Transfer Mold PFC Series with Compact Package

This article presents a new version of Mini Dual In-line Package Power Factor Correction
(DIPPFCTM) developed by Mitsubishi Electric Corporation for high power air conditioners
and general inverter use. In the new DIPPFC series, low thermal resistance was
realized by using an insulation sheet structure with high heat dissipation. Because of the
low thermal resistance, package size of the Mini DIPPFC is reduced compared to the
conventional large DIPPFC and input current rating is expanded up to AC 30Arms.
By Masahiro Kato, Teruaki Nagahara, Hisashi Kawafuji, Toshiya Nakano, Marco Honsberg
Power Device Works, Mitsubishi Electric Corporation, Japan
Configuration of DIPPFCTM
In recent years, high harmonic currents generated in electric power
systems are restricted in all electronic equipment. Especially in the
EU where IEC61000-3-2 is applied, the high harmonic current regula
tion are severe, and the application of PFC (Power Factor Correction)
is advanced. The power factor correction circuit shown in Figure
2 is now widely used. This circuit is composed of the diode bridge,
the switching device and the boost diode. In the DIPPFC, the highside
diode of the diode bridge has the function of boost diode, and
an IGBT is added in parallel with the low-side diode of the diode
bridge, as shown in Figure 3.
Therefore, DIPPFC has the functions of rectification and power factor
correction. DIPPFC includes a driver IC for the IGBTs as shown in
Figure 2.
New package structure
Figures 4 and 5 show cross-sectional drawings of a Mini DIPPFC
compared with a Large DIPPFC. DIPPFC (including DIPIPM) series
are simply made up of power chips (IGBTs, diodes), drive ICs and
assembly components (lead frame, Al/Au wire, resin, etc.). Bare
power chips and ICs are assembled directly on a lead frame and
connected by Al wire or Au wire, and then they are transfer molded.
Heat dissipation structure
In Large DIPPFC, the insulating layer between lead frame and builtin
heat-sink is formed by epoxy resin. In order to reduce the thermal
resistance, a ceramic-powder filler with high thermal conductivity was
incorporated in the epoxy resin However this technology has reached
its limits of insulation strength and heat dissipation through the epoxy
resin because of the fluidity properties of the filler.
To solve the problem, the new heat dissipation structure with insulating
resin sheet has been adopted in the Mini DIPPFC as shown in
Figure 5. The insulating resin sheet does not need very much fluidity,
in contrast to the epoxy resin, thus it is possible to increase the
amount of filler in the resin sheet. By using this resin sheet, the thickness
of the insulating layer can be thinner compared with that of the
epoxy resin isolation in the Large DIPPFC. Therefore, the thermal
dissipation can be improved considerably. As a result, the thermal
resistance was improved 35% compared to the Large DIPPFC (as
shown in Figure 6).
Compact Package size
Effective heat dissipation of the power chips is achieved by applying
the new heat dissipation structure with an insulating resin sheet,
thereby the power chip size could be shrunk appropriately. Through
Figure2