JP2023172145A - Method for manufacturing substrate - Google Patents

Abstract

To provide a method for manufacturing a substrate capable of suppressing dropout of conductive paste filled into a through-hole.SOLUTION: A method for manufacturing a substrate includes the following steps: the first step for forming a through-hole in a prepreg having a back surface and a front surface; the second step for placing a resin film on the back surface covering the through-hole; the third step for attaching the resin film to the back surface of the prepreg by heating the resin film and the back surface while cooling the through-hole; the fourth step for filling the through-hole with conductive paste from the front side of the prepreg.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a method of manufacturing a substrate.

2. Description of the Related Art Conventionally, a technique is known in which a through hole is formed in a substrate, the formed through hole is filled with a conductive paste, and a wiring is formed that connects the front surface and the back surface of the substrate to each other (for example, Patent Document 1).

Japanese Patent Application Publication No. 6-268345

When it is desired to pass a large current through the wiring formed in the through hole, it is required to increase the diameter of the through hole. In this case, the conductive paste filled in the through hole may fall off due to its own weight.

The present disclosure can be realized as the following forms.

(1) According to one embodiment of the present disclosure, a method for manufacturing a substrate is provided. This manufacturing method includes a first step of forming a through hole in a prepreg having a back surface and a front surface, a second step of disposing a resin film on the back surface covering the through hole, and cooling the through hole. a third step of heating the resin film and the back surface and pasting the resin film on the back surface of the prepreg; and a fourth step of filling the through hole with conductive paste from the front surface side of the prepreg. and. According to this form, by covering the through hole with a resin film and filling the through hole with a closed bottom with conductive paste, the conductive paste is prevented from falling out of the through hole, and the conductive paste is placed inside the through hole. Can hold paste. Furthermore, in the third step, the through hole is cooled and the resin film and the back surface are heated, so the resin film can be satisfactorily attached to the back surface of the prepreg while maintaining the shape of the through hole.
The present disclosure can also be realized in various forms other than the method of manufacturing a substrate. For example, it can be realized in the form of a substrate manufacturing apparatus, a control method for a substrate manufacturing apparatus, a computer program for realizing the control method, a non-temporary recording medium on which the computer program is recorded, and the like.

Flowchart of the manufacturing process of the board. FIG. 3 is a schematic diagram illustrating each step of the manufacturing process. A schematic cross-sectional view of a pressurizing device. Evaluation results regarding conductive paste retention status. First evaluation results regarding the resin film attachment method. Second evaluation results regarding the resin film attachment method. Measurement results of storage modulus and loss modulus of prepreg with respect to temperature.

A. Embodiment:
FIG. 1 is a flowchart of a manufacturing process that implements the method for manufacturing the circuit board 100 (FIG. 2). FIG. 2 is a schematic diagram illustrating each step. FIG. 3 is a schematic cross-sectional view of a pressurizing device 200 used in step P30, which will be described later. The circuit board 100 is used for, for example, an ECU (Engine Control Unit). In step P10 of FIG. 1, a through hole 12 is formed in the prepreg 10 using a drill 16 (FIG. 2). As shown in step P10 of FIG. 2, the prepreg 10 has a flat plate shape having a front surface 10a and a back surface 10b. The back surface 10b is arranged below the front surface 10a in the vertical direction. As the prepreg 10, for example, a glass cloth impregnated with an epoxy resin can be used. The through hole 12 is a through hole that penetrates from the front surface 10a to the back surface 10b. The prepreg 10 is used to form a connection wiring 14, which will be described later, that connects a wiring formed on a first substrate 60, which will be described later, and a wiring formed on a second substrate 70, which will be described later. There are various diameters D of the through holes 12, including through holes 12 having a diameter D of 0.3 mm or more. A connection wiring 14 formed inside a through hole 12 with a diameter D of 0.3 mm or more allows a larger current to flow than a connection wiring 14 formed inside a through hole 12 with a diameter D of less than 0.3 mm. be able to.

In step P20 of FIG. 1, a resin film 20 (FIG. 2) is placed on the back surface 10b of the prepreg 10 so as to cover the through hole 12. As the resin film 20, for example, a PET (polyethylene terephthalate) film can be used.

