JP4414367B2 - Pressed wiring board and insert molding method thereof - Google Patents

Description

  The present invention relates to a wiring board such as a control unit, and more particularly to an insert molding method for press wiring.

  A coated wiring is often used for a control unit wiring board of an automobile or the like. Recently, a method in which a press wiring is set in a mold and resin molding is also employed, but an exposed portion after the holding pin is removed at the time of molding is later closed with an adhesive.

  As described in Patent Document 1, the insert product molding apparatus includes a mold in which an insert product composed of a plurality of wirings is disposed, and a plurality of insert products that are provided in the mold so as to be movable forward and backward and hold the insert product at the tip. One having a holding pin is known. In resin molding by this apparatus, an insert is held by a holding pin at a predetermined position in the cavity, the molten resin is filled in the cavity, the holding pin is retracted from the cavity, and then the molten resin is further filled. Thereby, the molded product which sealed the whole surface of the insert product with resin is obtained.

  When molding with this molding apparatus, if the timing of retracting the holding pin from the cavity is before the filling of the molten resin is completed, the pin hole of the holding pin is sealed, but the insert product is moved by the movement of the molten resin. It will move. For this reason, the thickness of the resin molding part to be formed becomes non-uniform and a good molded product cannot be obtained. Conversely, if the timing of retracting the holding pin from the cavity is after completion of the filling of the molten resin, the movement of the insert product is small. However, since the resin around the holding pin has already formed a cooling and solidified layer, the resin that has flowed into the holding pin hole from the periphery of the holding pin does not fuse completely, and the resin molded part in which the insert product is sufficiently sealed There is a problem that cannot be formed.

  As one method for solving this problem, as proposed in Patent Document 2, each holding pin is provided with an electric heater, and is held at a temperature equal to or higher than the melting point of the resin when the molten resin is filled in the cavity. Heat the pin. Thereby, while suppressing the position of the insert product, the remaining of the unmelted portion due to the holding pin is suppressed, and a resin molded product in which the insert product is sufficiently sealed is formed.

Japanese Patent Laid-Open No. 55-91642 JP 2003-127185 A

  The above prior art has a problem when applied to an insert product that requires a large number of holding pins such as a press wiring board. With the technique described in Patent Document 2, a resin molded product in which the insert product is sufficiently sealed can be obtained. However, since the holding pin can be freely moved back and forth and the heater is attached, the mold structure becomes complicated and the cost is high, so that it is difficult to apply to a press wiring board using a large number of holding pins.

  In view of the problems of the prior art, an object of the present invention is to provide an insert molding method and a press wiring board that can sufficiently seal a press wiring without complicating a mold structure.

  The present invention for solving the above-mentioned problem is that a plurality of press wirings are arranged in a cavity in a mold, each press wiring is held by holding pins inserted from above and below the mold, and filled with resin. In a press wiring insert molding method for pulling out a holding pin, a stroke of the holding pin protruding into the cavity is made larger than a diameter of the holding pin.

  According to the present invention, since the holding pin stroke is larger than the holding pin diameter, when the molten resin reaches the holding pin in the mold, the holding pin is heated above the temperature of the other cavity by the heat of the molten resin. In addition, the molten resin in the vicinity of the holding pin can be filled while suppressing solidification of the molten resin in the other cavity portions (narrow portion effect). For this reason, when the holding pin is retracted upon completion of filling, the molten resin in the vicinity of the holding pin flows and fills the depletion, and a molded product in which the entire surface of the insert product is sealed with the resin is obtained.

  According to the present invention, since the resin surface including the press wiring can be sealed without post-treatment, there is an effect that a highly reliable press wiring board can be provided. This makes it possible to substitute a press wiring board that is advantageous for mass production as compared with the covered wiring.

  An embodiment of the present invention will be described with reference to the drawings. The insert product of this embodiment is a wiring board of an AT control unit mounted on an automobile. The control unit is used in a temperature environment of −40 to 155 ° C. and attached to a location where engine oil adheres. The control unit consists of a bracket made of steel to maintain grounding and mounting strength, press wiring for transmitting electrical signals, wiring board for inducing electrical isolation from the grounding and press wiring, and a cover covering the whole. Yes. The wiring board is injection-molded using the resin material PA66-GF33 in consideration of heat resistance and chemical resistance. The wiring board is composed of a resin portion for isolating from the bracket which is electrically grounded and a resin portion for enclosing the press wiring.

