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Method for a copper column as a 2nd-level interconnect at the substrate base layer

IP.com Disclosure Number: IPCOM000100668D
Publication Date: 2005-Mar-16
Document File: 4 page(s) / 32K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a copper (Cu) column as a 2nd-level interconnect at the substrate base layer. Benefits include improved functionality and improved reliability.

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Method for a copper column as a 2nd-level interconnect at the substrate base layer

Disclosed is a method for a copper (Cu) column as a 2nd-level interconnect at the substrate base layer.  Benefits include improved functionality and improved reliability.

Background

              Component-to-board solder-joint strength failure occurs during reliability stress testing. Typical stress tests include:

•             Temperature cycling, which represents the operating life of the product

•             Shock and vibration, which represent the shipment and handling environment

              The typical failures are fatigue or brittle joint cracking at high-stress areas. The cracking occurs at the solder ball and the component or board metal pads interface.

      Conventionally, the problem is solved using the following methods:

•             Increasing the metal pad diameter opening

•             Larger solder balls in a ball-grid array (BGA, see Figure 1)

•             Optimizing the solder-joint aspect ratio

•             Sacrificial balls in a high-stress area of the component ball fields

•             Electroless nickel immersion gold (ENIG)

 

      The ENIG (Ni3Sn4 and Ni) interface is more susceptible to having brittle solder joints (see Figure 2).

General description

      The disclosed method uses a copper base and eutectic/lead-free solder cap pillar shape structure as a 2nd-level interconnect at the substrate base layer.

Advantages

              The disclosed method provides advantages, including:

•             Improved functionality due to providing a copper column as a 2nd-level interconnect

•             Improved functionality due to meeting the finer pitch requirements of HDI packages and smaller form factors

•             Improved reliability due to complementing higher shear stress and avoiding inter-metallic layer fracture

•             Improved reliability due to providing high resistance to fatigue failure in comparison with pure eutectic solder balls

Detailed description

      The disclosed method includes a substrate-level...