WO2021170407A1

WO2021170407A1 - Method for producing an electric assembly

Info

Publication number: WO2021170407A1
Application number: PCT/EP2021/053160
Authority: WO
Inventors: Mario BRESECKE; Henri KRÜGER; Dieter WENGERTSMANN
Original assignee: Siemens Mobility GmbH
Priority date: 2020-02-28
Filing date: 2021-02-10
Publication date: 2021-09-02
Also published as: EP4074148A1; CN115211239A; DE102020202598A1

Abstract

The invention relates to a method for producing an electric assembly on the basis of a printed circuit board. The printed circuit board has a first conductor track structure, which has conductor tracks and is arranged on one face of the printed circuit board, hereinafter referred to as the primary face; a second conductor track structure, which has conductor tracks and is arranged on the other face of the printed circuit board, hereinafter referred to as the secondary face, and/or in an intermediate layer of the printed circuit board as an inner conductor track structure; and a number of vias, by means of which each conductor track of the first conductor track structure can be electrically connected to a conductor track of the second conductor track structure, wherein at least one first electric component is arranged on the primary face, said electric component being soldered to the first conductor track structure by means of a first soldering stage. According to the invention, at least one of the vias is closed solely on the primary face by a protective layer before at least one first electric component is arranged on the primary face and is soldered by means of the first soldering stage.

Description

description

Method of making an electrical assembly

The invention relates to a method for producing electrical assemblies and to electrical assemblies as such.

Among other things, the invention relates to a method for producing an electrical arrangement on the basis of a printed circuit board, which has: a first conductor track structure having conductor tracks on one side of the circuit board, hereinafter referred to as the primary side, a conductor track having a second conductor track structure on the other Side of the circuit board, hereinafter referred to as the secondary side, and / or is arranged as an internal conductor track structure in an intermediate layer of the circuit board, and a number of through-holes by means of which a conductor track of the first conductor track structure can be electrically connected to a conductor track of the second conductor track structure, with the Primary side, at least one first electrical component is arranged, which is soldered to the first conductor track structure by means of a first soldering step.

Such circuit boards are well known in the field of circuit board technology. It is also known to have at least one electrical component, for example in the form of a surface-mounted component (also called SMD (Surface Mounted Device) component) or a through-hole component, also known as a THD (Through-Hole Device) component put on the primary side and soldered to the first or second conductor track structure.

The invention is based on the object of providing a method that provides better results than previously known methods with regard to corrosion protection of through-contacts. According to the invention, this object is achieved by a method having the features according to patent claim 1. Advantageous embodiments of the method according to the invention are given in subclaims Un.

According to the invention, it is provided that at least one of the through contacts is closed exclusively on the primary side by means of a protective layer before at least one first electrical component is arranged on the primary side and soldered by means of the first soldering step.

A significant advantage of the method according to the invention is that by closing the through-contacts that remain unpopulated, the protective layer ensures that reliable corrosion protection is also achieved with regard to the primary side. If, for example, through contacts that remain unassembled are covered by components to be attached to the circuit board or later attached, it is not ensured that reliable corrosion protection can be guaranteed later in the context of later steps. The fact that, according to the invention, the vias on the primary side are coated with the protective layer before components are attached to the primary side ensures that no hidden vias can remain that are not protected with a suitable protective layer on the primary side.

According to a further development of the method according to the invention, any corrosion-inhibiting material that can withstand subsequent processing steps, for example soldering steps, can be used for the protective layer. However, it is considered to be particularly advantageous if the protective layer is formed by a solder stop layer, which acts as a solder stop in particular in the first soldering step. In order to protect conductor tracks that should not come into contact with solder material from being wetted with solder material, knows how to apply so-called solder mask to the conductor tracks before the first soldering step. This solder mask coating step can be used in an advantageous manner - with the creation of a synergy effect - in order to also close the unpopulated through contacts on the primary side. In other words, the solder mask has a double function in this case: on the one hand, it coats and protects the conductor tracks from solder material that could wet the conductor tracks in subsequent soldering steps, and on the other hand it serves as a top or primary-side seal for the through contacts that remain unpopulated ; Both protective functions can be achieved with this coating step.

Epoxy resin is preferably used as the solder mask.

