WO2012133090A1

WO2012133090A1 - Printed wiring board and method for manufacturing printed wiring board

Info

Publication number: WO2012133090A1
Application number: PCT/JP2012/057292
Authority: WO
Inventors: 岡　良雄; 直太上西; 春日　隆; 辰珠朴; 上田　宏; 寛富岡; 澄人上原
Original assignee: 住友電気工業株式会社; 住友電工プリントサーキット株式会社
Priority date: 2011-03-28
Filing date: 2012-03-22
Publication date: 2012-10-04
Also published as: CN102870505B; JP2012204803A; CN102870505A; JP5400823B2

Abstract

A printed wiring board has an insulating layer (3) between a first conductive layer (2) and a second conductive layer (4). The first and second conductive layers (2, 4) are connected by a blind via (5) comprising a conductor penetrating through the insulating layer (3). During the manufacturing of these printed wiring boards, it is determined whether blind via (5) are within specification or out of specification, the ones within specification being identified as within-specification blind vias, and the ones out of specification being identified as out-of-specification blind vias. Current is passed through the blind vias (5) in current-passing conditions such that the out-of-specification blind vias will break and the within-specification blind vias will not break.

Description

Printed wiring board and printed wiring board manufacturing method

The present invention relates to a printed wiring board having blind vias and a method for manufacturing the printed wiring board.

The blind via of the printed wiring board connects the first conductive layer and the second conductive layer with a conductor. When the connection state between the conductor and the first conductive layer or the second conductive layer is not good, there is a risk of disconnection due to long-term use of the printed wiring board. For example, when an electronic device on which a printed wiring board is mounted is exposed to a change in the environment, the printed wiring board may repeat expansion and contraction cycles, leading to disconnection at a defective portion of a blind via. For this reason, in the manufacturing process of a printed wiring board, the operation | work which detects the blind via with a poor connection state is performed.

Defective products in which there are few conductors filled in the blind via, the surface of the blind via is recessed, and the bottom of the blind via is exposed can be detected by visual inspection. On the other hand, defective products due to poor adhesion between the conductor and the metal layer inside the blind via, and defective products in which bubbles or insulating foreign substances exist inside the blind via cannot be detected by visual inspection.

As a method for detecting a defective blind via that cannot be detected by appearance inspection, for example, there is a method described in Patent Document 1. In this method, the printed wiring board is heated after a film is formed in the opening of the blind via. Since a defective blind via generates gas by heating, the coating on the defective blind via is deformed. Therefore, the quality of the blind via is determined by inspecting the appearance of the film for deformation.

JP 2007-173543 A

However, in the above conventional method, in order to detect out-of-standard, that is, defective blind vias, test blind vias are provided, and the test blind vias are inspected. Has not done the inspection. In order to improve the reliability of the printed wiring board, it is necessary to determine whether each blind via is good or defective.

Therefore, there is a demand for a technique that can determine whether or not an actual blind via constituting a circuit is within the standard. There is also a need for a printed wiring board that can easily determine whether a blind via is within the standard or not.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a printed wiring board that can easily determine whether a blind via is good or bad, and a printed wiring that can determine whether a blind via is within or outside of a standard. It is in providing the manufacturing method of a board.

(1) In one embodiment of the present invention, the first conductive layer and the first conductive layer are formed by a blind via having an insulating layer between the first conductive layer and the second conductive layer and including a conductor penetrating the insulating layer. A method for manufacturing a printed wiring board to which a second conductive layer is connected is provided. The manufacturing method determines whether the blind via is within the standard or out of the standard, recognizes that the blind via is within the standard, and identifies the non-standard blind via as the non-standard blind via. Energizing the blind via under a current-carrying condition in which the non-standard blind via is disconnected and the intra-standard blind via is not disconnected.

In this case, the non-standard blind via can be disconnected and the non-standard blind via can be disconnected by energization. As a result, it is possible to easily discriminate between the non-standard blind via and the non-standard blind via by the electrical inspection that is subsequently performed.

(2) It is desirable to distinguish between the non-standard blind via and the non-standard blind via by conducting an electrical inspection on the disconnection state of the blind via after energization of the blind via.

In this case, it is possible to easily grasp whether or not there is a non-standard blind via in the printed wiring board.

(3) In order to certify the blind via whose filling rate of the conductor with respect to the filling volume of the blind via is equal to or less than a first reference value as the non-standard blind via, based on the square of the first reference value, It is desirable to set energization conditions.

When the filling rate of the conductor with respect to the filling volume of the blind via is small, the following two actions are obtained. First, the cross-sectional area of the conductor connecting the first conductive layer and the second conductive layer is reduced. This increases the resistance of the blind via and increases the amount of heat generated by energization. Second, the heat capacity required to reach the disconnection state is reduced. Both the first action and the second action promote disconnection of non-standard blind vias.

∙ When a blind via with a filling rate equal to or lower than the first reference value is recognized as a non-standard blind via, it is desirable to set energization conditions based on the square of the first reference value. In this case, it is possible to increase the probability that a blind via having a filling rate equal to or less than the first reference value is selectively disconnected as a non-standard blind via.

(4) The heat capacity necessary for disconnecting the blind via with the filling rate of 1 and the amount of heat generated by the blind via when the blind via with the filling rate of 1 is energized under the energization condition. Therefore, it is desirable to set the energization condition so that the ratio of the heat generation amount to the heat capacity is a value that is greater than or equal to the square of the first reference value and smaller than 1.

If the energization condition is set so that the ratio of the calorific value to the heat capacity is 1 or more, the blind via with a filling rate of 1 may break. On the other hand, if the energization condition is set such that the ratio of the heat generation amount to the heat capacity is less than the square of the first reference value, there is a possibility that blind vias whose charging rate is equal to or less than the first reference value will not be disconnected.

On the other hand, if the energization condition is set as described in (4) above, it is possible to suppress the blind via having a filling rate of 1 from being broken and to open the blind via having a filling rate equal to or less than the first reference value. It can be suppressed.

(5) In order to certify a blind via whose contact ratio of the conductor to the first conductive layer is equal to or less than a second reference value as the non-standard blind via, the energization condition is set based on the second reference value. It is desirable.

