KR20090048813A - Conductive adhesive and flipchip bonding method using the same - Google Patents

Abstract

The present invention relates to a conductive adhesive and a flip chip bonding method using the same, and more particularly, to a conductive adhesive including a non-conductive ball for adjusting the distance between the semiconductor chip and the substrate and a flip chip bonding method using the same. Conductive adhesive according to the invention is a polymer resin having a thermosetting; A low melting solder ball dispersed in the polymer resin; And a nonconductive ball dispersed in the polymer resin and having a melting point higher than that of the low melting solder ball. The present invention includes a non-conductive ball for adjusting the gap between the semiconductor chip and the substrate inside the conductive adhesive, so that the flip chip bonding process can be performed at low cost simply by adjusting the pressure without any sophisticated control technique. It can shorten the processing time and increase the yield of the product.

Low Melting Solder, Conductive Adhesive, ACF, Flip Chip Bonding

Description

Conductive Adhesive and Flipchip Bonding Method Using the Same

The present invention relates to a conductive adhesive and a flip chip bonding method using the same, and more particularly, to a conductive adhesive including a non-conductive ball for adjusting the distance between the semiconductor chip and the substrate and a flip chip bonding method using the same.

Electronic packaging technology is a wide variety of systems fabrication technologies that cover all stages from semiconductor devices to finished products. Recent rapid development of semiconductor technology has already integrated more than one million cells, and non-memory devices tend to have a large number of I / O pins, large die size, high heat dissipation, and high performance. It is developing. However, the relative fact that electronic packaging technology for packaging such devices has not kept pace with the rapid semiconductor industry. Electronic packaging technology is a very important technology that determines the performance, size, price, and reliability of the final electronic product. In particular, electronic packaging technology has recently pursued high performance, ultra small / high density, low power, multifunction, ultra-fast signal processing, and permanent reliability. In electronics, the status is becoming more important.

In response to this trend, a flip chip bonding technique, which is one of techniques for electrically connecting a semiconductor chip to a substrate without using a lead, has recently been in the spotlight. The conductive adhesive used to bond the semiconductor chip to the substrate in the flip chip bonding process is generally composed of a conductive particle solder and an insulating resin having thermosetting and / or thermoplastic.

Recently, in order to strengthen electrical coupling between a semiconductor chip and a substrate, a conductive adhesive including a low melting point solder having a low melting point has been widely used. In the flip chip bonding method, the low melting solder particles are melted and fused with each other as the temperature increases, and the electrodes are electrically connected by wetting between the electrodes of the semiconductor chip and the substrate according to the wettability of the low melting solder. Connect. At this time, in order for the low melting point solder particles to be sufficiently fused and wetted, the interval between the electrode of the semiconductor chip and the electrode of the substrate should be maintained at a constant interval for a predetermined time.

The conventional flip chip bonding method forms a separate stand-off on the substrate surface so that the gap between the semiconductor chip and the substrate can be maintained by the stand off during the fusion and wetting of the low melting point solder. However, the conventional flip chip bonding method has the disadvantage of requiring expensive bonding equipment and sophisticated control techniques for forming standoffs.

An object of the present invention is to provide a conductive adhesive and a flip chip bonding method using the same, which can perform a flip chip bonding process using a low melting point solder at a low cost without high control technology.

One aspect of the present invention for solving the above problems is a polymer resin having a thermosetting; A low melting solder ball dispersed in the polymer resin; And a nonconductive ball dispersed in the polymer resin and having a melting point higher than that of the low melting solder ball.

According to another aspect of the present invention, there is provided a method including providing a conductive adhesive on the substrate, the conductive adhesive comprising a low melting solder ball, a polymer resin, a first nonconductive ball, and a second nonconductive ball; Aligning an electrode of the semiconductor chip with an electrode of the substrate; Applying a predetermined first pressure between the semiconductor chip and the substrate at a first temperature higher than a melting point of the low melting solder ball; And applying a second pressure higher than the first pressure between the semiconductor chip and the substrate at a second temperature higher than the first temperature, wherein the first nonconductive ball is higher than the melting point of the low melting solder ball. It has a melting point, the second non-conductive ball has a melting point higher than the melting point of the low melting point solder ball and provides a flip chip bonding method having a diameter smaller than the diameter of the first non-conductive ball.

Yet another aspect of the present invention provides a method of manufacturing a conductive adhesive comprising: providing a conductive adhesive on the substrate, the conductive adhesive comprising a low melting solder ball, a polymer resin, and a non-conductive ball having a melting point higher than a melting point of the low melting solder ball; Aligning an electrode of the semiconductor chip with an electrode of the substrate; Applying a predetermined pressure between the semiconductor chip and the substrate at a first predetermined temperature higher than a melting point of the low melting solder ball; And applying the predetermined pressure between the semiconductor chip and the substrate at a second temperature higher than the first temperature.

