Patent ID: 12237297

DETAILED DESCRIPTION

Hereinafter, example embodiments will be explained in detail with reference to the accompanying drawings.

FIG.1is a cross-sectional view illustrating a solder reflow apparatus in accordance with example embodiments.FIG.2is a side view illustrating the solder reflow apparatus ofFIG.1.FIG.3Ais a perspective view illustrating a closed state of a first mesh plate of the solder reflow apparatus ofFIG.1, andFIG.3Bis a perspective view illustrating an open state of the first mesh plate ofFIG.3A.FIG.4is a plan view illustrating a first cover member of the first mesh plate ofFIG.1.FIG.5is a plan view illustrating a second cover member of the second mesh plate ofFIG.1.FIG.6is a graph illustrating a temperature profile in a vapor generating chamber ofFIG.1.FIG.7is a graph illustrating a soldering profile in the vapor generating chamber ofFIG.1.

InFIGS.1to7, a solder reflow apparatus10may include a vapor generating chamber100(shown inFIG.2), a heater110, a substrate stage200, and a temperature gradient regulator300. In addition, the solder reflow apparatus10may further include a lifting driver configured to raise and lower the substrate stage200, an opening/closing driver configured to open and close the temperature gradient regulator300, and a temperature sensing portion configured to monitor temperature in the vapor generating chamber100. In example embodiments, the solder reflow apparatus10may be a vapor phase soldering apparatus configured to solder a solder paste by saturated vapor heated in the vapor generating chamber100.

The vapor generating chamber100may include a lower reservoir having an oven shape to accommodate a heat transfer fluid F and to provide a space101filled with vapor generated directly above the fluid when the fluid F is boiling. The vapor generating chamber100may extend in a vertical direction (Z direction) by a predetermined height. In the vapor generating chamber100, the heat transfer fluid may boil and the vapor may rise to the top, condense back to the liquid state at the top, and may flow back to the reservoir at the bottom.

The pressure inside the vapor generating chamber100may be maintained at atmospheric pressure. Alternatively, the vapor generating chamber100may be connected to an exhaust device such as a vacuum pump to adjust the pressure inside the vapor generating chamber100. The pressure inside the vapor generating chamber may be maintained at a predetermined pressure in order to change the boiling point of the heat transfer fluid or soldering environments.

The heat transfer fluid F may be a chemical material that is selected to provide the vapor necessary for vapor phase soldering. The heat transfer fluid may be selected in consideration of boiling point, environmental influences, and corrosiveness of the generated vapor. The heat transfer fluid may include an inert organic liquid. For example, the heat transfer fluid may include a Perfluoropolyether (PFPEs)-based Galden solution. The boiling point of the Galden solution may be 230° C.

The heater110may heat the heat transfer fluid F accommodated in the vapor generating chamber100to generate saturated vapors. The heater110may include an electrical resistor that is immersed in the heat transfer fluid F on the bottom of the vapor generating chamber100. Alternatively, the heater110may include a resistor in the form of a coil surrounding the reservoir tank. In addition or alternatively, a heater as a portion of a temperature control mechanism may be installed on a sidewall of the vapor generating chamber100to control the temperature of the vapor generating chamber100during a reflow process.

The substrate stage200may support an article S on which a solder process is performed in the vapor generating chamber100. The substrate stage200may include a mesh type support structure for supporting the article S. The mesh type support structure may include support wires202that define a plurality of openings201through which the vapor moves. For example, the article S may include a substrate20on which an electronic component30is mounted via a solder40.

The substrate stage200may be configured to be movable upward or downward within the vapor generating chamber100. The lifting driver for moving the substrate stage200upward and downward may include various types of actuators such as a transfer rail, a transfer screw, a transfer belt, etc. Both end portions of the substrate stage200may be supported by transfer rods210, respectively, and the substrate stage200may be moved up and down by the lifting driver.

As illustrated inFIG.2, the article S for soldering may be transferred into the vapor generating chamber100through a gate102of the vapor generating chamber100, and the article S may be loaded on the substrate stage200by a transfer mechanism104such as a guide rail or a transport pusher.

