JPH0469221A - Method for transfer molding of electrically conductive circuit - Google Patents

Abstract

PURPOSE:To prevent a transfer sheet from moving when a mold is clamped and to transfer a circuit pattern with high accuracy by fixing the transfer sheet on the mold by vacuum-sucking from a suction hole formed in the mold. CONSTITUTION:A transfer sheet 9 on which an electrically conductive circuit pattern is formed in advance is positioned at a specified position to either a fixed mold 4 or a movable mold 5 both under an opened condition. Then, the transfer sheet 9 is fixed on the mold 5 by vacuum-sucking from a suction hole 8 formed in the mold 5. A part of the transfer sheet 9 is positioned in a cavity 4a formed by the movable mold 5 and a fixed mold 4 by clamping the mold under this condition and then, molding is performed by injecting a resin in the cavity 4a and at the same time, the electrically conductive circuit pattern is transferred to a box-shaped molded item 1 with this circuit pattern 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides (1) a conductive circuit that can be used to accurately manufacture a three-dimensional molded printed wiring board, such as a box-shaped molded product with a conductive circuit pattern formed on the inner surface of the bottom; This invention relates to a transfer molding method.

[Conventional technology]

Conventional electronic devices use numerous printed wiring boards. This printed wiring board is made by press-molding copper foil, which is made by impregnating paper or glass cloth with thermosetting resin such as unsaturated polyester, epoxy, or polyimide resin, and laminating semi-cured prepreg and copper foil. It is made by etching the wiring on a laminated board and is built into a three-device housing.

In recent years, attempts have been made to form an S electric circuit pattern directly on the inner or outer surface of a single device housing and mount components thereon in order to save space or reduce costs in order to downsize electronic devices. This is a process in which circuits are added to three-dimensional molded products obtained by injection molding of thermoplastic resin, and the manufacturing method involves using a transfer sheet on which a pattern of conductive paste or the like is printed in advance on a film. A method of transferring, a method of forming a copper circuit by electroless plating after molding, etc. have been proposed.

[Problem to be solved by the invention]

However, these attempts still have many problems. In the case of the additive method, surface treatment was performed using a mixed solution of high concentration chromic acid and sulfuric acid.

This highly concentrated chromic acid is a chemical that causes pollution, and measures to prevent pollution have been required when using it. Also.

The manufacturing process is complicated, making quality control and cost reduction difficult, and it is also difficult to form patterns in the case of products with complex shapes.

How to obtain injection molded printed wiring boards by transfer method.

Although the process is simple and economically superior, there is a problem in that the circuit on the transfer sheet is transferred to a position shifted from the predetermined position on the surface of the molded product, making it impossible to transfer it accurately.

This invention was made in view of one or more circumstances. Circuits are transferred with high precision to three-dimensional molded products that make up slave device housings, etc., making injection molded printed wiring boards efficient.

It is an object of the present invention to provide a conductive circuit transfer molding method that can be manufactured with high quality and at low cost.

[Means to solve the problem]

As a result of intensive studies to solve the above problems, the inventors of the present invention found that
Even if the transfer sheet is positioned at a predetermined position with respect to the open mold and stopped, the transfer sheet will move slightly when the mold is closed, resulting in the position of the transferred circuit pattern changing. The present invention was completed by focusing on the fact that by preventing the movement of the transfer sheet when the mold is clamped, one circuit pattern can be transferred with high precision.

In other words, the present invention positions a transfer sheet on which a conductive circuit pattern has been formed in advance at a predetermined position with respect to either a fixed mold or a movable mold that is in an open state.
Next, the transfer sheet is fixed to the mold by vacuum suction from the suction hole formed in the mold, and the mold is clamped in this state, so that a part of the transfer sheet is attached to the movable mold. The gist of the present invention is a conductive circuit transfer molding method, which is characterized in that the conductive circuit is placed in a cavity formed by a fixed mold, and then a resin is injected into the cavity to perform molding, and at the same time, a conductive circuit pattern is transferred.

Here, the position of the suction hole formed in the mold is determined as appropriate depending on the shape of the molded product, the mold structure, etc., and may be in either a movable mold or a fixed mold, and the position facing the cavity. The suction hole may be provided to open at a position facing the cavity, or may be provided to open to the outside of the cavity.If the suction hole is provided to open at a position facing the cavity, after the mold is clamped, It is preferable to stop vacuum suction from the hole, supply pressurized fluid to the suction hole, and perform injection molding of the resin in this state.Furthermore, after the mold is clamped, stop the vacuum suction from the suction hole. , the pin installed in the suction hole is moved forward to close the tip of the suction hole.

It is also preferable to perform injection molding of the resin in this state.

