The plastics usedmust alsomeet international standards and norms. All manufacturers
of power electronics components are active worldwide, so their products must meet
NFF, UL, CSA, CCC, IEC, EN andVDE standards. For example, IGBTmodules used in
traction applicationsmust comply with NFF 16101 (the French fire protection standard).
According to UL 94 VO, all plastics usedmust be self-extinguishing, even at very small
wall thicknesses. They must also comply with UL 1557 (electrically isolated
semiconductor devices), IEC 60749 (mechanical and climatic test), IEC 60747-19
(discrete and isolated power semiconductor devices). Last but not least, plastics,
especially those in the low and medium power range, must comply with RoHS
regulations, which state that theymust be free of halogen and antimony trioxide
Ideally, the plastics usedmust not absorb anymoisture andmust be capable to be print-
on afterwards (e.g. lasermarking).
Tomeet these stringent requirements, polymer plastic
are used. None of the standard
polymers – PE (polyethylene), PP (polypropylene) and PVC (polyvinylchloride) – are
used in power semiconductor components, because of the properties that are required.
Instead, plastics such as PPS (polyphenylene sulphide) and PBT (poly butylene
terephthalate) are used in standard IGBTmodules and IPMs. PPS is a high temperature
resistant thermoplastic material that resists temperatures of up to 240°C in continuous
use. For short periods, such as in soldering, it can withstand temperatures of up to
270°C without damage. PPS also has exceptional electrical properties as a dielectric
non-conductor with a high CTI value. PBT is another thermoplastic material with a
typical initial temperature range of -50°C to 150°C. It can also withstand peak
temperatures of up to 280°C. It is very rigid, has a high degree of fastness, and is
dimensionally very stable. In addition, it has robust friction and wear resistance
properties and good electrical insulating properties. In terms of CTI value, however, PBT
has a lower value thanPPS.
PPA (polyphthalamide), PA (polyamide) and PET (polyethylene terephthalate) plastics
are being usedmore andmore frequently in high-voltage applications of IGBTmodules
from 2.5kV to 6.5kV blocking voltage. These plasticsmeet theNFF 16101 standard and
have very goodelectrical insulatingpropertieswithCTI values >400.
DCB (direct copper bonded) substrates, or simply DCB, are the most widely used
substrate materials in power electronics. They have been used for this purpose since
IGBT modules first began to be produced. Initially, DCB substrates were used only in
combination with copper baseplates. Nowadays, substrates are used in many IGBT
module solutions, evenwithout a baseplate.
DCB substrates comprise a ceramic dielectric insulator, towhich pure copper is applied
and bonded to the ceramic with great adhesive strength in a high temperature melting
2002/95/EC Directive on the restriction of the use of certain hazardous substances in electrical and electronic
equipment. This Directive requires Member States to ensure that, from 1 July 2006, new electric and electronic
equipment put on the market does not contain lead, mercury, cadmium, hexavalent chromium, polybrominated
biphenyls (PBB) or polybrominated diphenyl ethers (PBDE).
Antimony trioxide (Sb
is an inorganic compound that used to be used as a flameproofing agent or flame
retardant in plastics, includingproofing agents suchas casting resins and impregnating resins.
A polymer is a chemical compound comprised of chain or branchedmolecules (macromolecules) that consist of
the same or similar units, whichare known asmonomers.