DE102019210375A1 - Method of manufacturing a robust sensor - Google Patents

Abstract

A method for producing a sensor which has at least one sensor element comprising a first housing (1), the sensor element being arranged on a circuit carrier (3), the sensor element with the circuit carrier (3) being arranged in a cavity (4) of an injection molding tool is, after which the sensor element and the circuit carrier (3) are at least partially encapsulated, whereby a second housing (2) is formed, the feed direction (6) of the injection molding material through at least one sprue channel (5) into the cavity (4) with regard to a longitudinal direction (7) of the circuit carrier (3) and / or a base (8) of the first housing (1) has an angle of less than 120 °.

Description

The invention relates to a method according to the preamble of claim 1.

The invention is based on the object of proposing a method for producing a sensor which enables a relatively robust and / or leak-proof and / or inexpensive sensor.

This object is achieved according to the invention by the method according to claim 1.

The invention is preferably based on the idea that in the course of the method for producing a sensor which has at least one sensor element comprising a first housing, the first housing in particular embeds the sensor element, the sensor element being arranged on a circuit carrier, the The sensor element with the circuit carrier is arranged in a cavity of an injection molding tool, after which the sensor element and the circuit carrier are at least partially encapsulated, whereby a second housing is formed, the feed direction of the injection molding material through at least one sprue channel into the cavity with regard to a longitudinal direction of the circuit carrier and / or a base area of the first housing has an angle of less than 120 ° or an angle between 0 ° and 120 °, particularly preferably is aligned essentially parallel or has an angle of less than 30 ° or less than 10 °.

A sprue channel or injection channel or injection channel is preferably understood to mean the connection between an injection unit and the cavity, in particular the access to the cavity itself, as the end of the sprue channel, being referred to as the injection point or injection point.

The feed direction is expediently understood to mean the preferred direction or main direction of the injection molding material from the runner through the injection point into the cavity, in particular essentially a straight line from the runner through the injection point; this straight line expediently leads through the first housing or through the space around the first housing at a distance of less than 2mm.

The sensor element and a signal processing circuit are preferably integrated in a first electronic component or an ASIC.

The term “at least partially” is preferably also understood to mean the term “completely” or the term “partially”.

The circuit carrier is expediently designed as a leadframe or circuit board, a leadframe being understood in particular to be a connection frame or a metallic conductor carrier.

The first housing is preferably made of plastic, in particular of thermosetting plastic, particularly preferably epoxy. The first housing is expediently designed as a protective housing or a separate standard housing of the sensor element or chip or ASIC.

The injection molding material for forming the second housing is preferably thermoplastic, the material in particular comprising polyamide or PBT, polybutylene terephthalate or PPS, polyphenylene sulfide or PPA, polyphthalamide.

The injection molding material expediently has filling bodies or fillers for forming the second housing, in particular at least on the surface or generally. In particular, these fillers or fillers are round and / or essentially spherical and / or have a defined color, particularly preferably black or green or blue or red.

Alternatively, the fillers or fillers are preferably designed as fibers or fiber bundles, in particular made of glass or carbon.

It is expedient that the filler or packing elements make up a proportion of 15 to 50 percent by volume of the injection molding material for forming the second housing.

It is preferred that, before the first housing of the sensor element is arranged in the cavity of the injection molding tool, at least one connection surface on the outer surface of the first housing is activated and / or roughened by means of a plasma treatment and / or a laser treatment. In particular, the connection surface is activated with a laser, particularly preferably after which the at least partial overmolding of the first housing to form the second housing, the at least one connection surface being covered with the injection molding material of the second housing, takes place 2 hours or less after the laser activation.

The connection surface is expediently roughened by means of a laser. In particular, to form the connection surface, the surface of the corresponding area of the first housing is acted upon by roughening with the laser, with recesses being generated in the surface and the laser being directed and guided onto the surface and by it Power output is set forth that recesses are generated with at least two substantially different depths in the surface of the connecting surface. The recesses of essentially two different depths are preferably understood to mean that recesses of a first recess type and of a second recess type are generated which differ, in particular significantly, by the depth of the recesses.

The laser is particularly preferably controlled in such a way that it activates the surface in the roughened area. In particular, the first and second recesses or the recesses of the first and second recess type are generated essentially in a focus area of the laser, whereby the laser generates a plasma from the surface material, which is particularly advantageous for a better chemical bond in an injection molding process. When the plastic surface is roughened by means of the laser, active, free radical carbons are particularly preferably generated. It is very particularly preferred that several or relatively many, in particular more than a thousand or million, recesses are generated and recesses of essentially two different recess types are generated, which essentially differ from one another at least in their depth and each recess type by a defined depth or a defined depth interval is marked.

