JP2009158563A - Mounting device and mounting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems wherein it is difficult to machine a shape of a solder, used for bonding a package and a substrate from a usual sphere shape of a BGA package to a columnar shape before mounting, even though the shape of the solder used for the bonding is, preferably, a columnar shape for making the distortions produced relaxed, because of the difference in the linear expansion between the package and the substrate for obtaining higher bonding reliability. <P>SOLUTION: The mounting device has an absorption nozzle 4, capable of pulling up the BGA package 2 to a constant height in a partial reflow device for absorbing and mechanically pulling it to a fixed height, at a constant speed when the solder is melted, and holds the nozzle until the temperature becomes the hardening-completion temperature. This extends the solder which is spherical into a columnar shape. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a BGA mounting apparatus and a BGA mounting method for solder bonding a semiconductor package (hereinafter referred to as a BGA package) having a ball grid array (BGA) terminal, which is an electronic component, to a printed wiring board or the like. .

  Conventionally, as countermeasures against cracks in the solder joints of BGA packages, stress concentration due to thermal expansion differences can be achieved by penetrating and applying an underfill agent or by processing the shape of solder balls of BGA packages into columns. A technique for preventing the above has been disclosed (for example, see Patent Document 1).

JP-A-11-135673

  When an underfill agent is used, repair work becomes very difficult. In addition, there is a problem that an expected effect may not be obtained depending on the properties of the underfill agent, that is, the adhesive that permeates between the BGA package and the printed wiring board.

  In order to increase the reliability of the solder joint, it is preferable to form the solder in a columnar shape as disclosed in Patent Document 1. However, the shape of the solder of the BGA package which is generally distributed is a ball shape. Prior to mounting, it is difficult to process the solder shape of the BGA package from a ball shape to a column shape, and there is a problem that it causes an increase in cost.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a BGA mounting apparatus capable of obtaining high bonding reliability in solder bonding of a BGA package mounted on a printed wiring board.

  The mounting apparatus according to the present invention is a mounting apparatus for mounting a BGA electronic component having a ball solder electrode on a substrate, a holding means for holding the BGA electronic component, a heating means for heating the ball solder electrode, and the holding The BGA electronic component is positioned at a desired height position from the surface of the substrate in a state in which the ball solder electrode is melted by the heating unit and a driving unit that enables the device to move in a direction substantially perpendicular to the surface of the substrate. Control means for controlling the driving means so as to solidify the ball solder electrode at the height position is provided.

  According to the present invention, the solder joint shape of the BGA package after the solder joint can be made columnar. As a result, this columnar solder can absorb the distortion generated by the difference in linear expansion between the BGA package and the printed wiring board, and the reliability of the solder joint can be improved.

Embodiment 1.
FIG. 1 is a schematic front view showing a configuration of a local reflow apparatus 100 used for BGA mounting in the first embodiment. This local reflow apparatus 100 is an example of a BGA mounting apparatus.
This local reflow apparatus 100 is made to cope with the problem that the reliability of the joint portion is lowered due to a crack generated due to a difference in linear expansion between a BGA package having a BGA terminal and a printed wiring board. In particular, the local reflow device 100 is used to stretch the melted BGA ball.
The first embodiment will be described below with reference to the drawings.

  In FIG. 1, a local reflow apparatus 100 of the present invention includes a BGA suction nozzle 4, a component suction pad 41 attached to the tip of the BGA suction nozzle 4, an upper hot air generation heater 5, a lower hot air generation heater 6, The upper heating duct 7, the lower heating duct 8, the entire printed wiring board preheating device 10, the Z-axis control unit 9 for controlling the Z-axis direction (vertical direction) of the BGA suction nozzle 4, and the BGA suction nozzle 4 as Z The apparatus includes a Z-axis drive unit 12 that is driven in the axial direction, a vacuum sensor 13 that detects the suction pressure of the BGA suction nozzle 4, and a device control unit 20 that controls the operation of the entire apparatus.

