Patent Description:
<CIT> discloses an apparatus and method for attaching balls to a substrate for forming a ball grid array. The apparatus consists of two pole pieces, a magnetizing coil, and an excitation coil. The first pole piece has an alignment plate having a plurality of openings, and a plurality of tips which can be magnetized by the magnetizing coil to attract a ball into each opening. Once the balls are attracted into the openings, excess balls are removed and the substrate is aligned with the balls such that each ball is in contact with a respective pad on the substrate. The first pole piece having the balls and substrate position thereon is then placed into a receiving area of the second piece. An excitation coil is excited with a high frequency signal to heat the balls and reflow solder that has been previously applied thereto. The assembly is then cooled and removed from the device and the ball grid array is complete.

<CIT> discloses an apparatus and method to facilitate a positioning of a solder ball and a fixing of the solder ball and to obtain the solder ball, which can be stably mounted on a semiconductor device and an electronic component mounting substrate, wherein a nucleus formed of a magnetic metal or a magnetic alloy containing a magnetic metal as its main component is provided in the interior of the solder ball. In particular, in a solder ball, which is used for the connection of a semiconductor device and an electronic component mounting substrate, a nucleus formed of a magnetic metal or a magnetic alloy containing a magnetic metal as its main component is provided in the interior of the ball. The solder ball, for example, is formed into one having a nucleus, which is formed of a magnetic metal, in the interior of a solder. As the magnetic metal, nickel, iron, copper or the like is used. Moreover, the nucleus in the interior of the ball, for example, is formed into one with a surface coated with a metal having a good wettability with solder. As the metal having a good wettability with solder, copper, silver, gold, nickel, tin, zinc or the like is used and the metal having a good wettability with solder is coated on the surface of the nucleus by plating or the like.

The invention is defined by the features of claims <NUM> and <NUM>.

Apparatus and associated methods relate to a pick & place system that uses a magnetic core for both magnetic coupling with an assembly component and heating of the assembly component. The magnetic core has a component engagement surface configured to magnetically and thermally engage the component. A controller is configured to provide both AC current and DC current to an inductive coil wound about the magnetic core. DC current provided to the inductive coil induces a magnetic field within the magnetic core, thereby magnetically attracting the component when engaged with the component engagement surface. AC current provided to the magnetic core inductively heats the magnetic core, thereby heating the component when engaged with the component engagement surface [Insert text].

<FIG> are perspective views of a pick & place tool removing an adhesively-attached component from a system assembly. In <FIG>, pick & place tool <NUM> is in the process of removing adhesively-attached component <NUM> from system assembly <NUM>. Pick & place tool <NUM> is configured to both heat and magnetically attract adhesively-attached component. Such heating and magnetically attracting are coordinated so as to either attach a component to system assembly <NUM> of the remove the component, such as adhesively-attached component <NUM> from the system assembly <NUM>. Such heating and magnetically attracting functions are both performed by providing an electrical current to inductive coil <NUM>.

Magnetic attraction is performed by providing a DC current to inductive coil <NUM>. Such a DC current conducted by inductive coil <NUM> induces a magnetic field which can be oriented to either attract or repel a magnetic object proximate one side of the inductive coil. Such a magnetic field can be directed by core <NUM> about which inductive coil <NUM> is wound. Heating is performed inductively by providing an AC current to inductive coil <NUM>. Such an AC current can: i) inductively heat a conductive core, such as core <NUM> about which inductive coil <NUM> is wound; ii) inductively heat any conductive materials proximate thereto so as to be within an AC electromagnetic field induced by the AC current; and iii) conductively heat a component in contact with a conductive core, such as core <NUM>, inductively heated by the AC current.

To remove adhesively-attached component <NUM> from system assembly <NUM>, pick & place tool <NUM> moves component head <NUM>, which includes inductive coil <NUM> and core <NUM>, so as to align component head <NUM> with adhesively-attached component <NUM> in the x-y plane (e.g., a plane parallel to a level surface). Then, pick & place tool <NUM> then lowers (e.g., move in a negative z direction) component head <NUM> so as to engage component engagement surface <NUM> of core <NUM> with adhesively-attached component <NUM>. Then, pick & place tool <NUM> can heat adhesively-attached component, by providing an AC current to inductive coil <NUM>, so as to reduce an adhesion strength of adhesives that attach adhesively-attached component <NUM> to system assembly <NUM>. When such adhesives are heated, the adhesion strength of adhesively-attached component <NUM> to system assembly <NUM> can be significant reduced so that removal of adhesively-attached component <NUM> from circuit board assembly <NUM> is possible.

