The present disclosure relates to a power module having leadframe-less signal connectors, in particular for automotive applications, and to the assembling method thereof.
As known, electric and hybrid propulsion vehicles comprise control electronics of the electric motor. In particular, the control electronics associated with vehicles of this type comprises power modules which may include both power components and signal processing components.
For example, the control electronics associated with electric propulsion generally comprises power phase inverters (so-called inverters) and rectifiers capable of operating at even very high voltages, up to 1200 V.
To electrically couple the modules to each other and to the loads (electric motor and/or vehicle members), the control electronics further generally comprises suitable connection structures, including leads and connection pins of greater dimensions with respect to the signal conduction pins or electronic circuits used in other fields.
The modules are normally enclosed in a packaging body of insulating material, for example molded, or produced using a gel potted technique, wherein a plastic box is filled with an insulating gel and encloses the components, with protruding pins. In both cases, the package has a generally parallelepipedal shape, with two greater surfaces (upper and lower), and four lateral surfaces, of smaller area, with the electrical connection pins protruding therefrom.
The molded power modules are generally arranged on a shaped metal support, called a leadframe, which also forms the pins for both the power connection and the signal connection.
This involves a considerable layout complexity to avoid the presence of parasitic components, typically parasitic inductances, as well as requiring an accurate design to ensure the safety isolation distances (“clearance and creepage”) and not allowing an efficient use of available spaces.
Furthermore, the overall dimensions of the power module cannot be reduced as desired, due to the need to maintain safety distances.
Furthermore, it is not easy to modify the type of external pins or leads and the way they are connected to the external connection elements (for example to share existing solutions between press-fit connections, soldering, screwing, etc.), depending on the specific design.
The present provides at least one embodiment of a power module which overcomes the drawbacks of the prior art and provides at least one embodiment of an assembling method.
In practice, the power module houses a pillar, typically coupled to the substrate carrying the electronic components of the power module and facing one of the greater surfaces (typically, the upper surface) of the package. Alternatively, it may be attached directly to a component of the power module.
The pillar may be attached to the substrate by soldering, with or without filler material (soldering, welding and sintering), or with a conductive glue.
The pillar shape and the package are designed so as to compensate for any manufacturing dimensional variations as well as errors and inaccuracies in mutual positioning between the pillar attaching zone in the power module, the pillar and the pin or other external connection structure, due to process tolerances.
The pillar has an external connection end variable according to the type of connection: for example, the connection end may be flat, for surface mounting or for coupling to external pins by press-fit or soldering; the pillar may be formed in an integral manner with the external pin; the connection end may have a recess configured to allow connection with the external pin by press-fit or by screwing (presence of a thread); the pillar may have structures that prevents its extraction (undercuts, knurls, surface irregularities with protrusions or recesses); and the pillar may have any shape and section, for example it may have a cylindrical shape with a circular section.
The pillar is embedded in the housing so that its lateral sides are completely or almost completely surrounded by and in contact with a packaging mass that blocks and extends around the pillar.
For a better understanding of the present disclosure, some embodiments thereof are now described, purely by way of non-limiting example, with reference to the attached drawings, wherein:
The following description refers to the arrangement shown; consequently, expressions such as “above”, “below”, “upper”, “lower”, “right”, “left” relate to the attached figures and are not to be interpreted in a limiting manner.
The housing 2 has a generally parallelepipedal shape, with an upper surface 2A, a lower surface 2B and lateral surfaces 2C.
The housing 2 houses a substrate 10, carrying electronic components (here, two shown, indicated as first and second electronic components 15A, 15B).
Signal or power leads 4 protrude from lateral surfaces 2C of the housing 2, here two lateral surfaces 2C opposite to each other.
Connectors 5, generally signal but, if desired, also power connectors, extend through the housing 2, between the substrate 10 and the upper surface 2A. The connectors 5 may be arranged level, slightly protruding from the upper surface 2A or even slightly recessed with respect thereto.
In the embodiment of
In detail, in
The second conductive layer 13 is shaped so as to define a plurality of connection islands or regions 14.
A first, a second, a third and a fourth connection region 14A-14D are for example visible in
Here, the first and the second electronic components 15A, 15B, for example power components such as diodes, transistors, thyristors or IGBTs, or packaged discrete components are attached and electrically coupled to the first and, respectively, to the second connection regions 14A, 14B.
