JP2010287635A - Reflow device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform reflow on a thin heating object in a reduced pressure atmosphere with a simple configuration. <P>SOLUTION: A wafer W supported by a carrier tool (a slightly adhesive film 21, an inner peripheral ring 22 and an outer peripheral ring 23) is carried into a chamber 3. The wafer W is lowered and the slightly adhesive film 21 is closely adhered to a heating surface of a heater plate 7. A lid 8 is lowered and the slightly adhesive film 21 is pushed on the heating surface by an end surface of an elastic body 41. In initially heating and pre-heating it, nitrogen gas is filled in an air-tight space in the lid 8. Then, the space in the lid 8 is evacuated to have an almost vacuum atmosphere and is heated by the heater plate 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reflow apparatus capable of performing soldering, bump formation and the like in a substantially vacuum atmosphere.

  A reflow soldering apparatus is known in which a solder composition is supplied in advance to an electronic component or a printed wiring board and heated. Furthermore, a solder bump forming apparatus that forms solder bumps on electrodes formed on a semiconductor substrate (hereinafter referred to as a wafer) such as a single crystal silicon wafer is known. In the reflow apparatus, soldering defects (called voids) are generated due to bubbles. As one method for avoiding voids, it has been proposed to create a vacuum in a container in which an object to be processed is stored.

  For example, as shown in FIG. 7, with respect to the sealed chamber 71, gate valves 72a and 72b are provided at the inlet and the outlet, respectively, and the inside of the chamber 71 is evacuated. The object to be heated 73 is conveyed in the direction of the arrow in the chamber 71. Heating is performed by first being in close contact with the heater 74, the solder is melted, and soldering or bump formation is performed. Next, it is cooled by being in close contact with the cooling plate 75. After cooling, the gate valve 72b is opened and the heated object 73 is discharged outside.

  Further, it has been proposed to provide a defoaming device for removing bubbles in the object to be processed during the heat treatment process (see Patent Document 1). The defoaming device is divided into upper and lower parts and is configured by a vacuum container that can be opened and closed.

Japanese Patent Laid-Open No. 06-226484

  The configuration shown in FIG. 7 has a drawback that the transport mechanism for transporting the object to be heated 73 needs to be accommodated in the chamber 71, and the chamber 71 becomes large in size. Further, it is necessary to increase the thickness of the casing that constitutes the chamber 71, and there is a disadvantage that the apparatus becomes larger.

  In the heat treatment apparatus described in Patent Document 1, a defoaming apparatus is arranged independently of the heat treatment. For example, in a reflow apparatus in which a plurality of chambers (zones) are provided in the transport direction, the number of chambers increases. There was a problem. Furthermore, the thickness of the wafer is becoming very thin as 100 μm. Patent Document 1 has a problem in which processing on such a thin substrate is not considered.

  Accordingly, it is an object of the present invention to provide a reflow apparatus that can perform heating that melts solder in a substantially vacuum atmosphere with a simple configuration and that can heat a thin substrate.

In order to solve the above-described problem, the present invention is a reflow soldering apparatus that performs soldering by heating an object to be heated in a substantially reduced-pressure atmosphere,
A lid having an elastic peripheral end surface;
An elevating unit for elevating and lowering the object to be heated and the lid,
A heating plate arranged at a position where the object to be heated descends,
The object to be heated is
A heat-resistant slightly adhesive film attached to the end face of the frame so as to cover the opening;
It consists of a work affixed to the adhesive surface of a slightly adhesive film,
When the article to be heated is lowered by the elevating part, the slightly adhesive film is closely attached to the heating plate,
When the lid is lowered by the elevating part, the outer peripheral end surface of the lid is brought into close contact with the region between the outer peripheral position of the workpiece and the inner peripheral position of the frame,
This is a reflow soldering apparatus in which the heating process is performed in a substantially vacuum atmosphere by reducing the pressure in the space formed inside the lid.

  In this invention, since a thin workpiece | work is affixed on the slightly adhesive film stretched on the frame body, it can prevent that the curvature of a workpiece | work generate | occur | produces during a process. In this invention, since the solder is heated in a substantially vacuum atmosphere, the generation of voids can be reduced. Furthermore, since the volume of the vacuum part can be reduced, the part requiring strength is small, and the apparatus cost can be reduced.

