Semiconductor-component device assembled on a heat sink, assembly method, and lighting device for a motor vehicle including such a device

A device including at least one semiconductor component connected to an electrical connection element, the electrical connection element is attached to a heat sink and connected to a group of electrical wires, the group being linked mechanically and electrically to the electrical connection element by a single connector, the group being linked to the heat sink by holding means.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to the French application 1459309 filed on Sep. 30, 2014, which application is incorporated herein by reference and made a part hereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a semiconductor-component device assembled on a heat sink, the semiconductor component being connected to an electrical connection element.

The invention also relates to a method for assembling the aforementioned device, and to a lighting device for a motor vehicle incorporating such a device.

The present invention is specifically intended for use in the assembly of a light source in a motor vehicle lamp.

2. Description of the Related Art

In the domain of motor vehicle lighting, when using light-emitting diodes (LEDs, which are semiconductor components) as a light source, it is known to assemble these LEDs on an electrical connection element, for example a printed circuit board (PCB) to provide the electrical connection between the components assembled thereupon, and to subsequently position the LED/PCB assembly so obtained on a heat sink (typically a cooling rib). This heat sink, which is intended to cool the LED when in operation (and to act as a lamp cooling rib) is subsequently assembled in the lamp on a supporting element, such as a reflector of the lamp.

In particular, soldering the components onto the printed circuit board requires a method involving the application of soldering paste, the positioning of the components, and passing through a reflow oven, in which the soldering paste melts and then solidifies to attach the electronic components. These electronic components may include for example one or more LEDs, a connector, capacitors and resistors. Moreover, in order to ensure the electrical connection of the components to the rest of the vehicle, a first portion of the connector (female portion) is also welded to the board. The assembled board is then placed on the heat sink, which is subsequently placed on the supporting element of the lamp.

Once the heat sink has been placed on the related supporting element, the printed circuit board is connected electrically to the remainder of the vehicle by joining a second portion of the connector (male portion) to the first portion, the second connector portion being linked electrically to a group of electrical wires intended to operate the link.

Consequently, the placement of the heat sink on the supporting element is not hindered by the presence of floating electrical wires that could hinder the rapid assembly since these electrical wires are free to move and occupy the connection spaces formed between the heat sink and the supporting element.

However, although the method known from the prior art saves the operator assembling the semiconductor component from having to perform an additional electrical wire management step when positioning the heat sink on the related supporting element, this method presents a greater problem: it is costly in that, firstly, the choice of materials used to manufacture the first connector portion is determined by the installation requirements of the printed circuit board, i.e. high temperatures (within a range of approximately 200-300° C.), which the first connection portion must be able to withstand. These temperatures are the temperatures found during the soldering step of the first connection portion assembled on the printed circuit board. Secondly, the assembly method as known from the prior art is particularly lengthy since, once the heat sink has been positioned on the related lighting supporting element, it is then necessary to connect the second connector portion, linked to the group of electrical wires, to the first connector portion on the printed circuit board, which is done in a confined and therefore relatively inaccessible space formed between the supporting element and the heat sink, which may be difficult. This difficulty is further exacerbated by the presence of floating electrical wires which hinder the visibility of the operator when connecting the two connector portions, and which are also likely to come between the mechanical elements to be assembled, during this step of the method or during a subsequent step.

Subsequently, the method known from the prior art requires additional operations after connection of the two connector portions, which involve carrying out tests using dedicated hardware to check that the connection between the two connector portions has been made correctly.

The duration of the method known from the prior art undoubtedly results in a loss of profitability since it involves implementing such a method on a large scale (i.e. on a series of lamps on a production line).

SUMMARY OF THE INVENTION

The invention is intended to overcome the drawbacks in the prior art by providing an assembly method for a lighting device that is less costly while ensuring satisfactory reliability and easy—and therefore rapid—assembly of the different elements of the lighting device.

To overcome this problem, the invention proposes a device including at least one semiconductor component connected to an electrical connection element, the electrical connection element is attached to a heat sink and connected to a group of electrical wires, the group being linked mechanically and electrically to the electrical connection element by a single connector, the group being linked to the heat sink by holding means.

