Circuit carrier for receiving electronic components

Abstract

The invention relates to a circuit carrier (12) which has an electrical and / or mechanical function and in which electronic components can be accommodated. The circuit carrier (12) has, in the edge region (22) thereof, a structure (24) provided with a metallization (32), in particular in the form of a through-hole (28) and / or a cylindrical recess (30). According to the invention, at least the metallization (32) is partially removed on the circuit carrier (12) in the region of a metallization structure (24), which is designed in particular as a through-hole (28) and / or a cylindrical projection (30), up to a specific portion (46) of the material thickness (42) of the circuit carrier (12). The invention also relates to a method for producing a cohesively bonded connection (14) between a base circuit carrier (10) and a further circuit carrier (12).

Description

Technical Field

[0001] The invention relates to a circuit carrier which has an electrical and / or mechanical function and can accommodate electronic components, and which comprises a structure provided with a metallization in its edge region. The invention also relates to a method for producing a material-bonded connection between a fixing base and at least one further circuit carrier while avoiding the formation of cracks in the soldering points, the soldering parts electrically and mechanically connecting the circuit carrier and the fixing base to one another. Background Art

[0002] DE 10 2016 105 581 A1 relates to redirecting solder material to a visually inspectable surface of a circuit carrier. A circuit carrier is disclosed, which consists of a laminated material and has an electrical and / or mechanical function and can accommodate electronic components. In addition, solderable electrical contacts are present on the soldering surface of the circuit carrier. A solder flow path is formed on the circuit carrier so that when the electrical contacts are soldered to a fixed base, part of the solder material flows along the solder flow path in the direction of the circuit carrier surface, and due to the presence and collective shape of the solder material, it can be optically inspected after the solder connection between the fixed base and the electrical contacts of the circuit carrier has been made.

[0003] DE 10 2012 112 100 A1 relates to the design of a solderable surface of a circuit carrier. The circuit carrier comprises a structure provided with a metallization at its edge.

[0004] The circuit carrier can be mounted on the mounting base by applying solder material to the metallized surface of the mounting base. The metallized surface of the mounting base is designed so that it is geometrically arranged according to the metallized structure of the circuit carrier to be applied, so that a material-fitting solder connection can be formed between the metallized surface of the mounting base and the structure of the circuit carrier provided with a metallized portion at the edge. For mounting, the circuit carrier is arranged on the metallized surface of the base circuit carrier, to which solder material has been applied beforehand. The solder material is then melted. Due to the wetting of the metallized surface of the mounting base and the structure of the circuit carrier provided with the metallized portion, mechanical and electrical contact is obtained. Summary of the invention

[0005] According to the invention, a circuit carrier is provided which has an electrical and / or mechanical function and can accommodate electronic components, wherein the circuit carrier has structures provided with partial metallization in its edge region. On the circuit carrier, in the region of the metallization structures, no metallization is present at least up to a certain material thickness of the circuit carrier.

[0006] The solution proposed according to the invention makes it possible to prevent uneven shrinkage or expansion of the circuit carrier when the solder used within the scope of the material-fit connection solidifies during the curing process, thereby largely avoiding the formation of cavities in the soldering points or resulting thermal cracks.

[0007] Advantageously, the circuit carrier proposed according to the invention is implemented such that the structure provided with the partial metallization is connected to the contact material of the substantially horizontally extending anchor in the circuit carrier. As a result, the mechanical stability of the circuit carrier can be significantly improved, especially in the edge region of the circuit carrier.

[0008] In the case of the circuit carrier proposed according to the invention, the region of the circuit carrier without metallization has at its connection area a course which is essentially perpendicular to the surface of the circuit carrier.

[0009] The circuit carrier according to the invention can be produced in an advantageous manner by drilling a through hole in a laminated plate-like material and then metallizing its surface. In order to achieve partial metallization of the through hole over the thickness of the circuit carrier, a slightly larger cutting tool (e.g. a drill) can be used to partially remove the metallization applied on the inside of the through hole. After sawing through the laminated plate-like material, a structure that is, for example, in the form of a columnar surface and is only partially metallized relative to the thickness of the circuit carrier is obtained along the surface of the circuit carrier separated by sawing.

[0010] In another advantageous manner, the circuit carrier proposed according to the invention can be produced by drilling blind holes in a laminated sheet material and then metallizing its surface. After sawing through the laminated sheet material, a structure is obtained along the surface of the circuit carrier separated by sawing, for example, in the form of a columnar surface and only partially metallized relative to the thickness of the circuit carrier.