The wording that the laser is controlled in this way is preferably understood to mean that the laser is directed and guided onto the surface in this way and its power output is adjusted.

The connection surface is expediently designed for a material connection between the first and second housing.

It is preferred that the at least one connecting surface is designed in such a way that it extends annularly around the outer casing of the first housing, around the longitudinal axis of the circuit carrier, or is designed accordingly.

In particular, in the course of the overmolding and particularly preferably with regard to the direction of flow of the injection molding material in the cavity, anisotropy is achieved in the orientation of the fiber structure or fiber bundle. The fibers or fiber bundles behave differently in the transverse or longitudinal direction and / or the injection molding material together with the fibers / fiber structures has different properties in different directions, which can lead to a preferred increase in material strength

It is preferred that the flow of the injection molding material, which is fed into the cavity of the injection molding tool in the course of the formation of the second housing by means of the at least one sprue channel, occurs in the cavity by means of the internal geometry and / or one or more recesses and / or projections the inner jacket of the cavity and / or
a temperature control of at least one positioning pin and / or tool pin in the cavity and / or
the movement of at least one positioning pin and / or tool pin, in particular a movement for mixing the injection molding material, in the cavity, and / or
the positioning of the first housing to be overmolded relative to the formation of the geometry of the cavity,
is / are influenced and / or designed and / or adjusted in such a way that the injection molding material or a flow front of the injection molding material hits at least one connection surface, in particular all connection surfaces, at an angle of less than 30 ° on this connection surface,
so that a particularly tight and / or resilient and / or durable connection between the first and the second plastic housing is made possible.

The injection molding tool preferably has at least one heating and / or cooling element which is arranged in or on the housing of the cavity and which increases or decreases the temperature of the injection molding material at least in the area adjacent to the heating and / or cooling element.

It is expedient that the injection molding tool has an electronic control unit or is connected to one by means of which
the movement of the at least one positioning pin and / or tool pin is controlled and / or the
Temperature control of at least one positioning pin and / or tool pin, having a heating and / or cooling element, takes place in the cavity
and or
by means of which the at least one heating and / or cooling element, which is arranged in or on the housing of the cavity, is controlled,
in particular so that a particularly tight and / or resilient and / or durable connection between the first and the second
Plastic housing is made possible by generating one or more temperature changes in the injection molding material, which expediently changes at least one flow front of the injection molding material or the local viscosity changes relative to another local viscosity in the injection molding material, and / or
by increasing the mixing of the injection molding material during the encapsulation process is reached and / or the temperature or temperature distribution, in particular of the injection molding material, on the inner surface of the cavity is different from the temperature or temperature distribution on the first housing and / or that the injection molding material or a flow front of the injection molding material on at least one connecting surface, in particular all Joint surfaces, meets this joint surface at an angle of less than 30 °.

It is preferred that the direction in which the injection molding material is fed through the at least one sprue channel into the cavity is essentially directed towards the first plastic housing and / or the circuit carrier, in particular with a distance of less than 2 mm between the injection point and the first plastic housing and / or the circuit carrier.

The direction in which the injection molding material is fed through the at least one sprue channel into the cavity is particularly preferably oriented essentially directly to an outer edge and / or an end face of the first housing and / or the circuit carrier.

The injection point is expediently directed at the first plastic housing and / or at the circuit carrier,
whereby a primary flow of the injection molding material or a feed direction is so pronounced that the injection molding material strikes the first plastic housing and / or the circuit carrier at an angle between 0-120 °, whereby a flow front of the injection molding material is changed. Particularly expediently, one or two or more recesses are designed and arranged on the inner surface of the cavity, in particular essentially triangular or trapezoidal with regard to their cross section, and / or at least one projection on the inner surface of the cavity is designed and arranged so that the injection molding material is swirled , in particular of injection molding material that is thrown back from the first plastic housing and / or circuit carrier.

The injection molding tool is preferably designed in such a way that the injection point of the at least one runner is designed as a Venturi nozzle, this Venturi nozzle in particular having different cross-sections merging into one another, whereby the injection molding material is accelerated or decelerated with regard to the flow into the cavity.

The injection molding tool is expediently designed such that it has a single sprue channel and / with a single injection point.