When the contact ratio of the conductor to the first conductive layer decreases, the contact resistance between the first conductive layer and the conductor increases. This acts to promote blind via disconnection. On the other hand, in order to recognize a blind via whose contact rate is equal to or lower than the second reference value as a non-standard blind via, it is desirable to set an energization condition based on the second reference value. Accordingly, it is possible to increase the probability that a contact rate of the second reference value or less is selectively disconnected as a non-standard blind via.

(6) A heat capacity necessary for disconnecting the blind via having the contact rate of 1 and heat generated by the blind via when the blind via having the contact rate of 1 is energized under the energization condition. It is desirable to set the energization condition so that the ratio of the heat generation amount to the heat capacity is a value that is greater than or equal to the second reference value and less than 1.

If the energization condition is set so that the ratio of the calorific value to the heat capacity is 1 or more, the blind via with a contact rate of 1 may be broken. On the other hand, if the energization condition is set with the ratio of the calorific value to the heat capacity being less than the second reference value, there is a possibility that blind vias having a contact rate of the second reference value or less will not be disconnected.

On the other hand, if the energization condition is set as described in (6) above, it is possible to suppress the blind via having a contact rate of 1 from being disconnected and the blind via having a contact rate of not more than the second reference value from being disconnected. This can be suppressed.

(7) The conductor preferably contains silver particles having an average particle diameter of 0.5 μm to 2.0 μm and silver particles having an average particle diameter of 10 nm to 500 nm.

When the above energization is performed on a normal blind via formed using a conductive paste that does not contain silver particles having an average particle diameter of 10 nm to 500 nm, the blind via expands due to heating by energization. As a result, contact between silver particles may be reduced, and resistance may be increased.

On the other hand, even when the above energization is performed on a normal blind via formed using a conductive paste containing silver particles having an average particle diameter of 10 nm to 500 nm, the resistance hardly increases. This is because the surface of the silver particles of 10 nm to 500 nm or the whole is melted by heating by energization to increase the conduction path in the blind via. That is, in this type of blind via, the increase in resistance before and after energization is small compared to the conductive paste 30 that does not contain silver particles having an average particle diameter of 10 nm to 500 nm.

(8) It is desirable that at least one of the first conductive layer and the second conductive layer is formed of stainless steel.

Of the materials forming the conductive layer, stainless steel is known to be easily oxidized on the surface. For this reason, when the 1st conductive layer or the 2nd conductive layer is formed with stainless steel, the adhesive force of a conductor and a conductive layer falls by surface oxidation of stainless steel, and between a conductor and these conductive layers The contact resistance increases. Blind vias with surface oxidation may break in the future.

In contrast, in the present invention, at least one of the first conductive layer and the second conductive layer is formed of stainless steel. The reason for this is that blind vias in which the adhesive force between the conductor and the conductive layer is reduced due to the oxidation of stainless steel, or blind vias in which the contact resistance between the conductor and the conductive layer is increased, are out of specification. This is because it can be distinguished electrically.

(9) It is desirable to cover the blind via with a coating layer.

¡When power is supplied to the blind via, the non-standard blind via may burn out and generate dust. When the electronic components are mounted on the printed wiring board while the dust remains on the printed wiring board and operated as an electric circuit, the dust may be caught between the terminals of the electronic components and cause malfunction. .

In the present invention, in consideration of this point, the blind via is covered with a coating layer so that dust due to burning does not move. Thereby, it can suppress that the malfunctioning by a dust arises.

(10) The printed wiring board is preferably manufactured by the above manufacturing method.

In this case, since the blind via is energized according to the predetermined energization condition, the selected non-standard blind via contains almost no non-standard blind via. For this reason, even if the printed wiring board is deformed or expanded / contracted due to a change in the surrounding environment, the standard blind via is hardly broken. That is, the frequency of blind via disconnection due to deformation or expansion / contraction of the printed wiring board can be reduced as compared with a printed wiring board that is not energized.

According to the present invention, it is possible to provide a printed wiring board that can easily determine whether a blind via is acceptable or not, and a printed wiring board manufacturing method that can determine whether a blind via is within specifications.

Sectional drawing of the printed wiring board in one Embodiment of this invention. Sectional drawing which expands and shows the blind via of a printed wiring board. FIG. 3A to FIG. 3C are cross-sectional views in each manufacturing process of the printed wiring board. 4A to 4C show a cross-sectional structure of a non-standard blind via, FIG. 4A is a cross-sectional view of an unfilled blind via, and FIG. 4B is a blind containing an insulating foreign material. 4 is a cross-sectional view of a via, and FIG. 4C is a cross-sectional view of a blind via in which a part of a contact surface is in a non-contact state. The figure which shows typically the inspection method of the blind via of a printed wiring board. The figure which shows the model for guide | inducing energization conditions about a non-standard blind via with an unfilling. The graph which shows the relationship between the upper limit of the filling rate of a non-standard blind via, and JA / QA. The figure which shows the model for guide | inducing energization conditions about the blind via which has a non-contact part in a contact surface.

Hereinafter, an embodiment embodying the present invention will be described in detail.

Referring to FIG. 1, the cross-sectional structure of the printed wiring board will be described.

The printed wiring board 1 includes a first conductive layer 2 formed of a metal foil, an insulating layer 3 provided on the surface of the first conductive layer 2, and a predetermined wiring pattern provided on the surface of the insulating layer 3. The second conductive layer 4 is formed, the blind via 5 connecting the first conductive layer 2 and the second conductive layer 4, and the covering layer 11 covering the second conductive layer 4. Note that the first conductive layer 2 and the second conductive layer 4 are not electrically connected at portions other than the blind via 5.

The first conductive layer 2 is made of stainless steel, and the thickness of the first conductive layer 2 is 1 μm to 100 μm. In addition, as the 1st conductive layer 2, you may use the metal foil which consists of aluminum, iron, copper, nickel, titanium, molybdenum, chromium, zinc other than stainless steel.

