TWI567840B - Fabrication process and its welding method - Google Patents

Description

Flip chip packaging process and welding method thereof

The invention belongs to the technical field of flip chip packaging, in particular to providing a flip chip packaging process and a soldering method thereof, and precisely controlling the spraying range and the spraying dose of the flux through the 3D array nozzle printing device. Minimize the amount of flux remaining after metal welding, supplemented by a pressure tank to keep a limited amount of flux, so that the flux can be accelerated in the primer without solvent flushing and other flux removal. It effectively simplifies the flip chip packaging process and greatly improves production efficiency.

In the ever-changing generation of technology, high-tech electronic technology has come out one after another, making more humanized and functional electronic products constantly innovating and designing towards light, thin, short and small trends. In order to achieve the above requirements, it is necessary to meet the requirements of high-speed processing, multi-function, integration, small size, light weight, and low cost of electronic components. Therefore, the integrated circuit packaging technology is also becoming miniaturized and high. Density development. Among various packaging technologies, the Flip Chip package (F/C package) and other high-density integrated circuit packaging technologies that are electrically connected by bumps or solder balls are available. Shortening the wiring length and thus the signal transmission speed has gradually become the mainstream of high-density packaging.

Referring to FIG. 1 , a flow chart of a conventional flip chip packaging process includes the steps of: a. (Step 101) preparing a wafer having an active surface on which a plurality of conductive bumps are disposed. b. (Step 102) A circuit substrate is prepared, wherein the circuit substrate is provided with a bearing surface, and a bonding pad is disposed on each of the conductive bumps.

c. (Step 103) Filling the bearing surface of the circuit substrate with flux, and immersing each of the conductive bumps and the pad surface with Flux Dipping. d. (Step 104) Flip Chip and position the wafer so that the active surface of the wafer is disposed toward the bearing surface of the circuit substrate, and each of the conductive bumps is respectively bonded to each of the pads by the aid of a flux. Then, a reflow soldering operation is performed to form a flip chip package structure, so that signal transmission can be performed between the circuit substrate and the wafer.

e. (Step 105), performing flux removal (Flux Residue) operation. use The flux remaining after the flux is reflowed will react with the surrounding materials to cause corrosion. Therefore, it is necessary to remove the flux residue to remove the residual flux, so as to avoid corrosion of the flip chip package structure in the future. The execution process is: (e1) rinsing the flux remaining on the flip chip package structure by spraying with a solvent. (e2) Performing a further rinsing procedure on the flip chip package structure, for example, using deionized water for rinsing. (e3) performing a drying process on the flip chip package structure, for example, using a centrifugal device to remove residual deionized water by centrifugal force, or using a baking device to evaporate residual deionized water by high temperature baking. .

f. (Step 106), performing a plasma cleaning operation on the flip chip package structure, thereby improving the cleanliness and wettability of the surface of the flip chip package structure, and effectively improving the primer (eg, epoxy resin) in the next step. The filling is done to reduce bubble generation.

g. (Step 107), using a glue tool to perform a glue filling process, filling a primer between the wafer and the circuit substrate.

h. (Step 108), the flip chip package structure that completes the glue filling process is moved into an oven, and the primer is subjected to a heat curing process to completely cure.

As described above, after the reflowing operation is performed in step 104, since the flux residue is distributed over the bearing surface of the circuit substrate, complicated cleaning flux residue must be performed in step 105, resulting in a large amount of cleaning labor, equipment, site, material (water) , solvent) and energy consumption, and make the flip chip packaging process become tedious, seriously reducing production efficiency; in step 107, if the speed of the filling material flow is not properly controlled, it is easy to wrap the air in the primer, resulting in a bottom Air bubbles are generated in the glue, and if the cleaning operation is not completed in step 105, if the cleaning operation is not complete, the speed of the filling material may be uncontrollable and the air may be coated in the primer to form bubbles; or due to the increasingly uneven spacing of the pads The miniaturization, the bonding gap between the flip chip and the circuit substrate is also increasingly reduced, so that the capillary phenomenon of the filled material is not easy to flow, and it takes a longer time to cover the space under the wafer, and also the difficulty of covering the space under the wafer. The increase in degree leads to the presence of bubbles in the filler material, which makes the conductivity or thermal conductivity poor, and even affects the structure of the flip chip package. Lifetime; due to the increasingly finer pitch of the pad, the bonding gap between the wafer and the circuit substrate is also increasingly reduced, and the flux residue is interposed in the gap between the wafer, each of the conductive bumps and the circuit substrate, and the flux residue is removed using step 105. It has been difficult to remove the flux residue and it is necessary to improve it.

