Browse Prior Art Database

Short Free-Foot Design for Fine Pitch SMT Component

IP.com Disclosure Number: IPCOM000036661D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Manca, A: AUTHOR [+2]

Abstract

This invention describes methods of improving the solder attachment of a SMT leaded component. This is achieved by capturing the excess solder paste during the initial "pick and place" operation, and the subsequent solder reflow process (vapor phase or I.R.). Currently, the standard design of the foot of the lead tends to squeeze out the solder paste during the component attachment operation. This, together with the fine pitch lead design (0.050" or less), has the potential of causing adjacent pads to "short out". This invention describes methods by which the above problem can be eliminated. OPTION 1 (Fig. 1)

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Short Free-Foot Design for Fine Pitch SMT Component

This invention describes methods of improving the solder attachment of a SMT leaded component. This is achieved by capturing the excess solder paste during the initial "pick and place" operation, and the subsequent solder reflow process (vapor phase or I.R.). Currently, the standard design of the foot of the lead tends to squeeze out the solder paste during the component attachment operation. This, together with the fine pitch lead design (0.050" or less), has the potential of causing adjacent pads to "short out". This invention describes methods by which the above problem can be eliminated. OPTION 1 (Fig. 1)

This shows the design of the lead foot with a "relief" hole. This allows excess solder during the placement and solder reflow operation, to flow upward through the hole and onto the top surface of the foot. The upward flow of the solder into the hole will eliminate the present overflow condition of solder to bridge, and hence short with adjacent pads.

OPTION 2 (Fig. 2): The design of the foot of the lead shows a formed "relief" cavity, which will also prevent the excess solder from being squeezed out, causing solder bridging and shorting with adjacent pads.

Calculations show that the cavity design when compared with a normal lead, will displace approximately 21% less solder from the surface of the pad during the bonding operation.

Both of the above designs of Options 1 and 2 can be implemented using standar...