After the article S is loaded, the Galden solution F may be heated by the heater110and start to boil. The saturated vapor from the Galden solution may be distributed within the space101of the vapor generating chamber100. At this time, the density of the saturated vapor may vary depending on the height, and thus a temperature gradient may be formed.

In example embodiments, the temperature gradient regulator300(shown inFIG.1) may include at least one mesh plate (e.g., the first plate310, the second plate320) that extends in a horizontal direction (XY direction) within the vapor generating chamber100. The mesh plate may have a plurality of openings through which the vapor is allowed to move. The temperature gradient regulator300may divide the space into an upper zone and a lower zone with the mesh plate interposed therebetween, and may adjust the density of the vapor in the upper zone and the lower zone. Accordingly, the upper zone may be controlled to be maintained at a first temperature and the lower zone may be controlled to be maintained at a second temperature higher than the first temperature.

The temperature gradient regulator300may include the first plate310and the second plate320sequentially disposed from the bottom of the vapor generating chamber100. The first plate310and the second plate320may include a plurality of cover members that are operable in a retractable manner to allow movement of the substrate stage200. In addition or alternatively, the first plate310and the second plate320may be spaced apart from an inner wall of the vapor generating chamber100by a predetermined distance.

As illustrated inFIGS.2,3A, and3B, the first plate310may include a pair of first cover members312spaced apart from each other and second cover members314respectively installed to be movable on the first cover members312to allow the movement of the substrate stage200. The first plate310may be installed at a first height from the bottom of the vapor generating chamber100, and the second plate320may be installed at a second height higher than the first height from the bottom of the vapor generating chamber100.

The opening/closing driver for opening/closing operations of the first plate310may include an actuator configured to move the second cover member314on the first cover member312in a first direction (Y direction). For example, the actuator may include a linear actuator such as a Linear Motion (LM) guide or a ball screw.

A pair of the second cover members314may move in a direction to get closer to each other to a closed position, to block the movement of the substrate stage200therebetween. A pair of the second cover members314may move away from each other to an open position, to allow the movement of the substrate stage200therebetween.

Similarly, the second plate320may include a pair of third cover members322spaced apart from each other and fourth cover members324respectively installed to be movable on the third cover members322to allow the movement of the substrate stage200.

The opening/closing driver for opening/closing operations of the second plate320may include an actuator configured to move the fourth cover member324on the third cover member322in a first direction (Y direction). For example, the actuator may include a linear actuator such as a conveyance guide or a ball screw.

A pair of the fourth cover members324may move in a direction to get closer to each other to a closed position, to block the movement of the substrate stage200therebetween. A pair of the fourth cover members324may move away from each other to an open position, to allow the movement of the substrate stage200therebetween.

As illustrated inFIGS.4and5, the first cover member312and the second cover member314of the first plate310may include a plurality of first openings311that have a first size D1, and the third cover member322and the fourth cover member324of the second plate320may include a plurality of second openings321that have a second size D2 smaller than the first size D1.

For example, the first cover member312may include first fine wires313that define a plurality of the first openings311allowing the movement of the vapor. The third cover member322may include second fine wires323that define a plurality of the second openings321allowing the movement of the vapor. A thickness of the first fine wire313may be greater than a thickness of the second fine wire323.

The first openings and the second openings may have circular or polygonal shapes. The sizes and shapes of the first openings and the second openings, the thicknesses of the first fine wires and the second fine wires, etc. may be determined in consideration of the temperature profile in the zones divided by the first plate310and the second plate320.

As illustrated inFIG.6, a space above the second plate320may be defined as a third zone Z3 and may be maintained at a first temperature T1. A space between the first plate310and the second plate320may be defined as a second zone Z2 and may be maintained at a second temperature T2 higher than the first temperature T1. A space under the first plate310may be defined as a third zone Z1 and may be maintained at a third temperature T3 higher than the second temperature T2.

Temperatures of the first zone to the third zone may be determined in proportion to vapor density in each zone. Vapor density distribution in each zone may be determined according to the sizes of the first and second openings of the first plate310and the second plate320, the thicknesses of the first and second fine wires, or the like.