The third connection region 14C is coupled to one of the leads 4, in a not visible manner and ideally represented by a dashed line 16. In turn, the third connection region 14C is connected in a manner not shown (for example, through wires or through tracks formed in the second conductive layer 13) to one or both the electronic components 15A, 15B. However, the leads 4 may also be connected directly to the electronic components 15A, 15B.
The fourth connection region 14D carries and is electrically coupled to one of the pillars 8. In particular, the pillar 8 of
The pillar 8 is embedded in the housing 2 so that its lateral sides are almost completely surrounded by and in contact with the packaging mass 3 that blocks and extends around the pillar 8 in the housing 2.
As visible from
The pillar 8 here has a cylindrical shape with a circular base and extends from the fourth connection region 14D up to the upper surface 4A of the housing 2, perpendicular to the substrate 10.
In the embodiment of
The pillar 8 has dimensions generally linked to the dimensions of the power module 1. For example, it may have a height comprised between 2 and 7 mm (millimeters), in particular of about 4.5 mm, and a diameter comprised between 1 and 5 mm, for example of about 2 mm.
In the embodiment of
Alternatively, a pin 21 may be attached to the pillar 8, as shown in
In particular, here, “pin” 21 is intended as a rod-shaped element that allows a current to flow and has a height higher than or equal to that of the pillar 8.
For example, the pins 21 are of metal. They may have a height generally comprised between 2.8 and 14 mm, for example of 8 mm, and a circular section, in particular with a diameter comprised between 0.5 and 1.5 mm, for example of 0.8 mm.
Furthermore, in
The pins 21 may also have enlarged press-fit-type pin contact zones (not shown in
In one embodiment, the pins 21 may have two enlarged press-fit-type contact zones, as shown in
Furthermore, the pins 21 may have stop zones, as shown in
Alternatively, the pins 21 may have any base, for example square (with a side between 0.6 and 3 mm).
In
Furthermore, the pin 21 is attached to the pillar 8 by soldering or gluing. In both cases bonding material (not shown) may be provided between the pin 21 and the pillar 8, for example soldering filler material or a conductive glue.
Alternatively, the pin 21 may be soldered without filler material, for example by ultrasonic welding.
Alternatively, the pin 21 may be press-fit to the pillar 8, as shown in
In
In particular, as visible in
The pillar 8 and the pillar portion 28 may have structures which prevent undesired extraction thereof, such as protruding portions, recessing portions, undercuts, knurls, surface irregularities and the like.
For example,
In the example shown, the groove 30 is formed at about half the height or at a midway point of the pillar 8, but it may be arranged at any height.
Furthermore, here it extends throughout the perimeter of the pillar 8, but may be interrupted.
Alternatively, the surface of the pillar 8 may form one or more protruding annular structures, blocking the pillar 8 inside the packaging mass 3 forming the housing 2.
Alternatively, the surface of the enlarged head 31 may form knurls or protruding and/or recessing structures which block it inside the housing 2.
Alternatively, similarly to
In detail, in detail
The peripheral slot 38 includes an inclined surface 49 that is at an angle with respect to the upper surface 2A. The inclined surface 49 extends past or into the upper surface 2A. In at least the embodiment as shown in
In some embodiments, the inclined surface 49 extends past or into the upper surface 2A and terminates within the packaging mass before reaching a respective end of the pillar 8 that is opposite to the end 8A of the pillar 8.
The peripheral slot 38 here extends to a short distance from the end 8A, so that this end 8A is surrounded by an annular portion 39 of the material of the housing 2, wherein the annular portion 39 is in turn surrounded by the peripheral slot 38.
In
This configuration allows any height tolerances of the pillar 8 to be compensated, as explained hereinbelow with reference to
In
In the case shown, the ejector 40 has a non-flat head surface 41, with a bigger area than the end 8A of the pillar 8. In the illustrated example, the ejector 40 is hollow, but it may be solid; the following dimensional considerations are presented as if the ejector 40 were solid.