It is preferred that the inner geometry of the cavity is designed such that it has one or more recesses on the inner jacket of the cavity, which have a substantially triangular or trapezoidal cross-section and / or at least one of these recesses on opposite inner surfaces of the inner jacket the cavity are formed. The and / or one or more recesses and / or projections on the inner surface of the cavity are particularly preferably designed in such a way that the injection molding material is swirled during the overmolding.

It is expedient that the injection molding tool has at least one positioning pin for fixing the sensor element and / that of the circuit carrier, the injection molding tool additionally having at least one tool pin which protrudes into the cavity and / or can be extended, this tool pin not being used for fixing the sensor element and / Which of the circuit carrier is used and this tool pin is designed to be heatable and / or coolable. This additional tool pin is particularly preferably moved during the overmolding to form the second housing in the injection molding material.

A tool pin is preferably also understood to mean a positioning pin which, however, is not used to position an object to be overmolded in the cavity.

The inner geometry of the cavity is expediently designed so that it is at least partially adapted essentially to the geometry of the first housing, the distance from the inner wall of the cavity to the opposite surface of the first housing being essentially the same or with a change / variation of less than 30% of the distance, in particular along the lateral surface of the first housing around the longitudinal axis of the circuit carrier.

It is preferred that the second housing is designed in such a way that at least a first area of the first housing is exposed and / or is not embedded in the second housing. Alternatively, the second housing is preferably designed and the injection molding tool is designed in particular or the positioning of the sensor element or first housing in the cavity is designed such that the second housing has a recess with respect to the first housing.

It is useful that the first housing has at least one, in particular protruding Form-fit element, for a form-fit connection with the second housing. The form-fit element is designed, for example, in the form of a nose or rib, in this case in one piece with the first housing. At least one connection surface is preferably formed on the first housing essentially in the vicinity of the form-fit element and / or each form-fit element, in particular one connection surface is formed on the first housing on two opposite sides of the form-fit element.

Appropriately, before the injection molding process to produce the second housing, the housing material of the first housing is activated and / or roughened in the area of a connecting surface, in particular around an area of the first housing exposed with respect to the second housing. Preferably, free radical carbons are generated during roughening or activation by means of the laser. In the focus of the laser, where it strikes the material of the first housing, a plasma arises, for example, which promotes and / or enables a material connection between the first and second housing.

The invention also relates to a sensor which is produced by means of the method according to the invention and an injection molding tool for carrying out the method according to the invention. The sensor is expediently or is designed according to the method as a speed sensor, in particular as a wheel speed sensor or transmission speed or engine speed sensor.

List of reference symbols

1

first housing

2

second housing

3

Circuit carrier

4th

Injection mold cavity

5

Runner

6th

Infeed direction of the injection molding material

7th

Longitudinal direction of the circuit carrier

8th

Base area of the first housing

9

Positioning pin

10

Tool pen

11

Interface

12

Recesses in the inner jacket cavity

13

heater

14th

cooling

15th

Protrusion of inner jacket cavity

16

Released area of the first housing

17th

Form-fit element

18th

Flow front of the injection molding material which hits the connection surface

19th

slug

20th

Clamping the first housing in the tool

21st

Injection molding material

22nd

Injection point

• 1 ein Ausführungsbeispiel, bei welcher das Sensorelement mit dem ersten Gehäuse und dem Schaltungsträger in der Kavität des Spritzgusswerkzeugs positioniert sind und die Ausbildung des zweiten Gehäuses durch Umspritzen durchgeführt wird,
• 2 und 3 jeweils ein Ausführungsbeispiel eines Sensors, wobei die Ausbildung des ersten und zweiten Gehäuses veranschaulicht ist.

It show in a schematic representation,

• 1 an embodiment in which the sensor element with the first housing and the circuit carrier are positioned in the cavity of the injection molding tool and the second housing is formed by overmolding,
• 2 and 3 each one embodiment of a sensor, the formation of the first and second housing being illustrated.

1 shows an example of the first housing 1 of the sensor element and the associated leadframe 3 , as a circuit carrier in the cavity 4th the injection molding tool arranged. First case 1 , made of epoxy, is clamped in the tool at one end 20th , creating a part / area 16 of the first case 1 does not remain free with regard to the second housing.
First case 1 has connecting surfaces 11 on, fine dashed lines illustrate which lasers are activated. This is the exempt area 16 adjacent connection surface 11 is designed so that it is annular around the outer jacket of the first housing 1 , around the longitudinal axis of the circuit board 3 , extends or is designed accordingly, whereby the exposed area 16 is specially sealed against moisture, which in the finished sensor in operation, from the exposed area 16 of the first case 1 could penetrate or crawl between the first and second housing.

