Heat treatment method and apparatus

Abstract

The present invention relates to an apparatus and method for heat treating components, particularly electronic components, comprising a batch tray (10) and at least two component groups arranged on the batch tray, each component group having at least a first component and a second component connected or to be connected to the first component. The batch tray has at least two tray units (11) each housing a component group. Each tray unit has a tray (12) and a connecting member (13) for connecting the trays together, the connecting member being formed of at least one connecting element (14), the material of the connecting element and / or the tray being selected such that the connecting element and / or the tray thermally expands in at least one linear direction during heat treatment, which thermal expansion essentially matches the thermal expansion of the first component and / or the second component in that linear direction.

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for heat treating components, particularly electronic components, comprising a batch tray and at least two component groups arranged on the batch tray, each component group including at least a first component and a second component connected or to be connected to the first component, the batch tray having at least two tray units each housing a component group. [Background technology]

[0002] Electronic components and circuits are generally manufactured from a number of components, the components or groups of components being joined by a heat treatment to form a conductive connection. In particular, the components are joined and a conductive connection is formed between them, for example by soldering or sintering. The essential point is that the soldering or sintering uses a connection material that melts at least partially during the heat treatment or that diffuses to join and form the connection. For example, the conductive paths of a first component are conductively connected to the contacts of a second component, or electrically isolated areas are joined to obtain a mechanically stable component group. The heat treatment can be carried out in various ways, for example by local heating of the contacts or by heating of the entire component group. In such a manufacturing process, the component groups or components are held in the desired contact position relative to each other. This positioning of the components is usually carried out by means of a batch tray, on which the components are placed and which can accommodate several component groups. This allows these component groups to be heat treated simultaneously or successively, so that mass production can be carried out economically. Summary of the Invention [Problem to be solved by the invention]

[0003] Known methods and devices for heat treatment have the disadvantage that the parts to be joined experience large temperature differences associated with different degrees of thermal expansion, which can lead to warping of the parts, especially when cooling. For example, the cooling part, or the group of joined parts that is cooling, can warp or distort as a result of contraction. Differential thermal expansion of the parts has a greater effect on warping than temperature differences within the parts. Heating the batch tray can also cause inaccuracies in the relative position of the parts to be joined, making it difficult to maintain small tolerances. Depending on the position and fixation of the parts on the batch tray, unintended play or relative misalignment of the parts can occur as a result of the heat treatment. Furthermore, the entire batch tray can be deformed, which can lead to the group of parts not being located in the desired position, for example for a machine that uses actuators to crimp the parts together at their connection points. This can result in short circuits or other malfunctions in the group of parts.

[0004] SUMMARY OF THE PRESENT DISCLOSURE It is therefore an object of the present invention to provide an apparatus and method for heat treating a part that allows for more accurate and economical production. [Means for solving the problem]

[0005] This object is achieved by a device having the features of claim 1 and by a method having the features of claim 14.

[0006] An apparatus according to the present invention for heat-treating components, particularly electronic components, comprises a batch tray and at least two component groups arranged on the batch tray, each component group having at least a first component and a second component connected or to be connected to the first component, the batch tray has at least two tray units each accommodating a component group, each tray unit having a tray and a connecting member for connecting the trays to each other, the connecting member being formed of at least one connecting element, a material of the connecting element and / or the tray selected such that when the connecting element and / or the tray is heat-treated, the thermal expansion essentially matches the thermal expansion of the first component and / or the second component in that linear direction.

[0007] Thus, a plurality of component groups, each having at least two components that are electrically or non-electrically connected to each other during the thermal treatment, can be arranged in the batch tray. Each component group is arranged in a separate tray unit of the batch tray, the tray unit being composed of a tray and a connecting element. The batch tray can have 2+n tray units, i.e. as many tray units as can in principle be processed in the batch tray. The connecting element serves to attach the trays to each other and has at least one connecting element. When the batch tray is partially or totally heated during the thermal treatment of each component, a thermal expansion of the batch tray and at least one component or component group occurs. This thermal expansion occurs in at least one linear direction with respect to a common coordinate system of the batch tray and the component group therein. The material of the connecting element and / or the tray is selected such that the connecting element and the tray thermally expand during the thermal treatment and that the thermal expansion corresponds to the thermal expansion of at least one of the components. In this respect, thermal expansion refers to a thermal expansion at least in a linear direction, meaning a change in length. However, the thermal expansion can also relate to a surface or a volume, so that it can occur in multiple directions. Because the thermal expansion of the connection elements and the tray is approximately equal to the thermal expansion of one of the parts of a group of parts, the batch tray can compensate for the thermal expansion of that part to an extent that prevents unintended relative misalignment of the components during heat treatment and / or possible warping of the part during cooling after heat treatment, thereby enabling economical production of high quality groups of parts and maintaining tight tolerances during production.

