JP2007093307A - Inspection method for double-sided printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method on a double-sided printed wiring board for checking whether or not foreign matter exists between via holes and a circuit pattern. <P>SOLUTION: The plurality of via holes 4 for a circuit are formed in places other than a peripheral part of an insulating substrate 1. A plurality of through holes 5 for inspection are provided lengthwise and crosswise at regular intervals in the peripheral part of the insulating substrate 1 to form a test coupon 7 comprising a plurality of via holes 6 for inspection by filling the respective through holes 5 with a conductive paste 3. Further, metal layers 8 are formed on both sides of the insulating substrate 1, and then, circuit patterns 9 are formed by performing etching on places other than the peripheral part of the insulating substrate 1 while removing the metal layers 8 in the peripheral part of the insulating substrate 1. The surface thus exposed of the conductive paste 3 in the via holes 6 for inspection is observed to check whether or not foreign matter 15 exists. Based on the result thereof, it is determined whether or not the foreign matter 15 exists between the conductive paste 3 in the via hole 4 and the metal layers 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for inspecting the quality of a double-sided printed wiring board, more specifically, a double-sided printed wiring board capable of confirming whether or not there is a foreign object between a via hole and a circuit pattern in a conductive paste printed wiring board. It relates to the inspection method.

  As shown in FIG. 6A, the conductive paste printed wiring board is formed by filling a through hole 20 provided in the insulating substrate 1 with a conductive paste 3 to form a via hole 21, and the conductive paste 3 in the via hole 21. Is a printed wiring board in which interlayer connection of circuit patterns 9 provided on both surfaces of the insulating substrate 1 is performed (see, for example, Patent Document 1). Since this conductive paste printed wiring board has a feature that an electric / electronic element can be compactly mounted, in recent years, it is widely used in the field of various electric / electronic products. In particular, as shown in FIG. 6A, by completely filling the through hole 20 with the conductive paste 3, an electrical connection to the upper portion of the via land becomes possible, and a multi-layered directly connected via hole 21 called a stack via is formed. Thus, the mounting density can be increased.

  As described above, when the via hole 21 is formed by filling the conductive paste 3 into the through hole 20, electrical connectivity (conductivity) is a particularly problematic item compared to the plated through hole (not shown). ). As can be easily understood from what is shown in FIG. 6, the connection between the conductive paste 3 forming the via hole 21 and the circuit pattern 9 on the insulating substrate 1 is extremely important. If foreign matter 15 is present as in 6 (b), the connection reliability is significantly reduced. Further, when the discovery of the lot of the conductive paste printed wiring board including the foreign material 15 is delayed, the multilayering is advanced, and the production loss is too large when the defect is detected just before the completion. Therefore, when the conductive paste printed wiring board is used as a part of the build-up printed wiring board, it is very important to determine whether or not the conductive paste printed wiring board is manufactured.

By the way, in the conventional plated through-hole printed wiring board (not shown), a so-called daisy pattern is formed on the periphery of the insulating substrate 1, and the resistance value of this daisy pattern is measured to detect defects such as disconnection and short circuit. To be done. In this case, it is possible to easily detect defects such as no plating deposited on the inner wall of the through hole, and it is possible to extract most of the initial failures.
JP-A-6-268345

  However, as a main failure mode of the conductive paste printed wiring board, as shown in FIG. 6B described above, foreign matter 15 is present at the interface between the conductive paste 3 forming the via hole 21 and the circuit pattern 9 on the insulating substrate 1. There is a failure mode by entraining. In this case, unless the foreign matter 15 is present over the entire interface, the daisy pattern cannot detect an abnormality in the resistance value. That is, electrical connectivity can be temporarily ensured even if a small amount of foreign matter 15 is present. However, even if it is a conductive paste printed wiring board containing a small amount of foreign matter 15, if it is used with a thermal history, the electrical connectivity will be significantly reduced. Therefore, it is very important to confirm that no foreign matter 15 is present at the interface between the conductive paste 3 and the circuit pattern 9, but it is difficult to detect a small amount of foreign matter 15 only with the daisy pattern as described above. is there.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a double-sided printed wiring board inspection method capable of confirming whether or not there is a foreign object between a via hole and a circuit pattern. Is.