The invention also relates to a method for assembling a semiconductor component on a heat sink, the semiconductor component being connected to an electrical connection element, the method comprising:a first step in which a group of electrical wires is attached and connected to the electrical connection element,a second step in which the group is attached to the heat sink, anda third step in which the electrical connection element is attached to the heat sink.

Consequently, in relation to the specific application of the invention, which relates to the assembly of a light source in a motor vehicle lamp, the operator can then attach the group to the electrical connection element (for example a printed circuit board), attach the group to the heat sink, attach the printed circuit board to the heat sink, before placing the heat sink on the supporting element of the lamp in order, firstly, to obviate the need for the operator to handle the group when attaching the board and the heat sink and, secondly, to prevent the free movement of the group when assembling the lighting device.

Thus, the assembly of a semiconductor component on a heat sink according to the invention results not only in reduced assembly time since the operator can first easily connect the group to the printed circuit board before attaching and guiding the group into a non-restrictive position when assembling the board and the heat sink, but also in reduced manufacturing costs for the printed circuit board since it is no longer necessary to have a first connection portion positioned on the card and arranged to be connected to a second connection portion linked to the group of electrical wires.

Indeed, the invention enables the operator to use a single one-piece connector which can be attached to the printed circuit board. This connector is inserted into the metallized holes in the printed circuit board, to be attached by the selective wave soldering. The housing of the connector undergoes temperatures well below the temperatures of between 200° C. and 300° C. that are used in a conventional reflow oven.

Consequently, this single connector no longer has to be made from a material specifically designed to withstand the high temperatures found in a conventional reflow oven.

Additionally, the step in which the group of electrical wires is attached to the heat sink prevents, in operation, any wear of the group by friction against the surface or edges of the heat sink or of the supporting element since the group is no longer free to move under the effect of vibrations caused by operation of the motor vehicle, since it is held in a predetermined position.

According to different embodiments of the device according to the invention, which may be taken together or separately:the semiconductor component comprises at least one semi-conductive emitter chip, preferably a light-emitting diode,the heat sink is linked to a motor vehicle lamp supporting element, preferably to a motor vehicle lamp reflector, or inside a vehicle rear-light supporting element,the electrical connection element is a printed circuit board,the group is linked to the heat sink by holding means including at least a first lug projecting from a surface of the heat sink, the group of electrical wires being held between the lug and the surface,the holding means include a second lug projecting from the surface of the heat sink, the group of electrical wires being held between the first and second lugs and the surface,the group is linked mechanically to the heat sink by holding means comprising a first portion formed by a clamping ring through which the group passes and a second portion formed by a foot made of a thermally insulating material attaching the clamping ring to the heat sink, the heat sink is substantially L-shaped,the holding means are on one of the branches of the L-shape of the heat sink, andthe heat sink has openings.

According to different embodiments of the method according to the invention, which may be taken together or separately:the first step involves attaching and electrically connecting a connector, the connector being linked electrically and mechanically to the group, to the electrical connection element,the second step involves positioning the group between at least one first lug projecting from a surface of the heat sink and the surface of the heat sink, such that the group is held between the lug and the surface of the heat sink,the second step also involves positioning the group between a second lug projecting from the surface of the heat sink and the surface of the heat sink, such that the group is held between the first and second lugs and the surface of the heat sink,the second step involves moving the group through a clamping ring, the ring being extended by a foot made of a thermally insulating material, the ring being attached to the heat sink via the foot,the second attachment step of the group is carried out before or after the third step in which the electrical connection element is attached to the heat sink, andthe method according to the invention also includes a fourth step in which the heat sink is assembled on a supporting element of a motor vehicle lamp.

Finally, the invention relates to a lighting device for a motor vehicle incorporating the device according to the invention.

Other features and advantages of the invention are set out in the non-limiting description given below.

In these figures, similar elements are indicated using the same reference sign.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The steps for assembling an electronic semiconductor component1on a heat sink according to the first embodiment of the method according to the present invention are illustrated inFIGS. 1A to 1E.

The assembly method mentioned above includes a first step1ain which a group3of electrical wires is attached to a rear face of an electrical connection element5, which is a printed circuit board (PCB), the front face6of which carries the semiconductor component, for example a light emitting diode (LED)1(FIG. 1A). A variant of the embodiment in which the LED1is assembled on the PCB5involves the LED1being assembled directly on the heat sink, then connected to the PCB5, for example by wire solder.