Various types of adhesives can be used to attach adhesively-attached component <NUM> to circuit board assembly <NUM>. Various solders, metals, and other adhesives are commonly used to attach electronic components to such circuit board assemblies, such as circuit board assembly <NUM>. Such various adhesives can be used for conductive connection between leads of adhesively-attached component <NUM> and conduction traces of circuit board assembly <NUM>. Some adhesives can be used for physical attachment only of adhesively-attached component <NUM> and circuit board assembly <NUM>.

After the adhesive strength of the adhesives used to attach component <NUM> have been weakened, a DC current can be supplied to inductive coil <NUM>, so as to magnetically attract component <NUM> to component head <NUM>. After component <NUM> is magnetically coupled, pick & place tool <NUM> can raise (e.g., move in a positive z direction) component head <NUM> so as to lift component <NUM>, which is magnetically coupled to component head <NUM>. Then, pick & place tool <NUM> moves component head <NUM> so as to align component head <NUM> with parts removal bin. Finally, DC current is zeroed or inverted so as to drop component <NUM> into the aligned parts removal bin. Thus, AC and DC electrical current is sequenced so as to heat, magnetically couple, and remove component <NUM> from system assembly <NUM>. In the depicted embodiment such a sequence of electrical excitation includes first providing an AC current, then a DC current, and then either no current or inverting the DC current. For the reverse operation - placing and attaching a component to system assembly, such a sequence of electrical excitation signals would be appropriately changed. Such sequencing of electrical excitation signals will be described in more detail below.

<FIG> is a schematic diagram of a component head configured to both inductively heat and magnetically attract a component of a system assembly. In <FIG>, component head <NUM> includes inductive coil <NUM> wound about core <NUM>. Electrical excitation signals are provided to inductive coil <NUM> by controller <NUM>. Controller <NUM> sequences various electrical excitation signals in a manner that corresponds to specific operations performed by the pick & place tool. In the depicted embodiment, first DC excitation signal <NUM> is generated and provided to inductive coil <NUM>. During the time that DC excitation signal <NUM> is provided to inductive coil <NUM>, controller <NUM> is aligning an attached component to a location on the system assembly where such a component is to be attached. After DC excitation signal <NUM> is terminated, controller <NUM> generates AC excitation signal <NUM> to inductively heat adhesives that will attach the component to the system assembly. During the time that AC excitation signal <NUM> is provided, the controller can be providing downward force (e.g., force directed in a negative z direction) upon the component so as to ensure good thermal coupling between core <NUM> and the component.

<FIG> are schematic diagrams illustrating placement and detachment of a component on a system assembly. In <FIG>, component head <NUM> is aligned (e.g., in the x-y plane) with component <NUM>, which is adhesively attached to system assembly <NUM>. In the depicted embodiment component <NUM> is a cover for an electronic component attached to system assembly <NUM>. Component head can be used to pick & place any type of component to which component head <NUM> can couple. In some embodiments, as will be shown below, coupling can be augmented using a vacuum to provide additional or complimentary coupling between component head <NUM> and component <NUM>. In <FIG>, arrow <NUM> indicates that component head is being lowered so as to engage (e.g., contact), component <NUM>.

In <FIG>, AC excitation signal <NUM> is provided to inductive coil <NUM> so as to heat component <NUM>. Such heating can be performed for a predetermine time duration or an be performed until component <NUM> or core <NUM> reaches a predetermined temperature. In some embodiments, a component head <NUM> includes a temperature sensor configured to sense temperature of core <NUM> and/or of component <NUM>. After (or while) component <NUM> has been heated, DC excitation signal <NUM> is provided to inductive coil <NUM> so as to magnetically attract component <NUM> to component head <NUM>. In <FIG>, arrows <NUM> indicate that component head is being raised so as to remove component <NUM>, which is magnetically coupled to component head <NUM>, from system assembly <NUM>.