[Effect]

In the present invention, when the mold is clamped as described above, the transfer sheet is suctioned and held against one of the molds, so it does not move, and therefore, after the mold is clamped, the transfer sheet is formed by the mold. It is positioned with high precision at a predetermined position within the cavity. Therefore, the circuit pattern formed on the transfer sheet is accurately transferred to a predetermined position on the molded product.

In addition, when the suction hole is provided to open at a position facing the cavity, pressurized air is supplied to the suction hole of the mold during injection molding, or the tip of the suction hole is closed by moving the pin forward. This prevents the injected resin from flowing into the suction hole across the transfer sheet, making it possible to obtain a surface of the molded product without any damage to the shape of the suction hole.

〔Example〕

The present invention will be described in detail below with reference to an embodiment shown in one drawing. Note that the present invention is not limited to the embodiments described below.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the apparatus used for carrying out the method of the present invention, and FIG. 2 is a schematic cross-sectional view of a box-shaped molded product manufactured by the apparatus. It has a box-like shape, and a circuit pattern 2 is formed on the inner surface of the bottom.

In FIG. 1, 3 is a mold device of an injection molding machine.

This mold device 3 includes a fixed mold 4 having a cavity 4a.
The movable mold 5 includes a core portion 5a inserted into the cavity 4a, and a stripper plate 6 includes a hole 6a that fits into the outer periphery of the core portion 5a.

The stripper plate 6 is fixed to an ejector turbine 7 that passes through the movable mold 5, and is moved relative to the movable mold 5 as the ejector turbine 7 moves. A guide roller 6b is provided at a corner of the stripper plate 6 on the core portion 5a side. Movable mold 5
A plurality of suction holes 8 are opened in the distal end surface 5b (position facing the cavity 4a) of the core portion 5a.
is connected via passageway 22 to an external vacuum suction device (not shown). The suction holes 8 are for vacuum suction and fixation of the transfer sheet 9 as will be described later, and are provided in the number necessary for suction and fixation of the transfer sheet. For stripper plate 6.

A vertical positioning sensor lO and a horizontal positioning sensor 11 for detecting marks formed on the transfer sheet 9 are provided at positions facing the transfer sheet 9. These sensors10.
A photoelectric sensor is preferably used for 11. Note that instead of being provided on the stripper plate 6, these sensors 10 and 11 may be provided at appropriate positions near the stripper plate 6. An injection cylinder 12 can be connected to the fixed mold 4.

Above and below the mold device 3, there is a transfer sheet feeding device 14.
, feed pinch rollers 15, 16. A winding device 17 etc. is arranged, and a winding device 9A in which the transfer sheet 9 is wound around a paper tube 9
It is set in the feed-out device W14 in the form of
It is designed to be wound up. As shown in FIG. 3, this transfer sheet 9 has a circuit pattern 9b formed in advance on a film 9a such as a PET film or a PI film so as to be transferable.

Furthermore, there are vertical positioning marks 9C on the film 9a.
1 left and right positioning marks 9d are printed. The feed pinch rollers 15 and 16 are connected to pulse motors, servo motors, etc., and have a mechanism that allows adjustment of the feed amount.
The 0 winding device 17, which is designed to stop the transfer sheet 9 based on the detection signal c, is designed to stop the transfer sheet 9 as a whole so that the transfer sheet 9 can be finely adjusted in the left and right direction (width direction). The winding device 17 is movable in the direction and includes a drive device that moves the winding device 17 in the left and right directions. This drive device is controlled by a left-right positioning sensor 11 that detects left-right positioning marks 9d on the transfer sheet 9.

Next, a conductive circuit transfer molding method using the apparatus having the above configuration will be explained.

As shown in FIGS. 1 and 4 (al), when the movable mold 5 is in the open state away from the fixed mold 4, the feed pinch roller 15
．． 16 operates to feed the transfer sheet 9 by a predetermined amount, and transfer the new circuit pattern 9b of the transfer sheet 9 to the tip surface 5 of the movable mold 5.
Position it at a predetermined position on b and stop it. At this time, the vertical positioning mark 9c is detected by the vertical positioning sensor 10, and the transfer sheet 9 is stopped based on the signal, thereby accurately positioning the transfer sheet 9 in the vertical direction (longitudinal direction). Further, the left and right positioning sensor 11 detects the left and right positioning mark 9d, and the left and right drive device installed in the @ taking device 17 moves the winding device 17 left and right so that the mark 9d is at a predetermined position. As a result, the transfer sheet 9 can be accurately positioned in the left-right direction (width direction). The vertical positioning sensor 10 and the horizontal positioning sensor 11 may be provided on the upper and lower outer sides of the stripper plate 6 as described above, but they may be provided on the stripper plate 6 near the core portion 5a of the movable mold 5 as in the embodiment. If you keep it.

