14 Fundamentals of Advanced Materials …
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performance than the cored counterparts due to the shorter electrical path and the
higher pin counts [22, 23]. This can also mean faster signal transmission due to the
lack of a through hole like in conventional cored substrates. The main challenges
in enabling next generation packages will substrate warpage control in the case of
coreless packages, and finer line and space patterning. While there are many ways
of enabling line and space combinations to as tight as 1/1, it is important to keep
in mind that the existence of a concept of tighter line and space compared to a
previous generation of packaging does not necessarily make it manufacturable and
high yielding.. This makes the choice of packaging materials critical. New high T g
and low CTE materials, through design of molecules with higher-order structure,
nanoparticles, super-fine photosensitivity technology, and combination of electric
and optical technologies are expected to be some of the main possible solutions
moving forward [2].
14.3 Organic Substrate Materials
14.3.1 Materials Employed in Organic Substrate Production
For any substrate used for microelectronic packaging, its performance is determined
by two factors: bulk material properties and interface properties. The interface properties often result from the chemical nature of the bulk materials (including additives),
and the process of creating the interface. Over the past half a century, the materials for
organic printed wiring board (PWB) and substrate applications have gone through
significant advancement, both in available material varieties and material properties
to meet different application needs. However, the basic structural components of
PWB or substrate have remained almost unchanged. Generally, substrate and PWBs
consist of three structural components: reinforcements (i.e. mechanical reinforcement structure), an organic resin system, and a conductor. In the case of coreless
substrates, reinforcement is omitted.
Reinforcements are utilized to achieve desired mechanical and physical properties
such as substrate mechanical rigidity and strength, dimensional target and stability,
and coefficient of thermal expansion (CTE) matching. The most commonly employed
reinforcement is woven fiberglass. Other reinforcements include glass matte, linear
continuous-filament fiberglass, paper, aramid fiber, Teflon, and metals such as copperinvar-copper, aluminum, and fillers [3].
The resin system (including its additives) is used to build up layers and glue
all the layers together. The commercially available resin systems are epoxy resins,
epoxy blends, bismaleimide triazine (BT)/epoxy mixtures, cyanate ester, polyimide, polyester, polytetrafluoroethylene (PTFE), and alkylated polyphenylene ether
(APPE). Most resin systems contain additives to achieve desired properties. These
additives include curing agents and catalysts, adhesion promoters, flame retardants,
399
performance than the cored counterparts due to the shorter electrical path and the
higher pin counts [22, 23]. This can also mean faster signal transmission due to the
lack of a through hole like in conventional cored substrates. The main challenges
in enabling next generation packages will substrate warpage control in the case of
coreless packages, and finer line and space patterning. While there are many ways
of enabling line and space combinations to as tight as 1/1, it is important to keep
in mind that the existence of a concept of tighter line and space compared to a
previous generation of packaging does not necessarily make it manufacturable and
high yielding.. This makes the choice of packaging materials critical. New high T g
and low CTE materials, through design of molecules with higher-order structure,
nanoparticles, super-fine photosensitivity technology, and combination of electric
and optical technologies are expected to be some of the main possible solutions
moving forward [2].
14.3 Organic Substrate Materials
14.3.1 Materials Employed in Organic Substrate Production
For any substrate used for microelectronic packaging, its performance is determined
by two factors: bulk material properties and interface properties. The interface properties often result from the chemical nature of the bulk materials (including additives),
and the process of creating the interface. Over the past half a century, the materials for
organic printed wiring board (PWB) and substrate applications have gone through
significant advancement, both in available material varieties and material properties
to meet different application needs. However, the basic structural components of
PWB or substrate have remained almost unchanged. Generally, substrate and PWBs
consist of three structural components: reinforcements (i.e. mechanical reinforcement structure), an organic resin system, and a conductor. In the case of coreless
substrates, reinforcement is omitted.
Reinforcements are utilized to achieve desired mechanical and physical properties
such as substrate mechanical rigidity and strength, dimensional target and stability,
and coefficient of thermal expansion (CTE) matching. The most commonly employed
reinforcement is woven fiberglass. Other reinforcements include glass matte, linear
continuous-filament fiberglass, paper, aramid fiber, Teflon, and metals such as copperinvar-copper, aluminum, and fillers [3].
The resin system (including its additives) is used to build up layers and glue
all the layers together. The commercially available resin systems are epoxy resins,
epoxy blends, bismaleimide triazine (BT)/epoxy mixtures, cyanate ester, polyimide, polyester, polytetrafluoroethylene (PTFE), and alkylated polyphenylene ether
(APPE). Most resin systems contain additives to achieve desired properties. These
additives include curing agents and catalysts, adhesion promoters, flame retardants,