesive 2 is dripped on the template 3 and then is scraped to be flat on the back gold surface of the chip 4 by a scraper 1, so that a layer of highly conductive silver adhesive 2 is coated on the back gold surface of the chip 4, but because the highly conductive silver adhesive 2 has high fluidity, the chip 4 coated with the highly conductive silver adhesive 2 needs to be heated, so that the highly conductive silver adhesive 2 becomes a semi-cured adhesive layer with low fluidity so as to be bonded with a lead frame. In actual conditions, the bonding force between the semi-cured adhesive layer and the back gold surface of the chip is still insufficient, the semi-cured adhesive layer is easy to fall off from the chip, although the chip 4 is further heated, the bonding force between the adhesive layer and the chip 4 can be enhanced by completely curing the semi-cured adhesive layer, and the viscosity and the fluidity of the adhesive layer after complete curing are greatly reduced.

In the existing bonding method of the chip and the lead frame, in order to obtain a large enough bonding effect and ensure the reliability of chip connection, after the chip is bonded with the lead frame, a certain amount of high-conductivity silver adhesive needs to overflow from the periphery of the chip, but the viscosity and the fluidity of a completely cured adhesive layer are low, so that the chip cannot meet the requirements of effective bonding with the lead frame and the overflow amount.

Disclosure of Invention

The invention aims to provide a chip glue brushing method aiming at the problems that in the prior art, the bonding force between a semi-solidified glue layer and a back gold surface of a chip is insufficient, the semi-solidified glue layer is easy to fall off from the chip, although the chip is further heated so that the bonding force between the glue layer and the chip can be enhanced by completely solidifying the semi-solidified glue layer, the viscosity and the liquidity of the completely solidified glue layer are low, and the chip cannot meet the requirements of effective bonding with a lead frame and the overflow amount.

In order to achieve the purpose, the invention adopts the technical scheme that:

a method for brushing glue on a chip comprises the steps of brushing two to three layers of high-conductivity silver glue on the back gold surface of the chip, and heating the chip after each brushing so as to completely cure the high-conductivity silver glue on the innermost layer and semi-cure the high-conductivity silver glue on the outermost layer.

The semi-curing state and the curing state of the high-conductivity silver adhesive are comprehensively determined by the heating temperature and the heating time, and the temperature and the time required for different types of high-conductivity silver adhesives to reach the semi-curing state and the curing state may be different. The heating method (selecting a suitable heating temperature and time) for how to make the highly conductive silver paste reach the semi-cured state and the cured state is routine for those skilled in the art. If the time required for heating the high-conductivity silver paste to the fully cured state is A1 and the time required for heating the high-conductivity silver paste to the semi-cured state is A2 at a predetermined temperature, the high-conductivity silver paste gradually changes from the semi-cured state to the fully cured state when the heating time is A2 to A1. Coating two high-conductivity silver adhesive layers on the back gold surface of the chip: firstly, coating the innermost layer of the high-conductivity silver adhesive on the back gold surface of the chip, heating for a time of A1 at a preset temperature to form a completely cured state, then coating the outermost layer of the high-conductivity silver adhesive outside the completely cured layer, and heating for a time of A2, wherein the innermost layer of the high-conductivity silver adhesive is in a completely cured state and the outermost layer of the high-conductivity silver adhesive is in a semi-cured state. The innermost layer of the fully cured adhesive layer has strong bonding force with the back gold surface of the chip and is not easy to fall off, and the outermost layer of the semi-cured adhesive layer has certain viscosity and fluidity, can be effectively bonded with the lead frame and meets the requirement of the overflow amount. The method for coating three layers of the high-conductivity silver adhesive on the back gold surface of the chip is similar to the method for coating two layers of the high-conductivity silver adhesive, the type of the high-conductivity silver adhesive coated each time can be different, and the heating temperature and the heating time of each time can also be different. According to the invention, a mode of brushing more than three layers can be adopted, but the working procedures are greatly increased, the efficiency is reduced, and the practicability is low.

The chip glue brushing method solves the problem that a glue layer is easy to fall off from a chip, does not influence the bonding performance and the overflow quantity of the chip and the lead frame, and improves the processing quality of chip manufacturing.

Preferably, when three layers of the high-conductivity silver adhesive are coated on the back gold surface of the chip, the curing state of the high-conductivity silver adhesive in the middle layer is between the curing states of the innermost layer and the outermost layer.

