Patent Application
20090111299
This invention relates to a method and system for surface mounting an area array connector on to a circuit board and, more particularly, to a method and system for planarization of the connector leads to facilitate the reliable joining of the connector to the circuit board using solder.
This invention solves the leads coplanarity and soldering problem of a surface mount array connector. A known solution to this problem is to apply a load 11 to the top of a connector 10 which will deflect leads 12 of the connector 10 to conform to the flat surface of a circuit board 19 during the solder attach reflow process as shown in
U.S. Pat. No. 5,195,674 issued Mar. 23, 1993 to Nishi for REFLOW SYSTEM discloses a reflow system for heating solders temporarily attaching electronic components to a circuit board.
US Patent Application Publication 2004/0245648 A1 published Dec. 9, 2004 by Nagasawa et al. for BONDING MATERIAL AND BONDING METHOD discloses a bonding material and a bonding method which enable lead-free bonding that can replace high-temperature soldering. The material disclosed is a mixture of metallic nano-particles and an organic solvent. The bonding material can have two or more sintering temperatures.
US Patent Application Publication 2005/0243536 A1 published Nov. 3, 2005 by Chiba et al. for PRINTED CIRCUIT BOARD, PARTS MOUNTING METHOD AND MOUNTING POSITION VERIFYING METHOD discloses a printed circuit board that can suppress the positional displacement of parts mounted thereon. Spare marks are used for pre-alignment of components on the same circuit board prior to placing the components on the actual circuit board position for solder attach.
US Patent Application Publication 2006/0139902 A1 published Jun. 29, 2006 by Happoya for DOUBLE-SIDED COMPONENT-MOUNTED CIRCUIT BOARD AND METHOD FOR MANUFACTURING THE SAME discloses a double-sided component-mounted circuit board having a base shaped flatly and having a wiring pattern thereon with circuit components mounted on both faces of the base so as to be connected to the wiring pattern to configure the circuit. A rigid reinforcing member attaches to one side of the circuit board to facilitate the manufacture of a thin double sided surface mounted circuit board assembly.
Japanese Patent No. 02211995 A published Aug. 23, 1990 by Masaya et al. for PASTY SOLDER discloses a pasty solder for preventing a Manhattan phenomenon. The pasty solder is formed by mixing at least two kinds of solder particles of different melting points.
Japanese Patent No. 06140756 A published May 10, 1994 by Masao for CREAMY SOLDER AND MOUNTING OF ELECTRONIC CIRCUIT COMPONENT USING THE CREAMY SOLDER discloses a method for temporarily joining an electronic component to a circuit board using a solder paste alloy that has been mixed with higher melting conductive particles.
In one embodiment, it is primary purpose on the present invention to planarize the surface mount leads of an array connector using a solder reflow method. The advantages of using this invention over known solutions are improved surface mount leads coplanarity of the connector without the need for an external loading mechanism to force the leads to the circuit board, no additional thermal mass added to the reflow fixture which will facilitates the solder reflow thermal profile process, increased surface mount connector yields from the connector supplier (coplanarity tolerance of the leads may be relaxed slightly prior to applying the planarization invention), reduced rework of non-conforming connectors at the supplier, reduced circuit board assembly cycle time (less fixturing and reflow duration), and reduced fixture cost
System and computer program products corresponding to the above-summarized methods are also described and claimed herein.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with advantages and features, refer to the description and to the drawings.
The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains the preferred embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Referring to
The surface mount array connector 10 is mounted to the flat plate 13 using screws 17 that threads into connector guide blocks 18. It will be understood that this holds the connector 10 in contact with the solder paste 14 that is on the flat plate 13.
The fixtured connector 10 and flat plate assembly 13 is placed into a reflow oven. The oven is profiled to allow only the lower melting point solder particles to melt for a brief period of time above the melting point of the lower melt solder. The temperature and duration of the reflow process is controlled such that the higher melting solder particles do not melt. The resulting solder fillet structure will fill original coplanarity gaps 15 that were in the connector leads.
The “pasty range” of a slightly off-eutectic solder is used to create a coplanar surface on the leads of an array connector. The idea is to “freeze” the solder at the “pasty range” before it completely wets to the leads. These types of slightly off-eutectic solder remain viscous for a period of time at the lower melting point solder liquidus point. The solder paste used is a mixture of smaller size particles of low melting alloy (i.e. SnPbAg melts at 178 C) mixed with larger size particles of higher melting alloy (i.e. SnPb melts at 183 C). The smaller size low melt alloy will diffuse slower into the higher melt alloy and thus gain a longer time in the “pasty range”.
Referring to
The planarized connector in
The capabilities of the present invention can be implemented in software, firmware, hardware or some combination thereof.
As one example, one or more aspects of the present invention can be included in an article of manufacture (e.g., one or more computer program products) having, for instance, computer usable media. The media has embodied therein, for instance, computer readable program code means for providing and facilitating the capabilities of the present invention. The article of manufacture can be included as a part of a computer system or sold separately.
Additionally, at least one program storage device readable by a machine, tangibly embodying at least one program of instructions executable by the machine to perform the capabilities of the present invention can be provided.
The flow diagrams depicted herein are just examples. There may be many variations to these diagrams or the steps (or operations) described therein without departing from the spirit of the invention. For instance, the steps may be performed in a differing order, or steps may be added, deleted or modified. All of these variations are considered a part of the claimed invention.
While the preferred embodiment to the invention has been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.