[0008] The trays can be connected in a form-fitting manner to the connecting elements by respective fasteners. In principle the trays can be separated from one another, in other words they can be separate parts or elements that can be connected by connecting elements. The trays can thus be placed apart such that their thermal expansion is not influenced by their contact and is not propagated across the trays. At the same time no direct heat transfer between the trays occurs. Nevertheless the relative distance between the trays can be kept very accurate due to the form-fitting connection to the connecting elements. This is particularly advantageous if a relative distance between the trays is required in the course of a serial or parallel heat treatment with a suitable machine. The fasteners can for example comprise screws, pins and / or other fastening means. Furthermore, a plurality of connecting elements can be provided.

[0009] The connecting member may be composed of at least two connecting elements, which may be parallel profile bars that can connect spaced trays. For example, the profile bar may be a flat bar along whose length the trays are arranged. The profile bars are preferably identical to prevent the connecting member and the batch tray from warping during heat treatment. The profile bars may also be connected to the upper and / or lower surfaces of the tray such that the parts are in contact with or spaced from the profile bars when placed on the batch tray.

[0010] Each tray unit may be provided with at least one positioning aid and / or recess for receiving and positioning the first and / or second components. The tray units may be configured to position or receive additional components. Each tray unit or only selected tray units may be provided with positioning aids. The positioning aids may be, for example, pins, stops, rails, etc., and allow for accurate and shape-matched positioning of the components on the batch tray. Recesses may also be used in such a manner for positioning the components. For example, one or both of the components may be fully or partially inserted into the recess. In this case, particularly overlapping components may be easily connected to each other. For example, the first component may be a DBC substrate and the second component may be a lead frame.

[0011] The connecting element and the tray can be made of different materials. Using different materials for the tray and the at least one connecting element allows the thermal conductivity and thermal expansion coefficient of the batch tray to be affected separately. The materials can be selected such that the thermal expansion coefficient of the batch tray matches at least the thermal expansion coefficient of the component group or the first component and / or the second component. Alternatively, the connecting element and the tray can be manufactured of the same material.

[0012] However, the first and second components may be made of different materials. In principle, the components themselves may be made of different materials, resulting in different thermal conductivities and coefficients of thermal expansion for each component or group of components. Alternatively, the first and second components may be manufactured from the same material.

[0013] The material of the connecting element or the tray can be the same as the material of the first part. The material of the connecting element or the tray can therefore be selected depending on the material of the first part. The important point is that the material of the connecting element or the tray and the material of the first part have a maximum difference in thermal expansion coefficient of, for example, ±5×10 -6 / K, which makes it possible to particularly easily match the thermal expansion of the connecting element or the tray to the thermal expansion of the first part, depending on the geometry of the connecting element or the tray. In this respect, identical materials also mean essentially similar materials, such as, for example, copper and copper alloys.

[0014] The material of the connecting element or tray can be a material with an anisotropic coefficient of thermal expansion. The coefficient of thermal expansion of the material varies depending on the location of the structure of the material, e.g., the crystal lattice or the reinforcement. In this way, the connecting element or tray can be configured with different coefficients of thermal expansion. For example, the connecting element or tray can be configured with a particularly low thermal expansion in a particular linear direction such that no or very little relative displacement occurs between the components of the component groups when the batch tray is heated.

[0015] The material can be a composite material, graphite, preferably aluminum graphite, or a ceramic, preferably aluminum silicon carbide. The connection element and / or the tray can in particular be made of one of these materials. In particular, graphite, or a modified material of graphite, can have an anisotropic coefficient of thermal expansion. Furthermore, aluminum graphite has a particularly high thermal conductivity. If the tray is made of aluminum graphite, the component group can be heated particularly quickly via the tray, for example by means of a heating plate. In this way, cycle times can be significantly reduced. It is also possible to use materials with particularly low thermal conductivity, for example if the aim is to heat the component group only partially.

[0016] Furthermore, the material of the connection element or tray can be a metal, preferably copper or aluminum, or a ceramic. Copper and aluminum have a relatively high thermal conductivity, so these metals can be effectively used to form the connection element or tray. A high thermal conductivity and therefore a high thermal diffusivity is advantageous for the purpose of a fast introduction and release of thermal energy in the component group. At the same time, this thermal diffusivity can also be used to establish a small or large possible temperature gradient in the batch tray or the connection element or tray, thus facilitating or suppressing the thermal expansion during heating of the batch tray and the component group.