For example, the first temperature T1 may be 100° C., the second temperature T2 may be 170° C., and the third temperature T3 may be 230° C. Temperatures in the first zone to the third zone may be determined in consideration of a temperature profile of soldering. The solder40may include Sn—Ag—Cu (SAC) solder, Sn—Ag solder, etc. Since the boiling point of the SAC solder is 217° C., the temperature T3 of the third zone Z1, which is a reflow section, may be maintained at 230° C.

As illustrated inFIG.7, a soldering temperature profile corresponding to the temperature distribution of the first to third zones may be obtained during a solder reflow process. As the object S on the substrate stage200moves through the first to third zones Z1, Z2 and Z3 with time, a desired soldering temperature profile may be obtained.

FIGS.8A and8Bare cross-sectional views illustrating a first plate in accordance with example embodiments. InFIGS.8A and8B, at least one mesh plate (e.g., the first plate310) may include cover members312a,312band312chaving a telescopic structure that operates in a retractable manner.

The first cover member312amay be installed adjacent to a first sidewall of the vapor generating chamber100, the second cover member312bmay be installed to be movable in a first direction on the first cover member312a, and the third cover member312cmay be installed to be movable in the first direction on the second cover member312b.

As illustrated inFIG.8A, the second cover member312band the third cover member312cmay move to an open position adjacent to the first sidewall of the vapor generating chamber100to overlap each other, and thus, may allow the movement of the substrate stage200in the vertical direction.

As illustrated inFIG.8B, the second cover member312band the third cover member312cmay move toward a second sidewall opposite to the first sidewall of the vapor generating chamber100to a closed position, and thus, may block the movement of the substrate stage200in the vertical direction. Hereinafter, a method of performing a vapor phase reflow process using the solder reflow apparatus ofFIG.1will be described.

FIGS.9to12are cross-sectional views illustrating a method of performing a vapor phase reflow process in accordance with example embodiments. InFIGS.9to12, an article S for soldering may be loaded into the vapor generating chamber100, and the heat transfer fluid F in the vapor generating chamber100may be heated.

In example embodiments, a substrate20on which an electronic component30is mounted via a solder40may be transferred into the vapor generating chamber100through the gate102of the vapor generating chamber100, and then, the article S may be loaded on the substrate stage200by the transfer mechanism104such as a guide rail or a transfer pusher.

After the article S is loaded, the Galden solution F may be heated by the heater110and start to boil. The saturated vapor from the Galden solution may be distributed within the space101of the vapor generating chamber100. At this time, the vapor may be distributed into the first to third zones Z1, Z2 and Z3 through the first and second openings of the first plate10and the second plate320, respectively, and have a desired constant density in each zone.

Thus, the third zone Z3 above the second plate320may be maintained at the first temperature T1, the second zone Z2 between the first plate310and the second plate320may be maintained at the second temperature T2 higher than the first temperature T1, and the third zone Z1 under the first plate310may be maintained at the third temperature T3 higher than the second temperature T3.

As illustrated inFIG.10, after the article S is preheated in the first zone Z3, the article may be moved to the second zone Z2 and activated (soaked). The substrate20may be preheated to prevent various soldering defects and to provide a more solid and conductive joint. There may be a secondary vapor phase which is produced at a cooler temperature than the main vapor layer in the first and second zones Z3 and Z3. No soldering takes place in this zone, only a temperature rises.

As illustrated inFIGS.11and12, the article S may be moved to the third zone Z1 so that the solder40may be reflowed. When the article S is immersed in the vapor in the third zone Z1, the vapor may serves as a heat transfer medium. Since the temperature of the vapor and the temperature of the substrate20in the third zone Z1 are different from each other, vapor may be condensed on a surface of the article S to form a layer. The vapor condensing on the surface may transfer latent heat to the surface of the substrate20during condensation to reflow a solder paste. Then, after the solder40is soldered, the article S may move to the first zone Z3 via the second zone Z2 and then may be cooled. Accordingly, the solder joints may be cooled down and solidified.

FIG.13is a cross-sectional view illustrating a solder reflow apparatus in accordance with example embodiments. The solder reflow apparatus may be substantially the same as or similar to the solder reflow apparatus described with reference toFIG.1, except for an additional third plate. Thus, same reference numerals will be used to refer to the same or like elements and any further repetitive explanation concerning the above elements will be omitted.