In step P30 of FIG. 1, a resin film 20 is attached to the back surface 10b of the prepreg 10. In step P30, the resin film 20 and the back surface 10b are heated while the through hole 12 is cooled, and the resin film 20 is pressed toward the prepreg 10, so that the resin film 20 is attached to the back surface 10b of the prepreg 10. Can be attached. In step P30, a pressurizing device 200 shown in FIG. 3 is used. The pressurizing device 200 includes a pair of heaters 210 and a pair of cooling devices 220. The pair of heaters 210 are arranged to face each other with a laminate in which the prepreg 10 and the resin film 20 are laminated interposed therebetween. The heater 210 includes a heat transfer body 211 in which a through hole 212 is formed in a portion of the prepreg 10 facing the through hole 12, and a heating element (not shown) that heats the heat transfer body 211.

The pair of cooling devices 220 are arranged to face each other with the laminate of prepreg 10 and resin film 20 interposed therebetween. The cooling device 220 includes a circulation member 221 through which a refrigerant 230 flows, and a cooling body 222. Specifically, the circulation member 221 has a first surface facing the heater 210 and a second surface spaced apart from the first surface, and there is a space between the first surface and the second surface. , a space through which the refrigerant 230 flows is formed. The cooling body 222 is rod-shaped and stands upright from the first surface toward the heater 210 . The tip of the cooling body 222 is inserted into the through hole 212 of the heater 210. In this embodiment, the cooling body 222 has a diameter such that a slight gap is formed between the outer circumferential surface of the cooling body 222 and the circumferential surface of the through hole 212 of the heater 210.

Each of the pair of cooling devices 220 has a structure that is approximately plane symmetrical with respect to the plane of the laminate of the prepreg 10 and the resin film 20 as a plane of symmetry. However, the flow directions of the refrigerant 230 flowing through each of the flow members 221 of the pair of cooling devices 220 are opposite to each other. Thereby, the through hole 12 can be efficiently cooled.

As shown by the white arrows in FIG. 3, the pressurizing device 200 is configured such that each of the pair of heaters 210 and each of the pair of cooling devices 220 approaches the laminate of the prepreg 10 and the resin film 20. Moving. As a result, the through holes 12 of the prepreg 10 are cooled by the cooling body 222, and the resin film 20 and the front surface 10a and back surface 10b of the prepreg 10 are heated by the heater 210, and the resin film 20 and the front surface 10a and the back surface 10b of the prepreg 10 are The laminate is pressurized from both sides. Thereby, the resin film 20 can be softened while maintaining the film shape, and the resin film 20 can be attached to the back surface 10b of the prepreg 10, as will be described in detail later.

The temperature of the heater 210 is preferably lower than both the peak temperature of the storage modulus and the peak temperature of the loss modulus of the prepreg 10. This is because the hole shape of the through hole 12 can be maintained well. In this embodiment, the temperature of the heater 210 is 55°C.

By heating the resin film 20 with the heater 210, the adhesion of the resin film 20 to the prepreg 10 can be improved. Furthermore, by cooling the through hole 12 with the cooling body 222, deformation of the through hole 12 due to heating by the heater 210 can be suppressed. Therefore, the connection wiring 14 formed inside the through hole 12 can be formed satisfactorily.

As shown in an enlarged view in FIG. 3, the tip of the through hole 212 and the tip surface of the heat transfer body 211 close to the prepreg 10 are not flush with each other. Specifically, the tip of the through hole 212 is recessed by a distance C from the position of the tip surface of the heat transfer body 211 near the prepreg 10 in the vertical direction. Thereby, when the pressurizing device 200 presses the prepreg 10, damage to the prepreg 10 and the resin film 20 can be suppressed. In this embodiment, the distance C is approximately 0.1 mm.

