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Defect Reduction for Impedance Controlled Interconnect Device

IP.com Disclosure Number: IPCOM000207948D
Publication Date: 2011-Jun-16
Document File: 1 page(s) / 40K

Publishing Venue

The IP.com Prior Art Database

Abstract

Signal integrity requirements for interconnection devices drive physical characteristics which sometimes are in contrast to what would be considered optimal for surface mount attach to a printed circuit board. One such physical characteristic is thicker, stiffer signal leads. Thicker signal leads place higher stress on the solder joints, which is the method in which signals are commonly attached the printed circuit boards. This invention will document one way in which signal leads can be modified to provide for a more reliable interconnector between the device with the signal lead and the printed circuit board while still maintaining the overall signal integrity requirements of the system.

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Defect Reduction for Impedance Controlled Interconnect Device

Signal integrity requirements can result in attach leads which are stiff with very little compliance. Attach leads which are too stiff can lead to poorly formed solder joints which can become early life failures in field use conditions. It is not always possible to detect these poorly formed solder joints by standard inspection techniques. Even with good solder,

joints stiff leads can highly stress the solder joints through normal on/off

system thermal cycles. These thermal cycles cause stress by uneven expansion and contraction between the interconnection device and the printed circuit board due to difference in coefficients of thermal expansion in the interconnection device and the printed circuit board. If the leads cannot absorb the strain, the solder joints will be stressed. Leads that are too stiff for the solder joints between the interconnection device and the printed circuit board such that eventually the solder joint will have a lower life expectancy in the field and eventually fail.

Where the signal integrity requirements prevent using a thinner more compliant material for the entire lead, it is possible to thin out the solder-tail end of the lead to provide compliance and strain relief to the solder joint connection between the interconnection device and the printed circuit board. See figures 1a and 1b.

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Figure 1: 1a Left image; stan...