Therefore, in view of the problems existing in the above-mentioned conventional flip chip packaging process, how to develop a packaging process that is more ideal and practical, and that combines economic benefits, is actively related to the relevant industry. The goal and direction of research and development breakthroughs.

In view of this, the inventor has been engaged in the manufacturing development and design experience of related products for many years. After detailed design and careful evaluation, the inventor has finally obtained the practical invention.

In the conventional flip chip packaging process, since the flux residue is spread over the bearing surface of the circuit substrate, complicated flux residue removal operation must be performed, and the production efficiency is seriously reduced; the presence of bubbles in the filler material makes the conductivity or thermal conductivity poor. It even affects the service life of the flip chip package structure; the flux residue is mixed in the gap between the wafer, each of the conductive bumps and the circuit substrate, and the flux residue is removed, and it is difficult to remove the flux residue, which is improved. necessary.

In order to improve the above problems, the present invention provides a soldering method for a flip chip packaging process for manufacturing a flip chip package structure, wherein the flip chip package structure includes a wafer and a circuit substrate. The soldering method comprises the steps of: a. providing the wafer, wherein the wafer is provided with an active surface, and the active surface is provided with a plurality of conductive bumps, the conductive bumps being tin, silver, copper, gold, indium, lead, At least one of bismuth, zinc, and nickel, or other materials that are good for welding. The circuit substrate is provided, wherein the circuit substrate is provided with a bearing surface, and a soldering pad is disposed on each of the conductive bumps on the bearing surface.

c. Using a 3D Matrix Inkjet Printing device to precisely spray the flux (Flux) on the surface of each pad, and accurately control the flux through the programming of the 3D array nozzle printing device The spray range and the spray dose can effectively avoid spraying outside the solder pad area, wherein the flux is a liquid flux, and the liquid flux has a viscosity of 1 centipoise (cps, centipoises) to 100%. The scope of the mooring is mainly to remove the oxides on the surface of the solder and the surface of the soldered material, to achieve the necessary cleanliness of the soldered surface, to prevent re-oxidation of the surface during soldering, to reduce the surface tension of the liquid solder, and to obtain the wettability. improve.

d. Flip Chip and position the wafer so that the active surface of the wafer is disposed toward the bearing surface of the circuit substrate, and each of the conductive bumps is bonded to each of the pads via a flux. e. Finally, a metal welding operation is performed, so that the wafer is electrically and structurally connected to each of the pads on the circuit substrate by the conductive bumps to form the chip seal. The structure is configured to enable signal transmission between the circuit substrate and the wafer.

In the foregoing, the metal welding operation is to perform metal welding on the aligned wafer and the circuit substrate and each of the conductive bumps, so that each of the conductive bumps in the heat-melted or semi-molten state is bonded to the soldering surface of the circuit substrate. pad.

In the foregoing, the spraying of the flux uses the 3D array nozzle printing device to design a graphic of the computer, by predefining the coordinates of the plurality of nozzles and accurately positioning the positions of the pads on the circuit substrate and the desired spraying. Covering the range, and the 3D array nozzle printing device stacks a plurality of flux spray coatings in the form of 3D patterns.

The invention further provides a flip chip packaging process, the steps comprising: a. preparing a wafer, wherein the wafer is provided with an active surface, the active surface is provided with a plurality of conductive bumps, the conductive bumps are tin, silver and copper At least one of gold, indium, lead, antimony, zinc, and nickel, or other materials that are good for welding. b. Preparing a circuit substrate, wherein the circuit substrate is provided with a bearing surface, and a bonding pad is disposed on each of the conductive bumps.

c. spraying a flux onto each surface of the pad by using a 3D array nozzle printing device, and accurately setting the spraying range and the spraying amount of the flux through the programming of the 3D array nozzle printing device. Effectively avoid spraying over the area of each pad.

d. flipping the wafer to the ground so that the active surface of the wafer is disposed toward the bearing surface of the circuit substrate, and each of the conductive bumps is respectively joined to each of the pads via a flux, and then a metal welding operation is performed to make the wafer The conductive bumps are electrically and structurally connected to the pads on the circuit substrate to form a flip chip package structure, so that signal transmission can be performed between the circuit substrate and the wafer. e. Performing a plasma cleaning operation on the flip chip package structure to improve the cleanliness and wettability of the surface of the flip chip package structure, thereby effectively improving product reliability.