[0011] In another advantageous manner, the circuit carrier proposed according to the invention can be produced by drilling or milling an elongated hole in a laminated sheet material and then metallizing its surface. In order to achieve only partial metallization of the through-hole over the thickness of the circuit carrier, the metallization applied on the inside of the through-hole can be partially removed again using a milling cutter. After sawing through the laminated sheet material, only partially metallized surfaces are obtained along the surface of the circuit carrier separated by sawing relative to the thickness of the circuit carrier.

[0012] Furthermore, the invention relates to a method for producing a cohesive connection between a fastening base and a circuit carrier, wherein at least the following method steps are performed:

[0013] a) arranging the fixing base and the circuit carrier one above the other;

[0014] b) Producing a cohesive connection between the top side of the fastening base and the side edge of the circuit carrier.

[0015] In an advantageous development of the method proposed according to the invention, the material-bonded connection is produced according to method step b) as a solder connection.

[0016] In the method proposed according to the invention, in addition to partial removal of the metallization, material of the circuit carrier can also be removed.

[0017] Finally, the present invention relates to a circuit carrier in the manufacture of a PCB module The PCB module has circuit carriers stacked on top of each other to avoid the formation of thermal cracks.

[0018] Advantages of the present invention

[0019] By means of the circuit carrier proposed according to the invention or the method proposed according to the invention for producing a material-bonded connection in circuit carriers arranged one above the other, it is possible to create a circuit carrier module (PCB module, ), wherein the formation of thermal cracks is excluded. By means of the solution proposed according to the invention, when the material-fit connection between the circuit carriers stacked on top of each other, which is preferably designed as a solder connection, solidifies or solidifies, the stresses that occur in the connection due to the usually uneven shrinkage of the circuit carrier are significantly reduced. In the solution proposed according to the invention, no complete metallization is provided in the region of the metallization structure of the circuit carrier, but only a partial metallization. For production purposes, the metallization can be partially removed by subsequent cutting at the semi-open, i.e. halved through-hole, so that a reduction in thermal expansion differences in the vicinity of the structure can be achieved compared to the solutions known to date. The metallization can be designed as a recess, a planar structure, or as a protrusion. By reducing the length of the metallization, the uneven thermal expansion of the circuit carrier in its thickness direction can be reduced, whereby the stresses that occur when the solder material solidifies can be significantly reduced.

[0020] Preferably, the metallization, which is usually made of copper or another well-conducting metallic material, is removed by a subsequent machining process so that in the region of the structure a certain thickness of material of the metallization layer covering the circuit carrier is removed, wherein the structure can in particular be created as a metallization structure with a semi-open structure.

[0021] Furthermore, the solution proposed according to the invention makes it possible to arrange through-holes (PTH, plated through-holes) in edge regions relatively close to the side edges of the circuit carrier, which increases the mechanical stability of the circuit carrier in the edge region thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be described in more detail below with reference to the accompanying drawings, wherein:

[0023] Figure 1 shows a cross section with a fastening base and a circuit carrier connected thereto via a material connection at the top thereof,

[0024] Figure 2 shows the material behavior between the circuit carrier and the mounting base as the solder connection cools down,

[0025] Figure 3 Schematic diagram showing the uneven shrinkage process,

[0026] Figure 4 shows a cohesive connection between a base circuit carrier and a circuit carrier arranged thereon,

[0027] Figure 5 Schematic representation of partial material removal in the region of the metallization and in the edge region of the circuit carrier,

[0028] Figure 6 A further embodiment variant of the connection between base circuit carrier and circuit carrier is shown, in which the edge region of the circuit carrier is mechanically reinforced by means of a PTH (plated through hole). DETAILED DESCRIPTION

[0029] In the following description of embodiments of the invention, identical or similar elements are provided with the same reference numerals, wherein a repeated description of the elements is omitted in individual cases. The figures merely schematically illustrate the subject matter of the invention.

[0030] according to Figure 1 The view of FIG. 1 shows a module having at least one fixing base 10 and a circuit carrier 12 arranged above the fixing base 10. The two components 10, 12 are designed as a PCB. There may also be other designs for the fixing base 10 , such as a ceramic substrate. Figure 1 The two components schematically shown arranged one above the other, namely the fixing base 10 and the circuit carrier 12, are connected to each other in a materially bonded manner via a materially bonded connection 14, which is preferably designed as a solder connection 16. In the context of producing the solder connection 16, a solder 18 is used, which changes from a liquid state to a solidified state when the solder connection 16 cools. The electronic component can be applied to the fixing base 10 or the circuit carrier 12, which is only schematically shown here, for example by means of SMD (surface mounted device) technology.