The head surface 41 of the ejector 40 has a central zone 41A that is plane and a peripheral zone 41B protruding with respect to the central zone 41A and forming a step 42. The central zone 41A (typically circular, in case of pillar 8 with a circular section) has a greater area than the end 8A of the pillar 8, so as to rest flat on this end 8A and protrude laterally thereto with the step 42 arranged to partially surround, at a distance, the end 8A of the pillar 8.
Consequently, when the material of the housing 2 (for example resin), in a fluid phase, is injected into the mold 43, the resin covers the support 10 and the electronic components 15A, 15B, surrounds each pillar 8 and also gets into the gap existing between the step 42 of the ejector 40 and the end 8A of the pillar 8, creating the peripheral slot 38 and the annular portion 39.
Assuming that the power module 1 is arranged, with respect to a Cartesian coordinate system XYZ, with the axis of the pillar 8 directed parallel to axis Z, this solution allows compensation of any height inaccuracies of the pillar 8 or of the underlying layers of the substrate 10 (inaccuracies along the axis Z as in
In fact, the ejector 40 is rested on the end 8A of the pillar 8 with its central zone 41A, planar, and held in position by mechanical or pneumatic springs (not shown) capable of compensating for height errors of the end 8A of the pillar 8; the dimension of the central zone 41A allows compensation of any positioning errors along the axis X and/or the axis Y, as well as any small dimensional thickness tolerances, ensuring that the resin does not extend above the end 8A or form undesired peripheral burrs.
It should be noted that the “external” portion of the groove 38, not occupied by the ejector 40, is due to the shaping of the mold.
In detail, and as shown in
Each pin holder 45 is attached to the end 8A (not visible in
The pins 21 are then each interference-fit into a respective pin holder 45.
In detail, the power module 100 comprises a housing 102 formed by two half-shells (first half-shell 101A, second half-shell 101B) of insulating material, for example plastic. The two-half shells define an outer shell and define a cavity 103 that is between the first-half shell 101A and the second half-shell 101B. The second half-shell 101B includes an internal surface 109 that faces the internal surface 105 of the first half-shell 101A.
A gel material 104 is contained inside the half-shells 101A, 101B and blocks and locks the support 10 and the electronic components (not visible in
Here, the support 10 is attached to the first half-shell 101A and the power connector 5 extends through a hole 106 in the second half-shell 101B.
The power connector 5 shown in
In
Here, the mold (not shown) is such that the packaging mass 3 covers the end 8A of the pillar 8 and forms a protruding portion 3A.
The protruding portion 3A is then thinned to expose the pillar 8 and the pillar 8 is shortened, by a grinding operation.
Thereby, the end 8A of the pillar 8 is flush with the remaining part of protruding portion 3A of the packaging mass 3 (
This process may be applied to pillars of different shape, for example the embodiments of
In
In
The packaging mass 3 is then ground at the flat upper surface 3B to expose the pillar 8. The upper portion of the pillar 8 and the upper portion of the packaging mass 3 may be ground, so that the end 8A of the pillar 8 is flush with the packaging mass 3 (
Also this process may be applied to pillars of different shape, for example the embodiments of
In
In
Here, the packaging mass 3 and the pillar 8 are ground until completely removing the closed base 50 and form the end 8A of the pillar 8. Thereby,
Thereby, no resin or molding material may enter the axial recess 31 or threaded hole 33 during molding.
In the alternative to the embodiment of
The described power module and its assembling method have numerous advantages.
In particular, exploiting the upper surface 2A of the housing 2, 102 for signal/power electrical connection of the electric components allows the external surface of the housing to be to efficiently exploited, by simplifying the complexity of the connections at the substrate 10 level, reducing the parasitic inductances and the dimensions of the power module, while allowing the critical distances and the desired creepage to be maintained based on expected working voltages.
The solution is easily adaptable to pins of different type and to the desired bonding type (press-fit, soldering/welding).
The power connectors 5 are inexpensive and the assembling operations are simple, so that the power module 1, 100 has costs comparable with the known solutions.
Finally, it is clear that modifications and variations may be made to the power module and to the assembling method described and illustrated herein without thereby departing from the scope of the present disclosure, as defined in the attached claims.
For example, the different embodiments described may be combined to provide further solutions.
Furthermore, if allowed by the electronic components, the power connector 5 may be attached directly to contact pads of the devices internal to the power module.
