Sintering press, sintering press and pressing method

Abstract

The present invention relates to a pressing assembly (1) for applying pressure to an object or a region of an object, for example for a sintering press (100) to perform sintering of electronic components (11) on a substrate (12). The pressing assembly comprises a multi-rod actuator (20) provided with a plurality of presser rods (14), and a set of presser elements (2), each interposed between the presser rods (14) and the object (11) to be pressed for transferring the force applied by at least one presser rod to said object to be pressed. The set of presser elements comprises two or more mutually interchangeable presser elements (2a, 2b, 2c) so as to be engageable by a different number of presser rods (14).

Description

SINTERING PRESS, SINTERING PRESS AND PRESSING METHODDESCRIPTION

[0001] The present invention relates to pressing assemblies for industrial or laboratory machinery.

[0002] A pressing assembly can be employed, for example, in a sintering press in order to press electronic components onto a substrate by interposing sintering material or press casings of electronic components onto dissipative elements by interposing sintering material.

[0003] In general, such a pressing assembly can be applied in all contexts where there is a need to apply pressure to elements or specific regions of an object.

[0004] In the example of the sintering press, the components to be sintered must be subjected to a given temperature, e.g., 250°C, for a given time, e.g., 180 seconds, by applying a predefined constant pressure, e.g., 15 MPa, to a predetermined area.

[0005] Different project solutions of the pressing assembly are currently implemented in order to ensure the correctness of the process on every part to be pressed in the sintering press.

[0006] One of these solutions, described in W02020008287A1 to the same Applicant, for example, includes using independent presser elements for each object to be pressed. Such a constructional solution allowsprocessing, in the same cycle , obj ects requiring di f ferent working pressures and / or having a di f ferent thickness , intended as the geometric si ze along the axis orthogonal to the work plane of the press considered .

[0007] It is the obj ect of the present invention to propose a pressing assembly of the aforementioned type , but which allows being adapted to the di f ferent geometries of the obj ect to be processed and in particular accessing di f ferent pressing force intervals available .

[0008] Such an obj ect is achieved by a pressing assembly according to claim 1 , a sintering press according to claim 9 , and a pressing method according to claim 10 . The dependent claims describe preferred embodiments of the invention .

[0009] The features and advantages of the pressing assembly and the sintering press according to the invention will be however apparent from the following description of preferred embodiments thereof , given by way of a nonlimiting indication, with reference to the accompanying drawings , in which :Figure 1 is an elevation view of an example of a sintering press employing a pressing assembly according to the invention;Figures 2 and 2a show an enlarged, partial axial section view of the upper and lower parts of the closedpress and with the multi-rod actuator in an inactive configuration and in an active configuration, respectively; andFigures 3 and 3a are two views , an elevation view and a perspective view, of some presser rods and related presser elements of the pressing assembly according to the invention .

[0010] In said drawings , a pressing assembly for applying pressure to an obj ect or a region of an obj ect is indicated by reference numeral 1 as a whole . In the example of application shown in the drawings , the pressing assembly is employed in a sintering press 100 to perform sintering of electronic components 11 onto a substrate 12 .

[0011] In a general embodiment , the pressing assembly 1 comprises a multi-rod actuator 20 provided with a plurality of parallel presser rods 14 .

[0012] The multi-rod actuator 20 is configured to apply to each presser rod 14 a pressing force proportional to the thrust section of the presser rod 14 .

[0013] In an embodiment , the presser rods 14 are movable , when subj ected to an action of a pressuri zed fluid, between an inactive retracted position and an active advanced position along a pressing direction X . Note that the term "movable" means that each presser rod can, undercertain working conditions , perform a travel along the pressing direction X, for example due to the crushing of the sintering material during the pressing step . Such a travel can thus result in an axial movement - even imperceptible - of the presser rod, for example of the order of millimeters or tenths of a millimeter .

[0014] The pressing assembly 1 comprises a set of presser elements 2 adapted to cooperate with the presser rods 14 . Each presser element 2 of the set of presser elements is prismatic in shape , for example having a rectangular section . In particular, each presser element 2 is adapted to be interposed between the presser rods 14 and the obj ect 11 to be pressed for trans ferring the force applied by at least one presser rod 14 to the obj ect 11 to be pressed .