[0017] The thermal expansion coefficient α of the material of the connecting element and / or the tray M and the thermal expansion coefficient α of the material of the first component and / or the second component. m and 20×10 -6 / K or less, preferably 10×10 -6 / K or less, particularly preferably 5×10 -6 The thermal expansion coefficients may differ by less than 0.15 μm / K or may be equal. The values ​​stated herein relate to a temperature of 20° C. An approximately equal or equal thermal expansion coefficient results in a more homogeneous thermal expansion of the connection element and / or the tray compared to the first and / or second component or group of components. Furthermore, the materials of the connection element and the tray may have significantly different thermal expansion coefficients, which are suitable for the materials of the first and second components, respectively.

[0018] The thermal conductivity λ of the material of the connection element and / or the tray can be 100 W / (m·K) or more, preferably 200 W / (m·K) or more, particularly preferably 300 W / (m·K) or more. Such a high thermal conductivity of the material facilitates a rapid heating or cooling of the material, i.e. the connection element and / or the tray. As a result, the process of heat treatment of the component groups can be significantly accelerated, since the joining and post-treatment of the respective components can be carried out quickly. In principle, the thermal conductivity of the material of the connection element and the tray can be significantly different. In this way, an excellent heat transfer can be provided, in cases where a rapid heating of the component groups is desired.

[0019] Thermal diffusivity α of the connecting element and / or the tray V , α T and the thermal diffusivity α of the first part and / or the second part. 1B , α 2B and 5mm apart from each other. 2 / s or less, preferably 3 mm 2 / s or less, particularly preferably 1 mm 2 They can differ by up to 1 / s or can be equal. The values ​​stated refer to a temperature of 20°C. The thermal diffusivity is the thermal conductivity divided by the product of the density and the specific heat capacity. The connecting elements and / or the tray can have a geometry and mass such that a high or low thermal diffusivity is obtained by connecting the tray to the respective material of the connecting elements. This thermal diffusivity can be adapted to the thermal diffusivity of each component or group of components. If the respective heat is diffused uniformly in the connecting elements and / or the tray and in the respective components at the same time, a simultaneous (parallel) thermal expansion of the connecting elements and / or the tray and in the respective components can be achieved accordingly. Furthermore, a high thermal diffusivity allows a small temperature gradient in the batch tray. This is advantageous because it prevents the batch tray and the components to be joined from warping relative to the machine.

[0020] The method according to the invention for heat treating components, in particular electronic components, comprises placing at least two component groups on at least two tray units of a batch tray, each tray unit containing a component group, each component group consisting of at least a first component and a second component to be connected to the first component, the heat treatment or thermal energy of the heating device at least partially melting or diffusing a connection material to bond the first component to the second component in at least one connection area of ​​each of the first and second components, and at least one connection element of the trays and / or connection members for connecting the trays to each other of each tray unit thermally expands during the heat treatment in at least one linear direction, which thermal expansion essentially coincides with the thermal expansion of the first component and / or the second component in said linear direction. For the effects of the method according to the invention, please refer to the description of the effects of the device according to the invention.

[0021] The heating device can be used to melt solder as connection material or to sinter metal paste, preferably silver or copper paste, as connection material. The heating device can be a heating plate and / or a furnace. The method can be used for soldering electronic components using a soldering fixture or for silver-sintering or copper-sintering electronic components using a suitable machine. Soldering and sintering can be performed using a heating plate and / or a furnace of the machine. The batch tray can be in direct contact with the heating plate, which heats the component group. Alternatively, the batch tray can be heated together with the component group in a furnace.

[0022] During the thermal treatment of the first and second components, the connection element and / or the tray and the first and / or the second components can be heated or cooled at different rates. The material of the connection element and / or the tray can be selected such that the first and / or the second components thermally expand in the same way as the connection element and / or the tray. As a result, the thermal expansion of the connection element and / or the tray can compensate the thermal expansion of the first and / or the second components or of each component group, so that a homogeneous thermal expansion occurs at the same time. In this way, warping of the components is reduced and the contact of the connections of the components to the respective tray units is improved, so that a particularly good heat transfer is ensured between the tray units and the component groups.

[0023] During the heat treatment, the first part, the second part, and the tray can thermally expand and the first part, the second part, and the tray can be flush with one another, such that the parts and the tray do not change position relative to one another during the heat treatment.

[0024] During the heat treatment, a temperature gradient of less than 15 K, preferably less than 10 K, particularly preferably less than 5 K can be created in the tray. Advantageously, a small temperature gradient can also be realized due to a large thermal diffusivity, which ensures a homogeneous heat distribution in the tray. Warping due to a non-homogeneous heat distribution can be avoided in this way.