  FIG. 2 schematically shows a press wiring board which is an insert-molded product. The resin portion 2 for enclosing the press wiring 1 is manufactured by insert molding in which the press wiring 1 is set in a resin molding die. Since a large number of holding pins are provided so that the press wiring is not deformed at the time of molding, there are many holding pin marks 3 in the molded product.

  FIG. 1 is a partial sectional view showing a mold for resin molding according to one embodiment. The mold includes a lower mold holding pin 5 provided on the lower mold 4 and an upper mold holding pin 7 provided on the upper mold 6, and a drawing plate 8 for driving the lower mold holding pin 5 and the upper mold holding pin 7. The hydraulic cylinder 9 is provided. The extraction plate 8 can be driven by the hydraulic cylinder 9 via the wedge-shaped guide plate 10 at an arbitrary timing. The cavity 11 is formed in the outer shape of the product (wiring board), and the lower mold holding pin 5 and the upper mold holding pin 7 connected to the drawing plate 8 are provided in the cavity so as to protrude, and a plurality of presses are provided. Each wiring 12 is fixed.

  FIG. 3 schematically shows a fixed state of the wiring press in the cavity. The lower die holding pin 5 of the lower die 4 has a concave shape at the tip for fixing the press wiring 12. The upper mold holding pin 7 of the upper mold 6 is paired with the lower mold holding pin 5 to support the press wiring 12 and suppress its lateral movement. For example, the lower die holding pin 5 has a diameter a = 1.8 mm and a drawing stroke A = 2 mm, and the upper die holding pin 7 has a diameter b = 0.8 mm and a drawing stroke B = 1 mm. Stroke is large.

  Resin injection molding is performed using a mold having the above structure. As shown in FIG. 3, the press wiring 12 is set in the cavity of the lower mold 4. The lower die holding pin 5 is provided with a pull-in taper and can be easily set. Next, by closing the mold, the press wiring 12 is completely fixed by the lower mold holding pin 5 and the upper mold holding pin 7. Next, injection molding is performed.

  FIG. 4 schematically shows the injection molding state. In order to suppress movement / deformation of the press wiring 12 during molding, it is desirable that the molding conditions are set such that the mold temperature and the resin temperature are high and the injection speed is set low. As shown in the figure, the molded resin immediately after filling is divided into a solidified portion 32 and a molten portion 33, and details of the action will be described later.

  Immediately after the completion of filling, the hydraulic cylinder 9 is operated to move the holding pins 5 and 7 backward. FIG. 5 schematically shows a state after the holding pin retracts in the cavity. Retraction of the lower mold holding pin 5 and the upper mold holding pin 7 in the cavity 11 creates a space 21 and a space 24 around the press wiring 12, respectively. Along with this, a resin pressure at the time of molding causes the resin in the space 21 and the space 24. Flows in and the press wiring 12 is completely encapsulated by the resin.

  FIGS. 6A and 6B are schematic views showing a structure for pulling out the holding pin, where FIG. 6A shows before pulling, and FIG. A cavity 11 for forming a product includes an upper mold and a lower mold. The upper mold holding pin 7 and the lower mold holding pin 5 are each fixed to a drawing plate 8, and the drawing plate 8 is in contact with a wedge-shaped guide plate 10. The guide plate 10 is moved forward and backward by the hydraulic cylinder 9.

  (A) is the state in which the extraction plate 10 is most advanced, the upper plate holding pin 7 and the lower die holding fixed to the drawing plate 8 by bringing the drawing plate 8 into contact with the upper die 6 and the lower die 4 while pushing the spring 13. The pin 5 protrudes into the cavity 11 and the press wiring 12 is fixed. (B), when the guide plate 10 is retracted by the hydraulic cylinder 9, the extraction plate 8 is pushed back by the spring 13, and the upper mold holding pin 7 and the lower mold holding pin 5 are also pulled out of the cavity 11, and the press wiring 12 Get away from.

  Here, what is important is the timing of retracting the holding pin. The operation timing is obtained by a predetermined value of a pressure sensor or a temperature sensor in the mold cavity. It can also be obtained from the molding machine with signals such as filling start and VP switching position. It is better to fine-tune the timing with a timer after acquiring the signal.

  According to this mold structure, since the molten resin near the holding pin flows into the depletion generated after the holding pin is retracted, the depletion is filled and the resin surface is completely sealed. The operation will be described below.