During this first step1a, the group3of electrical wires is attached to the PCB5by means of a one-piece connector7(or single connector) linked electrically and mechanically to the group3such that the PCB5is connected physically and electrically to each of the electrical wires in the group3.

The connection is made by insertion, from the rear face of the PCB5, of a plurality of contacts7apresent on the one-piece connector7into the metallized connection holes7bformed in the PCB5, the connector7being then wave soldered directly to the PCB5.

FIG. 1bshows the second step1bin which the group3is attached to the heat sink2using means8for holding the group3.

The heat sink2is formed by a first portion P1and a second portion P2linked together directly and for example in a substantially L-shape, i.e. oriented such that a first plane tangential to the first portion P1and a second plane tangential to the second portion P2form a substantially right angle.

Preferably, the heat sink2has openings to enable the circulation of air.

In the first embodiment of the method according to the invention, the second step1binvolves moving the group3through a first portion of the holding means8, which is a clamping ring8a, the ring8abeing extended by a second portion of the holding means8, which is a click-fit foot8b.

The foot8bhas a click-fit branch8cand two fins8d,8d′ that bear against the heat sink2.

The click-fit branch8ccomes from an extremity of the foot8bto which each of the fins8d,8d′ are linked and has two elbows8e,8e′ (or fins) protruding from the click-fit branch8cin mutually opposing directions such as to form a click-fit arrow comprising the click-fit branch8cand the two elbows8e,8e′, this arrow being arranged to be inserted in a first orifice8fin the heat sink2, for example in the second portion P2of same.

Once the group3is engaged in the clamping ring8a, the click-fit branch8cis inserted (FIG. 1C) in the first orifice8fsuch that the elbows8e,8e′ pass through the first orifice8fentirely and that, once the click-fit branch8chas been inserted in the first orifice8f, the two fins8d,8d′ bear against a first face9of the second portion P2, while the elbows8e,8e′ bear against a second face9′ of the second portion P2opposite the first face9. Consequently, the foot8bis held against each of the first and second faces9,9′ of the second portion P2of the heat sink2, thereby linking the ring8ato the heat sink2.

Preferably, the click-fit branch8cand the two elbows8e,8e′ form a single arrow-shaped attachment part made of a flexible material, such that this attachment part can be easily inserted into the first orifice8fby simply pressing same, the connection part, and in particular the elbows8e,8e′ being deformable as they pass through the first orifice8fbefore subsequently returning to the original arrow shape, such that the elbows8e,8e′ can bear against the second face9′ of the second portion P2of the heat sink2.

Preferably, the foot8bis made of a thermally insulating material such that the group3is thermally decoupled from the heat sink2when the LED6is in operation and the heat sink2is being heated.

Once the group3has been attached to the heat sink2, the PCB5is attached, during a third step1c(FIG. 1C) to the first portion P1of the heat sink2.

The PCB5(FIG. 1C) is attached by any known means, for example by crimping at least one substantially cylindrical pin51protruding from the first portion P1of the heat sink2and arranged to be inserted into a second orifice52(or a cavity) made in the PCB5designed to tightly fit the pin51, which is then crushed to fill the orifice52such as to irreversibly connect the PCB5to the first portion P1of the heat sink2.

Preferably, the PCB5is in thermal contact with the heat sink2to enable same to control the temperature of the heat sink2and to modulate the intensity of the electrical current passing through the LED1in order to guarantee the reliability of same by preventing the minimum junction temperature of same from being exceeded. The temperature can be controlled using a thermistor connected to the LED1and to the PCB5.

Preferably, steps1ato1cof the first embodiment of the claimed method are carried out consecutively, although this is not obligatory.

Advantageously, the second step1bof attaching the group3is carried out before or after the third step1cof attaching the PCB5.

Since the group3and the PCB5are attached to the heat sink2to form a device forming a heat sink2/group3/PCB5assembly, as shown inFIGS. 3A and 3B, this assembly can then be assembled, during a fourth step1eillustrated inFIG. 1E, on a supporting element10of a motor vehicle lamp.

