JPH11142184A - Resin molded circuit apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To present a solder part of a circuit board from being melted when the whole of the circuit board is molded of resin. SOLUTION: An insulating coating material 28 is coated by a dispenser or the like to a solder face of a circuit board 11 where a Hall IC 16 and capacitors 20-22 are soldered. The insulating coating material 28 is preferably a material with good adhesion to the solder face and moisture resistance, e.g. silicon-based insulating moisture-proof material. After the insulating coating material 28 is set, the whole of the circuit board 11 is molded of a mold resin 29. At this time, the insulating coating material 28 having heat insulation properties can reduce the transmission of heat from the molten resin to the solder face of the circuit board 11. Even when a thermoplastic resin of a high melting point such as PPS, etc., is used as the mold resin 29, a temperature of a solder part when the circuit board is molded can be controlled to be not higher than a melting point of the solder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin molded circuit device formed by molding a circuit board on which circuit elements are soldered with resin.

[0002]

2. Description of the Related Art A resin-molded circuit device of this kind is provided with an IC, a capacitor,
After soldering circuit elements such as resistors, the whole is molded with resin to protect the circuit elements.

[0003]

Generally, a high melting point thermoplastic resin such as PPS (polyphenylene sulfide) is often used as a molding resin in consideration of heat resistance and rigidity. The melting temperature of the plastic resin at the time of molding is about 310 ° C., which is about 60 ° C. higher than the melting temperature of the solder of about 250 ° C. Moreover, since the viscosity of the molten resin during molding is high and the fluidity of the molten resin is low, the time during which the temperature of the molten resin affects the soldered portion of the circuit board during molding is increased. As a result, the soldered portion of the circuit board is exposed to a high temperature equal to or higher than the melting temperature of the solder for a long time during molding, and the heat melts the soldered portion, thereby reducing the bonding reliability of the soldered portion. In extreme cases, poor soldering or short-circuiting may occur.

[0004] The present invention has been made in view of such circumstances, and an object thereof is to prevent the soldered portion of a circuit board from being melted by heat during molding.
It is an object of the present invention to provide a resin molded circuit device which can prevent soldering failure and short circuit and can improve bonding reliability of a soldered portion.

[0005]

According to a first aspect of the present invention, there is provided a resin-molded circuit device according to the present invention, in which a soldering surface of a circuit board is coated with a heat-insulating coating material and then molded with a resin. It was done. In this case, since the heat insulating coating material is interposed between the molten resin to be molded and the soldering surface of the circuit board, the transfer of heat from the molten resin to the soldering surface of the circuit board is performed by the heat insulating material. It can be reduced by a heat insulating coating material having As a result, even when a high melting point thermoplastic resin such as PPS is used as the molding resin, the temperature of the soldering portion during molding can be suppressed to a temperature equal to or lower than the melting temperature of the solder. It is possible to prevent the soldered portion from being melted, prevent defective soldering and short-circuit, and improve the bonding reliability of the soldered portion.

In this case, it is preferable to use a heat-insulating coating material having a moisture-proof property.
In this way, even if cracks or the like occur in the molding resin and moisture enters the inside of the molding resin, the soldering surface (wiring pattern surface) of the circuit board is made of a moisture-proof heat-insulating coating material. Since it is covered, a decrease in insulation due to invasion of moisture can be prevented by the heat insulating coating material, and insulation reliability can be improved.

According to a third aspect of the present invention, there is provided a circuit board, comprising: a primary molded body of an easily-platable resin in which a plating underlayer for plating a wiring pattern is formed in a convex shape; And a secondary molded body of a hard-to-plate resin that is insert-molded so as to expose the surface of the portion, and a wiring pattern may be formed by plating on the plating base. With this configuration, not only a planar wiring pattern but also a three-dimensional wiring pattern can be formed in accordance with various shapes of the circuit board, and the degree of freedom in designing the circuit board shape can be increased.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is applied to a rotation detecting device will be described below with reference to the drawings. As shown in FIG. 3, the circuit board 11 is provided with a wiring pattern 12 by plating.
And a secondary formed body 1 formed by insert-molding the primary formed body 14 so as to expose the surface of the plated base portion 13.
And 5. The primary molded body 14 is made of an easily plating resin to which plating easily adheres, for example, a liquid crystal polymer (L
It is molded with a heat-resistant resin such as CP). In contrast,
The secondary molded body 15 is made of a hard-to-plate resin to which plating does not easily adhere, such as polyphenylene sulfide (PPS), liquid crystal polymer (LCP), and polyether sulfone (PE).
It is formed of a resin having chemical resistance to the electroless plating solution, such as S) and polyetherimide (PEI). Au, S is formed on the surface of the plating base portion 13 of the primary compact 14.
The wiring pattern 12 is formed by electroless plating of n, Ni, or the like.