According to a further development, after the circuit board has been fitted with electrical components, the primary side of the circuit board is coated at least in areas with through-contacts with a cover layer, which is in particular an acrylate resin or a varnish containing acrylate resin. In particular, the resulting arrangement on both sides of the circuit board can be coated with such a cover layer over the entire area or at least in partial areas.

Any material that is suitable for the electrical operation of the arrangement and offers good corrosion protection can be used as the material for the cover layer, for example silicone or silicone-containing paint. With a view to particularly good protective properties, especially good corrosion protection, it is considered advantageous if, after the circuit board has been fitted with electrical components, the resulting arrangement on both sides of the circuit board over the entire surface or at least in areas that are provided with through contacts is coated with a cover layer in the form of acrylate resin or an acrylate resin ent containing paint. Acrylate resin or acrylate resin The paint it contains is robust and not very gas-permeable, at least more robust and less gas-permeable than silicone.

According to a further development, after the circuit board has been equipped, the secondary side is coated over the whole area or at least in areas with through-contacts by means of a cover layer made of in particular acrylic resin or of a lacquer containing acrylic resin.

It is considered advantageous if all those through contacts remaining unequipped that are below half of these components after the installation of the first electrical component or components and are covered by these after fastening and soldering these components, with means of the protective layer on the primary side who closed before the first electrical components on the primary side attached and soldered ver as part of the first soldering step.

As part of the first soldering step, the first electrical component is soldered to one or more conductor tracks of the first conductor track structure.

According to a further development, after the first soldering step, at least one second electrical component is arranged on the primary side and soldered to, in particular, one or more conductor tracks of the second conductor track structure by means of a second soldering step.

According to a further development, plated-through holes are excluded from the coating by means of the protective layer and remain unsealed, which are used to arrange the at least one second electrical component.

In particular, all those electrically conductive through contacts on the inside wall side remain excluded from the coating by means of the protective layer and not closed, which - after assembly and after soldering of the first electrical component or components - for mounting the second electrical component or components on the primary side and for soldering the second electrical component or components to at least one of the second conductor tracks of the second conductor track structure.

According to a further development, through contacts, which are located below the second compo after the assembly of the at least one second electrical component, are closed by means of the protective layer on the primary side before the at least one first electrical component is arranged on the primary side and by means of the first Soldering step is soldered.

If the second conductor track structure is an inner conductor track structure which is arranged in an intermediate layer of the circuit board, it is advantageous if the electrically conductive through contacts or at least a subgroup thereof extend to the intermediate layer and the primary side and the intermediate layer extend electrically connect with each other.

If the second conductor track structure having the second conductor tracks is on the secondary side, the through-contacts or at least a subgroup thereof can extend through the circuit board and electrically connect the primary side to the secondary side.

According to a further development, the at least one second electrical component has connection contacts which, when the second component is arranged, are introduced into through-holes that are not covered by the coating with the protective layer, and the connection contacts are soldered to the second conductor track structure by means of the second soldering step.

According to a further development, a diameter of the through contacts is dimensioned such that by means of the Second soldering step, solder material is drawn from the secondary side in the direction of the primary side due to a Kapillaref fect and the vias are completely or at least partially filled with solder material.

According to a further development, a reflow soldering process is preferably carried out in the first soldering step and / or a wave soldering or wave soldering process is preferably carried out in the second soldering step.

The first components are preferably surface mount components. The second components are preferably through plug-in components.

The invention also relates to an electrical arrangement with a printed circuit board, the printed circuit board having: a first conductor track structure having a conductor track on one side of the circuit board, hereinafter referred to as the primary side, a second conductor track structure having a conductor track on the other side of the circuit board , hereinafter referred to as the secondary side, and / or is arranged as an internal conductor track structure in an intermediate layer of the circuit board, and a number of vias, by means of which a conductor track of the first conductor track structure can be electrically connected to a conductor track of the second conductor track structure, and at least one electrical component is arranged on the primary side and soldered to the first and / or second conductor track structure.

According to the invention, it is provided that at least one of the vias, which is arranged below the at least one electrical component, is closed exclusively on the primary side by means of a protective layer.

With regard to the advantages of the arrangement according to the invention and advantageous configurations of the arrangement according to the invention reference is made to the above statements in connection with the method according to the invention.

According to a further development of the arrangement, the protective layer is a solder resist layer.