f. using a glue tool to fill a primer between the wafer and the circuit substrate, the primer coating each of the conductive bumps for providing thermal stress and mechanical stress between the wafer and the circuit substrate The buffering function, and the trace flux residue remaining after performing the metal welding operation can be dissolved in the primer.

g. moving the flip chip package structure of the filling process into a pressure-resistant chamber, applying pressure to dissolve the flux residue remaining after the metal welding operation, and defoaming and curing the primer. In order to eliminate the bubble at the junction of the primer and the circuit substrate, the bubble at the junction of the primer and the wafer, and the bubble inside the primer, and heat the baking to make the primer completely Cured.

In the foregoing, the spraying of the flux uses the 3D array nozzle printing device to design a graphic of the computer, by predefining the coordinates of the plurality of nozzles and accurately positioning the positions of the pads on the circuit substrate and the desired spraying. Covering the range, and the 3D array nozzle printing device stacks a plurality of flux spray coatings in the form of 3D patterns.

In the foregoing, the flux is a liquid flux having a viscosity in the range of 1 centipoise to 100 centipoise.

In the foregoing, the primer component is an epoxy resin (Epoxy Resin) doped with a filler such as cerium oxide (S _i O ₂ ) powder.

In the foregoing, the method of filling the primer mainly uses the dispensing tool to point the liquid filling material to the edge of the wafer, and the filling material flows to the lower side of the wafer due to capillary phenomenon, and the wafer can be filled and A gap between the circuit boards.

In the foregoing, the pressure in the pressure chamber is set in a range of 10 ^-3 Torr to 30 atm, and the temperature in the pressure tank is set in the range of 20 to 500 degrees Celsius.

In the foregoing, the pressure applied to dissolve the flux residue in the primer and defoam and cure the primer is presented in an oscillating manner, and the range of variation is set to 10 ^-3 Torr to 30 atmosphere (atm) range.

The flip chip packaging process and the soldering method thereof of the invention accurately control the spraying range and the spraying dose of the flux by the 3D array nozzle printing device, so that the flux residue remaining after the metal welding operation is extremely small, supplemented by The pressure-resistant chamber carries the limited flux remaining in the flux, so that the flux can be accelerated to dissolve in the primer without solvent washing and the like to remove the flux residue, which effectively simplifies the flip chip packaging process and greatly improves the production efficiency; The trace amount of the flux residue can be dissolved in the primer, completely eliminating the trouble of removing the flux residue, and effectively improving the reliability of the product; the bubble is completely separated by the pressure difference formed by the pressure chamber through the pressure change. Extrusion and discharge completely solve the problem of bubble residue in the flip chip package structure.

The above described objects, structures, and features of the present invention will be apparent from the following description of the preferred embodiments of the invention.

[study]

101-108‧‧‧Steps

〔this invention〕

201-207‧‧‧Steps

300‧‧‧Flip chip package structure

310‧‧‧ wafer

311‧‧‧Active surface

320‧‧‧Electrical bumps

330‧‧‧Line substrate

331‧‧‧bearing surface

332‧‧‧ solder pads

340‧‧‧3D array nozzle printing device

341‧‧‧flux spray coating

350‧‧‧ nozzle

410‧‧‧Bottom glue

510‧‧ ‧ Pressure tank

Figure 1 is a flow chart of a conventional flip chip packaging process.

2 is a flow chart of a flip chip packaging process of a preferred embodiment of the present invention.

3A to 3F are schematic cross-sectional views showing the flip chip packaging process of FIG.

Referring to FIG. 2 and FIGS. 3A to 3F, wherein FIG. 2 is a flow chart of a flip chip packaging process according to a preferred embodiment of the present invention, and FIGS. 3A to 3F are cross-sectional views of the flip chip packaging process. The present invention provides a flip chip packaging process, the steps of which include: a. (Step 201) preparing a wafer 310, wherein the wafer 310 is provided with an active surface 311 on which a plurality of conductive bumps 320 are disposed ( As shown in FIG. 3A, the conductive bumps 320 are solder bumps formed by a general bumping process, and are composed of tin, silver, copper, gold, indium, lead, and antimony. At least one of zinc, nickel, or other materials that are good for welding.