[0025] Further advantageous embodiments of the method are evident from the characterizing recitations of the dependent claims which refer back to claim 1 of the device.

[0026] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a perspective view of a batch tray. [Diagram 2] FIG. 2 is a plan view of the batch tray. [Diagram 3] FIG. 3 is a cross-sectional view of the batch tray shown in FIG. 2 taken along line III-III. [Figure 4] FIG. 4 is a detailed view of part IV of the batch tray of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] All of Figures 1 to 4 show a batch tray 10 serving to accommodate a number of component groups (not shown), which are subjected to a heat treatment together with the batch tray. Each component group has at least a first component and a second component to be connected or joined to the first component in a conductive or non-conductive manner, the conductively joined connection between the two components being formed by at least partially melting or diffusing a connecting material such as solder or metal paste in a heat treatment. Alternatively, the purpose may simply be to heat treat already formed or already joined component groups.

[0029] The batch tray 10 forms an array of tray units 11, each of which can accommodate a group of components. Each tray unit 11 comprises a tray 12 and a connecting member 13 for connecting the trays 12. In particular, the connecting member 13 comprises two connecting elements 14 in this embodiment. Each connecting element 14 is a profile bar 15 made of copper. Alternatively, the profile bars 15 may be made of aluminium. The connecting elements 14 connect the trays 12 which are closely spaced apart in the illustrated arrangement by narrow gaps 16. The trays 12 are provided with a recess 17 for receiving a first component (not shown) of the group of components. The first component can be a DCB board. The recess 17 is configured so that the first component can be inserted and positioned or fixed in the desired position by a contour 18 of the recess 17. The trays 12 are made of aluminium graphite.

[0030] The batch tray 10 further includes fasteners 19 for form-fittingly connecting the connecting elements 14 to the tray 12. The fasteners 19 include screws 20 and pins 21 formed by or molded into the tray 12, with the pins 21 inserted into corresponding openings 22 in the connecting elements 14. The pins 21 engage the openings 22 to form-fit the tray 12 and the connecting elements 14. At the same time, each screw 20 secures the tray 12 to the connecting elements 14 in a form-fitting and force-fitting manner. Additionally, a shoulder 24 is formed on each longitudinal side 23 of the tray 12, the depth of which corresponds approximately to the height of the connecting elements 14. The connecting elements 14 are inserted into the shoulders 24 in a substantially flush manner, and the shoulders 24 are configured such that a slight gap 25 is formed between each connecting element 14 and the tray 12, the slight gap extending along the longitudinal or longitudinal axis 26 of the batch tray 10.

[0031] The aluminum graphite of each tray 14 has an anisotropic coefficient of thermal expansion. Also, each connection element 14 is provided with a positioning aid 27 for the component, which in this example is formed by a pin 28. This allows a copper plate or a lead frame (not shown) to be positioned precisely on the top surface 29 of the batch tray 20 as a second part, which can be produced in particular by means of a die cutting tool. In this way, the pin 28 can, for example, engage with an opening in the copper plate, allowing the copper plate to be positioned precisely.

[0032] A heat treatment can then be performed by contacting a heating plate (not shown) with the underside 30 of the batch tray 10, which heats the batch tray 10. The heating continues until a temperature is reached that at least partially melts the connection material, after which the batch tray 10 is again cooled and the connection material hardens, resulting in a bonded, electrically conductive connection between the first and second components.

[0033] When the batch tray is heated by means of a heating plate, the high thermal diffusivity of the aluminum graphite of the tray 12 ensures that the components heat up quickly in this region. The thermal expansion perpendicular to the longitudinal axis 26 is small, since the coefficient of expansion of the aluminum graphite in this direction is also small. The thermal expansion of the tray 12 along the longitudinal axis 26 is of little importance, since the trays 12 are separated by the gap 16. The connecting element 14 has essentially the same coefficient of expansion as the die-cut copper plate, and therefore essentially the same thermal expansion along the longitudinal axis 26 of the batch tray together with its copper plate. Thus, there is no possibility of the first and second parts being unintentionally displaced during the heat treatment, nor of deformation during cooling. The same applies to the thermal expansion of each tray 12 and each first part placed in the recess 17. Here, the thermal expansion of the tray 12 is also dimensioned in such a way that the first parts are not displaced in contact with the contours 18. In this way, particularly small tolerances can be maintained when manufacturing the electronic components, and the manufacturing process can be effectively facilitated.