According to a further development of the arrangement, the primary side of the printed circuit board is coated in areas with vias with a cover layer, which consists in particular of acrylic resin or of a varnish containing acrylic resin, and / or the secondary side of the printed circuit board is over the whole area or coated at least in areas with through contacts with a cover layer, which consists in particular of an acrylate resin or of a lacquer containing acrylate resin.

The invention also relates to a rail vehicle, in particular one with at least one traction converter. According to the invention it is provided that the rail vehicle, in particular its or one of its traction converters, has an electrical arrangement as described above and / or produced as described above.

The invention is explained in more detail with reference to Ausführungsbeispie len; show by way of example

Figure 1 shows an embodiment of a circuit board that can be used to produce an embodiment for an inventive arrangement,

FIG. 2 shows an exemplary embodiment of an arrangement according to the invention which can be produced on the basis of the printed circuit board according to FIG. 1,

FIG. 3, in the form of a flowchart, method steps of an exemplary embodiment for an inventive ßes method for producing the arrangement according to Figure 2, and

FIG. 4 shows an exemplary embodiment for a rail vehicle according to the invention.

In the figures, the same reference numerals are always used for identical or comparable components.

FIG. 1 shows, in a schematic cross section, a section of a printed circuit board 10 which is to be processed further to produce an electrical arrangement. The printed circuit board 10 has on one of its sides, hereinafter referred to as the primary side 11, a first conductor track structure 11a, which comprises a plurality of conductor tracks. On the opposite side, hereinafter referred to as secondary side 12, there is a second conductor track structure 12a, which also comprises a plurality of conductor tracks.

In the illustration according to FIG. 1, there are also through contacts coated on the inside wall side with conductive material B and thus electrically conductive on the inside wall side as vias, of which the through contacts 21 to 25 are used to electrically connect conductor tracks of the first conductor track structure 11a with conductor tracks of the second conductor track structure 12a connect to. The through contacts 21 to 25 thus remain unassembled and are not used to accommodate connection contacts of components to be placed on the circuit board 10.

The through contacts 26 and 27 are used to enable connection contacts of so-called through plug-in components to be passed through. Such Durchsteckbauele elements can be placed on the primary side 11 of the circuit board 10 and their connection contacts are passed through the Durchgangskon contacts 26 and 27 in order to connect them to the second conductor track structure 12a. The generally relatively thin conductor track structures 11a and 12a are not shown to scale in FIG. 1, but are shown very much thicker than they actually are, in order to illustrate the interaction with the through contacts.

FIG. 2 shows an exemplary embodiment of an electrical arrangement 50 produced on the basis of circuit board 10 according to FIG. 1, which includes circuit board 10 according to FIG. 1 as well as a first component 100 and a second component 200. The first component 100 is preferably a surface-mounted component, also called an SMD (Surface Mounted Device) component; The second component 200 is preferably a plug-in component, also called a THD (Through-Hole Device) component.

Of course, the circuit board 10 can also carry more surface-mounted components and more push-through components than shown here; 2 is limited to the components 100 and 200 mentioned only for reasons of clarity. Likewise only for reasons of clarity, the illustration according to FIG. 2 lacks the two conductor track structures 11a and 12a, which are shown in FIG. 1 and whose thickness is very small is.

The arrangement according to FIG. 2 is preferably produced using method steps that are shown in the form of a flow diagram in FIG. In the following, FIGS. 2 and 3 are referred to jointly.

To produce the arrangement according to FIG. 2, in a first method step 1000, the conductor track structures 11a and 12a according to FIG. 1 are first defined on the circuit board 10, for example by etching, as is generally known. The circuit board 10 provided with the conductor track structures thus serves as a base material for the following explanations, which is processed further. In a subsequent method step 1100, a protective layer in the form of a solder stop layer 30 is first applied to the primary side 11 of the printed circuit board 10 provided with the conductor track structures 11a and 12a. The solder stop layer 30 preferably covers all sections of the first conductor track structure 11a that are not to be covered with solder in the course of a subsequent first soldering step. In addition, as part of the coating of the circuit board 10 with the solder-stop layer 30, all those through-contacts that are not to be fitted or provided with push-through components to produce the arrangement according to FIG. 2 are closed on the primary side 11. In the illustration according to FIG. 2, the through contacts 21 to 25 that are not to be fitted are thus closed.