  In the method for inspecting a double-sided printed wiring board according to claim 1 of the present invention, a plurality of circuit through holes 2 are provided at locations other than the peripheral portion of the insulating substrate 1, and each circuit through hole 2 is filled with a conductive paste 3. Thus, a plurality of circuit via holes 4 are formed, a plurality of inspection through holes 5 are provided at equal intervals in the periphery of the insulating substrate 1, and the conductive paste 3 is filled in each inspection through hole 5. A test coupon 7 composed of a plurality of inspection via holes 6 is formed by the following, a metal layer 8 is then formed on both surfaces of the insulating substrate 1, and then the circuit pattern 9 is formed at locations other than the peripheral portion of the insulating substrate 1 by etching. And the metal layer 8 at the periphery of the insulating substrate 1 is removed, and the surface of the conductive paste 3 in the inspection via hole 6 thus exposed is observed to check for the presence of foreign matter. It is characterized in determining the presence or absence of a foreign object between the conductive paste 3 and metal layer 8 of use via hole 4.

  According to a second aspect of the present invention, in the first aspect, the diameter of the inspection via hole 6 is smaller than the diameter of the circuit via hole 4.

  According to a third aspect of the present invention, in the first or second aspect, the pitch between the inspection via holes 6 is smaller than the minimum pitch between the circuit via holes 4.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the daisy pattern 10 is formed in the peripheral portion of the insulating substrate 1.

  According to the double-sided printed wiring board inspection method of the first aspect of the present invention, it is possible to confirm whether or not there is a foreign substance between the circuit via hole and the circuit pattern.

  According to the invention of claim 2, since the inspection conditions are strict so that foreign matters are likely to exist between the inspection via hole and the metal layer, both surfaces having no foreign matter between the circuit via hole and the circuit pattern are provided. The printed wiring board can be identified with higher probability.

  According to the invention of claim 3, since the inspection conditions are strict so that foreign matter is likely to exist between the inspection via hole and the metal layer, both surfaces having no foreign matter between the circuit via hole and the circuit pattern are provided. The printed wiring board can be identified with higher probability.

  According to the fourth aspect of the present invention, it is possible to confirm the quality of the electrical connectivity between the conductive paste forming the circuit via hole and the metal layer forming the circuit pattern.

  Embodiments of the present invention will be described below.

(Embodiment 1)
In the present embodiment, a double-sided printed wiring board (conductive paste printed wiring board) is manufactured as follows, and its quality can be inspected immediately after manufacturing.

  That is, first, an insulating substrate 1 is prepared as shown in FIG. Although it does not specifically limit as the insulating substrate 1, For example, an unclad laminated board | substrate etc. can be used. This unclad laminated substrate can be obtained by removing the metal foil on one or both sides of a metal-clad laminate such as a copper-clad laminate by etching. The metal-clad laminate is obtained by stacking a plurality of prepregs impregnated with a thermosetting resin such as an epoxy resin on a base material 11 such as a glass cloth, and heating and pressurizing a metal foil such as a copper foil on one or both sides. Obtainable.

  Next, as shown in FIG. 1B, adhesive layers 12 are formed on both surfaces of the insulating substrate 1. The adhesive layer 12 can be formed by applying an epoxy resin or the like to the surface of the insulating substrate 1 with a roll coater or the like and drying it. The drying is preferably performed until the tackiness of the adhesive layer 12 is lost.

  Next, as shown in FIG. 1C, a release film 13 such as a PET film is attached to the surface of the adhesive layer 12 using a laminator or the like.

  Thereafter, the circuit pattern 9 is formed on the insulating substrate 1 and the test coupon 7 is formed. The test coupon 7 is formed outside the region 14 where the circuit pattern 9 is formed. Specifically, as shown in FIG. 3 (plan view), the circuit pattern formation region 14 is a portion other than the peripheral portion of the insulating substrate 1 (for example, the central portion). 1 will be formed in the peripheral portion. Hereinafter, this process will be described in detail.

  First, as shown in FIG. 1 (d), a plurality of circuit through-holes 2 are provided at locations other than the peripheral portion of the insulating substrate 1 (regions where the circuit pattern 9 is formed), and the peripheral portion (circuit pattern) of the insulating substrate 1 is provided. A plurality of inspection through-holes 5 are provided in a region where 9 is not formed. Any of the through holes 2 and 5 can be provided by using a drilling machine or the like, but since the foreign material 15 (for example, glass cloth, PP resin, etc.) such as resin smear is generated along with this drilling process, The inside of any of the through holes 2 and 5 is cleaned with high-pressure air.