In a variant embodiment, the assembly can also be assembled on a lamp supporting element before it is assembled on a rear light supporting element of the vehicle.

As shown inFIGS. 3A and 3B, performance of steps1ato1cresults in a first device comprising an LED1carried by the PCB5to which the LED1is electrically connected. The PCB5is attached to the first portion P1of the heat sink2and connected to the group3of electrical wires by the one-piece connector7. The group3is attached to the second portion P2of the heat sink2using the holding means8comprising the clamping ring8athrough which the group3passes and the foot8battaching the clamping ring8ato the heat sink2.

The fourth step1efor assembling the heat sink2on a supporting element10of a motor vehicle lamp is shown inFIGS. 4A and 4B. It is done by linking for example the first portion P1of the heat sink2to the supporting element10using connection means comprising for example:a screw10aarranged to pass through a third orifice present in the first portion P1and to be seated in a second cavity10bof the supporting element10having an internal screw thread matching the screw thread of the first screw, anda positioning pin10eof the reflector enabling the cooling rib to be positioned in the direction Y (horizontal axis perpendicular to the movement of the vehicle, the normal referenced used by the operator) through the oblong hole10d.

As shown inFIGS. 4A and 4B, the fourth step1eresults in a lighting device for a motor vehicle comprising the first device described above connected to the supporting element10of the lamp.

When carrying out this fourth step1e, placement of the heat sink2on the supporting element10is not hindered by the presence of floating electrical wires and is therefore quicker to complete than the assembly method in the prior art.

Furthermore, in the method according to the invention, the connector, since it is connected to the PCB5before attachment of this latter to the heat sink2, need not be a two-part connector, in particular, as explained above, a one-piece connector is preferred since this choice represents a material saving and, furthermore, this connector no longer needs to be soldered using a soldering method requiring a material specifically designed to withstand high temperatures of between 200° C. and 300° C.

A second alternative embodiment of the method according to the invention is shown inFIGS. 2A and 2B.

The second and fourth steps2b,2eof this second embodiment are the same as in the first embodiment.

On the other hand, this second embodiment differs from the first embodiment in that the second step2binvolves moving the group3between a first lug11aand a second lug11band a surface S of the heat sink2defined on the first face9of the heat sink2. As a result, the group3is held between the lugs11a,11band the surface of the heat sink2, each of the lugs11a,11bprojecting from the surface S. In a variant embodiment, only one lug is formed from the heat sink2to hold the group3, and it may be folded as required following positioning of the group in order to prevent any relative movement of the electrical group.

Potentially, the second portion P2of the heat sink2has a fourth orifice12, each of the lugs11a,11bprojecting from the edge of the fourth orifice12beneath the lugs11a,11blinking the first face9to the second face9′.

The presence of this fourth orifice12facilitates the placement of high-diameter groups3since, when placing this type of group3between the heat sink2and each of the lugs11a,11b, a portion of the group3, the diameter of which is for example greater than the distance L between the lugs11a,11band a horizontal plane passing through the surface S, may be seated in the orifice12and the group3is clamped between firstly the two lugs11a,11band secondly a first portion13and a second portion14of the surface S on either side of the orifice12.

In this context, the second embodiment of the assembly method is less costly and quicker than the first embodiment for this method. Indeed, since the group3is directly linked to the heat sink2by the lugs11a,11bprojecting from the surface S of the heat sink2, there is no need to use a specific part on the electrical group of the cooling rib.

The device obtained in the second embodiment of the method according to the invention therefore differs from the first device from the first embodiment of the assembly method in that the holding means8are first and second lugs11a,11bprojecting from the surface S (FIG. 2A) of the heat sink2, the group3of electrical wires being held between the first and second lugs11a,11band the surface S.

Although the description relates to a preferred embodiment of the method according to the invention and of the device obtained from such a method in which the semiconductor component is a light-emitting diode1, the heat sink2is a lamp cooling rib and the electrical connection element is the PCB5, it is understood that the present invention is not limited to these features, but that it also covers other embodiments involving other semiconductor components, other heat sinks for the semiconductor component, and other electrical connection elements.

While the system, apparatus, process and method herein described constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to this precise system, apparatus, process and method, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.