  The BGA suction nozzle 4 has a cylindrical shape with a hollow central portion, and is provided with a metal or heat-resistant resin component suction pad 41 at the tip. The BGA suction nozzle 4 is sucked by a vacuum device (not shown) and sucks the upper surface of the BGA package 2 by the suction force of the component suction pad 41.

The BGA suction nozzle 4 is connected to a Z-axis drive unit 12 such as a stepping motor or a manual dial gauge, and extends in the Z-axis direction (a direction that is substantially perpendicular to the bonding surface of the BGA package, also referred to as the up-down direction). It is movable.
When the Z-axis drive unit 12 inputs desired height information, movement speed, etc. from the Z-axis control unit 9, the BGA package 2 adsorbed on the tip of the BGA adsorption nozzle 4 is printed by controlling the driving of the stepping motor and the like. It is moved with respect to the board 1 at a desired speed, and is accurately positioned with respect to the printed wiring board 1 so as to be at a desired height position. As will be described later, the height of the upper surface of the BGA package 2 during melting of the solder is detected by using the output of the vacuum sensor 13. Of course, you may make it provide the position detection sensor which detects the upper surface height of the BGA package 2 at any time.
In the figure, an example in which the component suction nozzle 4 is used to hold the BGA package 2 is shown, but the holding mechanism of the BGA package 2 is not limited to this. You may make it chuck | suck and hold | maintain by pinching a part or more with a finger (three claw chuck). The BGA suction nozzle 4 is an example of a holding unit.

  The upper heating duct 7 has a box shape without a lower surface, and moves in the Z-axis direction together with the component suction nozzle 4 by being connected to the Z-axis driving unit. The upper heating duct 7 covers the entire BGA package 2 when the component suction nozzle 4 is sucking the BGA package 2 disposed on the printed wiring board 1, and is heated by the upper hot air generating heater 5 provided above. The temperature inside the upper heating duct 7 is made uniform so as to confine the hot air. The upper heating duct 7 is processed with a metal such as stainless steel.

  The upper hot air generating heater 5 is connected to the upper heating duct 7, and heats air blown from a fan (not shown) installed in the upper part of FIG. 1 and sends it as hot air 51 into the upper heating duct 7.

  The lower heating duct 8 has a box shape without an upper surface, and is installed below the printed wiring board 1. The printed wiring board 1 is heated from below so that hot air heated by the lower warm air generating heater 6 provided further below is confined in the lower heating duct 8.

  The lower warm air generating heater 6 is connected to the lower heating duct 8, and heats air blown from a fan (not shown) installed at the lower side of FIG. 1 and sends it as hot air 62 into the lower heating duct 8. The upper hot air generating heater 5 and the lower hot air generating heater 6 are examples of heating means.

  The entire printed wiring board preheating device 10 is, for example, a heating wire heater, and is provided below the printed wiring board 1 whose outer periphery is chucked and held, and the entire printed wiring board 1 other than the place where the BGA package is mounted. Heat.

The Z-axis control unit 9 is connected to the device control unit 20 and controls the operation of the BGA suction nozzle 4 in the Z-axis direction according to an instruction from the device control unit 20.
The apparatus control unit 20 controls the entire apparatus such as the adsorption operation of the BGA adsorption nozzle 4, the Z-axis operation, the heater control, the fan control, and the vacuum sensor detection process.

In the BGA package 2, an electronic circuit is mounted inside the package, and a plurality of BGA solder balls 3, which are ball-shaped solder electrodes, are bonded to the lower surface (back surface) of the package. The printed wiring board 1 is one in which other electronic components besides the BGA package 2 are mounted and soldered.
The BGA package 2 is an example of a BGA electronic component, and the printed wiring board 1 is an example of a substrate. In FIG. 1, a jig for fixing the printed wiring board and other electronic components on the printed wiring board are omitted and not shown.