In step P40 in FIG. 1, the conductive paste 50 is filled into the through holes 12 from the surface 10a side of the prepreg 10. Specifically, as shown in step P40 of FIG. 2, a metal mask 30 in which a through hole 32 is formed is placed on the surface 10a of the prepreg 10 so that the through hole 32 and the through hole 12 of the prepreg 10 overlap. be done. Thereafter, the squeegee 40 moves along the surface of the metal mask 30 while pushing the conductive paste 50 to spread the conductive paste 50. Thereby, the conductive paste 50 is filled into the through hole 12 . Thereafter, metal mask 30 is removed. The conductive paste 50 is a mixture of metal powder, binder, and solvent. Since the resin film 20 is attached to the prepreg 10 in advance, it is possible to suppress the conductive paste 50 filled in the through-hole 12 from falling off from the through-hole 12 .

In step P50 of FIG. 1, in this embodiment, the ambient temperature is set to 100° C., and the solvent contained in the conductive paste 50 is evaporated, so that the conductive paste 50 is temporarily hardened.

In step P60, a first substrate 60 (FIG. 2) is placed on the surface 10a of the prepreg 10, and pressure is applied from both sides of the laminate in which the first substrate 60, the prepreg 10, and the resin film 20 are laminated. . In this embodiment, the temperature applied to the laminate of the first substrate 60, prepreg 10, and resin film 20 is 100°C. The first board 60 is a printed board on which copper wiring is formed. As the base material of the first substrate 60, a glass cloth substrate, an epoxy resin substrate can be used. Copper wiring is formed in a portion of the first substrate 60 facing the through hole 12 . By pressurizing the prepreg 10 and the first substrate 60 in a stacked state, the conductive paste 50 and the first substrate 60 are brought into close contact with each other. Thereby, it is possible to suppress the conductive paste 50 from being peeled off from the through hole 12 together with the resin film 20 that is peeled off in the next step P70.

In step P70, the resin film 20 is peeled off from the prepreg 10. As described above, since the conductive paste 50 is in close contact with the first substrate 60, the state in which the conductive paste 50 is filled in the through hole 12 is maintained.

In step P80, the second substrate 70 (FIG. 2) is placed on the back surface 10b of the prepreg 10, and the laminate in which the first substrate 60, the prepreg 10, and the second substrate 70 are stacked is heated. Then, pressure is applied from both sides of the laminate, so-called hot pressing. The second substrate 70 is a substrate similar to the first substrate 60, and a copper wiring is formed in a portion of the second substrate 70 that faces the through hole 12. In this embodiment, the heating temperature is 150°C. As a result, as shown in the finished product of FIG. 2, the metal contained in the conductive paste 50 and the copper of the wiring formed on the first substrate 60 are melted, and the metal contained in the conductive paste 50 and the copper of the wiring formed on the first substrate 60 are melted. The copper of the wiring formed on the substrate 70 is melted to form the connection wiring 14 that connects the wiring formed on the first substrate 60 and the wiring formed on the second substrate 70, and this manufacturing process ends. .

The process P10 is also called the first process, the process P20 is also called the second process, the process P30 is also called the third process, and the process P40 is also called the fourth process.

B. Example:
B1. Attaching resin film:
FIG. 4 shows the evaluation results of the holding state of the conductive paste 50 in the through-hole 12 in Examples 1 to 9 and Comparative Examples 1 to 9. Examples 1 to 9 were manufactured by the manufacturing method described in the above embodiment, that is, by pasting the resin film 20 and then filling the conductive paste 50. Comparative Examples 1 to 9 were produced by filling the conductive paste 50 without attaching the resin film 20. Examples 1 to 9 differ from each other in hole diameter, which is the diameter D of the through hole 12. Similarly, Comparative Examples 1 to 9 are different in hole diameter, which is the diameter D of the through hole 12. The pore diameters of Examples 1 to 9 and Comparative Examples 1 to 9 are as shown in FIG. The application temperature, which is the temperature of the resin film 20 in Step P30 of Examples 1 to 9, was 55°C. The adhesion pressure, which is the pressure applied to the laminate of prepreg 10 and resin film 20 in step P30 of Examples 1 to 9, was 0.25 MPa. The resin film 20 of Examples 1 to 9 is a PET film with a thickness of 25 μm. The thickness of the prepreg 10 of Examples 1 to 9 and Comparative Examples 1 to 9 is 0.2 mm. The through holes 12 in Examples 1 to 9 and Comparative Examples 1 to 9 were formed using a drill 16. The same applies to the samples shown in FIGS. 5 and 6, which will be described later. The thickness of the metal mask 30 used in the process of filling the conductive paste 50 in Examples 1 to 9 and Comparative Examples 1 to 9 was 20 μm, and the squeegee 40 used was a urethane squeegee.