The present invention includes a non-conductive ball for adjusting the gap between the semiconductor chip and the substrate inside the conductive adhesive, so that the flip chip bonding process can be performed at low cost simply by adjusting the pressure without any sophisticated control technique. It can shorten the processing time and increase the yield of the product.

In addition, the present invention can improve the heat generation characteristics of a semiconductor by using a conductive adhesive having excellent thermal conductivity as an isotropic conductive adhesive in a bonding process between semiconductor wafers.

1 is a view showing the configuration of a conductive adhesive according to an embodiment of the present invention.

Referring to FIG. 1, the conductive adhesive 110 further includes a first nonconductive ball 113 and a second nonconductive ball 114 in addition to the low melting point solder ball 111 and the polymer resin 112. In one embodiment, the low melting solder ball 111 may be made of Sn / Bi and the like and may have a melting point of about 140 ° C. In addition, the polymer resin 112 may be made of a polymer insulating resin such as a phenol resin, melanin resin having a thermosetting.

The first non-conductive ball 113 and the second non-conductive ball 114 serve as a standoff for maintaining a constant gap between the electrode of the semiconductor chip and the electrode of the substrate during the fusion and wetting of the low melting point solder ball 111. To this end, the low melting point solder ball 111 is formed of a material that does not melt even at a temperature higher than the melting point, that is, a material having a melting point higher than the melting point of the low melting point solder ball 111. In addition, in order to adjust the gap in two steps in the bonding process, the first non-conductive ball 113 has a diameter larger than that of the second non-conductive ball 114. In one embodiment, the first non-conductive ball 113 may be composed of a polymer such as polymethyl methacrylate (PMMA), polycarbonate, polystyrene, etc., the second non-conductive ball 114 is a first The non-conductive ball 113 may be made of the same material or a glass-type material having a hardness greater than that of the first non-conductive ball 113.

Meanwhile, since the low melting solder ball 111 included in the conductive adhesive 110 has excellent electrical conductivity as well as thermal conductivity, the conductive adhesive 110 may be used in a bonding process between semiconductor wafers by using such a point. In other words, the conductive adhesive 110 may be used as an anisotropic conductive adhesive for electrically connecting the electrode of the semiconductor chip and the electrode of the substrate in the flip chip bonding process, and the thermal conduction between the semiconductor wafers may be facilitated in the bonding process between the semiconductor wafers. It can also be used as an isotropic conductive adhesive to improve the heat generating characteristics of the semiconductor. At this time, the first non-conductive ball 113 and the second non-conductive ball 114 serves to maintain a gap so that the low melting point solder balls 111 can be sufficiently fused and wet between the semiconductor wafers.

2A to 2C are diagrams for describing a flip chip bonding method according to a first embodiment of the present invention, and FIG. 2D is a diagram illustrating temperature and pressure according to time in a flip chip bonding method according to a first embodiment of the present invention. Graph showing change.

Referring to FIG. 2A, the conductive adhesive 210 may mix a low melting solder ball 211, a first nonconductive ball 213, and a second nonconductive ball 214 with a polymer resin 212 to form a film or pastry. ) Is formed between the semiconductor chip 220 and the substrate 230 to be bonded.

After aligning the semiconductor chip 220 and the substrate 230 using flip chip bonding equipment and applying pressure between the semiconductor chip 220 and the substrate 230, the first vision having the largest diameter inside the conductive adhesive 210 is formed. Pressure is applied to the conductive ball 213. Accordingly, the distance between the semiconductor chip 220 and the substrate 230 is determined according to the elasticity of the first nonconductive ball 213 and the pressure between the semiconductor chip 220 and the substrate 230.

At this time, since the diameter of the second non-conductive ball 214 is smaller than the diameter of the first non-conductive ball 213, the second non-conductive ball 214 is until the first non-conductive ball 213 is deformed It is not affected by the pressure applied between the semiconductor chip 220 and the substrate 230.

2B and 2D, when the temperature increases to pass the first temperature, which is the melting point of the low melting solder ball 211 at time 1, the low melting solder balls 211 fuse with each other to form the semiconductor chip 220 and the substrate 230. It is formed in the shape of a concave lens between the electrodes (221, 231). In one embodiment, when the low melting solder ball 211 is made of Sn / Bi, the first temperature may be 139 ° C to 141 ° C.

At this time, since the polymer resin 212 maintains a low viscosity of several hundred cps, the low melting point solder ball 211 does not affect the fusion and wetting. In addition, since the first nonconductive ball 213 and the second nonconductive ball 214 are made of a polymer having a very poor wettability property with respect to the low melting point solder ball 211, the first nonconductive ball 213 and the second The non-conductive ball 214 also does not affect the fusion and wetting of the low melting solder ball 211.