Next, the operation of the local reflow apparatus 100 used in the BGA mounting method according to the first embodiment will be described with reference to FIGS.
FIG. 2 is a flowchart showing the BGA mounting method in the first embodiment. FIG. 3 shows the operation status of the apparatus in the BGA mounting method. Note that (a), (b), (c), and (d) in FIG. 3 correspond to steps S03, S04, S05 to S06, and S07 in FIG. FIG. 4 is a diagram showing a temperature profile of the mounting process when Pb eutectic solder is used as a solder material as an example. In the temperature profile of FIG. 4, correspondence with steps S03 to S07 shown in FIGS. 2 and 3 is described.

  Here, an example will be described in which the BGA package 2 shown in FIG. 2 is joined to the printed wiring board 1 with the solder joint shape of the BGA solder balls 3 being columnar.

  In FIG. 2, first, the BGA package 2 is mounted on the printed wiring board 1 together with other mounting parts (not shown) by a normal reflow process (step S01). The shape of the BGA solder ball 3 after reflow is substantially ball-shaped.

  Next, the BGA suction nozzle 4, the upper heating duct 7, and the lower heating duct 8 that match the size of the BGA package 2 are selected (step S02). The BGA suction nozzle 4 has a hollow cylindrical shape inside, and is connected to a suction device (not shown) to suck the air inside the cylindrical shape. As described above, the component suction pad 41 is made of metal or heat-resistant resin, has a conical shape, and is hollow inside. The component suction pad 41 is at the tip of the BGA suction nozzle 4 and sucks the BGA package 2 by sucking air in the BGA suction nozzle. The upper heating duct 7 has a size that allows the BGA package 2 to enter the inside. If the size is too small, the BGA package may be damaged. If the size is too large, other mounting parts are included.

  Subsequently, the device control unit 20 moves the upper hot air generating heater 5, the lower hot air generating heater 6, and the entire printed wiring board preheating device 10 to melt the BGA solder balls 3 by hot air heating (step S03. FIG. 3 (a), corresponding to S03 in FIG. 4). The detection of the melting of the BGA solder ball 3 may be detected at the temperature by providing a temperature detection means in the upper heating duct 7 or may be detected by the elapsed time after heating.

  Next, the apparatus control unit 20 sends an instruction to the Z-axis control unit 9 to lower the BGA suction nozzle 4 located above the BGA package 2 and the component suction pad 41 attached to the tip thereof (step S04, FIG. 3 (FIG. 3). b), corresponding to S04 in FIG. The BGA suction nozzle 4 is sucked by a vacuum device. The vacuum sensor 13 detects the suction pressure of the BGA suction nozzle 4, and when the component suction pad 41 comes into contact with the BGA package and holds the BGA package 2, the suction pressure becomes negative, and the device control unit 20 Sends an instruction to the Z-axis control unit 9 to stop the lowering of the BGA suction nozzle 4. Here, the height position at which the suction pressure becomes negative and the lowering of the BGA suction nozzle 4 is stopped is referred to as a holding position. Since the BGA suction nozzle 4 continues to descend from the holding position and crushes the melted BGA solder ball 3, a short circuit occurs between the balls, so that the descent can be stopped at the moment when the suction pressure becomes negative. The descending speed and the function of the Z-axis drive unit 12 are adjusted in advance.

  Next, the apparatus control unit 20 outputs an instruction to the Z-axis control unit 9 to move the BGA suction nozzle 4 upward. By lifting the BGA package 2 sucked and held by the component suction pad 41 from the holding position to a predetermined height at a predetermined speed, the BGA solder ball 3 is stretched by a predetermined amount in the Z-axis direction (step S05, FIG. 3 ( c), corresponding to S05 in FIG. As an example, if the BGA solder ball 3 is a Pb solder ball having a diameter of about 0.7 to 0.8 mm, the BGA suction nozzle 4 is moved upward from the holding position to move the solder ball 3 to Z by about 0.2 to 0.5 mm. Stretch in the axial direction. The apparatus control unit 20 stops the BGA suction nozzle 4 at a position where the BGA suction nozzle 4 is moved upward by a predetermined amount from the holding position. By doing so, the BGA package is positioned at a desired height from the surface of the printed wiring board, and as a result, the BGA solder balls 3 are formed in a column shape.