  The principle of the present invention is to suppress a decrease in the temperature of the resin around the holding pin immediately after completion of the filling of the molten resin and prevent the resin from solidifying. FIG. 4 schematically shows the solidified state of the resin when the resin filling in the cavity is completed. According to the mold of this configuration, the resin state immediately after the filling is melted in the vicinity of the pin, The part away from the pin is solidified.

  In the mold of the present embodiment, a relationship of a <A is established between the diameter a of the lower die holding pin 5 and the stroke A, and b <B is established between the diameter b of the upper die holding pin 7 and the stroke B. ing. The lower mold holding pins 5 and the upper mold holding pins 7 protrude from the cavity surfaces of the lower mold 4 and the upper mold 6 in a convex shape. As a result, the narrow portion effect is generated, and the temperature of the molten resin is quickly transmitted to the pin portion to maintain a high temperature state. On the other hand, since the cavity surface dissipates heat to the outside, the resin temperature rapidly decreases. For this reason, the high temperature state of the resin in the vicinity of the pin portion is maintained, and immediately after completion of filling, the solidified portion 32 and the molten portion 33 are formed as shown in the figure. That is, the solidified layer is thinner in the vicinity of the lower mold holding pin 5 and the upper mold holding pin 7 than the surroundings, and when the lower mold holding pin 5 and the upper mold holding pin 7 are retracted, the filling pressure of the molten resin The solidified layer is easily destroyed to fill the voids, and the resin surface is completely sealed.

  FIG. 7 shows the experimental results of the sealing state of the resin depending on the relationship between the diameter of the holding pin and the stroke. For each combination of holding pin diameter and stroke, check the sealing state of the holding pin pull-out part, ○ if the drawing depletion is filled with resin and the press wiring is sealed, × not sealed As plotted. The broken line in the figure is the point where the diameter and stroke of the holding pin are equal. From this, it can be seen that the smaller the diameter of the holding pin and the longer the stroke, the more sealed it is. In particular, in the range where the stroke is larger than the diameter, almost all of the press wiring is sealed.

  In addition, since there is an influence of molding conditions such as the product size and shape, or the gate position, it may not be completely sealed depending on the location. In such a case, since the solidification rate in the vicinity of the pin can be further lowered by further increasing the drawing stroke of the holding pin that could not be sealed, the resin surface can be completely sealed.

  In this embodiment, a press wiring board is applied to an insert product. However, the present invention is not limited to this, and a large number of holding pins for holding the insert product are required, and the present invention can be used for products in which resin is poured by retreating the holding pins.

The fragmentary sectional view which shows the metal mold | die structure of this invention. The top view which shows the wiring board which is an insert molded product of this invention. The schematic diagram which shows the fixed state of the press wiring board press in a cavity. The schematic diagram which shows the solidification state of resin at the time of completing resin filling in a cavity. The schematic diagram which shows the state after the holding pin retreats in a cavity. The schematic diagram which shows the drawing-out state of a holding pin. Explanatory drawing which shows the sealing state of the holding pin extraction part by the relationship between the diameter of a holding pin, and a stroke.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,12 ... Press wiring, 2 ... Resin part, 3 ... Holding pin trace, 4 ... Lower die, 5 ... Lower die holding pin, 6 ... Upper die, 7 ... Upper die holding pin, 8 ... Extraction plate, 9 ... Hydraulic pressure Cylinder, 10 ... guide plate, 11 ... cavity, 13 ... spring, 21,24 ... space, 32 ... solidification part, 33 ... melting part.

Claims (4)

A plurality of press wirings are arranged in a cavity in the mold, each press wiring is held by a plurality of upper mold holding pins and lower mold holding pins inserted from the upper and lower sides of the mold , filled with resin, and held immediately after filling is completed. In the insert molding method of press wiring that pulls out pins,
An insert molding method for press wiring, wherein the movement stroke of each of the upper mold holding pin and the lower mold holding pin protruding into the cavity is made larger than the diameter of each of the upper mold holding pin and the lower mold holding pin .   2. The method for insert molding of press wiring according to claim 1, wherein a tip shape of one side of the holding pin is concave.   3. The method for insert molding of press wiring according to claim 1, wherein the holding pin is pulled out by operating a wedge-shaped plate. A plurality of press wirings are arranged in a cavity in the mold, each press wiring is held by an upper mold holding pin and a lower mold holding pin inserted from the upper and lower sides of the mold and filled with resin. In press wiring boards that are drawn and molded,
The press wiring board is molded by the method of any of claims 1 to 3, and press wires after withdrawal of the upper mold holding pins and the lower mold retaining pin, wherein Rukoto such buried by the resin Board.

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