  Here, the circuit through-holes 2 are provided as many as required based on the desired circuit pattern 9, but the inspection through-holes 5 have a quadrilateral shape as shown in FIG. Provide at equal intervals vertically and horizontally. In FIG. 4A, three types are shown, but the inner diameter of the inspection through hole 5 is preferably smaller, and the pitch between adjacent inspection through holes 5 is preferably smaller. In FIG. 4A, the central one is preferable to the left one, and the right one is preferable to the central one. The inner diameter of the inspection through hole 5 is preferably smaller than the inner diameter of the circuit through hole 2. These points will be described later.

  Next, as shown in FIG. 1 (e), a plurality of circuit via holes 4 are formed by filling each circuit through-hole 2 with a conductive paste 3, and the conductive paste 3 is formed in each inspection through-hole 5. A plurality of inspection via holes 6 are formed by filling. Although it does not specifically limit as the conductive paste 3, For example, a silver paste, a copper paste, etc. can be used, Moreover, As a method of filling the conductive paste 3 to each through-hole 2 and 5, Screen printing or the like can be employed. The test coupon 7 is formed of a plurality of inspection via holes 6.

  Next, as shown in FIG. 1F, when the release film 13 is peeled off, the conductive paste 3 protrudes from the surface of the adhesive layer 12 by the thickness of the release film 13.

  Next, as shown in FIG. 1G, metal layers 8 are formed on both surfaces of the insulating substrate 1 (the surfaces of the adhesive layer 12 and the conductive paste 3). The metal layer 8 can be formed by disposing metal foils 16 such as copper foils on both surfaces of the insulating substrate 1 and heating and pressing them under vacuum. Here, when the metal foil 16 is disposed, the foreign matter 15 is involved, and the state shown in FIG. 6B may be obtained, but even if such a state is obtained, as described later, The presence of the foreign matter 15 can be confirmed by the method according to the present invention. Examples of the foreign material 15 include glass cloth, PP resin, and the like, dust in the process, proteins derived from human skin, and the like.

  Next, a dry film (not shown) is laminated on the surface of the metal layer 8 shown in FIG. Thereafter, by performing etching using cupric chloride or the like, a circuit pattern 9 is formed at a location other than the peripheral portion of the insulating substrate 1 and the peripheral portion of the insulating substrate 1 as shown in FIG. All the metal layer 8 is removed. The dry film is peeled off using a sodium hydroxide solution or the like after etching.

  As described above, a double-sided printed wiring board (conductive paste printed wiring board) is manufactured. By forming the circuit pattern 9 and removing the metal layer 8 by etching, as shown in FIG. The surface of the conductive paste 3 in the inspection via hole 6 is exposed. Here, since the foreign matter 15 such as glass cloth or PP resin is not removed by etching, if the foreign matter 15 is caught between the conductive paste 3 and the metal layer 8 during the manufacturing process, it is exposed. By observing the surface of the conductive paste 3 in the inspection via hole 6, the presence or absence of the foreign matter 15 can be confirmed. FIG. 5 (plan view) shows the exposed surface of the conductive paste 3 in the inspection via hole 6, FIG. 5 (a) shows a state in which no foreign matter 15 exists, and FIG. 5 (b) shows a foreign matter. An example of a state in which 15 exists is shown.

  When the foreign matter 15 exists between the conductive paste 3 in the inspection via hole 6 and the metal layer 8, the foreign matter 15 also exists between the conductive paste 3 in the circuit via hole 4 and the metal layer 8. Therefore, the presence / absence of the foreign matter 15 between the conductive paste 3 of the circuit via hole 4 and the metal layer 8 is determined based on the result of observing the surface of the conductive paste 3 of the inspection via hole 6. It is something that can be done. That is, as a result of observing the surface of the conductive paste 3 in each inspection via hole 6, as shown in FIG. 5 (a), the conductive paste 3 in the circuit via hole 4 and the metal layer 8 The possibility that foreign matter 15 exists between them is low, and the double-sided printed wiring board can be determined to be a non-defective product as shown in FIG. On the other hand, as a result of observing the surface of the conductive paste 3 in each inspection via hole 6, if any one is in the state shown in FIG. 5B, the conductive paste 3 in the circuit via hole 4, the metal layer 8, The foreign matter 15 is likely to exist between the two, and the double-sided printed wiring board can be determined to be a defective product as shown in FIG.