Thereafter, the temperature and pressure increase to reach the first pressure and the second temperature at time 2, and the first pressure and the second temperature are maintained for a predetermined time (time 2 to time 3). At this time, the first pressure is a pressure lower than the deformation pressure of the first non-conductive ball 213. Here, the deformation pressure refers to the pressure at which deformation of the structure starts to occur when pressure is applied to the structure of a certain form. In one embodiment, the first pressure is between 100 g / cm ² and 300 g / cm ² and the second temperature is between 155 ° C. and 165 ° C.

The gap between the semiconductor chip 220 and the substrate 230 is determined by the elasticity and the first pressure of the first non-conductive ball 213 serving as a standoff, and this gap is sufficient fusion of the low melting solder ball 211. And for a predetermined time (time 2 to time 3) for the wetting. In one embodiment, the first pressure and the second temperature are maintained for approximately 70 seconds for sufficient fusion and wetting of the low melting solder ball 211.

2C and 2D, the pressure is increased after time 3 to reach the second pressure at time 4. At this time, the second pressure is higher than the deformation pressure of the first non-conductive ball 213 and lower than the deformation pressure of the second non-conductive ball 214. In one embodiment, the second pressure is between 300 g / cm ² and 600 g / cm ² .

As the second pressure is applied, the gap between the semiconductor chip 220 and the electrodes 221 and 231 formed on the surface of the substrate 230 decreases, and the second pressure is applied to the first nonconductive ball 213 and the second nonconductive ball ( The distance between the semiconductor chip 220 and the substrate 230 is determined by being dispersed in 214. The low melting solder balls 211 fused and wetted at the interval determined by the first pressure are formed in a convex lens shape as the interval is narrowed by the second pressure. Accordingly, the bonding area between the low melting solder ball 211 and the electrodes 221 and 231 may be maximized.

At the same time, the temperature increases with increasing pressure, reaching the third temperature at time 4. Here, the third temperature is a temperature higher than the temperature at which the curing reaction of the polymer resin 212 starts, that is, the thermosetting temperature of the polymer resin 212. When the temperature is decreased after maintaining the third temperature for a predetermined time (time 4 to time 5), the polymer resin 212 is cured at least about 70% to exhibit about 90% of the thermomechanical properties of the fully cured state. In one embodiment, the third temperature is between 179 ° C and 181 ° C. When the degree of curing of the polymer resin 212 is required to be 95% or more, an additional curing process of applying an atmospheric pressure or a second pressure at the third temperature may be performed.

A second embodiment using a conductive adhesive that does not include the first non-conductive ball to reduce the complexity of the process using two stages of pressure will now be described with reference to FIGS. 3A-3C.

3A to 3B are diagrams for describing a flip chip bonding method according to a second embodiment of the present invention, and FIG. 3C is a view illustrating temperature and pressure according to time in a flip chip bonding method according to a second embodiment of the present invention. Graph showing change.

Referring to FIG. 3A, the conductive adhesive 310 is manufactured by mixing the low melting solder ball 311 and the second non-conductive ball 313 with the polymer resin 312 in the form of a film or pastry, and bonding the semiconductor chip ( 320 is positioned between the substrate 330 and the substrate 330.

After the semiconductor chip 320 and the substrate 330 are aligned using flip chip bonding equipment, pressure is applied to the second non-conductive ball 313 when pressure is applied between the semiconductor chip 320 and the substrate 330. The distance between the semiconductor chip 320 and the substrate 330 is determined by the elasticity of the second nonconductive ball 313 and the pressure between the semiconductor chip 320 and the substrate 330.

Referring to FIGS. 3B and 3C, as the temperature is increased while maintaining the second pressure, the viscosity of the polymer resin 312 is lowered to several hundred cps, and the temperature melts in the low melting point solder ball 311 over time 1. As the temperature rises above the first temperature, the low melting point solder ball 311 changes from a solid state to a liquid state. Here, the second pressure is a pressure lower than the deformation pressure of the second nonconductive ball 313 similarly to the second pressure of the first embodiment. In one embodiment, the second pressure is between 300 g / cm ² and 600 g / cm ² .

At time 2 the temperature reaches the second temperature and is maintained for a predetermined time (time 2 to time 3). Accordingly, the low melting point solder balls 311 are fused with each other to form convex lenses between the semiconductor chip 320 and the electrodes 321 and 331 of the substrate 330. In one embodiment, the second temperature is between 155 ° C and 165 ° C.

Thereafter, the temperature increases again to reach the third temperature at time 4. Here, the third temperature is a temperature higher than the thermosetting temperature of the polymer resin 312 as in the third temperature of the first embodiment. If the temperature is decreased after maintaining the third temperature for a predetermined time (time 4 to time 5), the polymer resin 312 is cured at least about 70% to exhibit about 90% of the thermomechanical properties of the fully cured state. In one embodiment, the third temperature is between 179 ° C and 181 ° C. When the degree of curing of the polymer resin 312 is required to be 95% or more, an additional curing process may be performed to apply atmospheric pressure or second pressure at the third temperature.