In the embodiments of
Thinning of the packaging mass 3 may stop at the pillar 8, without shortening the latter.
A power module (1; 100) may be summarized as including a housing (2; 102) having a main surface (2A) and lateral surfaces (2C); a carrying substrate (10), inside the housing, the carrying substrate forming a plurality of connection regions (14A-14D) of conductive material; an electronic component (15A, 15B), inside the housing, attached to a first connection region (14A, 14B) of the plurality of connection regions (14A-14D); and an electrical connector (5), coupled to the electronic component (15A, 15B) or to a second connection region (14C) of the plurality of connection regions, the electrical connector (5) extending towards the main surface (2A) of the housing (2; 102), transversely thereto, and being accessible from the outside of the housing.
The electrical connector (5) may include a pillar element (8; 28) having one end (8A) facing the main surface (2A) of the housing.
The pillar element (8; 28) may have a solid cylindrical shape.
The electrical connector (5) may further include a rod-shaped element (21) soldered to the end (8A) of the pillar element (8) and extending from the main surface (2A) of the housing (2; 102) to the outside of the housing, in prosecution of the pillar element (8).
The electrical connector (5) may further include a pin holder (45) formed by an axially holed cylindrical body and provided with a flange end (48), the flange end being attached to the end (8A) of the pillar element (8) and extending from the main surface (2A) of the housing (2; 102) towards the outside thereof, in continuation of the pillar element (8).
The electrical connector (5) may further include a rod-shaped element (21) press-fit in the pin holder (45).
The pillar element (8) may have a cylindrical shape and include an axial hole (31).
The electrical connector (5) may further include a rod-shaped element (21) press-fit or screwed into the axial hole (31) and extending in prosecution of the pillar element (8).
The electrical connector (5) may further include a pin portion (29) monolithic with the pillar element (28), the pin portion (29) being rod-shaped and extending externally to the housing (2; 102) in prosecution of the pillar element (28).
The pillar element (8; 28) may have anti-extraction characteristics (30; 35), the anti-extraction characteristics including protruding and/or recessing structures (21A) and possibly stops (15).
The housing (2) may include a packaging mass (3) that is electrically insulating and forms the upper surface (2A) and the lateral surfaces (2C), wherein a recess (38) in the upper surface surrounds the end (8A) of the pillar element (8; 28).
The housing (102) may include a box housing an insulating gel (104) and may form a gel-potted package, wherein the box includes a hole (106) configured to allow the end (8A) of the pillar element (8) to pass through.
The electronic component (15A) may form a first electronic component and the housing (2; 102) may house a second electronic component (15B), the power module may further include electrical leads (4) extending from or on the lateral surfaces (3C) of the housing and electrically coupled to external connection regions (14C) formed by the carrying substrate (10) and electrically coupled to the first and/or the second electronic component (15A, 15B).
An assembling method for a power module, may be summarized as including forming a carrying substrate (10) having a plurality of connection regions (14A-14D) of conductive material; attaching an electronic component (15A, 15B) to a first connection region (14C) of the plurality of connection regions; attaching an electrical connector (5) to a second connection region (14D) of the plurality of connection regions or to the electronic component; and forming a housing (2; 102) having a main surface (2A) and lateral surfaces (2C) and enclosing the carrying substrate, the electronic component and the electrical connector so that the electrical connector extends up to the main surface of the housing and is accessible from the outside of the housing.
Forming a housing (2) may include molding packaging insulating material (3) with a mold (43) including an ejector (40) having a head surface (41), wherein the head surface (41) of the ejector has a central zone (41A) configured to abut against the electrical connector (5), and a peripheral zone (41B), of a greater area than the central zone (41A) and the electrical connector (5) and configured to be arranged laterally to the electrical connector (5).
The electrical connector (5) may comprise a pillar (9), wherein forming a housing (2) may comprise molding packaging insulating material (3) completely covering the pillar; and removing the packaging insulating material (3) from above the pillar, thereby the pillar has an exposed end flush with the main surface (2A) of the housing (2).
Removing the packaging insulating material may comprise grinding.
The various embodiments described above can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.
These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.
Number | Date | Country | Kind |
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102022000006617 | Apr 2022 | IT | national |