The through contacts 26 and 27 merely remain free of the solder stop layer 30, since these are subsequently intended to be used for inserting connection contacts 210 and 220 of the plug-in component 200.

In a subsequent method step 1200, the printed circuit board 10 is fitted on the primary side 11 with the first component 100 or all surface-mounted construction elements. The component assembly according to method step 1200 preferably includes the application of soldering paste to those conductor track sections of the first conductor track structure 11a that are to be soldered to connection contacts 110 and 120 of the first component 100.

Subsequently, the first component 100 is "reflow" soldered to the first conductor track structure 11a of the circuit board 10 as part of a first soldering step 1300, preferably within a reflow oven.

In a subsequent component placement step 1400, the second component 200 with its connection contacts 210 and 220 is placed on the primary side 11 of the circuit board 10, the connection contacts 210 and 220 being inserted into the through- gang contacts 26 and 27 are inserted into and preferably through them. It is advantageous if the connection contacts 210 and 220 extend as far as the second conductor track structure 12a on the secondary side 12.

In a subsequent second soldering step 1500, which is preferably a wave soldering or wave soldering process step, the second component 200 with its connection contacts 210 and 220 with the second conductor track structure 12a (see Figure 1) on the secondary side 12 of the circuit board 10 soldered. The solder 35 can pull itself up from the bottom or the secondary side 12 wetted with solder 35 by the capillary effect upwards into the through contacts 26 and 27; The same also applies to the through contacts 21 to 25 which are open at the bottom, if the cross-section is sufficiently large, even if this is not explicitly shown in FIG.

After the completion of the second soldering step 1500, the resulting assembly is preferably cleaned on both sides as part of a cleaning step 1600. In a subsequent drying step 1700, the assembly is dried.

After drying is complete, the entire assembly is provided with a covering layer 40 in the form of protective varnish, which is a silicone varnish or silicone-containing varnish, over the entire surface, both on the primary side 11 and on the secondary side 12 of the circuit board 10, as part of a painting step 1800 can. However, it is considered to be particularly advantageous if the cover layer 40 is acrylate resin or at least contains acrylate resin, that is to say forms an acrylate resin lacquer.

The painting in painting step 1800 also closes the unassembled vias 21 to 25 on the secondary side 12, so that all unassembled vias 21 to 25 of the circuit board 10 are now sealed or closed on both sides, namely on the Primary side 11 through the solder stop layer 30 and the overlying cover layer 40 and on the secondary side 12 through the cover layer 40 alone. After painting, the resulting arrangement 50 according to FIG. 2 is dried in a drying step 1900.

In summary, the method steps described in connection with FIGS. 2 and 3 ensure that unassembled through contacts, i.e. the through contacts 21 to 25, are closed on both sides and thus corrosion of the metallization on the inner wall is reliably prevented. FIG. 4 shows an exemplary embodiment for a rail vehicle 500 according to the invention, which has one or more traction converters 510. The traction converters 510 each have one or more arrangements 50, as have been described above in connection with FIGS. 1 to 3.

List of reference symbols

10 circuit board

11 primary side

11a first conductor track structure

12 secondary side

12a second conductor track structure

21-27 Vias

30 solder mask / protective layer

35 lot

40 cover layer

50 electrical arrangement

100 first component / surface mount component

110 connection contact

120 connection contact

200 second component / push-through component

210 connection contact

220 connection contact

500 rail vehicle

510 traction converter

1000 process step

1100 process step

1200 process step

1300 first soldering step

1400 component placement step

1500 second soldering step

1600 cleaning step

1700 drying step

1800 painting step

1900 drying step

B conductive material

Claims

1. A method for producing an electrical arrangement (50) on the basis of a printed circuit board (10), the printed circuit board (10) having:

- A first conductor track structure (11a) having conductor tracks on one side of the circuit board (10), hereinafter referred to as the primary side (11),

- A second conductor track structure (12a) having conductor tracks, which is arranged on the other side of the circuit board (10), hereinafter referred to as the secondary side (12), and / or as an internal conductor track structure in an intermediate layer of the circuit board (10), and

- A number of vias (21-25), by means of which in each case a conductor track of the first conductor track structure (11a) can be electrically connected to a conductor track of the second conductor track structure (11a), with at least one first electrical component (100) on the primary side (11) is arranged, which is soldered to the first conductor track structure (11a, 12a) by means of a first soldering step (1300), characterized in that at least one of the vias (21-25) is closed by means of a protective layer (30) exclusively on the primary side (11) before the at least one first electrical component (100) is arranged on the primary side (11) and is soldered by means of the first soldering step (1300).