[0015] In the continuation of the description, for simplicity of disclosure , the terms "upper" and " lower" , referring for example to the ends of the presser rods and the presser elements , or to the components of a press , are used with reference to a conventional but nonlimiting embodiment in which the pressing direction X is a vertical direction .

[0016] According to as aspect of the invention, the set of presser elements 2 comprises two or more mutually interchangeable presser elements 2a, 2b, 2c having, atleast at the upper end, an upper end surface 2' of presser element the plan projection of which, i.e., in a plane orthogonal to the pressing axis X, is sufficiently wide to intersect the plan projections of the lower end surfaces 14' of presser rod of at least two presser rods 14a, 14b, 14c when one of the interchangeable presser elements 2a, 2b, 2c is positioned between the presser rods and the object 11 to be pressed.

[0017] These end surfaces 2' , i.e., upper surfaces, of the interchangeable presser elements 2a-2c have a different profile along the pressing axis X so that the interchangeable presser elements are engageable by a different number of presser rods 14.

[0018] In other words, at least two presser rods 14a-14c are superimposed on each interchangeable presser element 2a-2c. Due to the different profile of the upper end 2' of the interchangeable presser elements, it is however possible to ensure that also only one, or in any case a number smaller than all the presser rods 14 superimposed on a presser element 2, when moved in advanced position, comes into contact with the upper surface 2' of the presser element.

[0019] Therefore, depending on which presser element of the mutually interchangeable presser elements is used in the pressing assembly and since the pressing force isproportional to the thrust section of the presser rods , di f ferent pressing forces can be obtained . Indeed, the total thrust section of the presser rods is given by the sum of the thrust sections of the individual presser rods capable of trans ferring the thrust force to the underlying presser element . Therefore , i f one or more presser rods move idly, i . e . , when they are in the advanced position and do not engage the underlying presser element due to the profile of the upper surface thereof , the total thrust section will be proportionately less than the maximum thrust section, given by the sum of the thrust sections of all the presser rods superimposed on a presser element .

[0020] In the example of pressing assembly 1 shown in Figures 2 and 2a, three di f ferent mutually interchangeable presser elements 2a, 2b, 2c are shown, but in the example they are simultaneously installed in a press . Three presser rods 14a, 14b, 14c are associated with each presser element 2a, 2b, 2c .

[0021] The enlarged view in Figures 3 and 3a show two interchangeable presser elements 2a, 2b adj acent to each other, for example at a di f ferent height , each of which being associated with three presser rods 14a, 14b, 14c .

[0022] Therefore , it should be noted that the term " interchangeable" is used to indicate that the same groupof presser rods 14a, 14b, 14c, consisting of at least two adjacent presser rods, can be associated with at least two different presser elements 2a, 2b, 2c, i.e., having at least the upper surface 2' with a different axial profile. This does not exclude such interchangeable presser elements from also being simultaneously employed in one press.

[0023] In an embodiment, a first presser element 2a of the interchangeable presser elements has a planar presser element end surface 2' so as to be simultaneously engageable by all the presser rods which can act on such a first presser element 2a, i.e., axially superimposed thereon .

[0024] At least one recess 2" is obtained in the end surface 2' of at least a second presser element of the interchangeable presser elements 2b, 2c, adapted to prevent the contact between the presser element end surface 2' and at least one presser rod 14a, 14b, 14c of the presser rods which can act on the first or second presser element 2a, 2b, 2c, i.e., of the presser rods superimposed on the first or second presser element.

[0025] In other words, at least one lowered zone 2" is formed in the upper end surface 2' of at least one presser element among the interchangeable ones. For example, the depth of such a lowered zone is greater thanthe travel of the presser rods 14 .

[0026] In an embodiment shown in the drawings , the multirod actuator 20 has a lower head 22 and an upper head 24 which j ointly and f luid-tightly delimit a compression chamber 26 .

[0027] An inlet passage 32 for the introduction of a pressuri zed fluid into the compression chamber 26 is formed in the upper head 24 .

[0028] The presser rods 14 are slidingly supported in the lower head 22 . In an embodiment , the upper ends 142 of the presser rods 14 protrude into the compression chamber 26 .

[0029] An actuation diaphragm 30 extends into the compression chamber 26 . When the compression chamber 26 is not pressuri zed, the actuation diaphragm 30 is in an inactive configuration, in which it is substantially flat ( Figure 2 ) , and in a preferred embodiment , it is spaced apart from a bottom wall 26a of the compression chamber 26 , from which the upper ends 142 of the presser rods 14 protrude .