In Examples 1 to 9 and Comparative Examples 1 to 9, after the conductive paste 50 was filled, the retention state of the conductive paste 50 in the through holes 12 was visually evaluated. Specifically, the case where the conductive paste 50 is not observed to come off from the through hole 12 is evaluated as "○", and the case where the conductive paste 50 is observed to come off from the through hole 12 is evaluated as "x". .

As shown in FIG. 4, in Examples 1 to 9, the conductive paste 50 was not observed to fall out of the through holes 12 regardless of the hole diameter, and the conductive paste 50 was not retained in the through holes 12. Ta. On the other hand, regarding Comparative Examples 1 to 9, in Comparative Example 1 where the hole diameter is 0.2 mm, the conductive paste 50 was held in the through hole 12, but in Comparative Examples 2 to 9 where the hole diameter is 0.3 mm or more. 9, the conductive paste 50 is not held in the through hole 12. This shows that by pasting the resin film 20, the conductive paste 50 can be held in the through hole 12 even if the hole diameter is 0.3 mm or more.

B2. Partial cooling:
FIG. 5 shows the evaluation results for the method of attaching the resin film 20 for Samples 1 to 4. In samples 1 to 4, a plurality of through holes 12 having different hole diameters were formed in the prepreg 10, and then the resin film 20 was attached. The size of the pore diameter is as shown in FIG. The "partial cooling" of the heating method shown in FIG. This is a method of heating. "Flat heating" of the heating method shown in FIG. 5 means that, unlike the above embodiment, in order to attach the resin film 20, the resin film 20 and the front surface 10a and the back surface of the prepreg 10 are heated without cooling the through hole 12. 10b and a heater. The application temperature of each of Samples 1 to 4 is as shown in FIG.

After attaching the resin film 20 to the prepreg 10, the adhesion state of the resin film 20 and the shape of the through hole 12 were evaluated. Specifically, in "Film adhesion", which indicates the result of evaluating the state of adhesion of the resin film 20, "◎" indicates a state in which the prepreg 10 is well adhered to the resin film 20, and a state in which it is normally adhered. A state of poor adhesion was evaluated as "△", and a state of no adhesion was evaluated as "x". In "Hole Shape Maintenance", which shows the results of evaluating the shape of the through hole 12, "◎" indicates that the shape of the through hole 12 is well maintained, "○" indicates that the shape is maintained normally, and "○" indicates that the shape of the through hole 12 is well maintained. A defective state was evaluated as "△", and a state in which the shape was extremely poor was evaluated as "x".

Regarding "film adhesion," Sample 1 received an evaluation of "△," while Samples 2 to 4 received an evaluation of "◎." Therefore, it can be seen that the resin film 20 can be bonded well when the bonding temperature is 55° C. or higher. Regarding "pore shape maintenance", sample 4 received an evaluation of "x", whereas sample 3 received an evaluation of "◎". Therefore, it can be seen that even when the bonding temperature is 60° C., the shape of the through hole 12 can be maintained well by cooling the through hole 12. In addition, in sample 1, since the resin film 20 was not well adhered to the prepreg 10, the evaluation of "hole shape maintenance" was omitted. From the above, it can be seen that by cooling the through-holes 12 at a pasting temperature of 55° C. or higher, the resin film 20 can be adhered to the prepreg 10 well while maintaining the shape of the through-holes 12 well.

B3. Pasting temperature of resin film:
FIG. 6 shows the evaluation results for the method of attaching the resin film 20 for Samples 5 to 10. Samples 5 to 7 and Samples 8 to 10 have different physical properties of the epoxy resin contained in the prepreg 10. Samples 5 to 7 use prepregs 10 containing epoxy resins with the same physical properties. Samples 5 to 7 have different bonding temperatures. Similarly, samples 8 to 10 use prepregs 10 containing epoxy resins with the same physical properties. Samples 8 to 10 have different bonding temperatures. The method of attaching the resin films 20 of Samples 5 to 10 was the same as in the above embodiment, and the resin films 20 were attached while the through holes 12 were being cooled. The evaluation methods for "film adhesion" and "pore shape maintenance" are the same as those described above, and therefore their explanations will be omitted.

