Metal working – Means to assemble or disassemble – With control means energized in response to activator...
Reexamination Certificate
1998-12-30
2001-07-17
Hughes, S. Thomas (Department: 3726)
Metal working
Means to assemble or disassemble
With control means energized in response to activator...
C029S743000
Reexamination Certificate
active
06260259
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a solder ball mounting device for mounting solder balls on a workpiece such as a substrate, and more particularly to an improvement of control means for controlling a pressure and a head position at the time of suction of solder balls in a BGA (ball grid alley) solder ball mounting device.
2. Description of the Related Art
In mounting a plurality of solder balls on a substrate with a solder ball mounting device, in general the following method is employed: A sucking plate having solder ball sucking holes is disposed under the lower surface of a sucking head, and vacuum pressure is utilized to suck solder balls in the sucking holes, and then the solder balls thus sucked are mounted on the substrate. A means has been developed that, in the ball sucking operation, solder balls in a solder ball supply box are caused to float. In order to employ this solder ball floating method to suck solder balls at high speed thereby to shorten the time required for sucking solder balls, it is necessary to increase the degree of vacuum; that is, the solder ball sucking operation is carried out with a large flow rate of solder balls (hereinafter referred to as “a large ball-sucking flow rate”, when applicable).
If, in order to increase the solder ball sucking speed, solder balls are sucked with a large ball-sucking flow rate by a high degree of vacuum, and held, then as shown in
FIG. 4
air leaks through the contact section of a solder ball
3
and a sucking plate
30
. The air leakage sucks an additional solder ball
31
. That is, two solder balls are absorbed (“a double ball phenomenon”). The contact surface of the sucking plate
30
and the solder ball
3
is not completely circular, and the solder balls
3
is not completely spherical, as a result of which a gap is formed therein. Through this gap, a force for sucking another solder ball
31
is formed, so that the double ball phenomenon occurs. If the degree of vacuum of the suction pressure is increased, the force of suction through the gap is increased, so that the frequency of occurrence of the double ball phenomenon is also increased.
SUMMARY OF THE INVENTION
An object of the invention is to provide a solder ball mounting device in which solder ball sucking pressure, and a sucking head position are suitably adjusted to prevent the occurrence of a double-ball phenomenon, thereby to perform a solder ball sucking operation with high efficiency.
In order to solve the above-described problems, there is provided a solder ball mounting device for mounting solder balls on a workpiece according to a first aspect of the invention, comprising: a solder ball supplying section in which the solder balls are stored; a sucking head having a plurality of solder ball sucking holes in a lower surface thereof; sucking means coupled to the sucking head so as to suck the solder balls in the solder ball sucking holes; lift means for vertically moving the sucking head; and pressure adjusting means for adjusting and setting degree of vacuum in the sucking head to a first pressure for sucking the solder balls, and to a second pressure which is lower in the degree of vacuum than the first pressure and is high enough to hold the solder balls sucked, wherein, when the sucking head is positioned at a lower position where the sucking head sucks the solder balls by means of the lift means, the pressure adjusting means adjusts and sets the degree of vacuum in the sucking head to the first pressure, and when the degree of vacuum in the sucking head reaches the first pressure, the lift means moves the sucking head upwardly, and thereafter the pressure adjusting means starts adjusting the degree of vacuum in the sucking head thereby setting to the second pressure.
Further, according to a second aspect of the invention, there is provided a solder ball mounting device for mounting solder balls on a workpiece, comprising: a solder ball supplying section in which solder balls are stored; a sucking head having a plurality of solder ball sucking holes in a lower surface thereof; sucking means coupled to the sucking head so as to suck the solder balls in the solder ball sucking holes; wherein, when the solder balls are to be sucked in the sucking holes, the sucking head are moved up and down plural times to suck solder balls, and the solder balls thus sucked are mounted on the workpiece; and pressure setting means for adjusting and setting degree of vacuum in the sucking head to (i) a first pressure with which the solder balls are sucked by the sucking head when the sucking head is moved downwardly, and (ii) a second pressure which is higher than the first pressure and high enough to hold the solder balls sucked when the sucking head is moved upwardly.
Still further, according to a third aspect of the present invention, there is provided a method for setting a position and degree of vacuum of a sucking head provided in a solder ball mounting device for mounting solder balls on a workpiece, comprising the steps of: (A) moving the sucking head from a higher position to a lower position at which the solder balls are to be sucked in solder ball sucking holes formed in a lower surface of the sucking head; (B) reducing a pressure in the sucking head to a first pressure so as to suck the solder balls in the solder ball sucking holes after the step (A); (C) moving the sucking head from the lower position to the higher position; and (D) increasing the pressure in the sucking head from the first pressure to a second pressure at which the solder balls are hold in the solder ball sucking holes at the same time of step (C).
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Hughes S. Thomas
Jimenez Marc
Shibuya Kogyo Co. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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