It is a top view, a front view, and a side view of an embodiment of the present invention. It is the top view and sectional drawing of an example of the workpiece conveyance jig | tool in one Embodiment of this invention. It is the top view and sectional drawing of other examples of the workpiece conveyance jig | tool in one Embodiment of this invention. It is sectional drawing for demonstrating the chamber of the heating process of one Embodiment of this invention. It is a perspective view for demonstrating the temperature profile of one embodiment of this invention. It is an approximate line figure for explaining each process of one embodiment of this invention. It is a basic diagram for demonstrating the conventional reflow apparatus.

Embodiments of the present invention will be described below. The description will be made in the following order.
<1. First Embodiment>
<2. Modification>
The embodiments described below are preferred specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is not limited to the present invention in the following description. Unless otherwise specified, the present invention is not limited to these embodiments.

<1. First Embodiment>
"Outline of reflow equipment"
FIG. 1 is a front view, a plan view, and a cross-sectional view of an entire reflow apparatus according to an embodiment of the present invention. The reflow apparatus has three chambers (zones) 1, 2 and 3 arranged in a line. The chambers are separated by a partition, and an opening necessary for transporting the wafer W as an object to be heated is formed in the partition.

  The chamber 1 is a loading / unloading chamber. The wafer W attached to the transfer jig is loaded from the chamber 1 and the wafer W after the reflow process is unloaded from the chamber 1. The wafer W is a single crystal silicon wafer having a thickness of 0.5 mm to 1.5 mm and a diameter of 120 mm to 300 mm, for example. A process for forming bumps on a wafer, a process for soldering a silicon chip to a conductor, a process for soldering a flip chip to a conductor, and the like are performed by a reflow apparatus. Since the wafer W is thin, the wafer W is held by a transfer jig as will be described later. The housing part 4 above the chamber 1 is openable and closable.

  The wafer W held by the jig is placed on the loop-shaped arm 5. When the arm 5 is transferred by the horizontal transfer mechanism 6, the wafer W is transferred. The horizontal conveyance mechanism 6 is configured by, for example, a ball screw. In FIG. 1, a state in which the wafer W is positioned in each chamber is shown. However, the wafer W is sequentially transferred from the chamber 1 to the chamber 2 and the chamber 3, and is heated in the chamber 3. After the heating, the wafer 3 is sent from the chamber 3 to the chamber 2 and cooled. After the cooling, the wafer W held by the jig is taken out in the chamber 1.

  The chamber 3 as a heating zone is provided with a heating plate (hereinafter referred to as a heater plate) 7. The heater plate 7 heats the wafer W attached to a jig that is in close contact with or close to the heating surface. A large number of small holes are formed in the heater plate 7, and the jig (adhesive film with the wafer W attached) is sucked to bring the fine adhesive film into close contact with the heating surface. As the heater plate 7, for example, a plate having a heater inside is used. The heater plate 7 is fixed.

  The chamber 3 is provided with a lid 8 that is raised outward and has an elastic body on the outer peripheral end face so as to be movable up and down. For example, the lid 8 has a cylindrical shape with the opening facing downward. In the chamber 3, the lid 8 is placed on the wafer W so as to cover the wafer W fixed to the slightly adhesive film. The air in the space formed inside the lid 8 is exhausted by a vacuum pump or the like (not shown). Then, heating is performed in a substantially vacuum atmosphere, and the solder is melted.

  In the chamber 3, as described later, heating (heating heating), preheating (preheating), and main heating are performed. This heating is performed in a substantially vacuum atmosphere. Heating and preheating are performed in an inert gas such as a nitrogen atmosphere. The lid 8 is provided with a plurality of ports (not shown) in order to perform nitrogen replacement or to make a vacuum. A nitrogen generator, a vacuum pump, and the like are connected to the plurality of ports via valves.

  A cylinder 9 for raising and lowering the lid 8 is provided in the chamber 3. The wafer W is moved up and down by the cylinder 10. The cylinders 9 and 10 are lifting mechanisms using air pressure. The cylinder 10 raises and lowers the wafer W by raising and lowering the arm 5. Therefore, the cylinder 10 is moved in the horizontal direction integrally with the arm 5.