  As described above, according to the method for inspecting a double-sided printed wiring board according to the present invention, it is confirmed whether or not there is a foreign substance 15 between the circuit via hole 4 and the circuit pattern 9 without destroying the double-sided printed wiring board. It is something that can be done.

Next, in this embodiment, a more preferable form will be described. First, in the step shown in FIG. 1 (d), it is preferable to perform drilling so that the inner diameter of the inspection through hole 5 is smaller than the inner diameter of the circuit through hole 2. That is, as shown in FIG. 1E, it is preferable that the diameter D ₁ of the inspection via hole 6 is smaller than the diameter D ₂ of the circuit via hole 4. As a result, foreign matter 15 is easily sandwiched between the inspection via hole 6 and the metal layer 8, and the inspection conditions become stricter. Therefore, a double-sided printed wiring board having no foreign matter 15 between the circuit via hole 4 and the circuit pattern 9 can be obtained. It can be distinguished with high probability.

Further, as shown in FIG. 1 (e), it is preferable that the pitch P ₁ between the inspection via holes 6 is smaller than the minimum pitch P ₂ between the circuit via holes 4. Even if it does in this way, since it becomes easy to pinch the foreign material 15 between the via hole 6 for an inspection and the metal layer 8, and inspection conditions become severe, double-sided printing without the foreign material 15 between the via hole 4 for a circuit and the circuit pattern 9 is carried out. The wiring board can be discriminated with a higher probability. Note that the number and position of the circuit via holes 4 vary depending on the desired circuit pattern 9, and the circuit via holes 4 may not be equally spaced, so the smallest pitch among the circuit via holes 4 may be used. One (minimum pitch) P ₂ is selected, and this is used as a comparison target to determine the pitch P ₁ between the inspection via holes 6.

  Further, as shown in FIG. 3 and FIG. 4B, it is preferable to form a daisy pattern 10 (daisy chain) on the periphery of the insulating substrate 1 after the test coupon 7 is formed. The daisy pattern 10 can be formed simultaneously with the formation of the circuit pattern 9 as follows, for example. That is, first, at the stage shown in FIG. 1D, a plurality of through holes (not shown) are arranged in two rows in addition to the inspection through holes 5 in the peripheral portion of the insulating substrate 1. Next, in the step shown in FIG. 1E, the conductive paste 3 is filled in each through hole. Thereafter, through the steps shown in FIG. 1 (f) to FIG. 1 (h), each through hole filled with the conductive paste 3 is connected to one by the metal layer 8 and electrically connected, thereby FIG. A daisy pattern 10 as shown in b) can be obtained. Thus, if the daisy pattern 10 is also formed, the quality of the electrical connectivity between the conductive paste 3 forming the circuit via hole 4 and the metal layer 8 forming the circuit pattern 9 is also confirmed. It is something that can be done.

(Embodiment 2)
In the present embodiment, a double-sided printed wiring board (conductive paste printed wiring board) is manufactured as follows, and its quality can be inspected immediately after manufacturing.

  That is, first, as shown in FIG. 2 (a), a metal foil 16 such as a copper foil is prepared, and a substantially conical circuit bump 17 and an inspection cone are provided on one side of the metal foil 16 as shown in FIG. 2 (b). A plurality of bumps 18 are formed. Any of the bumps 17 and 18 can be formed using a conductive paste 3 such as a silver paste or a copper paste. Note that the circuit bumps 17 are formed at locations other than the peripheral portion of the insulating substrate 1, and the inspection bumps 18 are formed at locations corresponding to the peripheral portion of the insulating substrate 1. . Further, both the bumps 17 and 18 are formed to be substantially the same height and longer than the thickness of the insulating substrate 1.

  Next, as shown in FIG. 2C, the bump forming surface 19 of the metal foil 16 is superimposed on one surface of the insulating substrate 1 and heated and pressed. Then, the circuit bumps 17 and the inspection bumps 18 penetrate the insulating substrate 1, and the tips of the bumps 17 and 18 protrude from the opposite surface of the insulating substrate 1. In addition, as the insulating substrate 1, the thing similar to the thing of Embodiment 1 can be used.