Subsequently, the device control unit 20 stops the operation of the upper hot air generating heater 5, the lower hot air generating heater 6, the entire printed wiring board preheating device 10, and the fan. The BGA suction nozzle 4 holds the BGA package 2 up to a certain height until the solder is solidified (183 ° C. in the case of lead eutectic solder) (step S06, FIG. 3C, FIG. 4). Corresponding to S06).
Since the BGA solder ball 3 is in a molten state, it is necessary to sufficiently suppress mechanical rattling and vibration.

  When the solder is solidified, the vacuum suction of the BGA suction nozzle 4 is stopped (step S07, corresponding to S07 in FIG. 3D and FIG. 4).

  As described above, according to the present embodiment, the solder joint shape of the BGA package can be made columnar in the mounting process, and it is not necessary to make the solder shape of the BGA package columnar in advance as in the prior art. By forming the columnar solder in the mounting process, the columnar solder absorbs the distortion generated by the difference in linear expansion between the BGA package and the printed wiring board, and the highly reliable BGA package can be mounted. .

Embodiment 2.
In the first embodiment, columnar solder is formed by lifting the BGA package 2 by the Z-axis control unit 9 while the BGA solder ball 3 is melted. In the second embodiment, the printed wiring board 1 is lowered. As a result, columnar solder is formed.

  The configuration of the BGA mounting apparatus 100 is the same as that shown in FIG. 1 and the same reference numerals are assigned and description thereof is omitted. In the second embodiment, a jig (stage) holding the printed wiring board 1 is chucked. A Z-axis jig control unit (not shown) that performs Z-direction control is further provided, and the apparatus control unit 20 can control the Z-axis jig control unit.

FIG. 5 is a flowchart showing the BGA mounting method in the second embodiment. Although the flow is the same as the flow of the BGA mounting method of the first embodiment shown in FIG. 2, in the second embodiment, step S15 in FIG. 5 is different from that of the first embodiment (FIG. 2).
In the second embodiment, in step S14, the BGA suction nozzle 4 gradually descends in the vacuum state and stops descending when the vacuum sensor becomes negative pressure, and holds the BGA package 2.
In the next step S15, in the second embodiment, the apparatus control unit 20 controls the Z-axis jig control unit (not shown) to hold the printed wiring board 1 by a predetermined amount for chucking (stage). ) Is lowered. For example, if the BGA solder ball 3 is a Pb solder ball having a diameter of about 0.7 to 0.8 mm, the jig (stage) holding the printed wiring board 1 for chucking is lowered about 0.2 to 0.5 mm. The solder ball is stretched in the Z-axis direction. The apparatus control unit 20 stops at a position where the jig (stage) is lowered by a predetermined amount from the holding position. By doing so, the BGA package is positioned at a desired height from the surface of the printed wiring board, and as a result, the BGA solder balls 3 are formed in a column shape.

  Subsequently, the device control unit 20 stops the operation of the upper hot air generating heater 5, the lower hot air generating heater 6, the entire printed wiring board preheating device 10, and the fan. The jig (stage) that holds the printed wiring board 1 for chucking is held at a position where the printed wiring board 1 is lowered to a certain height until the solder is solidified (183 ° C. in the case of lead eutectic solder). .

  As described above, according to the present embodiment, the solder joint shape of the BGA package can be made columnar by lowering the jig (stage) holding the printed wiring board 1 by chucking. Unlike the prior art, the solder shape of the BGA package need not be made columnar in advance. By forming the columnar solder in the mounting process, the columnar solder absorbs the distortion generated by the difference in linear expansion between the BGA package and the printed wiring board, and the highly reliable BGA package can be mounted. .