The insulating layer 3 is formed of a resin material having excellent flexibility. For example, the insulating layer 3 is formed of a polyester resin, a polyamide resin, or a polyimide resin. The insulating layer 3 has a thickness of 5 μm to 200 μm.

The second conductive layer 4 is made of copper. In addition to copper, the second conductive layer 4 may be formed of, for example, aluminum, nickel, gold, alloys thereof, solder, or the like. Further, in order to increase the adhesion between the second conductive layer 4 and the insulating layer 3, the second conductive layer 4 may contain nickel and chromium. When the second conductive layer 4 is made of copper and a copper alloy, an additional layer is provided between the second conductive layer 4 and the insulating layer 3, and this additional layer is formed on the surface of the second conductive layer 4. You may comprise by the nickel plating layer formed and the gold plating layer formed on the surface of the nickel plating layer.

The covering layer 11 is formed of the same resin material as that of the insulating layer 3. For example, a polyester resin, a polyamide resin, or a polyimide resin is used for forming the coating layer 11. The thickness of the coating layer 11 is 5 μm to 200 μm.

The blind via 5 is composed of a conductor 7 that connects the first conductive layer 2 and the second conductive layer 4. The conductor 7 is obtained by heat-curing the conductive paste 30. The blind via 5 has a diameter of 10 μm to 200 μm and a depth of 5 μm to 200 μm. The conductive paste 30 includes a conductive filler and an epoxy resin (cured product). The volume ratio between the conductive filler and the epoxy resin is 60:40.

As the conductive paste 30, a paste in which two kinds of conductive fillers having different average particle diameters are dispersed in an epoxy resin is used. The epoxy resin functions as a binder. As the first conductive filler 21, silver powder having an average particle size of 0.5 μm to 2.0 μm is used, and as the second conductive filler 22, silver powder having an average particle size of 10 nm to 500 nm is used. In addition, as the 1st electroconductive filler 21 and the 2nd electroconductive filler 22, the powder of silver coat copper powder, platinum, gold | metal | money, copper, nickel, and palladium other than silver powder can be used. An average particle diameter shows the value (D50) of the integrated value 50% in the integrated distribution of a particle diameter. The integrated distribution is obtained from a value obtained by volume-converting the radius of the particle measured based on the image analysis of 500 particles observed by a scanning electron microscope (SEM). It is determined by a particle size distribution measuring device.

The epoxy resin in the conductive paste 30 is thermosetting and is used by being dissolved in an organic solvent. Since the conductive paste 30 is filled in the through holes 6 by screen printing or the like, a solvent having excellent printability is used as the organic solvent of the conductive paste 30. For example, carbitol acetate or butyl carbitol acetate is used.

The cross-sectional structure of the blind via 5 will be described with reference to FIG.

The blind via 5 is formed by filling the through-hole 6 penetrating the insulating layer 3 and the second conductive layer 4 with the conductive paste 30 and performing a heat treatment. By the heat treatment, the solvent in the conductive paste 30 is removed, and the conductive paste 30 is cured and contracted so that the conductive fillers are in contact with each other in a pressed state. Since two types of conductive fillers having different average particle diameters are used, when the through-hole 6 is filled with the conductive paste 30, the second conductive filler 22 is inserted into the gap between the first conductive fillers 21. Enters. For this reason, the blind via 5 formed using the two types of

conductive fillers

21 and 22 having different average particle diameters has a through hole compared to the blind via 5 formed using only the first conductive filler 21. 6 has a high density of

conductive fillers

21 and 22 and a small resistance value. Further, since there are many contact points between the

conductive fillers

21 and 22, the resistance change when the conductor 7 expands is smaller than that of the blind via 5 formed using only the first conductive filler 21.

An example of a method for manufacturing the printed wiring board 1 will be described with reference to FIG. 3A to 3C are cross-sectional views for explaining a method of manufacturing the printed wiring board 1. FIG.

First, as shown in FIG. 3A, the second conductive layer 4 is formed on the upper surface of the insulating layer 3 by a semi-additive method.

Next, as shown in FIG. 3B, by filling the through holes 6 of the second conductive layer 3 and the insulating layer 4 with the conductive paste 30, the first conductive layer 2 and the second conductive layer 4 are separated. It is electrically connected via the conductive paste 30. The filling of the conductive paste 30 is performed by a screen printing method. After the conductive paste 30 is filled, the conductive paste 30 is heated and cured.

Next, as shown in FIG. 3C, a coating layer 11 is laminated on the surface of the second conductive layer 4, and the second conductive layer 4 and the conductor 7 are covered with the coating layer 11. Specifically, a polyimide-based photosensitive cover coat ink is applied on the surface of the second conductive layer 4 and the surface of the conductor 7 by screen printing or the like, then dried, further exposed and developed, and polyimide A film-like coating layer 11 made of resin is formed. The printed wiring board 1 is formed by the above steps.

Incidentally, the property of the conductive paste 30 varies among lots, and the property of the conductive paste 30 changes with time. In addition, there are variations in the printing operation, and the surface state of the first conductive layer 2 is various, and the surface is oxidized, the surface is uneven, or the plating solution is attached to the surface. There are things. Due to these factors, various defective products are formed in the manufacturing process of the blind via 5.

The various defective products of the blind via 5 will be described with reference to FIGS.

As shown in FIG. 4A, the unfilled portion 50 may be formed inside the blind via 5 or air bubbles may be contained inside the blind via 5. In the following description, the blind via 5 in which the unfilled portion 50 exists and the blind via 5 including bubbles are referred to as “unfilled blind via 5X”.

The unfilled portion 50 inside the blind via 5 is generated due to an inappropriate viscosity of the conductive paste 30 or an execution time of the printing process being too short. The factors that cause bubbles to enter inside the blind via 5 are that the conductive paste 30 contains bubbles inside itself, and bubbles are formed when the conductive paste 30 is filled in the through holes 6. And so on. Some of the bubbles or the unfilled portion 50 may disappear due to the heat treatment process of the blind via 5, but some may remain. The bubbles or the unfilled portion 50 reduces the amount of the conductor 7 in the blind via 5, and thus increases the resistance value of the blind via 5.

