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Method for interlocking features and a periodic array of metal vias on metal core substrates

IP.com Disclosure Number: IPCOM000007804D
Publication Date: 2002-Apr-24
Document File: 4 page(s) / 94K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for interlocking features and a periodic array of metal vias on metal core substrates. Benefits include improved reliability.

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Method for interlocking features and a periodic array of metal vias on metal core substrates

Disclosed is a method for interlocking features and a periodic array of metal vias on metal core substrates. Benefits include improved reliability.

Background

      Severe cracking and delamination of the organic build-up layers occur when metal core substrates are used in packages to reduce die thin-film stresses (see Figure 1). The cracking is driven by the stiffness mismatch between the metal core [low coefficient of thermal expansion (CTE, 3 ppm/c), high modulus (150 Gpa)] and the organic build-up layers [high CTE (90 ppm/c), low modulus (2 Gpa)]. When the metal core is compared with the wireless technology core [CTE (15 ppm/c), modulus (15 Gpa)], a 5-times higher CTE ratio occurs between metal core/build up than the other core/build up. Similarly, a 10-times higher modulus ratio occurs between the metal core/build-up than the wireless core/build up. The result is high stresses at the metal core/build-up interface, causing the build-up layer to delaminate from the metal core.

      No effective conventional solutions have been identified. The use of build-up layers with a lower CTE than 90 ppm/c is one possible approach.

General description

      The disclosed method is a combination of features that decrease interfacial cracking between a metal core and organic build-up layers. The key elements include:

§         Interlocking features such as dimples are made on the top and bottom surface of the metal core substrate by fabricating methods such as wet or dry etching, lasers, and mechanical methods, such as stamping and embossing. The dimples can be placed across the entire metal core surface or in local regions such as package high stress areas. The dimples act to arrest any delamination/cracking that initiates at the interface between the metal core and build-up layer by a combination effect of crack blunting and crack re-initiation/redirection, causing the crack to travel a longer path.

§         A matrix array of metal via anchors are formed on both surfaces of the metal core substrate after application of the first organic build-up layer. The size and spacing of the metal vias are designed so that they do not crack or shear by the high shear stress that arises due to mismatch in the CTE between the build-up layers (high CTE) and the metal core (low CTE). The anchors a...