InFIG.13, a temperature gradient regulator300of a solder reflow apparatus11may further include a third plate330disposed under a first plate310. In example embodiments, the third plate330disposed under the first plate310may include a plurality of third openings331that have a third size D3 greater than a first size D1. The third plate330may have a structure substantially the same as or similar to that of the first plate310.

A space above the second plate320may be defined as a third zone Z3 and may be maintained at a first temperature T1. A space between the first plate310and the second plate320may be defined as a second zone Z2 and may be maintained at a second temperature T2 higher than the first temperature T1. A space between the third plate330and the first plate310may be defined as a third zone Z1 and may be maintained at a third temperature T3 higher than the second temperature T2.

In one embodiment, the temperature gradient regulator300may further include a fourth plate disposed above the second plate320in place of or together with the third plate330. The fourth plate disposed on the second plate320may include a plurality of fourth openings that have a third size smaller than the second size D2.

A space between the second plate320and the fourth plate may be defined as the third zone Z3 and may be maintained at the first temperature T1. A space above the fourth plate may be defined as a fourth zone and may be maintained at a fourth temperature lower than the first temperature T1.

Hereinafter, a method of manufacturing an electronic device using the solder reflow apparatus ofFIG.1will be described. For example, the electronic device is a semiconductor package. However, it will be understood that the manufacturing method of the electronic device in accordance with example embodiments is not limited thereto.

FIG.14is a flowchart illustrating a method of manufacturing an electronic device in accordance with example embodiments.FIGS.15to21are views illustrating a method of manufacturing an electronic device in accordance with example embodiments.FIG.15is a plan view illustrating a strip substrate on which semiconductor chips are mounted.FIGS.16,18and19are cross-sectional views taken along the line A-A′ inFIG.15.

InFIGS.14to18, first, a substrate20including a plurality of substrate pads22may be provided, a solder paste24may be coated on the substrate pads22of the substrate20(S100inFIG.14), and a solder40may be disposed on the solder paste24(S110inFIG.14).

As illustrated inFIG.15, the substrate20may be a multilayer circuit board as a package substrate having an upper surface and a lower surface opposite to each other. The substrate20may be a strip substrate for manufacturing a semiconductor strip such as a Printed Circuit Board (PCB).

The substrate20may have first and second side portions S1 and S2 extending in a direction parallel to a second direction parallel to the upper surface and facing each other, and third side portions S3 and S4 extending in a direction parallel to a first direction (X direction) perpendicular to the second direction and facing each other. When viewed from a plan view, the substrate20may have a quadrangular shape. The substrate20may have a predetermined area (e.g., 77.5 mm×240 mm).

The substrate20may include a mounting region MR on which a semiconductor chip is mounted and a cutting region CR surrounding the mounting region MR. A plurality of electronic components (e.g., semiconductor chips)30may be disposed on the mounting regions MR of the substrate20, respectively. For example, tens to hundreds of electronic components (e.g., semiconductor chips)30may be arranged in a matrix form on the substrate20.

As illustrated inFIG.16, a solder paste24may be coated on each of the plurality of substrate pads22of the substrate20. A pitch between the substrate pads22of the substrate20may be within a range of several tens of microns.

The solder paste24may be printed onto the substrate pads22of substrate20. For example, the solder paste24may be printed by a stencil printer. A stencil may be a metal foil having a plurality of openings corresponding to an array of solders that are subsequently placed. During printing, the solder paste24may be printed to fill the openings of the stencil. The solder paste24may include solder power and flux. The flux may include resin, solvent, activator, antioxidant, etc. Alternatively, the solder paste may be coated to a surface of the solder40formed on the electronic components (e.g., semiconductor chips)30.

As illustrated inFIG.17, a solder40may be formed on the electronic component30mounted on the substrate20. The electronic component30may be a semiconductor chip. Alternatively, the electronic component may be a semiconductor package. In this case, the substrate20may be a module board.

A plurality of input/output pads32may be formed on a first surface31aof the electronic component30. The solders40may be respectively formed on the input/output pads32. After forming an Under Bump Metal (UBM) on the input/output pad32, the solder40may be formed on the under bump metal.