b. (Step 202) Preparing a circuit substrate 330, wherein the circuit substrate 330 is provided with a bearing surface 331, and a bonding pad 332 is disposed on each of the conductive bumps 320 corresponding to each of the conductive bumps 320 (as shown in FIG. 3B). .

c. (Step 203) spraying a flux onto the surface of each of the pads 332 by using a 3D array nozzle printing device 340, and precisely controlling the spraying of the flux through the programming of the 3D array nozzle printing device 340. The range and the spraying dose are effective to avoid the overflow of the flux sprayed on the surface of each of the pads 332. The spraying of the flux is defined by using the 3D array nozzle printing device 340 to define the graphic of the computer. The coordinates of the plurality of nozzles 350 accurately position the respective pads 332 on the circuit substrate 330 and the range of the desired spray, and the 3D array nozzle printing device 340 stacks a plurality of simulated 3D graphics layer by layer. Flux spray coating 341 (as shown in Figure 3C), wherein the flux is a liquid flux, the main function of which is to remove the oxides from the solder and the surface of the soldered base material to achieve the necessary cleanliness of the solder surface. Prevents reoxidation of the surface during soldering, reduces the surface tension of the liquid solder, and significantly improves the wetting performance.

d. (Step 204) flipping the wafer 310 into position to make the wafer 310 The active surface 311 is disposed toward the bearing surface 331 of the circuit substrate 330, and each of the conductive bumps 320 is respectively soldered to the pads 332 (as shown in FIG. 3D), and then a metal bonding operation is performed to make the wafer The conductive bumps 320 are electrically and structurally connected to the pads 332 on the circuit substrate 330 to form a flip chip package structure 300, so that signals can be made between the circuit substrate 330 and the wafer 310. Transmission, the metal welding (for example, reflow) performed here is to perform metal welding of the aligned wafer 310 and the circuit substrate 330 and each of the conductive bumps 320 and each of the pads 332 so as to be in a heated or semi-molten state. Each of the conductive bumps 320 is bonded to each of the pads 332 on the bearing surface 331 of the circuit substrate 330.

e. (Step 205) Perform a plasma cleaning operation on the flip chip package structure 300 to improve the cleanliness and wettability of the surface of the flip chip package structure 300, thereby effectively improving product reliability.

f. (Step 206) filling a primer 410 (shown in FIG. 3E) between the wafer 310 and the circuit substrate 330 using a glue tool, the primer 410 coating each of the conductive bumps 320 for The function of providing thermal buffer and mechanical stress between the wafer 310 and the circuit substrate 330 is provided, wherein the primer 410 is, for example, an epoxy resin doped with a filler such as cerium oxide (S _i O ₂ ) powder. It is miscible with the trace flux residue remaining after performing the metal welding operation. The liquid filling method performed here mainly uses the dispensing tool to point the liquid filling material to the edge of the wafer 310, and the filling material flows to the lower side of the wafer 310 due to capillary phenomenon, and can be filled on the wafer 310 and A gap between the circuit substrates 330.

g. (Step 207) The flip chip package structure 300 that completes the glue filling process is moved into a pressure-resistant chamber 510, so that the primer 410 dissolves the flux residue and removes various bubbles and curing procedures (as shown in FIG. 3F). ), the air bubbles at the junction of the primer 410 and the circuit substrate 330, the bubbles at the junction of the primer 410 and the wafer 310, and the bubbles inside the primer 410 are removed, and the primer 410 is heated and baked. It is fully cured, wherein the pressure in the pressure chamber 510 is set in the range of 10 ^-3 Torr to 30 atm, and the temperature is set in the range of 20 to 500 degrees Celsius. During the bubble process, the pressure system exhibits an oscillating change, and the bubble is completely squeezed out from the periphery of the primer 410 by the pressure difference formed by the change in pressure.

The flip chip packaging process of the present invention and the soldering method thereof are carried out in step 203 The 3D array nozzle printing device 340 accurately controls the spraying range and the spraying amount of the flux, so that the flux residue remaining after performing the metal welding operation in step 204 is extremely small, and the trace amount of the flux residue can be in the step. In 207, it is dissolved in the primer 410. Compared with the conventional flip chip packaging process, since the flux residue is distributed over the bearing surface of the circuit substrate, the flux residue must be removed by solvent rinsing, etc., and the present invention effectively simplifies the flip chip packaging process. , greatly improving production efficiency.