Positioning is performed by detecting a positioning mark near the circuit pattern to be positioned on the tip surface 5b,
This is preferable because extremely accurate positioning is possible.

When the positioning of the transfer sheet 9 with respect to the tip end surface 5b of the movable mold 5 is completed, vacuum suction is applied to the suction hole 8 as shown in FIG. As a result, the transfer sheet 9 is transferred to the movable mold 5.
is vacuum-adsorbed and fixed to the distal end surface 5b.

Next, the ejector pin 7 (see FIG. 1) is retracted by the ejector cylinder (not shown), and the ejector pin 7 (see FIG. 1) is retracted by the ejector cylinder (not shown), and as shown in FIG.
9, the stripper plate 6 is fitted into the core portion 5a of the movable mold 5. As a result, the transfer sheet 9 is placed over the core portion 5a and placed. At this time, the circuit pattern portion of the transfer sheet 9 is fixed to the tip end surface 5b of the movable mold 5 by suction, so that it does not move.

Note that the feeding of the transfer sheet 9 at this time is carried out by the feeding device 1.
4 and the winding device 17, and at this time, the tension of the transfer sheet is suitably adjusted using a powder brake or the like.

Next, mold clamping is performed, and as shown in FIG. 4 1dl, the movable mold 5 and the stripper plate 6 are pressed against the fixed mold 4, and the cavity 4a is closed with the core portion 5a.

Thus, the transfer sheet 9 is placed at a predetermined position within the cavity 4a.
is accurately positioned and cent.

After that, as shown in FIG. 4 f8), the injection cylinder 12
The molten resin is injected into the cavity 4a through the gate of the fixed mold 4 to form the molded product 20. At the same time, the circuit pattern of the transfer sheet 9 is transferred to the surface of the molded product 20. If the hole diameter is small, the resin may be injected with the transfer sheet fixed by suction, or the resin may be injected with the suction released. However, if the hole diameter of the suction hole 8 is large, In this case, the molten resin flows into the suction hole 8 with the transfer sheet 9 sandwiched therebetween, and there is a risk that traces of the shape of the suction hole will be formed on the surface of the molded product. If there is such a possibility, it is necessary to provide a mechanism to prevent it. As shown in FIG. 5, such a mechanism includes a switching solenoid valve 23 provided in a passage 22 connecting the suction hole 8 of the movable mold to a vacuum suction device, and a pressurized fluid such as Examples include those connected to a pressurizing device that supplies pressurized air. With this mechanism, after the transfer sheet 9 is vacuum-adsorbed and the mold is clamped,
By switching the switching solenoid valve 23, pressurized air can be applied to the suction hole 8, and the flow pressure of the resin can be counteracted by sandwiching the transfer sheet when the resin is injected. Further, as another mechanism, as shown in FIG. 6, there can be mentioned one in which a pin 24 is provided in the suction hole 8 to close the hole. When this mechanism is provided, after suction of the transfer sheet 9 and mold clamping are completed, the pins 24 are advanced to the parting surface to close the holes, and injection molding is performed in this state, thereby preventing the generation of shape marks.

When the transfer molding shown in FIG. 4+81 is completed, the mold is opened and the molded product 20 is attached to the core part 5a of the movable mold 5, as shown in FIG.
drawn from a.

Next, as shown in FIG. As shown in Figure 4+81, the transfer sheet 9 is deformed inward and peeled off from the molded product 20. As a result, a molded product 20 with a circuit pattern on the bottom inner surface is formed, and unnecessary portions are removed. As a result, a box-shaped molded product 1 shown in FIG. 2 is obtained.

Thereafter, the portion of the transfer sheet 9 that has been transferred is wound up by the winding device 17, and the position of the primary circuit pattern is set on the movable mold 5.
position on the distal end surface 5b, and return to the state shown in FIG. 4+81.

By repeating the same operation and performing continuous transfer molding, the circuit pattern is transferred with high precision to the inner surface of the bottom of the two-box molded product, and injection molded printed wiring boards can be manufactured efficiently, with high quality, and at low cost. can be manufactured.

Although the above embodiments described the case where a circuit pattern is transferred to the inner surface of the bottom of a box-shaped molded product, the present invention is not limited to this case, but can be applied to the outer surface of a box-shaped molded product or the inner surface of a molded product of other shapes. Alternatively, it is also applicable to transferring a circuit pattern to an external surface. In that case, a mold with a shape and structure appropriate to the molded product will be used, but the suction holes provided to fix the transfer sheet are not necessarily in the cavity of the movable mold as shown in the example of the drawing. It is not necessary to form it in a facing position, and depending on the mold structure, it may be provided so as to open to the outside of the cavity, or furthermore, it may be provided on the fixed mold side.

Next, an example in which molding transfer was actually performed by applying the method of the present invention using the apparatus shown in FIG. 8 will be shown below together with a comparative example.