2. The method according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the protective layer (30) is a solder stop layer (30) which acts as a solder stop in particular in the first soldering step (1300).

3. The method according to any one of the preceding claims, characterized in that After the circuit board (10) has been equipped with electrical components (100), the primary side (11) of the circuit board (10) is coated at least in areas with vias with a cover layer (40), which consists in particular of acrylate resin or of a varnish containing acrylate resin will.

4. The method according to any one of the preceding claims, characterized in that after the circuit board (10) has been populated, the secondary side (12) is coated over the entire surface or at least in areas with through-contacts by means of a cover layer (40) made of acrylic resin in particular or of a varnish containing acrylic resin will.

5. The method according to any one of the preceding claims, characterized in that after the first soldering step (1300) at least one second electrical component (200) on the primary side (11) is arranged and by means of a second soldering step (1500) with the second conductor track structure (12a) is soldered.

6. The method according to claim 5, d a d u r c h g e k e n n z e i c h n e t that

Vias (26, 27) are excluded from the coating by means of the protective layer (30) and remain unsealed, which serve to arrange the at least one second electrical component (200).

7. The method according to any one of claims 5 or 6, d a d u r c h g e k e n n z e i c h n e t that

Vias (25), which after the arrangement of the at least one second electrical component (200) are below half of the second component (200), closed by means of the protective layer (30) on the primary side (11) before the at least one first electrical component (100) is arranged on the primary side (11) and is soldered by means of the first soldering step (1300).

8. The method according to claim 6, characterized in that the at least one second electrical component (200) has a number of connection contacts (210, 220) which, when the second component (200) is arranged, in from the Beschich device with the protective layer (30) recessed vias (26-27) are introduced, and the connection contacts (210, 220) are soldered to the second conductor track structure (12a) by means of the second soldering step (1500).

9. The method according to any one of claims 5 to 8, characterized in that a diameter of the vias (21-27) is measured such that by means of the second soldering step (1500) Lotma material due to a capillary effect from the secondary side (12) in the direction of the primary side (11) is pulled and the through contacts (21-27) completely or at least partially fills with solder material.

10. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that

- In the first soldering step (1300) a re-melting soldering device is carried out and / or

- In the second soldering step (1500) a wave soldering or surge soldering process is carried out.

11. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that

- The first components (100) are surface-mounted compo elements (100) and / or

- The second components (200) are push-through components.

12. Electrical arrangement (50) with a printed circuit board (10), the printed circuit board (10) having: - A first conductor track structure (11a) having conductor tracks on one side of the circuit board (10), hereinafter referred to as the primary side (11),

- A number of vias (21-25), by means of which a conductor track of the first conductor track structure (11a) can be electrically connected to a conductor track of the second conductor track structure (12a), and wherein at least one electrical component (100) is arranged on the primary side (11) and is soldered, characterized in that at least one of the vias (21), which is arranged under half of the at least one electrical component (100), is closed by means of a protective layer (30) exclusively on the primary side (11).

13. Arrangement (50) according to claim 12, d a d u r c h g e k e n n z e i c h n e t that the protective layer (30) is a solder stop layer (30).

14. The arrangement according to claim 13, characterized in that the primary side (11) of the printed circuit board (10) is coated in areas with vias with a cover layer (40), which consists in particular of acrylate resin or of a varnish containing acrylate resin, and / or the secondary side (12) of the printed circuit board (10) is coated over the entire surface or at least in areas with vias with a cover layer (40), which consists in particular of an acrylate resin or of a varnish containing acrylate resin.

15. Rail vehicle (500), in particular rail vehicle with traction converter (510), characterized in that the rail vehicle (500), in particular its or one of its traction converters (510) has an electrical arrangement (50) according to one of claims 12 to 14 and / or an electrical arrangement (50) according to one of claims 1 to 11 has been produced.