First case 1 is by positioning pin 9 additionally fixed. The injection molding material 21st is by snail 19th into the cavity 4th conveyed, through sprue 5 , which in the injection point 22nd in cavity 4th flows out. Runner 5 is designed as a Venturi nozzle, for example.

The injection molding tool also includes several recesses 12 as well as a head start 15th on the inner surface of the cavity 4th , these recesses 12 have a substantially triangular or trapezoidal cross-section. The injection molding tool also includes a tool pin 10 , which is designed to be heatable.
There is also a heating element in the housing of the cavity 13 as a heater and a cooling element 14th arranged for cooling.

First is the injection molding material 21st at an angle of less than 15 ° between the feed direction 6th of the injection molding material to the longitudinal direction 7th of the circuit board 3 through the sprue 5 into the cavity 4th injected, aligned with the circuit carrier 3 whereby turbulence or changes in direction of flow fronts of the injection molding material arise.

In the course of the process, the flow of the injection molding material is also determined 21st , by means of the internal geometry on the inner surface of the cavity 4th , especially through the recesses 12 , by means of the temperature control and the movement of the tool pin 10 , for example to mix the injection molding material and to influence the temperature by the heating element 13 and the cooling element 14th influenced so that the injection molding material or a flow front 18th or flow fronts 18th of the injection molding material at an angle of less than 30 ° onto these connecting surfaces 11 hits and is there with the first housing 1 connects.

The temperature of the injection molding material 21st is set to 80 to 90 ° C according to the example. In doing so, heating element13 and cooling element 14th the temperature on the inner surface of the cavity is different from the temperature of the injection molding material, which is around the first housing 1 applies or envelops this, set.

The injection molding material 21st for the formation of the second housing, for example, it is designed as a polyamide and has filling bodies or fillers, which are designed as glass fibers or glass fiber bundles.

2 Fig. 10 shows an exemplary engine speed sensor. A sensor element, not shown, has a leadframe 3 connected as a circuit carrier and electrically contacted, the sensor element in the first housing 1 is embedded or the sensor element has a first housing 1 on. First case 1 has interface 11 on, fine dashed lines illustrate which laser is activated. This is the exempt area 16 , which is the area of the first housing 1 not from housing 2 is enclosed, adjacent connection surface 11 designed so that they are annular around the outer shell of the first housing 1 , around the longitudinal axis of the circuit board 3 , extends or is designed accordingly, whereby the exposed area 16 is specially sealed against moisture, which in the finished sensor in operation, from the exposed area 16 of the first case 1 could penetrate or crawl between the first and second housing.

In the vicinity or next to or in the immediate vicinity of the connection surface 11 , have the first and second housings 1 , 2 one form-fit element each 17th on, these two mutually associated form-locking elements 17th interlock positively. The form-fit element 17th of the first case 1 is designed as a rib which, according to the example, is also annular around the outer jacket of the first housing 1 , around the longitudinal axis of the circuit board 3 , extends or is designed accordingly. The second case 2 has a corresponding groove as a form-fit element 17th on, in which the rib of the first housing engages and forms a positive connection. As a result, the relative forces between the first and second housing are essentially reduced by the form-fit element 17th added, creating interface 11 , which is materially connected, at least partially with the second housing during overmolding, is mechanically relieved and the tightness of this material connection is maintained.

The form-fit element 17th as a rib on the first housing is used in the formation of the first housing 1 generated, while the corresponding form-fit element, the groove of the second housing 2 , in which the rib engages, when overmolding the first housing 1 with the injection molding material to form the second housing 2 is produced.

3 FIG. 10 shows an exemplary wheel speed sensor with first and second housings 1 and 2 . The first case 1 encloses an ASIC, not shown, comprising a sensor element and a signal processing circuit. The first housing has rib-shaped or nose-shaped form-locking elements 17th which are on the top and on the bottom of the first housing 1 are arranged and each have a cut-out area 16 limit where the first housing 1 not from the second housing 2 is enclosed or encapsulated. In addition to the form-fit element 17th of the first housing is in each case with regard to the cut-out area 16 remote side, a laser-activated connection surface on the first housing 1 arranged, by means of which the first and second housing are connected to one another in a substantially cohesive manner during the injection molding of the second housing. As a result, the connection between the first and second housing is particularly sealed with regard to the exposed areas. The second case 2 each laterally outside, facing away from the exposed area, and from above or below, encompasses the form-fit elements, i.e. L-shaped according to the example, and thus forms a mutual form-fit that absorbs relative forces between the first and second housing and the material connections on the connecting surfaces Force relieved.