Example 1 A transfer sheet was used in which a circuit pattern was formed using conductive Ag paste on a PET film (50 pm).

Transfer molding was performed by the method described above, and pattern positional deviations in the vertical and horizontal directions at the reference position of the molded body were measured.

Note that the diameter of the suction hole 8 is 1. (A ln- one was used, and the penetration of the transfer sheet into the suction holes was visually determined. ABS resin was used as the base resin.

Comparative Example 1 In Example 1 above, the mold was clamped without suction fixing the transfer sheet. Other conditions are the same as in Example 1.

Example 2 The diameter of the suction hole 8 is 3. Same as Example 1 except that Qmsφ was used.

Example 3 The diameter of the suction hole 8 is 3. A vacuum cleaner of Omφ was used, and a pressure device was connected to its suction hole 8 as shown in FIG. After the transfer sheet was fixed by suction and the mold was clamped, injection molding was performed with 2.0 kg/- of pressurized air acting on the suction holes 8. Other conditions are the same as in Example 1.

Example 4 The diameter of the suction hole 8 is 3. A pin 24 was used in the suction hole 8 as shown in FIG.

After suction fixing the transfer sheet and clamping the mold, the suction hole 8
The pin 24 installed in the mold was advanced to the parting surface, and injection molding was performed with the hole closed. Other conditions are the same as in Example 1.

Transfer position accuracy of the above transfer molding examples and comparative examples.

Results of visual judgment of the shape family of suction holes on the surface of the molded product.

Shown in Table 1.

Table 1 As is clear from the results in Table 1, Examples 1 to 1 of the present invention
4, the positional deviation in the vertical direction compared to the comparative example,
Both the left and right positional deviations have been significantly reduced. Note that when a suction hole 8 with a diameter of 3.0 m is used (Example 2), a shape group is generated due to the suction hole 8, which deteriorates the shape of the molded product. (
Example 3) By blocking the suction hole 8 with a pin (Example 4), it was possible to suppress the occurrence of the shape group of the suction hole 8 and obtain a molded product with a good appearance.

〔Effect of the invention〕

As described above, according to the present invention, a circuit pattern can be transferred to a high degree on the surface of a molded product, and an injection molded printed wiring board can be manufactured efficiently, with high quality, and at low cost. It will be done.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view showing one embodiment of the apparatus used to carry out the method of the present invention, Fig. 2 is a schematic cross-sectional view of a box-shaped molded product manufactured by the apparatus, and Fig. 3 is a transfer sheet used in the apparatus. A plan view of a part of Fig. 4 (at, (bl, fc
l, tdl. (el, (fl, (g), (hl is a schematic sectional view explaining the forming transfer operation by the above device, FIG. 5 is a schematic sectional view of a part of the device used in another embodiment of the present invention, 6
The figure is an enlarged cross-sectional view of a part of a movable mold used in still another embodiment of the present invention. 1-Box-shaped molded product, 2.-Circuit pattern, 3-.-Mold device 4-Fixed mold, 4a-Cavity, 5-Movable mold, 5
a--core portion, 5b--tip surface, 6--stripper plate, 8--suction hole, 9--transfer sheet, 9a--film. 9b-circuit pattern, 10-vertical positioning sensor, 11
- Left and right positioning sensor, 12... - Injection cylinder, 14
Delivery device, 15. 16-Feed pinch roller,
17 - Winding device. Agent Patent Attorney Kyo Matsu Sanga 4 Zuannobu IBL Fang 5 Zuga 6

Claims (3)

[Claims] (1) A transfer sheet on which a conductive circuit pattern has been formed in advance is positioned at a predetermined position relative to either a fixed mold or a movable mold that is in an open state, and then the conductive circuit pattern is formed in that mold. The transfer sheet is fixed to the mold by vacuum suction from the suction hole, and the mold is clamped in that state, so that a part of the transfer sheet is placed inside the cavity formed by the movable mold and the fixed mold. 1. A conductive circuit transfer molding method characterized in that a conductive circuit pattern is transferred at the same time as the molding is performed by injecting a resin into the cavity. (2) In the conductive circuit transfer molding method according to claim 1. The suction hole is formed to open at a position facing the cavity, and after the mold is clamped, vacuum suction from the suction hole is stopped, pressurized fluid is supplied to the suction hole, and the resin is heated in this state. A conductive circuit transfer molding method characterized by performing injection molding. (3) In the conductive circuit transfer molding method according to claim 1,
The suction hole is formed to open at a position facing the cavity, and after the mold is clamped, the vacuum suction from the suction hole is stopped, and the pin installed in the suction hole is advanced to close the tip of the suction hole. A conductive circuit transfer molding method characterized by closing the plug and performing resin injection molding in that state.