  As described above, in the present embodiment, a work for providing a plurality of circuit through-holes 2 at locations other than the peripheral portion of the insulating substrate 1 (the region 14 where the circuit pattern 9 is formed) and the circuit through-holes 2 are electrically conductive. The operation of filling the conductive paste 3 to form the plurality of circuit via holes 4 can be performed simultaneously. That is, the process corresponding to FIGS. 1D to 1F can be performed by the process shown in FIG. Similarly, the work of providing a plurality of inspection through holes 5 in the peripheral portion of the insulating substrate 1 (the region where the circuit pattern 9 is not formed), and the plurality of inspection through holes 5 filled with the conductive paste 3 The operation of forming the via hole 6 can be performed simultaneously. The test coupon 7 is formed of a plurality of inspection via holes 6. Further, in the present embodiment, since drilling by a drilling machine or the like is not required, foreign matter 15 such as resin smear (for example, glass cloth, PP resin, etc.) is not easily generated.

  Here, the circuit via holes 4 are provided as many as required based on the desired circuit pattern 9, but the inspection via holes 6 are formed in a quadrilateral shape vertically and horizontally as shown in FIG. Provide at intervals. Although FIG. 4A shows three types, the diameter of the inspection via hole 6 is preferably smaller, and the pitch between adjacent inspection via holes 6 is preferably smaller. In 4 (a), the central one is preferable to the left one, and the right one is preferable to the central one. The diameter of the inspection via hole 6 is preferably smaller than the diameter of the circuit via hole 4. These points are as described in the first embodiment. In the present embodiment, the shape of the via hole is not a columnar shape but a conical shape. Therefore, the diameter of the via hole means the diameter of the bottom surface of the cone.

  Next, as shown in FIG. 2D, metal layers 8 are formed on both surfaces of the insulating substrate 1. Here, since the metal layer 8 is already formed on one surface of the insulating substrate 1 with the metal foil 16 as shown in FIG. 2C, the metal foil 16 such as a copper foil is formed on the other surface of the insulating substrate 1. And the remaining metal layer 8 is formed by heating and pressing under vacuum. Here, when the metal foil 16 is disposed, the foreign matter 15 is involved, and the state shown in FIG. 6B may be obtained, but even if such a state is obtained, as described later, The presence of the foreign matter 15 can be confirmed by the method according to the present invention. Examples of the foreign material 15 include glass cloth, PP resin, and the like, dust in the process, proteins derived from human skin, and the like.

  Next, a dry film (not shown) is laminated on the surface of the metal layer 8 shown in FIG. Thereafter, etching is performed using cupric chloride or the like to form a circuit pattern 9 at a location other than the peripheral portion of the insulating substrate 1 as shown in FIG. All the metal layer 8 is removed. The dry film is peeled off using a sodium hydroxide solution or the like after etching.

  As described above, a double-sided printed wiring board (conductive paste printed wiring board) is manufactured. By forming the circuit pattern 9 and removing the metal layer 8 by etching, as shown in FIG. The surface of the conductive paste 3 in the inspection via hole 6 is exposed. Here, since the foreign matter 15 such as glass cloth or PP resin is not removed by etching, if the foreign matter 15 is caught between the conductive paste 3 and the metal layer 8 during the manufacturing process, it is exposed. By observing the surface of the conductive paste 3 in the inspection via hole 6, the presence or absence of the foreign matter 15 can be confirmed. FIG. 5 (plan view) shows the exposed surface of the conductive paste 3 in the inspection via hole 6, FIG. 5 (a) shows a state in which no foreign matter 15 exists, and FIG. 5 (b) shows a foreign matter. An example of a state in which 15 exists is shown.

  When the foreign matter 15 exists between the conductive paste 3 in the inspection via hole 6 and the metal layer 8, the foreign matter 15 also exists between the conductive paste 3 in the circuit via hole 4 and the metal layer 8. Therefore, the presence / absence of the foreign matter 15 between the conductive paste 3 of the circuit via hole 4 and the metal layer 8 is determined based on the result of observing the surface of the conductive paste 3 of the inspection via hole 6. It is something that can be done. That is, as a result of observing the surface of the conductive paste 3 in each inspection via hole 6, as shown in FIG. 5 (a), the conductive paste 3 in the circuit via hole 4 and the metal layer 8 The possibility that foreign matter 15 exists between them is low, and the double-sided printed wiring board can be determined to be a non-defective product as shown in FIG. On the other hand, as a result of observing the surface of the conductive paste 3 in each inspection via hole 6, if any one is in the state shown in FIG. 5B, the conductive paste 3 in the circuit via hole 4, the metal layer 8, The foreign matter 15 is likely to exist between the two, and the double-sided printed wiring board can be determined to be a defective product as shown in FIG.