As shown in FIG. 4B, an insulating foreign material 51 may be present inside the blind via 5. In the following description, the blind via 5 including the insulating foreign material 51 is referred to as “foreign-material-containing blind via 5Y”.

As a factor that foreign matter enters inside the blind via 5, there is a case where the insulating foreign matter 51 is included in the conductive paste 30, and an insulating property when filling the through-hole 6 with the conductive paste 30 by a printing method or the like. For example, foreign matter 51 may be mixed. The insulating foreign matter 51 is generated, for example, when the insulating layer 3 is missing in the transport process of the printed wiring board 1. Since the insulating foreign matter 51 does not conduct electricity, it increases the resistance of the blind via 5 when mixed.

As shown in FIG. 4C, the contact surface 7A between the conductor 7 and the first conductive layer 2 may not be in contact with each other. In the following description, the blind via 5 in which the conductor 7 and the first conductive layer 2 are in partial contact or the blind via 5 in which the conductor 7 and the first conductive layer 2 are not in contact is referred to as “partial contact”. It is called "blind via 5Z".

The non-contact state between the conductor 7 and the first conductive layer 2 is that the conductor 7 and the first conductive layer 2 are peeled off due to expansion or contraction of the conductor 7 in the heat treatment process of the blind via 5, and printed in the manufacturing process. It is formed by applying an external force to the wiring board 1. Further, the blind via 5 in a non-contact state is formed due to a decrease in adhesive force due to oxidation of the surface of the first conductive layer 2. When the conductor 7 and the first conductive layer 2 are in a non-contact state, the resistance of the blind via 5 is increased.

In the unfilled blind via 5X and the foreign-containing blind via 5Y, there is a portion where the cross-sectional area is small in the axial direction of the blind via 5. Since the portion has a small cross-sectional area, the force is likely to concentrate, or the current is likely to be concentrated to be overheated, so that there is a risk of disconnection at the portion.

Further, the partial contact blind via 5Z has a larger contact resistance between the conductor 7 and the first conductive layer 2 than the blind contact 5 in a normal contact state, or starts from the non-contact state portion. As a result, it is likely to be disconnected at the relevant part.

As described above, the unfilled blind via 5X, the foreign-containing blind via 5Y, and the partial contact blind via 5Z are more likely to be disconnected than the normal blind via 5. For this reason, the inspection for determining the quality of the blind via 5 is performed during the manufacturing process.

Referring to FIG. 5, the pass / fail judgment inspection of the blind via 5 will be described.

In the pass / fail judgment inspection, the standard blind via 5A and the non-standard blind via 5B are distinguished. The non-standard blind via 5B is in a disconnected state, and further, a marking is given so that both can be discriminated visually.

The standard blind via 5A has a filling ratio with respect to the filling volume of the blind via 5 larger than the first reference value C, and a contact ratio at the contact surface 7A between the conductor 7 and the first conductive layer 2 is the second reference. Points larger than the value D.

The non-standard blind via 5B is that the filling rate with respect to the filling volume in the blind via 5 is equal to or less than the first reference value C, and the contact rate at the contact surface 7A between the conductor 7 and the first conductive layer 2 is equal to or less than the second reference value D. Refers to things.

The filling volume in the blind via 5 indicates the volume of the hole defined by the through hole 6 and the first conductive layer 2. When the filling rate is 1, it is assumed that the volume of the conductor 7 and the filling volume in the blind via 5 match.

Energization and electrical inspection are performed by one inspection machine. As shown in FIG. 5, the head of the inspection machine is provided with a first probe 40A for energization and a second probe 40B for electrical inspection. The first probe 40A includes a first terminal 41 and a second terminal 42 that face each other along the axial direction. The first terminal 41 is connected to a current circuit. The second probe 40B includes a third terminal 43 and a fourth terminal 44 that face each other along the axial direction. The third terminal 43 and the fourth terminal 44 are connected to a voltage measuring device 60 that measures the voltage between both terminals. Then, the resistance value of the conductor 7 is derived from the current flowing through the first terminal 41 and the measured voltage.

When conducting the electrical inspection and electrical inspection of the blind via 5, the first terminal 41 and the third terminal 43 are connected to the conductor 7, and the second terminal 42 and the fourth terminal 44 are connected to the first conductive layer 2. The

The pass / fail judgment inspection of the blind via 5 includes a step of energizing the blind via 5 (hereinafter referred to as “energization step”), and a step of performing an electrical inspection of the blind via 5 after energization for a predetermined time (hereinafter referred to as “below”). And “marking the blind via 5 based on the result of the electric inspection” (hereinafter, “marking process”). Hereinafter, each step will be described.

In the energization process, a current of a predetermined condition (hereinafter referred to as “energization condition”) is passed through the blind via 5. Thereafter, the non-standard blind via 5A and the non-standard blind via 5B are discriminated as follows in the electrical inspection process.

In the electrical inspection process, when the resistance value of the blind via 5 to be inspected is equal to or greater than the determination value, it is determined that the blind via 5 is in a disconnected state, that is, the blind via to be inspected is a non-standard blind via 5B. I do. When the resistance value of the blind via 5 to be inspected is less than the determination value, it is determined that the blind via 5 is not disconnected, that is, the blind via to be inspected is the intra-standard blind via 5A.

In the marking process, marking is performed around the blind via 5 with respect to what is determined to be a non-standard blind via 5B. The size of the mark can be determined visually.

Next, with reference to FIGS. 6 to 8 and Table 1, a setting formula for deriving the energization condition of the blind via 5 will be described.

In the energization process, it is necessary not to disconnect the non-standard blind via 5A and to disconnect the non-standard blind via 5B. Such energization conditions are set by a setting formula. The energization condition setting formula is obtained based on a model of the non-standard blind via 5B.

There are two types of non-standard blind via failure models. The first model corresponds to the unfilled blind via 5X and the foreign-containing blind via 5Y. The second model corresponds to the partial contact blind via 5Z. Since the setting formulas for the energization conditions are different for each model, these setting formulas will be described.

The first model will be described with reference to FIG.