<FIG> is a side-elevation view of an embodiment of a pick & place tool configured to inductively heat and adhesively-attach/detach a component. In <FIG>, adhesively-attached component <NUM>, is shown attached to system assembly <NUM> via solder balls <NUM>. Component head <NUM> includes inductive coil <NUM>, and complementary high-permeability members 34T and 34B. Complementary pair of high-permeability members 34T and 34B can be positioned on opposite sides of system assembly <NUM> about adhesively-attached component <NUM>. At least one of complementary pair the of high-permeability members 34T and 34B includes central pedestal 36T (which operates as core <NUM> operates in the embodiments depicted in <FIG> and). In the depicted embodiment, top high-permeability member 34T includes central pedestal 36T. "Top" here refers to the one of complementary high-permeability members 34T and 34B that is situated on the same side of system assembly <NUM> as the side that adhesively-attached component <NUM> is situated. The term "bottom" is used to refer to the other one of complementary high-permeability members 34T and 34B that is situated on the opposite side of system assembly <NUM> as the side that adhesively-attached component <NUM> is situated. The terms "top" and "bottom" need not be indicative of a particular orientation of circuit board assembly <NUM>. Instead, the terms "first" and "second" can be used to distinguish between complementary high-permeability members 34T and 34B.

A magnetic field can be induced in complementary high-permeability members 34T and 34B via inductive coil <NUM> circumscribing central pedestal 24T of the complementary pair of high-permeability members 34T and 34B. Coil driver <NUM> is configured to generate an AC current in inductive coil <NUM> circumscribing central pedestal 36T, thereby inducing the magnetic field therein. Because high-permeability members 34T and 34B are made of high-permeability materials, any magnetic fields induced therein are channel via the high-permeability members so as to minimize losses to the magnetic field induced. The magnetic field takes the path of "least resistance," which is a metaphor for the closed path of highest permeability. By directing the magnetic field, via complementary high-permeability members 34T and 34B, complementary high-permeability members 34T and 34B shield from magnetic field exposure circuitry outside an interior cavity defined by interior surfaces of high-permeability members 34T and 34B. Only the circuitry within such a cavity will be exposed to the magnetic field.

At least one of complementary pair the of high-permeability members 34T and 34B has a peripheral pedestal. In the depicted embodiment both top and bottom high-permeability members 34T and 34B have central pedestals - central pedestals 36T and 36B, respectively. Central pedestal 36T is configured to direct a magnetic field induced therein through the adhesively-attached component. Peripheral pedestals 38T and 38B are configured to provide a return path for the magnetic field about a periphery of the adhesively-attached component. Inductive coil is wound about central pedestal 36T. Thus configured, central pedestal 36T functions as core <NUM> functions in the embodiments depicted in <FIG>.

In operation, complementary high-permeability members 34T and 34B are positioned on opposite sides of the circuit board assembly about the adhesively-attached component <NUM>. High-permeability members 34T and 34B are positioned in clam-shell fashion so as to substantially enclose adhesively-attached component <NUM> within the interior cavity defined by interior surfaces of high-permeability members 34T and 34B. A magnetic field is then induced within high-permeability members 34T and 34B via AC excitation of inductive coil <NUM> by coil driver <NUM>. The magnetic field induced is directed through adhesively-attached component <NUM> so as to induce AC currents with any conductive material within or below adhesively-attached component <NUM>, thereby heating such conductive materials. Any solders, leads, circuit board traces, etc., which are located in this region where the magnetic field is directed will then heat due to these induced AC currents. Such heating can either directly heat the adhesives (e.g., if solder adhesives are located in this region) or indirectly heat the adhesives (e.g., via thermal conduction from the heated conductive materials to the adhesives).

One the adhesives have been heated, adhesively-attached component <NUM> can be removed from circuit board assembly <NUM>. Various methods of removing adhesively-attached component <NUM> from circuit board assembly <NUM> can be employed. For example, top high-permeability member 34T can be raised, and adhesively-attached component <NUM> can be manually removed using a tool, tweezers, etc. In some embodiments, top high-permeability member 34T can be equipped with a suction system to as to vacuum attach top high-permeability member 34T to a top surface of adhesively-attached component <NUM>. Then, by raising top high-permeability member 34T, vacuum attached component <NUM> will be removed thereby.

Claim 1:
A system (<NUM>) for heating, picking, and placing a component (<NUM>) of an assembly (<NUM>), the system comprising:
a magnetic core (<NUM>) having a component engagement surface configured to magnetically and thermally engage the component of the assembly;
an inductive coil (<NUM>) wound about the magnetic core; and a controller (<NUM>) that provides a DC signal and an AC signal to the inductive coil, the DC signal inducing a magnetic field within the magnetic core, thereby magnetically attracting the component when engaged with the component engagement surface, the AC signal inductively heating the magnetic core, thereby heating the component when engaged with the component engagement surface, characterized in that the magnetic core has a vacuum aperture (<NUM>) along a length of the magnetic core between the component engagement surface and another surface, the system further comprising:
a vacuum component extractor configured to provide vacuum within the vacuum aperture, thereby providing vacuum coupling of the component when engaged with the component engagement surface.