Innovative Semi-Additive Process Technologies for IC Substrate Build-Up Layers

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Systek SAP is a family of high performance build-up processes for IC substrate RDL that provide multiple process flows for different materials as well as revolutionary technology innovations in the desmear, conditioning, activation and metallization steps.

Systek semi-additive processes provide the optimal metallization seed layer for unclad build-up substrates. With Systek SAP, new design possibilities in IC substrate manufacturing of high density circuitry are now available for fine-line, ultra fine-line and flex materials. IC Substrate manufacturers of new, very high density designs are adopting the Systek SAP family of processes to boost manufacturing capabilities, control costs, and improve the selection of designs they can develop.

Systek SAP Desmear Technology

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Systek SAP starts with a four-step desmear process that can be calibrated to optimally prepare multiple substrate materials, depending on the fabricator’s choice of design. The first step is the Systek Sweller 120, a solvent-based sweller that modifies the surface of the build-up material to be more wettable. This is then followed by the Systek Oxidizer 200 and Systek Neutralizer 200, a permanganate etch / neutralizer system that removes laser debris and increases topography. The desmear process is completed with the Systek GE 360 glass etch which promotes uniform palladium adsorption on glass surfaces of the build-up material.

The Systek SAP desmear steps provide minimum roughness on the build-up film substrate while consistently ensuring a clean via sidewall and copper target pad for superior copper-to-copper adhesion at all copper interfaces.

Systek GE 360

The Systek GE 360 is an innovative glass etch process that uniformly frosts glass substrates while removing loose glass spheres with minimal attack. The unique glass etch solution is free of sulfuric acid which allows for improved adhesion and increased peel strength on glass build-up substrate materials.

Systek SAP Conditioner Technology

The Systek SAP conditioner process is a three-step system that ensures adsorption of the palladium catalyst into the substrate. The process starts with the Systek Conditioner 400, a chemical bond enhancing pre-conditioner bath, followed by the Systek Conditioner 460, a cationic resin and glass conditioner bath. Conditioning is completed with the Systek Oxidizer 500, a target pad activating micro etch. Working together, these three processes allow unparalleled activation capability for electroless copper initiation in hard-to-reach and hard-to-clean areas of the build-up layer.

Systek Conditioner 400

The Systek Conditioner 400 is an alkaline solution with functional organics used to increase peel strength capability. The bath removes loose glass spheres and attaches functional groups to the surface to increase surface energy resulting in superior wetting difficult-to-reach areas such as the target pad wedge. Additionally, the process provides the optimal surface for the subsequent Systek Condition 460.

Systek Oxidizer 500

To ensure proper micro via structure reliability, an optimized micro etchant process that gently lifts any remaining debris and residues from the micro via target pads is required. The Systek Oxidizer 500 is a highly controlled micro etch bath that works specifically with the wedge geometry to create superior copper to copper bonding during the subsequent activation and electroless copper metallization step. The process is particularly useful for restoring the copper topography of recast copper that appears on the target pads during UV laser drilling.

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Systek SAP Copper Technology

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The Systek SAP copper metallization process includes a palladium activation system, an electroless copper metallization process, and an optional anti-tarnish. The Systek Activate 620 / Systek Reducer 700 is an ionic palladium activator system that works specifically with the conditioner technology to provide a highly active surface for metallization. The Systek Copper 850 is a zero-stress electroless copper plating bath.

Systek Copper 850

Following activation of the substrate the micro via structures enter the final electroless copper plating stage. The Systek SAP Copper 850 is an electroless copper plating process with stellar physical properties. The bath ensures complete and uniform coverage of the surface with just 0.25 to 1 micron thick, stress-free copper. The deposit allows for reduced roughness on the substrate surface, resulting in improved signal properties without sacrificing adhesion. The bath operates at a low temperature of 25 to 38 °C and is suitable for SAP build-up for IC substrate designs on flex, rigid-flex and rigid materials.

While traditional electroless copper is known for its poor elongation and high internal stress properties, the electroless deposit produced by the Systek SAP Copper 850 is stress free and has 10 to 16% elongation tested according to ASTM-E-345.

Systek SAP Flex Process for Polyimide

The challenges of metallization on bare polyimide are addressed by Systek SAP Flex, a semi-additive metallization process that utilizes a highly adherent electroless nickel tie coat as the initiation layer.

The flex system is a complete process including pre-treatment, NiP seed layer deposition and flash copper plating for excellent photo resist adhesion. The completely optimized desmear, conditioning, and activation technologies are specially designed to address the unique aspects of plating on PI. The Systek SAP Nickel 910 tie coat is an alkaline electroless nickel process that deposits a high quality nickel-phos deposit with 3-5% phosphorous and low stress for excellent adhesion on smooth substrates. The nickel tie-coat is flash plated with copper, followed by Systek copper via fill technology for pattern plating. After resist-stripping, the process is completed by the specially formulated Systek NiEtch 900 nickel-copper sulfuric peroxide differential etch. The etch is then followed by Systek Pd Remover 975 to remove any residual Pd seed from the activation step.

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