In the first model, it is assumed that no current flows through the bubbles, the unfilled portion 50, and the insulating foreign matter 51. Then, regardless of the shape and number of the bubbles, the unfilled portion 50 and the insulating foreign matter 51, the blind via 5 is disconnected according to the filling rate, that is, the ratio of the volume of the conductor 7 to the filled volume in the blind via 5. Set the area. For example, when the filling rate of the blind via 5 in which the conductor 7 is completely filled is 1 and the sectional area of the conductor 7 is represented by S, the sectional area of the blind via 5 having a filling rate of 0.3 is “S X0.3 ".

In such a first model, a setting equation for deriving an energization condition in which the filling rate is less than the first reference value C is obtained as follows. The “energization condition in which the filling rate is not greater than the first reference value C” means that the blind via 5 whose filling rate is not greater than the first reference value C is recognized as a non-standard blind via 5B, An energization condition for disconnecting the outer blind via 5B.

The energization conditions are firstly required to disconnect the blind via 5 having a filling rate equal to or less than the first reference value C, and secondly, to prevent the blind via 5 having a filling rate of 1 from being disconnected. Hereinafter, each requirement will be described.

The conditions for breaking the blind via 5 whose filling rate is the first reference value C are as follows.

Suppose that the amount of heat generated by the blind via 5 when energized is J1. On the other hand, the heat capacity from the state in which the blind via 5 is at room temperature to the state in which the conductor 7 is melted and disconnected is defined as Q1. Then, a conditional expression for breaking the blind via 5 whose filling rate is the first reference value C is given as follows.

J1 / Q1 ≧ 1 (1)
On the other hand, the condition that the blind via 5 having a filling rate of 1 is not disconnected is as follows.

Suppose that the amount of heat generated by the blind via 5 when energized is JA. On the other hand, the heat capacity from the state in which the blind via 5 is at room temperature to the state in which the conductor 7 is melted and disconnected is defined as QA. Then, a conditional expression for preventing the blind via 5 having a filling rate of 1 from being disconnected is given as follows.

JA / QA <1 (2)
In general, the heat generation amount (J) is given as “J = I ² · t · R” where “I” is the energization current, “t” is the energization time, and “R” is the resistance of the blind via 5. The specific resistance of the conductor 7 is “ρ”, the contact resistance between the conductor 7 and the first conductive layer 2 is “Rc”, the ratio of heat generated by the contact resistance to the heating of the conductor 7 is “α”, and the conductor 7 is “S”, the resistance R is given as “R = (ρ · d + α · Rc) / S”. In the first model, since it is assumed that the filling rate and the cross-sectional area are in a proportional relationship, the resistance is inversely proportional to the filling rate based on this assumption and the above equation of resistance. That is, the relationship between the heat generation amount (JA) of the blind via 5 having a filling rate of 1 and the heat generation amount (J1) of the blind via 5 having a filling rate of the first reference value C is as follows.

J1 = JA / C (3)
The heat capacity (Q) from the state where the blind via 5 is at room temperature to the state where the conductor 7 is melted and disconnected is defined as “H” as the heat capacity density of the conductor 7 and the filling volume in the blind via 5 is “V”. When the temperature difference between the room temperature and the melting temperature of the conductor 7 is “Td”, “Q = H · V · Td” is given. In this equation, since the heat capacity density “H” and the temperature difference “Td” can be regarded as constants, the heat capacity (Q) is proportional to the volume of the conductor 7. That is, the relationship between the heat capacity (QA) of the blind via 5 with a filling rate of 1 and the heat capacity (Q1) of the blind via 5 with a filling rate of the first reference value C is as follows.

Q1 = QA · C (4)
When the above formulas (1) and (2) are put together and modified based on the above formulas (3) and (4), the following formula, that is, the energization condition setting formula is established.

C ² ≦ JA / QA <1 (5)
That is, by setting the current and energization time so as to satisfy the above formula (5), the blind via 5 having a filling rate of 1 is not disconnected, and the blind via 5 having a filling rate of not more than the first reference value C is set. It can be disconnected.

With reference to Table 1 and FIG. 7, the disconnection result when the blind via 5 having a filling rate of 1 and the blind via 5 having a filling rate of 0.4 is energized under various energization conditions will be described. Whether or not the above-described energization condition setting formula for deriving an energization condition for disconnecting the blind via 5 having a filling rate of 0.4 or less and not disconnecting the blind via 5 having a filling rate of 1 is valid. To consider.

Samples for this test were prepared as follows. As the blind via 5 having a filling rate of 1, a through hole 6 having a radius of 30 μm and a depth of 25 μm is formed in the insulating layer 3 and the second conductive layer 4 by a UV-YAG laser, and the conductive paste 30 is formed in the through hole 6. And the conductive paste 30 was heat-cured.

As the blind via 5 having a filling rate of 0.4, a through hole 6 having a radius of 19 μm and a depth of 25 μm is formed in the insulating layer 3 and the second conductive layer 4 by laser, and the through hole 6 is filled with the conductive paste 30. Then, the conductive paste 30 was heat-cured. That is, the non-standard blind via 5B was formed based on the first model.

In order to obtain JA / QA of the formula (5), the calorific value (JA) was obtained as follows.

As described above, the heat generation amount is given as “JA = I ² · t · R”. The resistance R is given by “R = (ρ · d + α · Rc) / S”. The following values were used as parameters other than the current I and the energization time t.
The specific resistance (ρ) of the conductor 7 was set to 1.0 × 10 ⁻⁴ Ω · cm.
The depth (d) of the blind via 5 was 25 μm.
The cross-sectional area (S) of the conductor 7 was a circle area with a radius of 30 μm.
The contact resistance (Rc) between the conductor 7 and the first conductive layer 2 (stainless steel) was 2.4 × 10 ⁻⁶ Ω · cm ² .
The ratio (α) that the heat generated by the contact resistance contributes to the heating of the conductor 7 was set to 0.5. This value was set on the assumption that half of the calorific value at the contact portion was transferred to the conductor 7 and the other half was transferred to the first conductive layer 2.

The heat capacity (QA) was determined as follows.