[0030] When the compression chamber 26 is pressuri zed, the actuation diaphragm 30 deforms so as to act on the upper ends 142 of the presser rods 14 for trans ferring the pressure in the compression chamber onto each single presser rod 14 ( Figure 2a ) .

[0031] As it can be seen in Figure 2a, in an embodiment , when the actuation diaphragm 30 deforms , it also rests against the bottom wall 26a of the compression chamber 26 . The deformed actuation diaphragm 30 thus acts simultaneously on all the presser rods 14 , and a force equal to the product of the pressure of the fluid in the pressuri zation chamber times the thrust surface of the presser rod acts on each presser rod 14 .

[0032] In an embodiment , each presser rod 14 is slidingly housed with shape coupling in a respective presser rod cavity 144 formed in the body of the multi-rod actuator 20 , in particular in the portion of the body forming the lower head 22 .

[0033] In an embodiment , each presser rod 14 is provided with a mechanical stop element adapted to limit the movement of the presser rod 14 from the retracted position to the advanced position .

[0034] Indeed, in the presence of a very high pressure acting on the actuation diaphragm 30 , the actuation diaphragm 30 could deform to such an extent as to penetrate cavity 144 of the presser rod, causing an excessive movement of the rod in the advanced direction and wearing out early due to the contact with the edge delimiting the presser rod cavity 144 at the top . The presence of the mechanical stop prevents the occurrenceof this situation and makes the rod travel certain and repeatable .

[0035] For example , the mechanical stop blocks the presser rod 14 in a position such that the upper surface thereof is coplanar to the bottom wall 26a of the compression chamber 26 .

[0036] For example , as shown in Figures 3 and 3a, the mechanical stop element consists of a stem head 146 radially enlarged with respect to the remaining part of the body of the presser rod 14 .

[0037] In other words , the presser rods are shaped like mushrooms or nails with an enlarged head .

[0038] The upper portion of the presser rod cavity 144 can have a section complementary to that of the head 146 of the presser rods , i . e . , it can have a greater diameter than the remaining part of the presser rod cavity 144 . When the presser rod 14 is in advanced position, the head 146 thereof is thus completely received in the upper portion of the respective rod cavity 144 . For example , the upper surface of the presser rod can be coplanar to the bottom wall 22a of the compression chamber 26 .

[0039] Note that , especially when employing the pressing assembly in a sintering press , the travel of the presser rods from the retracted position to the advanced position is functional to the application of a force to therespective obj ects to be sintered - by means of the respective presser elements - and therefore substantially corresponds to the lowering in height that the obj ect to be sintered undergoes when it is pressed onto the substrate .

[0040] In other words , even when the presser rods are in the retracted position, they can already be in contact with the respective presser elements (with the exception of the presser rods superimposed on lowered zones of the respective presser elements ) so that the action of the pressuri zed fluid on the upper surface of the presser rods , through the actuation diaphragm for example , directly and instantly results in a force acting on the presser elements .

[0041] In such embodiments , it is the same presser element 2 that maintains the respective presser rod ( s ) 14 in the retracted position, which otherwise would be brought to the advanced position by gravity, i f positioned vertically .

[0042] Therefore , in the presence of a recess 2" , or lowered zone , obtained in the upper end surface 2 ' of a presser element 2 , the overlying presser rod 14 , since it does not abut against the presser element 2 , can be brought to the advanced position without transmitting the force of the actuation means , for example the actuationdiaphragm 30 , to the presser element 2 since this is trans ferred to the mechanical stop formed by the housing seat 144 of the presser rod itsel f .

[0043] In an embodiment , the pressing assembly 1 comprises a heating unit 40 adapted to heat the presser elements 2 so as to press the obj ects 11 under a desired temperature condition, for example for the sintering proces s .

[0044] In an embodiment , through holes 42 adapted to house the presser elements 2 are formed in the heating unit 40 . This heating unit 40 is provided with heating means , e . g . , electric resistors 44 , for heating the presser elements 2 housed in the through holes 42 .

[0045] In an embodiment , the lower ends of the presser rods 14 have a configuration adapted to reduce as much as possible the trans fer of heat from the presser elements to the presser rods . For example , the lower ends of the presser rods 14 are semi-spherical in shape .