Embodiment 3.
In the first and second embodiments, the BGA suction nozzle 4 is lowered while the BGA solder ball 3 is melted so that the component suction pad 41 sucks the BGA package 2. There may be a case where a positional shift occurs relative to the printed wiring board 1.
In the case where the positional deviation at the time of suction cannot be ignored, the BGA suction nozzle 4 may be lowered to hold the BGA package 2 while the BGA solder ball 3 is solidified.
Thereafter, as in the first embodiment, the BGA suction nozzle 4 may lift the BGA package 2 and stretch the BGA solder ball 3 by the Z-axis control unit 9, or the print may be performed as in the second embodiment. The jig (stage) holding the wiring board 1 may be lowered and the BGA solder ball 3 may be extended.

  According to the present embodiment, it is possible to prevent misalignment when adsorbing the BGA package and form the solder joint shape of the BGA package in a columnar shape. There is no need to keep it columnar. By forming the columnar solder in the mounting process, the columnar solder absorbs the distortion generated by the difference in linear expansion between the BGA package and the printed wiring board, and the highly reliable BGA package can be mounted. .

Embodiment 4.
In the first to third embodiments, the component suction pad 41 is described as having a conical shape, but is not limited to this conical shape. As an example, the tip of the BGA adsorption nozzle may be separated into a plurality of nozzles, and each of the separated nozzles may adsorb each part in the surface of the BGA package.

It is a front view which shows the structure of the local reflow apparatus used for the BGA mounting method in Embodiment 1 which concerns on this invention. It is a figure which shows the flow of the BGA mounting method in Embodiment 1 which concerns on this invention. FIG. 2 illustrates an operation state of an apparatus in the BGA mounting method according to the first embodiment of the present invention. It is the figure which showed an example of the temperature profile in the BGA mounting method of Embodiment 1 which concerns on this invention. It is a figure which shows the flow of the BGA mounting method in Embodiment 2 which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Printed wiring board, 2 BGA package, 3 BGA solder ball, 4 BGA adsorption nozzle, 5 Upper warm air generation heater, 6 Lower warm air generation heater, 7 Upper heating duct, 8 Lower heating duct, 9 Z-axis control part, 10 Printed wiring board whole preheating device, 11 electrode pad, 12 Z-axis drive unit, 13 vacuum sensor, 20 device control unit, 41 component suction pad, 51 hot air, 61 hot air, 100 local reflow device.

Claims (4)

A mounting apparatus for mounting a BGA electronic component having a ball solder electrode on a substrate,
Holding means for holding the BGA electronic component;
Heating means for heating the ball solder electrode;
Driving means for allowing the holding means to move in a direction substantially perpendicular to the surface of the substrate;
In a state where the ball solder electrode is melted by the heating means, the driving means is controlled so that the BGA electronic component is at a desired height position from the surface of the substrate, and the ball solder electrode at the height position. Control means for solidifying,
A mounting apparatus comprising: The control means moves the holding means by a predetermined amount in the substantially vertical direction with reference to a height position from the surface of the substrate of the BGA electronic component in a state where the ball solder electrode is melted. 2. The mounting apparatus according to claim 1, wherein the BGA electronic component is controlled to be at a desired height position from the surface of the substrate. The mounting apparatus according to claim 2, wherein the control unit detects the reference height position based on a suction pressure when the holding unit sucks the BGA electronic component. A mounting method for mounting a BGA electronic component having a ball solder electrode on a substrate,
A first step of heating the ball solder electrode of the BGA electronic component mounted on the substrate by the heating means;
A second step of moving the holding means for holding the BGA electronic component in a direction substantially perpendicular to the surface of the substrate and away from the surface of the substrate after the first step;
A third step of solidifying the ball solder electrode by stopping heating by the heating means after the second step;
The mounting method characterized by having.

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