The heat capacity is given as “QA = H · V · Td” as described above. Here, the following values were used as parameters.
The filling volume (V) of the blind via was calculated by regarding the through hole 6 of the blind via 5 as a cylinder having a radius of 30 μm and a depth of 25 μm.
The difference (Td) between the room temperature and the melting temperature of the conductor 7 was calculated using a silver melting temperature of 962 ° C. and a room temperature of 20 ° C.
The heat capacity density (H) of the conductor 7 was 2.02 J / (K · cm ³ ).

The value of the heat capacity density (H) of the conductor 7 is based on the fact that the volume ratio of the conductive filler (silver particles) to the epoxy resin is 60:40, and the heat capacity of the conductive filler itself and the heat capacity of the epoxy resin itself. And calculated by proportional distribution. Here, 2.48 J / (K · cm ³ ) was used as the heat capacity density of the conductive filler (silver particles). As the heat capacity density of the epoxy resin, 1.32 J / (K · cm ³ ) was used.

Each energization condition shown in Table 1 is whether or not the energization condition setting formula (the above formula (5)) for breaking the blind via 5 having a filling rate of 0.4 or less as a non-standard blind via 5B is valid. This is the condition set to confirm

The first to third conditions in Table 1 are conditions set so that the value of JA / QA satisfies the above formula (5). That is, the energization condition is set so that the value of JA / QA corresponds to a value between 0.16 (= 0.4 ² ) and 1.0. When energization was performed under these energization conditions, the blind via 5 having a filling rate of 0.4 could be disconnected. Further, the blind via 5 having a filling rate of 1 could be present without being disconnected.

The fourth condition and the fifth condition in Table 1 are conditions set so that the value of JA / QA is smaller than the lower limit value of the above formula (5). That is, the energization condition is set so that the value of JA / QA is smaller than 0.16 (0.4 ² ). When energization was performed under these energization conditions, the blind via 5 having a filling rate of 0.4 could not be disconnected.

The sixth condition in Table 1 is a condition set so that the value of JA / QA is larger than the upper limit value of the above formula (5). That is, the energization condition is set so that the value of JA / QA is greater than 1. When energization was performed under these energization conditions, the blind via 5 having a filling rate of 1 was disconnected.

According to the above results, by setting the energization conditions so as to satisfy the above formula (5), the blind via 5 having a filling rate of 0.4 or less can be disconnected, and the blinding rate is 1. The via 5 can be prevented from being disconnected.

FIG. 7 illustrates the energization condition setting formula. The vertical axis represents the value of JA / QA, that is, the ratio between the heat generation amount JA and the heat capacity QA in a blind via having a filling rate of 1. The horizontal axis represents the upper limit value of the filling rate of the non-standard blind via 5B. Each point in FIG. 7 shows a disconnection result under each energization condition shown in Table 1.

The range where JA / QA is 1 or more indicates a range where all blind vias 5 having a filling rate of 1 to 0 are disconnected (all blind via disconnection range). That is, under the energization conditions in this range, there is a possibility that all the blind vias 5 are disconnected.

In a range where JA / QA satisfies “C ² ≦ JA / QA <1”, the blind via 5 with a filling rate of the first reference value C or less can be disconnected, and the blind via 5 with a filling rate of 1 is disconnected. Indicates the range (selectable disconnection possible range) that is not allowed That is, under the energization conditions in this range, the blind via 5 having a filling rate equal to or lower than the first reference value C can be disconnected.

The range satisfying “JA / QA <C ² ” indicates a range in which the blind via 5 having the filling rate of the first reference value C cannot be disconnected (range where disconnection is not possible). That is, under the energization conditions in this range, the blind via 5 having a filling rate equal to or lower than the first reference value C cannot be disconnected.

Next, the energization condition setting formula corresponding to the second model will be described below with reference to FIG.

The second model models the blind via 5 having a non-contact portion on the contact surface 7A between the conductor 7 and the first conductive layer 2. In this model, it is assumed that the blind via 5 does not include bubbles or unfilled portions 50 or insulating foreign matter 51. That is, the filling rate is 1.

In such a second model, a setting equation for deriving an energization condition in which the contact rate is less than the second reference value D is obtained as follows. The “energization condition in which the contact rate is less than or equal to the second reference value D” means that the blind via 5 whose contact rate is less than or equal to the second reference value D is defined as a non-standard blind via 5B. The energization condition for disconnecting. Here, the contact rate represents the ratio of the contact area between the conductor 7 and the first conductive layer 2 with respect to the reference area, with the size of the contact surface 7A between the conductor 7 and the first conductive layer 2 as a reference area. Shall.

The energization conditions are firstly required to disconnect the blind via 5 whose contact rate is equal to or less than the second reference value D, and secondly, not to disconnect the blind via 5 whose contact rate is 1. Hereinafter, each requirement will be described.

The conditions for breaking the blind via 5 whose contact rate is the second reference value D are as follows.

Suppose that the heat generation of the blind via 5 due to energization is J2. On the other hand, the heat capacity from the state where the blind via 5 is at room temperature to the state where the conductor 7 is melted and disconnected is defined as Q2. Then, a conditional expression for disconnecting the blind via 5 whose contact rate is the second reference value D is given as follows.

J2 / Q2 ≧ 1 (6)
The condition for preventing the blind via 5 having a contact ratio of 1 from being disconnected is obtained in the same manner as in the first model. That is, when the following conditional expression is satisfied, the blind via 5 is not disconnected.

JA / QA <1 (7)
Generally, the calorific value (J) is given as “J = I ² · t · R” as described above. Since the resistance is considered to be inversely proportional to the contact rate, when the resistance when the contact rate is 1 is represented by RA, the resistance when the contact rate is the second reference value D is represented by “RA / D”. Then, the relationship between the heat generation amount (JA) of the blind via 5 having a contact rate of 1 and the heat generation amount (J2) of the blind via 5 having a contact rate of the second reference value D is as follows.

J2 = JA / D (8)
The heat capacity (Q) required from the state in which the blind via 5 is at room temperature to the state in which the conductor 7 is melted and disconnected is irrelevant to the contact rate. The relationship between QA) and the heat capacity (Q2) of the blind via 5 whose contact rate is the second reference value D is as follows.