In the flip chip packaging process of the present invention and the soldering method thereof, the flux residue remaining after the metal fusion is performed in step 204 is extremely small, and the trace amount of the flux residue may be dissolved in the primer 410 in step 207. Therefore, there is no trouble of removing the flux residue. Compared with the conventional flip chip packaging process, the bonding gap between the wafer and the circuit substrate is increasingly reduced due to the increasingly finer pitch of the pad, and the flux residue is mixed with the wafer and each of the conductive bumps. In the gap between the block and the circuit substrate, the flux residue is used to remove the flux residue, and it has been difficult to remove the flux residue. The present invention effectively improves the reliability of the product in the flip chip packaging process.

In the flip chip packaging process and the soldering method thereof, in step 207, the bubble is completely squeezed out by the pressure difference formed by the pressure change of the pressure chamber 510, which is compared with the conventional flip chip packaging process. The pad pitch is increasingly finer, and the bonding gap between the flip chip and the circuit substrate is also increasingly reduced, so that the difficulty of filling the space under the wafer by the filled adhesive material increases, and the existence of bubbles in the rubber filling material is completely solved by the present invention. The problem of air bubbles remaining in the flip chip package structure.

The present invention has been described with reference to the preferred embodiments of the present invention. However, those skilled in the art can change and modify the present invention without departing from the spirit and scope of the invention. Such changes and modifications shall be covered in the scope defined by the following patent application.

201-207‧‧‧Steps

Claims (9)

A flip chip packaging process, the steps comprising: (a) preparing a wafer, the wafer is provided with an active surface, the active surface is provided with a plurality of conductive bumps; (b) preparing a circuit substrate, the circuit substrate is provided with a bearing surface a solder pad is disposed on each of the conductive bumps on the bearing surface; (c) a flux is sprayed onto each of the pads by a 3D array nozzle printing device, and the device is printed by the 3D array nozzle Programming, controlling the spray range and the spray dose of the flux; (d) flipping the wafer to the position so that the active surface of the wafer is disposed toward the bearing surface of the circuit substrate, and each of the conductive The bumps are respectively connected to the pads via the flux, and then a metal fusing operation is performed to electrically and structurally connect the conductive bumps to the pads on the circuit substrate. a flip chip package structure; (e) using a glue tool to fill a gap between the wafer and the circuit substrate, the primer coating each of the conductive bumps for generating between the wafer and the circuit substrate Thermal stress and machinery The stress provides a buffering function; (f) the flip chip package structure that completes the filling process is moved into a pressure-resistant chamber, and pressure is applied to dissolve the flux residue remaining after the metal welding operation in the primer and The primer is subjected to a defoaming and curing process to eliminate bubbles at the junction of the primer and the circuit substrate, bubbles at the junction of the primer and the wafer, and bubbles inside the primer, and heat the primer. Bake it to fully cure. The flip chip packaging process of claim 1, wherein the flux is a liquid flux having a viscosity of from 1 centipoise (centipoises) to 100 centipoise. The flip chip packaging process of claim 1, wherein the 3D array nozzle printing device defines a graphic of the computer by pre-defining coordinates of the plurality of nozzles and accurately positioning each pad on the circuit substrate. The position and the range of the desired spray, and the 3D array nozzle printing device layer-by-layer stacks a plurality of flux spray coatings that follow the 3D pattern. The flip chip packaging process of claim 1, wherein the primer component is epoxy resin (Epoxy Resin). The flip chip packaging process of claim 1, wherein the method of filling the primer uses the dispensing tool to point the liquid filling material to the edge of the wafer, and the filling material flows to the edge due to capillary phenomenon. The wafer is underneath and fills the gap between the wafer and the circuit substrate. The flip chip packaging process of claim 1, wherein the pressure in the pressure chamber is set in a range of 10 ^-3 Torr to 30 atmospheres (atm). The flip chip packaging process of claim 1, wherein the pressure applied to dissolve the flux residue in the primer and defoam and cure the primer is presented in an oscillating manner, the change The range is set between 10 ^-3 Torr to 30 atmospheres (atm). The flip chip packaging process of claim 1, wherein the temperature in the pressure chamber is set between 20 degrees Celsius and 500 degrees Celsius. The flip chip packaging process of claim 1, wherein the step (d) and the step (e) further comprise performing a plasma cleaning operation on the flip chip package structure, thereby improving the flip chip package structure. The cleanliness and wettability of the surface enhance the reliability of the product.