JP6248749B2 - Method for forming multilayer wiring structure and wiring board - Google Patents

Description

  The present invention relates to a method for forming a multilayer wiring structure in which wirings and vias are formed using metal ink, and a wiring board.

  Many wiring boards on which electronic components are mounted have a multilayer wiring structure. In recent years, a method for forming a multilayer wiring structure using an ink jet printer has been developed.

  In a general method for forming a multilayer wiring structure using an ink jet printer, the following steps are performed in order.

  First, using an ink jet printer, a desired wiring pattern is printed on a substrate with ink containing fine metal particles (hereinafter referred to as “metal ink”). Thereafter, heat treatment is performed to fire the metal ink. As a result, the metal particles in the ink are bonded to each other, and a wiring (first layer wiring) having good conductivity is obtained.

  Next, an ink containing an insulating material (hereinafter referred to as “insulating ink”) is printed on the wiring and the substrate using an inkjet printer. At this time, the insulating ink is prevented from adhering to the portion to be the contact hole. After the insulating ink is printed, the insulating ink is baked by performing a heat treatment. Thereby, an insulating layer having a contact hole at a predetermined position is obtained.

  Next, after filling the contact hole with metal ink using an ink jet printer, heat treatment is performed to fire the metal ink. As a result, the metal particles in the ink filled in the contact hole are combined to form a via.

  Next, a desired wiring pattern is printed on the insulating layer and the via by metal ink using an inkjet printer. Thereafter, heat treatment is performed to fire the metal ink. Thereby, the wiring of the second layer is obtained.

  In this way, a multilayer wiring structure can be obtained by repeatedly performing printing and firing of metal ink and printing and firing of insulating ink.

JP 2008-294244 A JP 2006-32535 A

  It is an object of the present invention to provide a method for forming a multilayer wiring structure that uses a metal ink to form a multilayer wiring structure having high wiring shape stability and high reliability of electrical connection between a via and a wiring.

  According to one aspect of the disclosed technology, a step of forming a first wiring on a substrate, a step of forming an insulating layer having a contact hole on the substrate and the first wiring, and the contact Filling the hole with metal ink to form a via; depositing metal ink on the insulating layer; surrounding the via away from the second wiring and the via; Forming a bank connected to the wiring, attaching a metal ink on the via, forming a via protective film separated from the bank, attaching a metal ink to the inside of the bank, and There is provided a method for forming a multilayer wiring structure including a step of forming a cover film connecting the via protection film and the bank.

  According to the method for forming a multilayer wiring structure according to the above aspect, a multilayer wiring structure having high wiring shape stability and high reliability of electrical connection between the via and the wiring can be obtained.

FIG. 1 is a flowchart illustrating a method for forming a multilayer wiring structure according to an embodiment. FIG. 2 is a diagram (part 1) illustrating the method for forming the multilayer wiring structure according to the embodiment. FIG. 3 is a diagram (part 2) illustrating the method for forming the multilayer wiring structure according to the embodiment. FIG. 4 is a diagram (part 3) illustrating the method for forming the multilayer wiring structure according to the embodiment. FIG. 5 is a diagram (part 4) illustrating the method for forming the multilayer wiring structure according to the embodiment. FIG. 6 is a diagram (No. 5) illustrating the method for forming the multilayer wiring structure according to the embodiment. FIG. 7 is a view (No. 6) illustrating the method for forming the multilayer wiring structure according to the embodiment. FIG. 8 is a schematic perspective view showing an example of a wiring board having a multilayer wiring structure formed by the method of the embodiment.

  The general method for forming a multilayer wiring structure using the above-described ink jet printer has the following problems.

  That is, the via formed by the metal ink has a fine gap between the metal particles. For this reason, the next time the wiring pattern is printed, the metal ink adhering to the vicinity of the via is absorbed into the via by capillary action, which causes a connection failure between the via and the wiring. There are things to do.