[0031] The at least one solder connection 16 has an edge region 22, by means of which the at least one fastening base 10 and the circuit carrier 12 are connected to one another in an electrically conductive manner. Figure 12. A plurality of metallization structures 24 are arranged one after another in the drawing plane of FIG. The metallization structure can be characterized by a substantially semi-open geometry 26, also referred to as a castellated hole. For example, the metallization structure 24 in the semi-open geometry 26 can be a cylindrical recess 30 or the like, which has been sawn through and is provided with a lined metallization 32. Other variant embodiments include a planar metallization structure 24. Such a structure 24 is characterized by a metallization 32, which is made of an electrically conductive material, preferably copper or a copper-containing mixture or the like.

[0032] The metallization 32 is applied as a layer 34 to the metallization structure 24. The layer 34 is applied with a layer thickness 36. The layer thickness 36 is in the range between approximately 20 μm and approximately 60 μm.

[0033] Stresses arising from the uneven thermal expansion behavior in the cohesive connection 14 , which is preferably designed as a solder connection 16 , can cause cracks, which in the context of crack formation and crack propagation 38 , 76 can lead to interruptions in the electrical connection and thus to impaired functionality of such a connected PCB module.

[0034] In addition, according to Figure 1 It can also be seen from the view of FIG. 1 that the circuit carrier 12 arranged on the upper side 44 of the fastening base 10 is produced from a material 40 . The material thickness of the material 40 of the circuit carrier 12 is denoted by the reference numeral 42 .

[0035] From the basis Figure 2 The cooling behavior of the contact material 48, ie the solder, from which the material-bonded connection 14 in the form of the solder connection 16 is produced can be schematically seen in the sequence of figures 14. At the time of production of the material-bonded connection 14 in the form of the solder connection 16, the solder 18, ie the contact material 48, has a very high maximum temperature of 70 (T π ). At this point in time, the solder 18 used is liquid and begins to cool. During the transition temperature range 72 resulting from the cooling, individual solidified particles 75 are formed in the melt of the solder 18, as can be seen from the temperature drop according to Figure 2 is derived from the sequence of accompanying drawings.

[0036] As from Figure 2 It can also be seen that, upon further cooling of the melt of solder 18 at solidification temperature 74 , almost completely solidified solder 18 is formed in the form of solidified particles 75 . Figure 2 It is shown that a cavity 76 is formed in the region of the metallization 32 , which cavity is caused by the detachment of solidified particles 75 from the upper side of the metallization 32 or the contact material 48 . This results in a crack propagation 38 .

[0037] Figure 3A cylindrical recess 30, for example, with a semi-open geometry 26 is shown schematically. The hatching or dots here illustrate the change (contraction) of the dimensions of the circuit carrier 12 in the Z direction, i.e. in the thickness direction of the circuit carrier 12, when the circuit carrier 12 is cooled from 210° C. to 190° C. The dark dotted areas in the region of the semi-open geometry 26 have the smallest change. The arrows that start from the semi-open geometry 26, here from the metallization 32, cause the crack formation shown above during the cooling process, as shown in FIG. Figure 2 This is schematically shown in FIG. 7 , where the arrows show different expansion behaviors and thus non-uniform contraction 78 .

[0038] Figure 4 A module according to the conventional prior art is shown, which comprises a circuit carrier 12 located above, which is connected in a materially bonding manner to the top 44 of the fastening base 10 via a materially bonding connection 14 designed as a solder connection 16. Via the solder 18, the contact material 48 of the metallization 32 or the contact material 48 applied to the top 44 of the fastening base 10 is connected to one another in a materially bonding and electrically conductive manner.

[0039] From the basis Figure 4 It can be seen from the view that the circuit carrier 12 has in its edge region 22 anchors arranged in strips and extending essentially horizontally into the material 40 of the circuit carrier 12. The anchors serve to improve the mechanical properties of the circuit carrier 12, in particular in its edge region 22.

[0040] Figure 4 It is shown that at the side edge 41 of the material 40 of the circuit carrier 12, the metallization 32 applied here in the region of the semi-open geometry 26 is designed to run continuously along the entire material thickness 42. The metallization 32 applied as a layer 34 of copper or another electrically conductive material is designed with a layer thickness 36. This embodiment corresponds to the prior art and does not correspond to an embodiment of the disclosed invention.