As illustrated inFIG.18, the electronic component30may be disposed on the substrate20such that the solder40is interposed between the input/output pad32of the electronic component30and the solder paste24. The semiconductor chips may be mounted on the substrate20by a flip chip bonding method. Then, a vapor phase reflow soldering may be performed (S120).

InFIG.19, the substrate20on which the electronic component30is mounted may be loaded into the vapor generating chamber100of the solder reflow apparatus10ofFIG.1, and while the substrate20is sequentially moved to the first to third zones Z3, Z2 and Z1, the heat transfer fluid in a vapor state may be brought into contact with the surface of the substrate20to heat the solder paste24, thereby reflowing the solder40and thus, a solder (bump)40may be formed between the substrate pad22and the input/output pad32.

In example embodiments, as the substrate is moved through the vertically arranged first to third zones, a desired heating temperature profile over time may be implemented. In particular, after the substrate20is loaded, the Galden solution F may be heated by the heater110and start to boil. The saturated vapor from the Galden solution may be distributed within the space101of the vapor generating chamber100. At this time, the vapor may be distributed into the first to third zones Z3, Z2 and Z1 through the first and second openings of the first plate310and the second plate320, respectively, and may have a desired constant density in each zone.

Thus, the third zone Z3 above the second plate320may be maintained at the first temperature T1, the second zone Z2 between the first plate310and the second plate320may be maintained at the second temperature T2 higher than the first temperature T1, and the third zone Z1 under the first plate310may be maintained at the third temperature T3 higher than the second temperature T3.

After the article S is preheated in the first zone Z3, the article may be moved to the second zone Z2 and activated (soaked). The substrate20may be preheated to prevent various soldering defects and to provide a more solid and conductive joint. There may be a secondary vapor phase which is produced at a cooler temperature than the main vapor layer in the first and second zones Z3 and Z3. No soldering takes place in this zone, only a temperature rises.

When the article S is immersed in the vapor in the third zone Z1, the vapor may serves as a heat transfer medium. Since the temperature of the vapor and the temperature of the substrate20in the third zone Z1 are different from each other, vapor may be condensed on a surface of the article S to form a layer. The vapor condensing on the surface may transfer latent heat to the surface of the substrate20during condensation to reflow a solder paste.

Then, after the solder40is soldered, the article S may move to the first zone Z3 via the second zone Z2 and then may be cooled. Accordingly, the solder joints may be cooled down and solidified.

InFIG.20, a molding member50may be formed on the substrate20to cover the electronic components (e.g., semiconductor chips)30(S130).

In example embodiments, the molding member50may be formed on the substrate20by a transfer molding apparatus. The substrate20may be disposed in a molding space of a mold of the molding apparatus, and a sealing material may flow at high temperature and under high pressure when a lower mold and an upper mold are clamped, so that the liquid sealing material flows inside the molding space and is solidified to form the molding member covering the electronic components (e.g., semiconductor chips)30. For example, the sealing material may include an Epoxy Mold Compound (EMC).

InFIG.21, the substrate20may be sawed by a sawing process to complete semiconductor packages60. In one embodiment, external connection members such as solder balls may be formed on outer connection pads on a lower surface of the substrate20, and the cutting region CR of the substrate20may be removed by a cutting device such as a blade. Accordingly, the semiconductor packages P may be individualized from the substrate20.

Through the above processes, a semiconductor package including a logic device or a memory device and a semiconductor module including the same may be manufactured. The semiconductor package may include logic devices such as Central Processing Units (CPUs), Main Processing Units (MPUs), or Application Processors (APs), or the like, and volatile memory devices such as Dynamic Random Access Memory (DRAM) devices, Host Buffer Memory (HBM) devices, or non-volatile memory devices such as flash memory devices, Parallel RAM (PRAM) devices, Magnetic RAM (MRAM) devices, Resistive RAM (ReRAM) devices, or the like.

The foregoing is illustrative of example embodiments and is not to be construed as limiting thereof. Although a few example embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in example embodiments without materially departing from the novel teachings and advantages of the present disclosure. Accordingly, all such modifications are intended to be included within the scope of example embodiments as defined in the claims.