Claims

1. An apparatus for heat treating components, particularly electronic components, comprising a batch tray (10) and at least two groups of components arranged on the batch tray, each group of components having at least a first component and a second component connected or to be connected to the first component, the batch tray having at least two tray units (11) each containing a group of components; Features include: Each tray unit has a tray (12) and a connecting member (13) for connecting a plurality of the trays to each other, the connecting member being formed of at least one connecting element (14), the material of the connecting element and / or the tray being selected to thermally expand in at least one linear direction when the connecting element and / or the tray is heat treated, and the thermal expansion essentially coincides with the thermal expansion of the first part and / or the second part in the linear direction. A device that does this.

2. 10. The apparatus of claim 1, 10. A device according to claim 9, wherein said trays (12) are connected in a form-fitting manner to said connecting elements (14) by respective fasteners (19).

3. 10. The apparatus of claim 1, The device is characterized in that the connecting member (13) is composed of at least two connecting elements (14), said connecting elements being parallel sections (15) connecting the spaced apart trays (12).

4. 10. The apparatus of claim 1, The apparatus is characterized in that each of the tray units (11) is provided with at least one positioning aid (27) and / or recess (17) for receiving and positioning the first component and / or the second component.

5. 10. The apparatus of claim 1, A device characterized in that the connecting element (14) and the tray (12) are made of different materials.

6. 10. The apparatus of claim 1, The apparatus, wherein the first part and the second part are formed of different materials.

7. 10. The apparatus of claim 1, A device characterized in that the material of said connecting element (14) or said tray (12) is the same as the material of said first part.

8. 10. The apparatus of claim 1, A device characterized in that the material of the connecting element (14) or the tray (12) is a material with an anisotropic coefficient of thermal expansion.

9. 10. The apparatus of claim 1, A device characterized in that the material is a composite material, graphite, preferably aluminum graphite, or ceramic, preferably aluminum silicon carbide.

10. 10. The apparatus of claim 1, A device characterized in that the material of said connecting element (14) or said tray (12) is metal, preferably copper or aluminum, or ceramic.

11. 10. The apparatus of claim 1, The thermal expansion coefficient (α Ｍ ) and the thermal expansion coefficient (α) of the material of the first part and / or the second part. ｍ ) and each other 20 × 10 －６ / K or less, preferably 10 × 10 －６ / K or less, particularly preferably 5 × 10 －６ 1. A device characterized in that the values ​​of the sine wave number 1 and the sine wave number 2 differ by a difference of not more than 1 / K or are equal to each other.

12. 10. The apparatus of claim 1, 1. An apparatus characterized in that the thermal conductivity (λ) of the material of the connecting element (14) and / or the tray (12) is 100 W / (m·K) or more, preferably 200 W / (m·K) or more, particularly preferably 300 W / (m·K) or more.

13. 10. The apparatus of claim 1, The thermal diffusivity (α Ｖ , α Ｔ ) and the thermal diffusivity (α) of the first component and / or the second component １Ｂ , α ２Ｂ ) are 5 mm apart from each other ２ / s or less, preferably 3 mm ２ / s or less, particularly preferably 1 mm ２ An apparatus characterized in that the values ​​are different or equal by a difference of not more than 1 / s.

14. A method for heat-treating components, particularly electronic components, comprising: at least two component groups arranged on at least two tray units (11) of a batch tray (10), each tray unit containing a component group, each component group consisting of at least a first component and a second component to be connected to the first component; and heat-treating the components in a heating device to at least partially melt or diffuse a connection material, thereby bonding the first component to the second component in at least one connection region of each of the first and second components. Features include: The trays (12) of each tray unit and / or at least one connecting element (14) of the connecting member (13) for connecting the trays to each other undergo thermal expansion in at least one linear direction during the heat treatment, and this thermal expansion essentially coincides with the thermal expansion of the first part and / or the second part in the linear direction. The way it is.

15. 15. The method of claim 14, The method, characterized in that the heating device is used for melting solder as a connecting material or for sintering a metal paste, preferably a silver paste or a copper paste, as a connecting material, and the heating device is a heating plate and / or a furnace.

16. 15. The method of claim 14, wherein during heat treatment of the first and second parts, the connecting element (14) and / or the tray (12) and the first and / or second parts are heated or cooled at different rates, and the material of the connecting element and / or the tray is selected so that the first and / or second parts thermally expand in the same manner as the connecting element and / or the tray.

17. 15. The method of claim 14, The method of claim 1, wherein the first part, the second part, and the tray (12) thermally expand during heat treatment, causing the first part, the second part, and the tray to lie flush with one another.

18. 15. The method of claim 14, 10. The method according to claim 1, wherein a temperature gradient of not more than 15 K, preferably not more than 10 K, particularly preferably not more than 5 K is created in the tray (12) during the heat treatment.

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