[0041] exist Figure 4 In the embodiment variant of the material-bonded connection 14 shown in the drawing, which is preferably designed as a solder connection 116 made of solder 18, a schematic curve 80 of the coefficient of thermal expansion (CTE) occurs along the axis of the recess 30 as shown. Due to the layered structure of the circuit carrier 12, the thermal expansion of the base material is greater than the thermal expansion of the material of the metallization 32 of the recess 30. Therefore, the coefficient of thermal expansion of the circuit carrier 12 in the region of the metallization 32 of the recess 30 is smaller than the thermal expansion at a certain distance from the recess 30. This is shown in the schematic curve of the thermal expansion plotted corresponding to the first difference relative to the distance 80 indicated by the double arrow 82.

[0042] From the basis Figure 5The material of at least the subsequent part of the contact material 48 of the metallization 32 is shown in the view of FIG. 4 . Depending on the type of production, there may also be a removal 66 of the material 40 of the circuit carrier 12 in the region of the side walls 41 of the circuit carrier 12 . This material removal of the material 40 of the circuit carrier 12 is indicated by the reference numeral 60 . Figure 5 In the schematic diagram of FIG. 5 , both materials, namely the contact material 48 of the metallization 32 and the material 40 of the circuit carrier 12 are removed to approximately the same extent, so that an exposed area 52 is obtained. Figure 5 As shown in , the material removal 60 of the metallization 32 and the material 40 can be performed after the via is fully metallized by machining, for example by means of "back drilling". Figure 5 It turns out that after the partial material removal 60 , a slightly concavely arranged side wall 41 of the material 40 of the circuit carrier 12 is present in a manner radially offset relative to the remainder 62 of the total material thickness 42 of the circuit carrier 12 . Figure 5 In the view of FIG. 1 , the remaining anchoring element 50 is also shown, which extends substantially in the horizontal direction into the material 40 of the circuit carrier 12 .

[0043] By Figure 5 The region 52 produced in the edge region 22 of the circuit carrier 12 and exposed by the metallization 32 of the metallization structure 24 produces a CTE which is also Figure 5 A reduced second difference 84 is schematically indicated in FIG.

[0044] Combined with Figure 4 Compared to the first difference 82 shown in the arrangement of , the occurring difference 80 in the coefficient of thermal expansion (CTE) is significantly smaller in absolute size.

[0045] With regard to the material 60 removed in the region of the side walls 41 of the circuit carrier 12, it should be noted that the material can either be subsequently removed substantially along the vertical course 54, or the material removal 60 of the contact material 48 of the metallization 32 and also the material removal 60 relative to the material 40 of the circuit carrier 12 can be carried out with a taper 56 (see also the material removal 60 according to Figure 6 of the view).

[0046] from Figure 6 Another embodiment of the PCB module can be derived from Figure 6 From the view of Figure 5 In the PCB module shown here, the circuit carrier 12 is connected to the contact material 48 on the upper side 44 of the base circuit carrier 10 by means of solder 18 via a material connection 14 designed as a solder connection 16, and thus electrically conductively, wherein a plurality of electronic components (not shown in detail here) can be arranged on the circuit carrier. Figure 5Unlike the embodiment variant shown in FIG. 1 , the material 40 of the circuit carrier 12 arranged on the top passes through the PTH 86 (plated through hole). By arranging it in the edge region 22 of the circuit carrier 12, the mechanical stability of the circuit carrier 12 is improved. Figure 6 : It can be seen from the view that between the material of the plated-through hole 86 and the metallization 32 at the outer edge of the material 40 of the circuit carrier 12, that is, at the side wall 41, the metallization 32 composed of copper or another electrically conductive material extends as a layer 3 with a layer thickness 36. Between the layer 34, the metallization 32 and the material of the plated-through hole 86, the individual connecting webs 88 extend essentially in the horizontal direction. Figure 6 Only two connecting webs one above the other are shown in the view of FIG.

[0047] from Figure 6 It can also be seen from the view of FIG. 5 that an exposed region 52 is also shown here, which is produced at least partially by removing the contact material 48 of the metallization 32. Figure 6 The view of FIG. 1 additionally shows partially removed material 60 of the circuit carrier 12. Figure 5 , the exposed area 52 extends with a certain thickness 46, for example 50%, relative to the material thickness 42 of the circuit carrier 12. The remainder 62 extends over the entire material thickness 42 of the material 40 of the circuit carrier 12 minus the thickness 46 of the exposed area 52. In this case, if necessary, depending on the production method, a radial offset occurs on the one hand between the new side edge 41 of the material 40 obtained after the machining process and the layer 34 of the metallization 32. A chamfer 64 is formed due to the machining process.