Q2 = QA (9)
When the above formulas (6) and (7) are put together and modified based on the above formulas (8) and (9), the following energization condition setting formula is established.

D ≦ JA / QA <1 (10)
That is, by setting the current and energization time so as to satisfy the above formula (10), the blind via 5 having a contact rate of 1 is not disconnected, and the blind via 5 having a contact rate of the second reference value D is set. It can be disconnected.

As described above, according to the energization condition based on the above formula (5) or formula (10), the non-standard blind via 5B set as non-standard using a predetermined parameter can be disconnected. As to which of the two formulas is adopted, for example, the formula corresponding to the type is selected based on the type of failure that is likely to occur in the manufacturing process of the printed wiring board 1. That is, in the manufacturing process of the printed wiring board 1, unfilled blind vias 5X and foreign matter-containing blind vias 5Y often occur, and when the partial contact blind via 5Z hardly occurs, a defect standard is set for the filling rate, The energization condition is set based on the above formula (5). On the other hand, when the partial contact blind via 5Z often occurs, a failure standard is set for the contact rate, and the energization condition is set based on the above equation (10). Further, when any defect of the unfilled blind via 5X, the foreign-containing blind via 5Y, and the partial contact blind via 5Z occurs, the energization condition is derived based on the above formula (5) and the above formula (10), and the most severe Select a condition.

According to the present embodiment described above, the following effects can be obtained.

(1) An energization condition is set such that the blind via is disconnected if it is out of standard and is not disconnected if it is within the standard, and the blind via 5 is energized based on the energization condition. Thereby, it is possible to easily discriminate between the non-standard blind via 5A and the non-standard blind via 5B by electrical inspection.

(2) After the blind via 5 is energized, the blind via 5 is subjected to electrical inspection to distinguish between the standard blind via 5A and the non-standard blind via 5B by marking. Thereby, it is possible to easily grasp whether or not the non-standard blind via 5B exists in the printed wiring board 1.

(3) When the blind via 5 in which the filling ratio of the conductor 7 with respect to the filling volume of the conductive material in the blind via 5 is equal to or less than the first reference value C is the non-standard blind via 5B, the energization condition is the first reference value C. Is set based on the square of. Thereby, it is possible to increase the probability that the blind via 5 whose filling rate is equal to or less than the first reference value C will be selectively disconnected as the non-standard blind via 5B.

(4) The energization condition is set so that the ratio of the heat generation amount to the heat capacity (JA / QA) is a value equal to or larger than the first reference value C square and smaller than 1. Thereby, it can suppress that the blind via 5 with a filling rate of 1 breaks, and can suppress that the blind via 5 whose filling rate is below the 1st reference value C does not break.

(5) When determining that the blind via 5 whose contact ratio with respect to the contact surface 7A between the first conductive layer 2 and the conductor 7 is equal to or less than the second reference value D is out of specification, the energization condition is the second reference It is set based on the value D. Thereby, the probability that the blind via 5 whose contact rate is equal to or less than the second reference value D is selectively disconnected as the non-standard blind via 5B can be increased.

(6) The energization conditions are set so that the ratio of the heat generation amount to the heat capacity (JA / QA) is equal to or larger than the second reference value D and smaller than 1. Thereby, it can suppress that the blind via 5 with a contact rate of 1 breaks, and can suppress that the blind via 5 whose contact rate is below the 2nd reference value D does not break.

(7) The above energization and electrical inspection are performed on the printed wiring board 1 having the blind via 5 containing silver particles having an average particle diameter of 10 nm to 500 nm. In this case, the increase in the resistance of the blind via 5 before and after energization can be reduced as compared with the case where the energization is performed to the blind via 5 that does not contain silver particles having an average particle diameter of 10 nm to 500 nm. That is, it is possible to suppress deterioration of the standard blind via 5A that may occur due to the energization.

(8) When the first conductive layer 2 is energized with respect to the blind via 5 formed of stainless steel, the blind via in which the adhesive force between the conductor 7 and the first conductive layer 2 is reduced due to oxidation of the stainless steel. 5 or a blind via whose contact resistance between the conductor 7 and the first conductive layer 2 is increased can be distinguished from the non-standard blind via 5A by being electrically distinguished from the standard non-standard blind via 5A. Furthermore, it is possible to easily determine whether or not the printed wiring board 1 includes the non-standard blind via 5B by performing an electrical inspection and marking. Thereby, when the printed wiring board 1 is used as a component of an electric device, the printed wiring board 1 including the nonstandard blind via 5B can be easily removed.

(9) The blind via 5 is covered with a coating layer so that dust due to burning does not move. Thereby, it can suppress that the malfunctioning by the said dust arises in the electronic device using the printed wiring board 1. FIG.

(10) In the printed wiring board 1 of this embodiment, the pass / fail judgment inspection of the blind via 5 is performed. The non-standard blind via 5A selected by energization contains almost no non-standard blind via 5B. Therefore, even if the printed wiring board 1 is deformed or expanded / contracted due to environmental changes, the standard blind via 5A is hardly disconnected. That is, the frequency with which the blind via 5 is disconnected due to deformation or expansion / contraction of the printed wiring board 1 can be reduced compared to a printed wiring board that is not energized.
(Other embodiments)
The embodiment of the present invention is not limited to each of the above embodiments, and can be modified as follows. Further, the following modifications may be implemented in combination with each other.

In the above embodiment, when JA / QA obtains the energization condition satisfying the above formula (5) or formula (10), parameters other than the current and energization time among the parameters of JA / QA are set based on physical quantities. ing. That is, among JA / QA = (I ² · t · R) / (H · V · Td), the value of “R / (H · V · Td)” is determined from the physical quantity. Here, again, JA is the amount of heat generated by the blind via 5 with a filling rate of 1, QA is the heat capacity of the blind via 5 with a filling rate of 1, I is the energizing current, t is the energizing time, and H is the energizing time of the conductor 7. Thermal capacity density, V is the filling volume of the blind via, Td is the difference between the room temperature and the melting temperature of the conductor 7, and R is the resistance of the blind via 5.