As shown in FIG. 1 and FIG.
Hall IC 16 (circuit element) at the front end (left end in the figure)
Is assembled. Terminal 17 of this Hall IC 16
[FIG. 2B] is inserted into a through hole (not shown) of the circuit board 11 and soldered to the lower surface (soldering surface) of the circuit board 11 to hold and electrically connect the Hall IC 16. And go.

A bias magnet 18 is mounted on the back side of the Hall IC 16. The terminals of the capacitors 20 to 22 (circuit elements) are soldered to the soldering surface of the circuit board 11, and three terminals 23 to 23 are provided at the rear end (right end in the drawing) of the circuit board 11. 25 are projected upward, and each of these terminals 23 to 25 is connected to a hall IC.
Wiring pattern 12 formed on circuit board 11 with 16 and capacitors 20 to 22 [only a part is shown in FIG. 2A]
And through hole 27 (the inner peripheral surface is plated)
And are electrically connected by

Further, the entire surface of the soldering surface of the circuit board 11 is coated with a heat insulating coating material 28 by a dispenser or the like (not shown). As the heat insulating coating material 28, a material having good adhesion to the soldering surface and having a moisture proof property, for example, a silicon-based heat and moisture proof material may be used.

After curing of the thermal insulation coating material 28, FIG.
As shown in FIG.
Is molded. As the mold resin 29, a resin having high rigidity and excellent heat resistance, for example, a high melting point thermoplastic resin such as polyphenylene sulfide (PPS) is preferably used.

A connector housing 30 for connecting the terminals 23 to 25 to an external terminal (not shown) and a mounting bracket 31 are integrally formed on the molded body of the molding resin 29. The mounting bracket 31 is made of metal. The bush 32 is insert-molded. An O-ring 34 made of rubber is mounted in a groove 33 formed on the outer periphery of the molded body of the mold resin 29.

The rotation detecting device constructed as described above is provided with an O-ring 3 in a mounting hole (not shown) of a mounting target portion such as a vehicle body.
The four parts are fitted, and screws (not shown) are inserted into the bushes 32 of the mounting bracket 31 to be fixedly mounted on the vehicle body or the like.
A front end face (Hall IC 16) of the rotation detecting device faces a signal rotor (not shown) fitted to a crankshaft or the like of the engine via a predetermined gap, and the rotation detector detects the rotation speed of the signal rotor from the Hall IC 16 according to the rotation speed. The pulse signal of the frequency is output.

When manufacturing the rotation detecting device having the above configuration, the Hall IC 16 and the capacitors 20 to
After soldering 22, the entire surface of the soldering surface of the circuit board 11 is coated with a heat insulating coating material 28 by a dispenser or the like (not shown). After the heat insulating coating material 28 is cured, the entire circuit board 11 is
9. Molding is performed.

In this case, since the heat-insulating coating material 28 is interposed between the molten resin of the mold resin 29 and the soldering surface of the circuit board 11, heat is transferred from the molten resin to the soldering surface of the circuit board 11. It can be reduced by the heat insulating coating material 28 having heat insulating properties. Accordingly, even when a high melting point thermoplastic resin such as PPS is used as the mold resin 29, the temperature of the soldering portion during molding can be suppressed to a temperature equal to or lower than the melting temperature of the solder.

The present inventor conducted a test for examining the relationship between the coating thickness of the heat insulating coating material 28 and the heat insulating effect during molding, and the test results are shown in FIG. If there is no insulation coating material (equivalent to the conventional)
When the soldered part of the circuit board is directly exposed to a high temperature higher than the melting temperature of the solder during molding, the heat melts the soldered part and reduces the bonding reliability of the soldered part, or in extreme cases May cause poor soldering or short circuit.