[0048] The invention also relates to a method for producing a material-fit connection 14 between a mounting base 10 and a further circuit carrier 12 arranged above it. The mounting base 10 and the circuit carrier 12 are designed as a PCB (PCB=printed circuit board). In the method proposed according to the invention, the following method steps are performed:

[0049] a) arranging the fixed base 10 and the circuit carrier 12 to overlap each other;

[0050] b) A cohesive connection is produced between the top of the fastening base 10 and the side edge 41 of the circuit carrier 12 .

[0051] In the method proposed according to the invention, according to method step b), the material-bonded connection 14 is preferably produced as a solder connection 16 consisting of a solder 18 .

[0052] The exposed regions 52 at the side walls 41 of the material 40 of the circuit carrier 12 by means of the method proposed according to the invention improve the thermal expansion behavior of the material 40 or 18 , 48 , so that excessive stresses are avoided, so that cracks 76 or crack propagations 38 do not even occur.

[0053] In addition, the present invention relates to a circuit carrier 12 in a PCB module The PCB module has circuit carriers 10, 12 stacked one on top of the other in order to avoid thermal crack formation.

[0054] The invention is not limited to the embodiments described herein and the aspects emphasized therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of the practice of a person skilled in the art.

Claims

1. A circuit carrier (12) for accommodating an electronic component, the circuit carrier having in its edge region (22) a metallized structure (24), in particular a cylindrical recess (30), which is lined with a metallization (32), characterized in that In the region of the structure (24), in particular in the region of the cylindrical recess (30), at least the metallization (32) is partially removed at least to a certain thickness (46) of the material thickness (42) of the circuit carrier (12).

2. The circuit carrier (12) according to claim 1, characterized in that In the edge region (22) of the circuit carrier (12), material (40) of the circuit carrier (12) is partially removed, with the exception of the metallization (32) of the structure (24).

3. The circuit carrier (12) according to claim 1, characterized in that The metallization (32) extends horizontally via anchors (50) into the material (40) of the circuit carrier (12) in order to improve the mechanical strength.

4. The circuit carrier (12) according to claim 1, characterized in that A cylindrical recess (30) and / or a through-hole (28) and / or a PTH (86) (plated through-hole) extends in the edge region (22) of the circuit carrier (12).

5. The circuit carrier (12) according to claim 1, characterized in that The metallization (32) is connected in the edge region (22) of the elongated through-hole (28) and / or cylindrical recess (30) to the contact material (48) of the anchoring element (50) which is designed essentially in strip form and extends in the horizontal direction.

6. The circuit carrier (12) according to claim 1, characterized in that As a result of at least partial material removal (66) of the metallization (32), an exposed region (52) of the circuit carrier (12) has a substantially vertical extent (54).

7. The circuit carrier (12) according to claim 1, characterized in that As a result of at least partial material removal (66) of the metallization (32), an exposed region (52) of the circuit carrier (12) substantially has a taper (56).

8. The circuit carrier (12) according to any one of claims 1 to 7, characterized in that By removing material (66) of at least a portion of the metallization (32), the exposed region (52) is radially offset relative to the metallization (32).

9. The circuit carrier (12) according to claim 1, characterized in that By removing material (66) of at least a portion of the metallization (32), a chamfer (64) is formed on at least a remaining portion (62) of the metallization (32).

10. A method for producing a cohesive connection (14) between a base circuit carrier (10) and a circuit carrier (12) according to any one of claims 1 to 9, comprising at least the following method steps: a) arranging the basic circuit carrier (10) and the circuit carrier (12) one above the other; b) producing a material-bonded connection (14) between the top side (44) of the base circuit carrier (10) and a side edge (41) of the circuit carrier (12) in the region of the structures (24).

11. The method according to claim 10, characterized in that According to method step b), a solder connection (16) is produced.

12. A circuit carrier (12) according to any one of claims 1 to 9 in manufacturing a PCB module The invention relates to a method for manufacturing a PCB module, wherein the PCB module comprises circuit carriers (10, 12) stacked on top of each other to avoid the formation of thermal cracks.

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