Metal fusion bonding – Process – Preplacing solid filler
Reexamination Certificate
1999-12-28
2001-12-04
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
Preplacing solid filler
C228S180220, C438S614000
Reexamination Certificate
active
06325280
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to making connections between integrated circuit (IC) packages and circuit boards.
Ball grid array (BGA) packages are becoming increasingly popular because of their low profiles and high densities. The rounded solder ball contacts of a BGA are generally soldered directly to corresponding surface mount pads of a printed circuit board rather than to plated thruholes which receive pins from, for example, a pin grid array IC package. However, once a BOA package is soldered to the printed circuit board, the soldered balls of the EGA package are difficult and expensive to inspect. Moreover, the packages are difficult to remove, for example, in situations where the IC package requires repairing or upgrading.
SUMMARY OF THE INVENTION
This invention relates to making a reliable low loss electrical interconnection between electrical contacts of individual substrates while duplicating the mating condition normally present between the solder ball of a ball grid array package (BGA) and an electrical contact area (e.g., surface mounted land) on one of the substrates. The term “substrate” is intended to mean any base member having electrical contact areas, including printed circuit boards, IC chip substrates or the packages supporting such chip substrates.
The electrical interconnection is provided with an intercoupling component (e.g., socket, adaptor or header assembly) including terminals which are positioned within an array of holes in an insulative support member and configured to electrically connect the array of connection regions of a substrate to an array of connection regions of another substrate. The array of holes in the support member are located in a pattern corresponding to the array of electrical connection regions of the substrate.
Soldering a BGA package to an intercoupling component is often preferable to soldering the package directly to a circuit board (e.g., motherboard). Using an intercoupling component facilitates removing the BGA package in situations where the package needs to be repaired or replaced. Moreover, because the intercoupling component generally has a lower mass than a motherboard, less heat is required to solder it to a BGA package; thus the BGA is subjected to less thermal stress.
In one application of the invention, an intercoupling component is in the form of a socket assembly which is soldered to a printed circuit board. The socket assembly receives another intercoupling component in the form of a pin adaptor assembly carrying a BGA package.
In one aspect of the invention, a method of providing such an intercoupling component includes positioning terminals within holes of an insulative support member and attaching a solder ball to each of the terminals. Attaching the solder ball to the terminals is accomplished using a fixture having a number of recesses located in a pattern corresponding to a pattern of the holes to the insulative support member; filling each of the recesses with a solder ball; positioning the insulative support member over the fixture so that an end of each of the terminals contacts a corresponding solder ball; soldering the solder ball to the end of the terminal while maintaining the generally spherical shape of the solder ball; and removing the insulative support member from the fixture. The solder balls are generally soldered by passing the insulative support member with terminals and solder balls through a reflow apparatus.
Each terminal element includes an elongated electrically conductive member having first and second ends, the first ends configured to be electrically connected to corresponding ones of the array of electrical connection regions disposed on the first substrate. The second ends of the terminals receive the solder balls.
Preferred embodiments of the above described inventions may include one or more of the following features for preventing the solder ball from melting around or along the side of the terminal when it is attached. For example, the holes may be sized to allow the second end of the terminals to be press-fit into the insulative support member so that only the surface of the second end of the terminals is exposed to the solder ball. The terminals may include solder resist coated around, but not on, the exposed surface of the second ends of the terminals. An insulative sheet member may be disposed over the lower surface of the support member and may include an array of holes sized to receive the second end of the terminals with a snug fit. The insulative sheet member may include a conductive circuit pattern (e.g., a ground plane or circuit traces).
Solder flux is provided to the second ends of the terminals. The terminals include, along their outer periphery, a pair of securing members. Upon being positioned within the insulative support member, a first one of the pair of securing members is positioned a length, relative to the upper surface of the support member, equal to about one-third the thickness of the insulative support member. Similarly, a second one of the pair securing members is positioned a length, relative to the opposite lower surface of the support member, equal to about one-third the thickness of the insulative support member.
In another aspect of the invention, the intercoupling component described above includes a pair of securing members disposed along the outer periphery of the terminal element. The terminal elements, upon being positioned within the insulative support member, include a first one of the pair securing members positioned a length, relative to the upper surface of the support member, equal to about one-third the thickness of the insulative support member. Similarly, a second one of the pair securing members is positioned a length, relative to the opposite lower surface of the support member, equal to about one-third the thickness of the insulative support member. In one embodiment, the first holes are sized to allow the second end of the terminal elements to be press-fit into the insulative support member so that substantially only the surface of the second end of the terminal elements are exposed. The intercoupling component also includes terminals having a solder ball, of the type normally used with BGA packages, preattached to at least one of the ends of the terminal. The solder ball electrically connects to an electrical connection region, such as a land of a substrate (e.g., printed circuit board). The other end of the terminal may also include a solder ball or may be adapted to electrically connect to a contact (e.g., pin terminal or socket terminal) of another substrate (e.g., pin adapter or socket).
The terminal with a preattached solder ball not only provides the desired mating condition of the solder ball to the circuit board, but is also solderable to a contact without having to apply additional solder paste or having to attach solder preforms to the ends of the socket terminals.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments and from the claims.
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Advanced Interconnections Corporation
Dunn Tom
Fish & Richardson P.C.
Johnson Jonathan
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