On the other hand, when the soldering surface of the circuit board 11 is coated with the heat insulating coating material 28 as in the above embodiment, a sufficient heat insulating effect can be obtained even if the coating film thickness is 5 μm. The temperature of the soldering portion at this time can be suppressed to a temperature equal to or lower than the melting temperature of the solder. As the coating thickness of the heat insulating coating material 28 increases from 5 μm to 10 μm and 50 μm, the heat insulating effect increases. However, if the coating thickness exceeds 50 μm, the heat insulating effect does not improve much even if the coating film thickness increases. Therefore, it is considered appropriate that the coating film thickness is about 5 μm to 50 μm.

As described above, by coating the soldering surface of the circuit board 11 with the heat insulating coating material 28, the temperature of the soldering portion during molding can be suppressed to a temperature lower than the melting temperature of the solder. It is possible to prevent the soldered portion from being melted by heat at the time, to prevent poor soldering and short-circuit, and to improve the bonding reliability of the soldered portion.

If the molding resin 29 is P
Even if the temperature of the soldering part at the time of molding may exceed the melting temperature of the solder by using a thermoplastic resin having a melting point higher than that of PS, the soldering surface of the circuit board 11 may be coated with the heat insulating coating material 28. Since the cover is covered, the outflow of the molten solder can be prevented, and the soldered portion can be kept in the original state after the molding.

Further, in the above-described embodiment, since a heat-insulating coating material 28 having a moisture-proof property is used, it is assumed that cracks or the like occur in the molded resin 29 and moisture enters the interior of the resin 29. In addition, it is possible to prevent the insulation property of the soldering surface (wiring pattern surface) of the circuit board 11 from lowering due to the invasion of moisture by the heat insulating coating material 28, and to improve the insulation reliability.

Incidentally, if a high melt viscosity resin (for example, PPS high flow or the like) having a melt viscosity at the same level as nylon at the time of molding is used as the mold resin 29, the temperature of the molten resin at the time of molding affects the soldered portion. The time is shortened, and the melting of the soldered portion can be more reliably prevented.

In the circuit board 11 of the above embodiment, the primary molded body 14 is insert-molded into the secondary molded body 15 and the wiring pattern 12 is formed by plating on the exposed portion (plating base 13) of the primary molded body 14. However, a general printed circuit board may be used.

In addition, the scope of application of the present invention is not limited to the rotation detecting device as in the above embodiment, but is widely applied to a configuration in which a circuit board on which circuit elements are soldered is molded with resin. it can.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view of an entire apparatus showing an embodiment in which the present invention is applied to a rotation detecting apparatus.

2A is a plan view of a circuit board on which circuit elements are mounted, and FIG. 2B is a cross-sectional view taken along line AA of FIG.

FIG. 3 is a partially enlarged longitudinal sectional view of a circuit board for describing a method of forming a wiring pattern.

FIG. 4 is a view showing a test result for examining a relationship between a coating film thickness of a heat insulating coating material and a heat insulating effect during molding.

[Explanation of symbols]

11: circuit board, 12: wiring pattern, 13: plating base, 14: primary molded body (easy plating resin), 15: secondary molded body (hard plating resin), 16: Hall IC (circuit element), 20-22: capacitor (circuit element), 28:
Insulation coating material, 29 ... Mold resin.

Claims (3)

[Claims] 1. A resin molded circuit device formed by molding a circuit board to which a circuit element is soldered with a resin, wherein a heat insulating coating material is coated on a soldering surface of the circuit board. Molded circuit device. 2. The resin-molded circuit device according to claim 1, wherein the heat-insulating coating material has a moisture-proof property. 3. The circuit board according to claim 1, further comprising: a primary molded body of an easily-plated resin in which a plating base part to be subjected to plating for a wiring pattern is formed in a convex shape, and exposing a surface of the primary molded body to the plating base part. The resin-molded circuit device according to claim 1, wherein a wiring pattern is formed by plating on the base portion of the plating, and a secondary molded body of a difficult-to-plate resin that is insert-molded as described above. .