After heating is finished, the highly conductive silver adhesive on the innermost layer is completely cured, the highly conductive silver adhesive on the outermost layer is semi-cured, and the state of the highly conductive silver adhesive on the intermediate layer is between the completely cured state and the semi-cured state through controlling the temperature and the time of the highly conductive silver adhesive on the intermediate layer. Different from brushing two layers, the high-conductivity silver adhesive from the innermost layer to the outermost layer is gradually changed from a completely cured state to a semi-cured state, and the transition is smooth, so that the three high-conductivity silver adhesive layers have strong binding force and are not easy to layer.

Preferably, before the back gold surface of the chip is coated with the innermost layer of the high-conductivity silver adhesive, the back gold surface of the chip is subjected to plasma cleaning. The cleanliness of the back gold surface of the chip is improved, and the bonding force between the adhesive layer and the back gold surface of the chip is enhanced.

Preferably, two layers of the high-conductivity silver adhesive are coated on the back gold surface of the chip. Simple process and high efficiency. The method comprises the following steps:

m1, coating the innermost layer of the high-conductivity silver adhesive on the back gold surface of the chip, and heating the chip for A1 time, wherein A1 represents the time for the innermost layer of the high-conductivity silver adhesive to be completely cured at a preset temperature;

m2, coating the outermost layer of the high-conductivity silver adhesive on the surface of the innermost layer of the high-conductivity silver adhesive in M1, and heating the chip for A2 time, wherein A2 represents the time for semi-curing the outermost layer of the high-conductivity silver adhesive at a preset temperature.

There are various combinations of temperatures and durations required for the highly conductive silver paste to reach a fully cured state, which are conventional technical means for those skilled in the art, and various combinations of temperatures and durations required for the highly conductive silver paste to reach a semi-cured state, which are also conventional technical means for those skilled in the art. By designing the heating temperature and the time length of the two times, when the outermost layer of the high-conductivity silver adhesive is semi-cured, the innermost layer of the high-conductivity silver adhesive reaches a complete curing state in the two heating processes, so that the heating utilization rate can be improved, but the defect is that the technical personnel in the field need to reasonably design the heating temperature and the time length of the two times, and the difficulty is increased. The highly conductive silver adhesive on the innermost layer reaches a complete curing state through innermost heating, the highly conductive silver adhesive on the outermost layer is coated on the surface of the fully cured state of the innermost layer, and the highly conductive silver adhesive is heated to a semi-curing state, so that the heating utilization rate is not high, but the design difficulty of technicians in the field is reduced.

Preferably, in M2, the thickness of the high-conductivity silver paste painted on the outermost layer is 10-20 microns.

The highly conductive silver adhesive on the innermost layer is completely cured, the fluidity is poor, and the overflow amount is small. In order to ensure the overflow amount, the thickness of the high conductive silver paste coated on the outermost layer is required to be ensured to be 10-20 microns, and the overflow amount is too large to pollute the chip when the thickness exceeds the range. Note that the thickness herein refers to the thickness when the outermost layer is painted, and not to the thickness after the highly conductive silver paste of the outermost layer is heated to a semi-cured state.

Preferably, the thickness of the high-conductivity silver adhesive coated every time is the same.

The high-conductivity silver adhesive with different thicknesses is coated by the method, different templates need to be replaced, the thickness of the high-conductivity silver adhesive coated each time is the same, the number of the templates can be reduced, and the heating mode can be simplified.

Preferably, the heating temperature for the chip after each brushing is the same. The heating mode of changing the curing degree of the high-conductivity silver adhesive is simpler by changing the heating time under the condition of the same temperature.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. according to the chip glue brushing method, a one-time glue brushing method in the prior art is improved into two-time to three-time glue brushing, the bonding force between the innermost fully-cured glue layer and the back gold surface of the chip is strong, the outermost semi-cured glue layer has certain viscosity and fluidity, the highly-conductive silver glue can be effectively bonded with a lead frame, the overflow amount is ensured, the three-time glue brushing mode is adopted, the highly-conductive silver glue from the innermost layer to the outermost layer is gradually changed from a fully-cured state to a semi-cured state, the transition is smooth, and the bonding force between the whole highly-conductive silver glue layers is strong, and the layers are not prone to. The chip glue brushing method solves the problem that a glue layer is easy to fall off from a chip, does not influence the bonding performance and the overflow quantity of the chip and the lead frame, and improves the processing quality of chip manufacturing.