  As described above, according to the method for inspecting a double-sided printed wiring board according to the present invention, it is confirmed whether or not there is a foreign substance 15 between the circuit via hole 4 and the circuit pattern 9 without destroying the double-sided printed wiring board. It is something that can be done.

Next, in this embodiment, a more preferable form will be described. First, at the stage shown in FIG. 2B, both bumps are preferably formed on the metal foil 16 so that the diameter of the inspection bump 18 is smaller than the diameter of the circuit bump 17. That is, as shown in FIG. 2C, it is preferable that the diameter D ₁ of the inspection via hole 6 is smaller than the diameter D ₂ of the circuit via hole 4. As a result, foreign matter 15 is easily sandwiched between the inspection via hole 6 and the metal layer 8, and the inspection conditions become stricter. Therefore, a double-sided printed wiring board having no foreign matter 15 between the circuit via hole 4 and the circuit pattern 9 can be obtained. It can be distinguished with high probability.

Further, as shown in FIG. 2C, it is preferable that the pitch P ₁ between the inspection via holes 6 is smaller than the minimum pitch P ₂ between the circuit via holes 4. Even if it does in this way, since it becomes easy to pinch the foreign material 15 between the via hole 6 for an inspection and the metal layer 8, and inspection conditions become severe, double-sided printing without the foreign material 15 between the via hole 4 for a circuit and the circuit pattern 9 is carried out. The wiring board can be discriminated with a higher probability. Note that the number and position of the circuit via holes 4 vary depending on the desired circuit pattern 9, and the circuit via holes 4 may not be equally spaced, so the smallest pitch among the circuit via holes 4 may be used. ones select (minimum pitch) P _2, as the object of comparison this is what determines the pitch P ₁ between the inspection via hole 6.

  Further, as shown in FIG. 3 and FIG. 4B, it is preferable to form a daisy pattern 10 (daisy chain) on the periphery of the insulating substrate 1 after the test coupon 7 is formed. The daisy pattern 10 can be formed simultaneously with the formation of the circuit pattern 9 as follows, for example. That is, first, in the stage shown in FIG. 2B, a plurality of conical bumps (not shown) are arranged in two rows in addition to the inspection bumps 18 on the periphery of the insulating substrate 1. These conical bumps also penetrate the insulating substrate 1 as shown in FIG. Thereafter, through the steps shown in FIGS. 2 (d) to 2 (e), a plurality of via holes (not shown) formed by conical bumps are connected by a metal layer 8 to be electrically connected. A daisy pattern 10 as shown in FIG. 4B can be obtained. Thus, if the daisy pattern 10 is also formed, the quality of the electrical connectivity between the conductive paste 3 forming the circuit via hole 4 and the metal layer 8 forming the circuit pattern 9 is also confirmed. It is something that can be done.

  Hereinafter, the present invention will be specifically described by way of examples.

Example 1
First, as shown in FIG. 1A, an FR-4 grade unclad substrate (“R1621” manufactured by Matsushita Electric Works Co., Ltd., thickness 0.1 mm) was prepared as the insulating substrate 1.

  Next, as shown in FIG. 1B, the adhesive layer 12 was formed on both surfaces of the insulating substrate 1. The adhesive layer 12 was formed by applying an epoxy resin to the surface of the insulating substrate 1 with a roll coater and drying it. Drying was performed at 60 ° C. until the tackiness of the adhesive layer 12 disappeared. The thickness of the adhesive layer 12 is 30 μm.

  Next, as shown in FIG.1 (c), the PET film ("T-60" by Toray Industries, Inc., thickness 38 micrometers) was stuck on the surface of the contact bonding layer 12 using the laminator. This sticking was performed under conditions of a temperature of 80 ° C. and a pressure of 0.05 MPa.

  Next, as shown in FIG. 1 (d), 1200 circuit through holes 2 (hole diameter 0.15 mm) are provided in places other than the peripheral portion of the insulating substrate 1, and 2800 pieces are provided in the peripheral portion of the insulating substrate 1. The through-hole 5 for inspection (hole diameter 0.10 mm) was provided. Any through hole was provided using a drilling machine, and after drilling, the inside of any through hole was cleaned with high-pressure air.