  In the chamber 2, the wafer W that has been completely heated is cooled. A cooling plate 11 is provided in the chamber 2. The cooled wafer W is transferred from the chamber 2 to the chamber 1 and taken out from the chamber 1.

"Transfer jig"
As shown in FIG. 2, the wafer W is attached to the adhesive surface of the slightly adhesive film 21. Since the wafer W is as thin as 0.5 mm, warping is likely to occur. By affixing the wafer W to the slightly adhesive film 21, warpage of the wafer W can be prevented. The slightly adhesive film 21 is obtained by applying an adhesive component having a slightly adhesive force to a polymer material such as a PET base material, and has heat resistance against heat applied during soldering. The adhesive strength of the slightly adhesive film 21 is such that the wafer W can be easily removed after the processing is completed, and the wafer W is not peeled off during the transfer and processing.

  The slightly adhesive film 21 is stretched on the inner peripheral ring 22 as a frame, and the outer peripheral ring 23 is fitted to the inner peripheral ring 22 so that it can be stretched without sagging. Wafer W is affixed to the inner surface of the slightly adhesive film 21. The wafer W has a circular shape, and the slightly adhesive film 21 stretched on the inner peripheral ring 22 also has a circular shape. The diameter of the slightly adhesive film 21 stretched on the inner peripheral ring 22 is slightly larger than that of the wafer W. The inner ring 22 and the outer ring 23 are made of a metal material such as stainless steel.

  As shown in FIG. 3, a slightly adhesive film 21 ′ in which a large number of small holes 24 are formed and the wafer W is adsorbed through the small holes 24 may be used. The position where the small hole 24 is formed coincides with the position where the small hole for suction formed in the heater plate 7 is formed. A positioning mechanism is added to match. Alternatively, the diameter of the small hole 24 may be larger than the diameter of the small hole formed in the heater plate 7 so as not to be affected by the positional deviation. When using the slightly adhesive film 21 ′ in which the small holes 24 are formed, it is necessary to perform evacuation from the heater plate 7 side.

“Structure of chamber for heating”
In FIG. 4, as indicated by a two-dot chain line, the wafer W attached to the transfer jig (the slightly adhesive film 21, the inner peripheral ring 22 and the outer peripheral ring 23) is transferred into the chamber 3. The wafer W is lowered by the cylinder 10, and the slightly adhesive film 21 is brought into close contact with the heating surface of the heater plate 7 by suction from the heater plate 7 side.

Further, the lid 8 is lowered by the cylinder 9, and the slightly adhesive film 21 is pressed against the heating surface by the end surface of the heat-resistant elastic body 41 provided on the end surface of the lid 8.
A region where the slightly adhesive film 21 is exposed is formed between the outer peripheral position of the wafer W and the inner position of the inner peripheral ring 22, and the end face of the elastic body 41 is exposed. Pressed. Furthermore, by having the elastic body 41, the elastic body 41 and the adhesive surface of the slightly adhesive film 21 can be in close contact with each other even if there is some mechanical dimensional error in the height direction.

  Thus, an airtight space is formed inside the lid 8. The lid 8 is provided with ports 42a and 42b. Each port is connected to a pipe, and a valve is provided for the port or the pipe. As will be described later, the atmosphere in the space inside the lid 8 is replaced with an inert gas (nitrogen). Further, the space inside the lid 8 is evacuated to make a substantially vacuum atmosphere.

"Reflow processing"
The chamber 3 described above controls the temperature of the wafer W according to the temperature profile during reflow. FIG. 5 schematically shows an example of the temperature profile. The horizontal axis is time, and the vertical axis is the surface temperature of the wafer W. The first section is the temperature raising section R1 where the temperature rises due to heating, the next section is the preheating (preheating) section R2 where the temperature is substantially constant, the next section is the main heating section R3, and the last section is This is the cooling unit R4. As a temperature profile, a profile 51 shown by a solid line in FIG. 5 is representative. The present invention can be applied to the profile 52 indicated by the broken line and the profile 53 indicated by the broken line.