Meanwhile, even when the conductive adhesive according to the embodiment of the present invention is used as an isotropic conductive adhesive in the semiconductor wafer bonding process, the gap between the semiconductor wafers needs to be maintained for a predetermined time so that the low melting solder balls are sufficiently fused and wetted between the semiconductor wafers. have. Accordingly, the other bonding processes except for the alignment of the semiconductor chip and the substrate in the bonding methods described with reference to FIGS. 2A through 3C may be equally applied to the semiconductor wafer bonding process.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

1 is a view showing the configuration of a conductive adhesive according to an embodiment of the present invention.

2A to 2C are diagrams for describing a flip chip bonding method according to a first embodiment of the present invention.

2D is a graph showing changes in temperature and pressure with time in the flip chip bonding method according to the first embodiment of the present invention.

3A to 3B illustrate a flip chip bonding method according to a second embodiment of the present invention.

3C is a graph showing changes in temperature and pressure with time in the flip chip bonding method according to the second embodiment of the present invention.

Claims (17)

Thermosetting polymer resins; A low melting solder ball dispersed in the polymer resin; And Non-conductive ball dispersed in the polymer resin and having a melting point higher than the melting point of the low melting solder ball Conductive adhesive comprising a. The method of claim 1, Wherein the nonconductive ball is comprised of a first nonconductive ball and a second nonconductive ball having a diameter smaller than the diameter of the first nonconductive ball. The method of claim 2, And the hardness of the second nonconductive ball is greater than the hardness of the first nonconductive ball. The method of claim 2 or 3, The first nonconductive ball is made of a polymeric material, And the second nonconductive ball is made of the same material as the first nonconductive ball or a material of glass type. The method of claim 4, wherein The first nonconductive ball is a conductive adhesive consisting of polymethyl methacrylate (PMMA), polycarbonate, or polystyrene. In the flip chip bonding method for bonding a semiconductor chip to a substrate, (a) providing a conductive adhesive on the substrate comprising a low melting solder ball, a polymer resin, a first nonconductive ball and a second nonconductive ball; (b) aligning an electrode of the semiconductor chip with an electrode of the substrate; (c) applying a first predetermined pressure between the semiconductor chip and the substrate at a first temperature higher than the melting point of the low melting solder ball; And (d) applying a second pressure higher than the first pressure between the semiconductor chip and the substrate at a second temperature higher than the first temperature Wherein the first nonconductive ball has a melting point higher than the melting point of the low melting point solder ball, and the second nonconductive ball has a melting point higher than the melting point of the low melting point solder ball and is larger than a diameter of the first nonconductive ball. Flip chip bonding method having a small diameter. The method of claim 6, And a hardness of the second nonconductive ball is greater than a hardness of the first nonconductive ball. The method of claim 6, And wherein the first pressure is less than the strain pressure of the first nonconductive ball. The method of claim 6, And the second pressure is greater than or equal to the deformation pressure of the first nonconductive ball and less than the deformation pressure of the second nonconductive ball. The method of claim 6, The polymer resin is a thermosetting resin, And the second temperature is equal to or greater than the thermosetting temperature of the polymer resin. The method of claim 6, The first temperature is 155 ℃ to 165 ℃, the second temperature is 179 ℃ to 181 ℃ flip chip bonding method. The method of claim 6, The first pressure is 100 g / cm ² to 300 g / cm ² , The second pressure is 300 g / cm ² to 600 g / cm ² Flip chip bonding method. In the flip chip bonding method for bonding a semiconductor chip to a substrate, (a) providing a conductive adhesive on the substrate comprising a low melting solder ball, a polymer resin and a non-conductive ball having a melting point higher than the melting point of the low melting solder ball; (b) aligning an electrode of the semiconductor chip with an electrode of the substrate; (c) applying a predetermined pressure between the semiconductor chip and the substrate at a predetermined first temperature higher than the melting point of the low melting solder ball; And (d) applying the predetermined pressure between the semiconductor chip and the substrate at a second temperature higher than the first temperature Flip chip bonding method comprising a. The method of claim 13, And said predetermined pressure is less than a strain pressure of said nonconductive ball. The method of claim 13, The polymer resin is a thermosetting resin, And the second temperature is equal to or greater than the thermosetting temperature of the polymer resin. The method of claim 13, The first temperature is 155 ℃ to 165 ℃, the second temperature is 179 ℃ to 181 ℃ flip chip bonding method. The method of claim 13, The predetermined pressure is 300 g / cm ² to 600 g / cm ² Flip chip bonding method.

Images