Claims (13)

A method for producing a sensor which has at least one sensor element comprising a first housing (1), the sensor element being arranged on a circuit carrier (3), the sensor element with the circuit carrier (3) being arranged in a cavity (4) of an injection molding tool is, after which the sensor element and the circuit carrier (3) are at least partially encapsulated, whereby a second housing (2) is formed, characterized in that the feed direction (6) of the injection molding material through at least one runner (5) into the cavity (4) has an angle of less than 120 ° with respect to a longitudinal direction (7) of the circuit carrier (3) and / or a base area (8) of the first housing (1). Procedure according to Claim 1 , characterized in that the flow of the injection molding material, which is fed into the cavity (4) of the injection molding tool during the formation of the second housing (2) by means of the at least one sprue channel (5), in the cavity (4) by means of the internal geometry and / or one or more recesses (12) and / or projections (15) on the inner surface of the cavity (4) and / or a temperature control of at least one positioning pin (9) and / or tool pin (10) in the cavity (4) and / or the movement of at least one positioning pin (9) and / or tool pin (10), in particular a movement for mixing the injection molding material, in the cavity (4), and / or the positioning of the first housing (1) to be overmolded relative to the formation of the The geometry of the cavity (4) is / are influenced and / or designed and / or adjusted in such a way that the injection molding material or a flow front of the injection molding material is applied to at least one connection surface (11) , in particular all connection surfaces (11), hit this connection surface at an angle of less than 30 °, so that a particularly tight and / or resilient and / or durable connection between the first (1) and the second (2) plastic housing is made possible . Procedure according to Claim 1 or 2 , characterized in that the feed direction (6) of the injection molding material through the at least one sprue channel (5) into the cavity (4) is directed essentially at the first plastic housing (1) and / or at the circuit carrier (3). Procedure according to Claim 3 , characterized in that the feed direction (6) of the injection molding material through the at least one sprue channel (5) into the cavity (4) essentially directly onto an outer edge and / or an end face of the first housing (1) and / or the circuit substrate (3 ) is aligned. Method according to at least one of the Claims 1 to 4th , characterized in that before the arrangement of the first housing (1) of the sensor element in the cavity (4) of the injection molding tool, at least one connecting surface (11) on the outer surface of the first housing (1) is activated and / or roughened by means of a plasma treatment and / or laser treatment. Procedure according to Claim 5 , characterized in that the connection surface (11) is activated with a laser, in particular after which the at least partial overmolding of the first housing (1) to form the second housing (2), wherein the at least one connection surface (11) with the injection molding material of the second Housing (2) is covered, 2 hours or less after laser activation takes place. Method according to at least one of the Claims 1 to 6th , characterized in that the inner geometry of the cavity (4) is designed so that it has one or more recesses (12) on the inner surface of the cavity, which have a substantially triangular or trapezoidal cross-section and / or at least one of these Recesses (12) are formed on opposite inner surfaces of the inner shell of the cavity (4). Method according to at least one of the Claims 1 to 7th , characterized in that the injection molding tool has at least one positioning pin (9) for fixing the sensor element and / that of the circuit carrier, the injection molding tool additionally having at least one tool pin (8) which protrudes into the cavity (4) and / or can be extended, wherein this tool pin (8) is not used to fix the sensor element and / that of the circuit carrier (3) and wherein this tool pin (8) can be heated and / or cooled. Procedure according to Claim 8 , characterized in that this additional tool pin (8) is moved during the overmolding to form the second housing (2) in the injection molding material. Method according to at least one of the Claims 1 to 9 , characterized in that the inner geometry of the cavity (4) is designed so that it is at least partially adapted essentially to the geometry of the first housing (1), the distance from the inner wall of the cavity (4) to the opposite surface of the first housing (1) is essentially the same, in particular along the lateral surface of the first housing (1) around the longitudinal axis (7) of the circuit carrier (3). Method according to at least one of the Claims 1 to 10 , characterized in that the second housing (2) is designed such that at least a first area (16) of the first housing (1) is exposed and / or is not embedded in the second housing (2). Method according to at least one of the Claims 1 to 11 , characterized in that the first housing (1) has at least one, in particular protruding, form-fitting element (17) for a form-fitting connection with the second housing (2). Procedure according to Claim 12 , characterized in that essentially in the vicinity of the form-fit element (17) and / or each form-fit element (17), at least one connecting surface (11) is formed on the first housing (1), in particular on two opposite sides of the form-fit element (17 ) each have a connecting surface (11) formed on the first housing (1).

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