On the other hand, a specific parameter can also be obtained from an actual measurement value as follows. For example, the minimum value X of “I ² · t” that satisfies JA / QA = 1 may be obtained by actual measurement, and “R / (H · V · Td)” may be obtained based on this minimum value X. .

In the above embodiment, the energization condition is set based on the conditional expression (5) or the conditional expression (10). Instead, the conditional expression (5) or the conditional expression (10) is used as the actual inspection result. And the energization condition may be obtained based on this correction formula.

In the above embodiment, the disconnection state of the blind via 5 is determined based on the measured value of the resistance of the blind via 5 by electrical inspection. Instead, the disconnection state of the blind via 5 may be determined based on the current amount or voltage value of the blind via 5.

The present invention can also be applied to the printed wiring board 1 having the following conditions. For example, the first conductive layer 2 and the second conductive layer 4 are connected by two blind vias 5, the first blind via 5 is determined to be defective, and the second blind via 5 has almost no current. The present invention can be applied to the case where the two blind vias 5 are arranged so as not to flow. That is, when the blind via 5 is energized, no current flows between the first conductive layer and the second conductive layer through a path other than the blind via 5 to be inspected, or even if a current flows. The condition is that the value does not affect the determination result.

In the above embodiment, energization is performed between the conductor 7 and the first conductive layer 2, but instead, energization may be performed between the conductor 7 and the second conductive layer 4. Between the conductor 7 and the second conductive layer 4, a decrease in the contact ratio between the two affects the quality of the blind via, and therefore the energization condition is set based on a model that approximates the second model. That is, when the blind via 5 whose contact ratio with respect to the contact surface between the conductor 7 and the second conductive layer 4 is equal to or less than the third reference value is set as the non-standard blind via 5B, the energization condition is set based on the third reference value. To do.

In the above embodiment, the present invention is applied to the printed wiring board 1 having the blind via 5 formed by the conductive paste 30, but the present invention is applied to the printed wiring board 1 having the blind via 5 formed by electroplating. The invention can also be applied.

In the above embodiment, the present invention is applied to the printed wiring board 1 in which the first conductive layer 2 connected to the conductor 7 is stainless steel, but the material for forming the first conductive layer 2 is not limited to this. . For example, the present invention can be applied to the printed wiring board 1 in which the first conductive layer 2 is formed of copper.

In the above embodiment, the manufacturing method of the present invention is applied to the printed wiring board 1 having two conductive layers, but the present invention can also be applied to a multilayer printed wiring board having three or more conductive layers. .

1: printed wiring board, 2: first conductive layer, 3: insulating layer, 4: second conductive layer, 5: blind via, 6: through hole, 7: conductor, 7A: contact surface, 11: coating layer, 21: First conductive filler, 22: Second conductive filler, 30: Conductive paste, 40A: First probe, 40B: Second probe, 41: First terminal, 42: Second terminal, 43: Third Terminal: 44: Fourth terminal, 50: Unfilled portion, 51: Insulating foreign matter, 60: Voltage measuring device.

Claims

A printed wiring board having an insulating layer between a first conductive layer and a second conductive layer, wherein the first conductive layer and the second conductive layer are connected by a blind via having a conductor penetrating the insulating layer. In the manufacturing method of
Determine whether the blind via is within the standard or non-standard, certify that the standard is within the standard, and certify the non-standard blind via as the non-standard blind via,
A method of manufacturing a printed wiring board, comprising: energizing the blind via under an energizing condition in which the non-standard blind via is disconnected and the intra-standard blind via is not disconnected.
In the manufacturing method of the printed wiring board of Claim 1,
A method of manufacturing a printed wiring board, comprising: distinguishing between the non-standard blind via and the non-standard blind via by performing an electrical inspection on a disconnection state of the blind via after energization of the blind via.
In the manufacturing method of the printed wiring board of Claim 1 or 2,
In order to certify the blind via whose non-standard blind via has a filling ratio of the conductor with respect to the filling volume of the blind via as a non-standard blind via, the energization condition is determined based on the square of the first reference value. A method of manufacturing a printed wiring board, comprising: setting.
In the manufacturing method of the printed wiring board according to claim 3,
A heat capacity necessary to bring the blind via having a filling rate of 1 into a disconnected state;
With respect to the amount of heat generated by the blind via by energizing the blind via having the filling rate of 1 under the energization condition,
The method of manufacturing a printed wiring board, wherein the energization condition is set so that a ratio of the heat generation amount to the heat capacity is a value equal to or larger than a square of the first reference value and smaller than 1.
In the manufacturing method of the printed wiring board of Claim 1 or 2,
In order to recognize the blind via whose contact ratio of the conductor to the first conductive layer is equal to or less than a second reference value as the non-standard blind via, the energization condition is set based on the second reference value. A method for producing a printed wiring board.
In the manufacturing method of the printed wiring board according to claim 5,
A heat capacity necessary for bringing the blind via having the contact ratio of 1 into a disconnected state;
Regarding the amount of heat generated by the blind via by energizing the blind via having the contact rate of 1 under the energization condition,
The method of manufacturing a printed wiring board, wherein the energization condition is set so that a ratio of the heat generation amount to the heat capacity is a value that is greater than or equal to the second reference value and less than 1.
In the method for manufacturing a printed wiring board according to any one of claims 1 to 6,
The method for producing a printed wiring board, wherein the conductor includes silver particles having an average particle diameter of 0.5 μm to 2.0 μm and silver particles having an average particle diameter of 10 nm to 500 nm.
In the method for manufacturing a printed wiring board according to any one of claims 1 to 7,
At least one of said 1st conductive layer and said 2nd conductive layer is formed with stainless steel, The manufacturing method of the printed wiring board characterized by the above-mentioned.
In the method for manufacturing a printed wiring board according to any one of claims 1 to 8,
The method of manufacturing a printed wiring board, wherein the blind via is covered with a coating layer.
A printed wiring board manufactured by the method for manufacturing a printed wiring board according to any one of claims 1 to 9.