  The temperature raising portion R1 is a period in which the wafer W is heated from room temperature to a preheating portion R2 (for example, 150 ° C. to 170 ° C.). The preheating portion R2 is a period for performing isothermal heating to eliminate heating unevenness of the wafer W. The main heating portion R3 (for example, 230 ° C. to 250 ° C. at the peak temperature) is a period in which solder, for example, lead-free solder is melted and bonding or bump formation is completed. The heat treatment of R1 to R3 is performed in the chamber 3. The last cooling unit R4 is a period in which the wafer W is rapidly cooled. The wafer W is cooled by the cooling plate 11 in the chamber 2.

  In the temperature raising portion R1, as shown in FIG. 6A, in the space in the lid 8 replaced with nitrogen, the slightly adhesive film 21 is brought into close contact with the heating surface of the heater plate 7, and the workpiece W is heated. For adhering to the heating surface, suction may be performed from the heater plate side, but the cylinder 9 may only press the end surface of the lid 8 against the heating surface.

  In the preheating part R2, as shown in FIG. 6B, the cover 8 is held in a state where the opening of the cover 8 is covered with the slightly adhesive film 21 so that the nitrogen atmosphere in the space in the cover 8 is maintained. The bonded wafer W is moved upward. The state shown in FIG. 6B can be realized by controlling the cylinders 9 and 10. Furthermore, the distance separating the slightly adhesive film 21 and the heating surface of the heater plate 7 is selected so that the temperature change of the preheating portion R2 on the temperature profile occurs. Since the temperature change of the preheating portion R2 is only slightly increased, the heating surface of the heater plate 7 and the slightly adhesive film 21 are separated from each other.

  In the main heating portion R3, as shown in FIG. 6C, nitrogen in the space in the lid 8 is sucked through one or both of the ports 42a and 42b to make a substantially vacuum atmosphere, and the slightly adhesive film 21 is on the heater plate 7 side. Is brought into close contact with the heating surface. In order to heat the wafer W by conduction heat, the heater plate 7 is required to bring the slightly adhesive film 21 and the heating surface into close contact with each other. When using a slightly adhesive film 21 ′ having a large number of small holes 24 as shown in FIG. 3, a vacuum atmosphere can be formed by suction from the heater plate 7 side, and the slightly adhesive film 24 ′ can be used as a heating surface. It can be adhered.

<2. Modification>
The present invention is not limited to the above-described embodiment of the present invention, and various modifications and applications can be made without departing from the gist of the present invention. For example, the number of chambers (zones) may be increased, and the entrance side transport unit and the exit side transport unit may be provided separately. Further, a chamber responsible for heating in an inert gas atmosphere and a chamber responsible for heating in a vacuum atmosphere may be provided separately.

W ... Wafer 1, 2, 3 ... Chamber 7 ... Heater plate 8 ... Heater plate 9, 10 ... Cylinder 11 ... Cooling plate 21, 21 '... Slightly adhesive film 22 ... Inner ring 23 ... Outer ring 24 ... Small hole 41 ... Elastic body

Claims (4)

A reflow soldering apparatus for performing soldering by heating an object to be heated in a substantially reduced pressure atmosphere,
A lid having an elastic peripheral end surface;
An elevating part for elevating and lowering the object to be heated and the lid;
A heating plate disposed at a position where the object to be heated descends,
The heated object is
A heat-resistant slightly adhesive film attached to the end face of the frame so as to cover the opening;
It consists of a work affixed to the adhesive surface of the above slightly adhesive film,
When the object to be heated is lowered by the elevating unit, the slightly adhesive film is in close contact with the heating plate,
When the lid is lowered by the elevating part, the outer peripheral end surface of the lid is brought into close contact with the region between the outer peripheral position of the workpiece and the inner peripheral position of the frame,
A reflow soldering apparatus in which a heating process is performed in a substantially vacuum atmosphere by reducing the pressure in a space formed inside the lid.   The reflow soldering apparatus according to claim 1, wherein the space is filled with an inert gas in a preheating step before the heating step.   The reflow soldering apparatus according to claim 1, wherein in the preheating step, the temperature change is controlled to be moderate by separating the slightly adhesive film and the heating plate.   The reflow soldering apparatus according to claim 1, wherein a plurality of holes are formed in the slightly adhesive film.

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