[0046] In an embodiment , the presser elements 2 housed in the heating unit can be easily removed by pulling from the heating unit 40 in order to be replaced .

[0047] Note that in addition to allowing a selection of the pressing forces , the interchangeability of the presser elements provides further advantages of use , such as low maintenance invasiveness in the case of mal functioning or damage to a part of the presser elements and thepossibility of replacing them also in order to adapt to di f ferent working heights . For example , di f ferent working heights can occur when there is a desire to vary the height of a substrate without modi fying the design of the product to be pressed, or when the thickness of one or more of the components involved in the pressing process varies , while maintaining the pressures and geometrical arrangements previously adopted .

[0048] Note that the proposed pressing assembly can have a greater number of presser rods than the number of presser elements . The use of presser elements which take advantage of a greater or lesser number of presser rods allows extending the range of forces applicable to the obj ect subj ected to pressing .

[0049] By making two close presser rods , the same force equivalent to a single presser rod with upper surface equal to the sum of the upper surfaces of the first two rods can be obtained, thus selectively taking advantage of the force transmitted from one to the other or from both by employing a suitable presser element .

[0050] The present invention also relates to a sintering press 100 comprising a pressing assembly 1 as described above .

[0051] As explained above , a sintering press 100 can be employed in certain electronic applications in whichelectronic power components such as IGBTs , thermistors , MOSFETs , for example , must be fastened to a substrate by interposing a sintering paste . In order for each component to be sintered correctly, it must be pressed by the sintering press under conveniently controlled temperature conditions .

[0052] In other applications , the device to be subj ected to the sintering proces s by means of a press can consist of a casing containing an electronic board formed by electronic components and substrate . Such a casing is pressed onto a dissipative element .

[0053] In other applications , the sintering press 100 can be employed to perform rolling processes in which the obj ect to be subj ected to sintering does not comprise any electronic component .

[0054] For simplicity of disclosure , in the continuation of the present description of a sintering press , any one of electronic components , casings thereof , or obj ects intended for rolling will be referred to as an obj ect to be sintered . Similarly, any element involved as the sintering obj ect playing the role of structural support will be referred to as a substrate, such as the substrate for electronic components or a massive dissipative element in the case of sintering electronic casings onto dissipative elements , for example .

[0055] In a general embodiment , the press comprises a mounting structure 80 which extends vertically and supports a base 90 at the bottom and an upper block 60 at the top .

[0056] The base 90 is adapted to support at least one substrate 12 .

[0057] The upper block 60 supports or embodies the pressing ass e mb 1 y 1 .

[0058] The mounting structure 80 can be provided with longitudinal guides 82 along which at least one of the upper block 60 and the base 90 translates vertically with respect to the other, for example by means of a hydraulic or electric actuator, between an open or inactive press position and a closed or active press position .

[0059] The base 90 and the upper block 60 , with the longitudinal guides 82 thereof , form the die of the sintering press 100 .

[0060] As described above , the pressing assembly 1 is configured to apply a preset pressure to a pressing area of the obj ects 12 to be sintered . For example , the pressing area is the upper flat side of the body of the obj ects to be subj ected to pressing .

[0061] The heating unit 40 can be in the lower part of the pressing assembly 1 , in which there are formed the through holes 42 for housing the presser elements 2 . Forexample, the heating unit 40 can be heated up to 350°C.

[0062] The multi-rod actuator 20 is positioned above the heating unit 40.

[0063] In certain embodiments, the body of the multi-rod actuator 20 is cooled by means of an appropriate cooling circuit in order to keep it at a constant temperature even when the heating unit is at high temperatures.

[0064] The present invention also relates to a pressing method for applying a desired pressure to objects or specific regions thereof.

[0065] The pressing method includes employing, in a press 100, the above-described pressing assembly 1 for carrying out a selection of the force to be applied to a presser element 2, and then to one or more respective objects or regions of an object 11 to be pressed.

[0066] In particular, the selection of the pressing force is carried out using one presser element 2 among two or more interchangeable presser elements, where the end surfaces 2' , i.e., the upper surfaces, of such interchangeable presser elements 2 have a different profile along the pressing axis X so that the interchangeable presser elements are engageable by a different number of presser rods 14.

[0067] Once a presser element 2 among the interchangeable presser elements 2a, 2b, 2c is selected and installed inpress 100 , the multi-rod actuator 20 can be actuated so as to actuate all the presser rods 14 .