  Next, as shown in FIG. 1E, 1200 circuit via holes 4 are formed by filling each circuit through hole 2 with a conductive paste 3, and each test through hole 5 is formed with a conductive paste. 3, a test coupon 7 composed of 2800 inspection via holes 6 was formed. As the conductive paste 3, a paste containing silver as a main component was used. As a method for filling the through holes 2 and 5 with the conductive paste 3, screen printing was employed.

  Next, as shown in FIG. 1F, when the PET film was peeled off, the conductive paste 3 protruded from the surface of the adhesive layer 12 by the thickness of the PET film.

  Next, as shown in FIG. 1G, metal layers 8 were formed on both surfaces of the insulating substrate 1. The metal layer 8 was formed by disposing copper foil on both surfaces of the insulating substrate 1 and heating and pressing it at 180 ° C. for about 1 hour under vacuum.

  Next, a dry film (not shown) was laminated on the surface of the metal layer 8 shown in FIG. Thereafter, etching is performed using cupric chloride to form a circuit pattern 9 at a location other than the peripheral portion of the insulating substrate 1 as shown in FIG. All the metal layer 8 was removed. The dry film was peeled off using a sodium hydroxide solution after etching.

  A double-sided printed wiring board (conductive paste printed wiring board) was produced as described above. Then, when the surface of the exposed 2800 inspection via holes 6 was observed, it was confirmed that no foreign matter 15 existed. Based on this result, it can be determined that there is no foreign matter 15 between the 1200 circuit via holes 4 and the metal layer 8. When the cross section was actually observed, it was confirmed that no foreign material 15 was present.

(Example 2)
A double-sided printed wiring board (conductive paste printed wiring board) was produced in the same manner as in Example 1 except that cleaning with high-pressure air was not intentionally performed after drilling. Then, when the surfaces of the exposed 2800 inspection via holes 6 were observed, it was confirmed that the foreign matter 15 was present on the surfaces of the 35 inspection via holes 6. Based on this result, it can be determined that the foreign matter 15 is also present between the 1200 circuit via holes 4 and the metal layer 8. When the cross section was actually observed, it was confirmed that the foreign material 15 was present between the 15 circuit via holes 4 and the metal layer 8.

An example of embodiment of this invention is shown and (a)-(h) is sectional drawing. The other example of embodiment of this invention is shown, (a)-(e) is sectional drawing. It is a top view which shows an example of a double-sided printed wiring board. It is what expanded a part same as the above, (a) is a top view of an example, (b) is a top view of another example. An example of the via hole for an inspection is shown, (a) is a top view in the state without a foreign material, (b) is a top view in the state with a foreign material. An example of a double-sided printed wiring board is shown, (a) is a sectional view of a non-defective product, and (b) is a sectional view of a defective product.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulating board 2 Through hole for circuit 3 Conductive paste 4 Via hole for circuit 5 Through hole for inspection 6 Via hole for inspection 7 Test coupon 8 Metal layer 9 Circuit pattern 10 Daisy pattern

Claims (4)

  A plurality of circuit through holes are provided at locations other than the peripheral portion of the insulating substrate, and a plurality of circuit via holes are formed by filling each circuit through hole with a conductive paste, and a plurality of circuit via holes are formed in the peripheral portion of the insulating substrate. Formed test coupons consisting of a plurality of inspection via holes by providing inspection through holes at equal intervals in the vertical and horizontal directions and filling each inspection through hole with conductive paste, and then formed metal layers on both sides of the insulating substrate. After that, etching is performed to form a circuit pattern in a portion other than the peripheral portion of the insulating substrate and the metal layer in the peripheral portion of the insulating substrate is removed, and the surface of the conductive paste in the inspection via hole thus exposed is observed. The double-sided printing is characterized in that the presence or absence of foreign matter is confirmed and the presence or absence of foreign matter between the conductive paste of the circuit via hole and the metal layer is determined based on the result. Inspection method of wiring board.   2. The method for inspecting a double-sided printed wiring board according to claim 1, wherein the diameter of the inspection via hole is smaller than the diameter of the circuit via hole.   3. The method for inspecting a double-sided printed wiring board according to claim 1, wherein a pitch between the inspection via holes is smaller than a minimum pitch between the circuit via holes.   4. The double-sided printed wiring board inspection method according to claim 1, wherein a daisy pattern is formed on a peripheral portion of the insulating substrate.

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