Drawings

FIG. 1 is a schematic diagram of a prior art chip glue application;

the labels in the figure are: 1-scraper, 2-highly conductive silver adhesive, 3-template and 4-chip.

Fig. 2 is a flowchart of a chip glue brushing method in embodiment 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

In the method for brushing the adhesive on the chip in the embodiment, the gold-back surface of the chip is coated with two to three layers of high-conductivity silver adhesive, and the chip is heated after each coating, so that the high-conductivity silver adhesive on the innermost layer is completely cured, and the high-conductivity silver adhesive on the outermost layer is semi-cured.

In this embodiment, before the back gold surface of the chip is coated with the innermost layer of the highly conductive silver adhesive, the back gold surface of the chip is subjected to plasma cleaning.

In this embodiment, the back gold surface of the chip is coated with two highly conductive silver adhesive layers, so that the adhesive coating process can be simplified, and the efficiency can be improved. Further, the high-conductivity silver adhesive layer is coated in the same type, optionally, 8008HT high-conductivity silver adhesive is adopted as the high-conductivity silver adhesive, and the 8008HT high-conductivity silver adhesive has larger silver powder particles and good electrical conductivity and thermal conductivity. The 8008HT high-conductivity silver adhesive is heated to a semi-cured state at 100-120 ℃ for about 120 minutes, and the fully cured state is formed at 170-190 ℃ for about 90 minutes. In other possible embodiments, other types of highly conductive silver paste, such as 8008MD conductive silver paste, may be used.

In this embodiment, the thickness of the highly conductive silver paste coated each time is the same, which is beneficial to reducing the number of templates, and the heating mode is also beneficial to being simplified under the condition of the same thickness of different glue layers.

In this embodiment, the thickness of the highly conductive silver paste coated on the outermost layer is 10 to 20 micrometers. Optionally, 15 microns, and the thickness of the high-conductivity silver paste layer painted twice is 15 microns. The bonding performance of the whole high-conductivity silver adhesive layer and the lead frame is guaranteed, and meanwhile, the phenomenon that the chip is polluted due to overlarge overflowing amount between the chip and the lead frame is avoided.

As shown in fig. 1, the method for brushing glue on a chip in this embodiment includes the following steps:

m10, brushing a layer of 8008HT high-conductivity silver adhesive with the thickness of 15 microns on the back gold surface of the chip;

m20, heating the high-conductivity silver adhesive at 180 ℃ for 90 minutes until the high-conductivity silver adhesive is completely cured;

m30, coating a layer of the high-conductivity silver adhesive with the thickness of 15 microns on the surface of the completely cured adhesive layer;

m40, heating the high-conductivity silver adhesive at 110 ℃ for 120 minutes until semi-solidification.

In the embodiment, different heating temperatures are adopted after two times of painting, but the same heating temperature can also be adopted, and the curing degree of the highly conductive silver paste is changed by changing the heating time length under the condition that the thickness and the heating temperature of each painting are the same, wherein the setting of the heating temperature and the heating time length is a conventional technical means for a person skilled in the art.

Example 2

The difference between the method for brushing the adhesive on the chip in the embodiment and the embodiment 1 is that the back gold surface of the chip is brushed with three high-conductivity silver adhesive layers. The thickness of the high-conductivity silver adhesive layer coated for three times is 10 micrometers.

The method comprises the following steps:

p10, coating a layer of 8008HT high-conductivity silver adhesive with the thickness of 10 microns on the back gold surface of the chip;

p20, heating the high-conductivity silver adhesive at 180 ℃ for 30 minutes;

p30, coating a layer of the high-conductivity silver adhesive with the thickness of 10 microns on the surface of the adhesive layer after the heating in the P20;

p40, heating the chip at 180 ℃ for 15 minutes;

p50, coating a layer of the high-conductivity silver adhesive with the thickness of 10 microns on the surface of the adhesive layer after the heating in the P40;

p60, heating the highly conductive silver paste at 180 ℃ for 45 minutes.

After the steps, the high-conductivity silver adhesive layer on the innermost layer is heated at 180 ℃ for 90 minutes to be in a completely cured state, the high-conductivity silver adhesive layer on the outermost layer is heated at 180 ℃ for 45 minutes to be in a semi-cured state, and the high-conductivity silver adhesive layer on the middle layer is heated at 180 ℃ for 60 minutes to be in a state between the completely cured state and the semi-cured state.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.