[0068] Those skilled in the art may make changes and adaptations to the embodiments of the pressing assembly, the sintering press , and the pressing method according to the invention or can replace elements with others which are functionally equivalent in order to meet contingent needs without departing from the scope of the following claims . Each of the features described as belonging to a possible embodiment can be made irrespective of the other embodiments described .

Claims

CLAIMS1. A pressing assembly (1) for applying pressure to an object or a region of an object, for example for a sintering press (100) to perform sintering of electronic components (11) on a substrate (12) , comprising:- a multi-rod actuator (20) provided with a plurality of parallel presser rods (14) , the multi-rod actuator (20) being configured to apply to each presser rod (14) a pressing force proportional to the thrust section of the presser rod;- a set of presser elements (2) , each presser element of said set of presser elements being prismatic in shape and being adapted to being interposed between the presser rods (14) and the object (11) to be pressed for transferring the force applied by at least one presser rod to said object to be pressed, wherein said set of presser elements comprises two or more mutually interchangeable presser elements (2a, 2b, 2c) having, at least at the end facing the presser rods, a presser element end surface (2' ) the plan projection of which is sufficiently wide to intersect the plan projections of the presser rod end surfaces of at least two presser rods (14a, 14b, 14c) when one of the interchangeable presser elements is positioned between the presser rods and the object to be pressed, and wherein said end surfaces (2' )of the interchangeable presser elements have a different profile so that the interchangeable presser elements are engageable by a different number of presser rods (14) .

2. A pressing assembly according to claim 1, wherein a first presser element (2a) of the interchangeable presser elements has a planar presser element end surface (2' ) so as to be simultaneously engageable by all the presser rods (14a, 14b, 14c) which can act on said first presser element, and wherein at least one recess (2") is formed in the end surface (2' ) of at least a second presser element (2b, 2c) of the interchangeable presser elements, adapted to prevent the contact between said presser rod end surface and at least one presser rod of the presser rods which can act on the first or second presser element .

3. A pressing assembly according to claim 1 or 2, wherein the multi-rod actuation unit is configured to act simultaneously on all the presser rods.

4. A pressing assembly according to any one of the preceding claims, wherein the multi-rod actuator has a front head (22) and a rear head (24) which jointly and f luid-tightly delimit a compression chamber (26) , and wherein : an inlet passage (32) for the introduction of a pressurized fluid into the compression chamber isobtained in the rear head (24) ;- the presser rods (14) are slidingly supported in the front head (22) , the rear ends (142) of said presser rods protruding into the compression chamber (26) , an actuation diaphragm (30) extends into the compression chamber (26) , which deforms when the compression chamber (26) is pressurized so as to act on said rear ends of the presser rods for transferring the pressure in the compression chamber onto each single presser rod (14) .

5. A pressing assembly according to any one of the preceding claims, comprising a heating unit (40) for the presser elements, in which through holes (42) adapted to house the presser elements are obtained and provided with heating means (44) for heating the presser elements.

6. A pressing assembly according to any one of the preceding claims, wherein each presser rod (14) is slidingly housed with shape coupling in a respective presser rod cavity (144) formed in the body of the multirod actuator.

7. A pressing assembly according to the preceding claim, wherein each presser rod is provided with a mechanical stop element adapted to limit the movement of the presser rod from the retracted position to the advanced position.

8. A pressing assembly according to the preceding claim, wherein the mechanical stop element is made of a stem head (146) radially enlarged with respect to the remaining part of the body of the presser rod.

9. A sintering press comprising a pressing assembly (1) according to any one of the preceding claims and a base (90) facing the pressing assembly (1) and adapted to support at least one substrate (12) , at least one of said pressing assembly (1) and lower base (90) being axially translatable with respect to the other between a retracted inactive position and an advanced pressing position, wherein the objects (11) to be sintered are engageable by the presser elements.

10. A pressing method for applying a desired pressure to elements or specific regions of an object, comprising the steps of:- providing a pressing assembly according to any one of claims 1-8;- carrying out a selection of the force to be applied to a presser element;- actuating the multi-rod actuator so as to activate all the presser rods; wherein the selection of the force to be applied is carried out using one presser element among two or more interchangeable presser elements, where the end surfacesof such interchangeable presser elements have a different profile along the pressing axis so that the interchangeable presser elements are engageable by a different number of presser rods.

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