Regarding "film adhesion," Sample 5 received an evaluation of "△," while Samples 6 and 7 received an evaluation of "◎." Regarding "pore shape maintenance", sample 7 received an evaluation of "△", while sample 6 received an evaluation of "◎". Therefore, it can be seen that for the prepregs 10 of Samples 5 to 7, when the attachment temperature is 55° C., the resin film 20 can be adhered to the prepreg 10 well while maintaining the shape of the through hole 12 well.

Regarding "film adhesion", sample 8 was evaluated as "△", whereas samples 9 and 10 were evaluated as "◎". Regarding "hole shape maintenance", sample 10 is evaluated as "△", whereas sample 9 is evaluated as "◎". Therefore, it can be seen that for the prepregs 10 of Samples 8 to 10, when the attachment temperature is 60° C., the resin film 20 can be adhered to the prepreg 10 well while maintaining the shape of the through hole 12 well.

FIG. 7 shows the measurement results of changes in the storage modulus and loss modulus of the prepregs 10 of Samples 5 to 10 with respect to temperature. As shown in FIG. 7, the storage modulus has a peak at 56.5°C. The loss modulus has a peak at 58.5°C. As shown in FIG. 6, the application temperature of Sample 7 was 60° C., which was higher than both the peak temperature of storage modulus and the peak temperature of loss modulus. From these results, if the application temperature is set higher than either the peak temperature of the storage modulus or the peak temperature of the loss modulus, the prepreg 10 will flow and the hole shape of the through hole 12 can be maintained well. I know it will disappear. The same applies to the prepregs 10 of Samples 8 to 10, and in Sample 10 where the application temperature is higher than either the peak temperature of storage modulus or the peak temperature of loss modulus, the hole shape of through hole 12 is good. The result is that it cannot be maintained. As described above, by setting the bonding temperature to a temperature lower than either the peak temperature of the storage modulus or the peak temperature of the loss modulus, the shape of the through-hole 12 can be maintained well.

According to the embodiment described above, the manufacturing process includes a step P20 of disposing the resin film 20 on the back surface 10b covering the through hole 12 formed in the prepreg 10, and a step P20 of disposing the resin film 20 on the back surface 10b while cooling the through hole 12. and a step P30 of heating the back surface 10b and attaching the resin film 20 to the back surface 10b of the prepreg 10. By covering the through hole 12 with a resin film 20 and filling the through hole 12 with a closed bottom with the conductive paste 50, the conductive paste 50 is prevented from falling out of the through hole 12, and the through hole 12 is filled with conductive paste. The paste 50 can be retained. Furthermore, in step P30, the resin film 20 and the back surface 10b are heated while cooling the through hole 12, so the resin film 20 can be satisfactorily attached to the prepreg 10 while maintaining the shape of the through hole 12. .

The present disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from the spirit thereof. For example, the technical features of the embodiments corresponding to the technical features in each form described in the column of the summary of the invention may be Alternatively, in order to achieve all of the above, it is possible to perform appropriate replacements or combinations. Further, unless the technical feature is described as essential in this specification, it can be deleted as appropriate.

10... prepreg, 10a... front surface, 10b... back surface, 12... through hole, 14... connection wiring, 16... drill, 20... resin film, 30... metal mask, 32... through hole, 40... squeegee, 50... conductive paste , 60... First substrate, 70... Second substrate, 100... Circuit board, 200... Pressure device, 210... Heater, 211... Heat transfer body, 212... Through hole, 220... Cooling device, 221... Distribution member, 222 ...cooling body, 230...refrigerant, P10-P80...process

Claims (1)

A method for manufacturing a substrate, the method comprising:
A first step of forming a through hole in a prepreg having a back surface and a front surface;
a second step of arranging a resin film on the back surface to cover the through hole;
A third step of heating the resin film and the back surface while cooling the through hole and pasting the resin film on the back surface of the prepreg;
A manufacturing method comprising: a fourth step of filling the through hole with a conductive paste from the surface side of the prepreg.

Images