  In order to avoid such a problem, it is conceivable to increase the amount of metal ink applied when printing the wiring pattern. However, since the amount of ink absorbed in the via changes depending on the size of the via and the firing conditions, increasing the amount of metal ink applied when printing the wiring pattern results in large variations in the width and thickness of the wiring. As a result, the shape stability of the wiring is lowered.

  In addition, in order to prevent the metal ink from spreading out, a pattern (hereinafter referred to as “bank”) surrounding a predetermined area is formed with the metal ink, and after the metal ink is baked, the metal ink is printed again on the entire inner surface of the bank. A method has been proposed. It is conceivable to form a connection portion between a wiring and a via using this method. That is, on the insulating layer, a wiring and a bank connected to the wiring and surrounding the via are formed. Thereafter, metal ink is printed on the inner side of the bank to electrically connect the wiring and the via.

  However, when the above method is actually performed, the density of the metal particles increases at the outer edge of the ink applied to the inner side of the bank, and the coffee stain phenomenon occurs in which the density of the metal particles decreases at the center. The connection resistance between the two becomes high.

  In the following embodiments, in a method for forming a multilayer wiring structure in which wiring and vias are formed using metal ink, formation of the multilayer wiring structure having high wiring shape stability and high reliability of electrical connection between the via and the wiring. A method will be described.

(Embodiment)
FIG. 1 is a flowchart illustrating a method for forming a multilayer wiring structure according to an embodiment. 2 to 7 are a cross-sectional view and a plan view showing a method for forming the multilayer wiring structure. 2 to 7, (a) schematically shows a plane in the vicinity of the via formation region, and (b) schematically shows a cross section in the vicinity of the via formation region.

  First, in step S11, using an ink jet printer, as shown in FIGS. 2A and 2B, metal ink is adhered on the insulating substrate 11 in a predetermined pattern. Thereafter, heat treatment is performed to fire the metal ink, and the first-layer wiring 12 is formed.

  The metal ink contains metal nanoparticles such as gold (Au), silver (Ag), or copper (Cu), a dispersant for preventing secondary aggregation of the metal nanoparticles, and an organic solvent. . In the present embodiment, a metal ink containing silver nanoparticles is used. In the step of firing the metal ink, for example, heat treatment is performed at a temperature of about 150 ° C. for about 30 minutes.

  Next, in step S12, an insulating ink is attached onto the substrate 11 and the wiring 12 using an ink jet printer, and then the insulating ink is baked, as shown in FIGS. 3A and 3B. Thus, the insulating layer 13 is formed. At this time, the contact hole 13a is formed by preventing the insulating ink from adhering to the portion to be the via.

  As the insulating ink, for example, an ink containing a polyimide precursor and a solvent can be used. In the step of baking the insulating ink, heat treatment is performed at a temperature and time corresponding to the type of the insulating ink.

  Next, in step S13, metal ink is filled into the contact hole 13a using an ink jet printer. Thereafter, in step S14, the metal ink filled in the contact hole 13a is baked to form the via 14 as shown in FIGS. 4 (a) and 4 (b). In the step of firing the metal ink, heat treatment is performed at a temperature and time corresponding to the type of insulating ink. For example, heat treatment (baking of metal ink) is performed at a temperature of 150 ° C. for 30 minutes.

  Next, in step S15, a metal ink is deposited on the insulating layer 13 using an ink jet printer, and then the metal ink is dried, and as shown in FIGS. 5A and 5B, the wiring 15a and A bank 15b is formed. The wiring 15a is formed in a desired pattern. The bank 15 b is formed so as to connect to the wiring 15 a and surround the via 15. However, it is important that the bank 15 b does not contact the via 14.

  Next, in step S16, a metal ink is attached on the via 14 and the insulating layer 13 in the vicinity thereof using an ink jet printer, and then the metal ink is dried, as shown in FIGS. 6 (a) and 6 (b). Thus, the via protection film 16 is formed. It is important to form the via protective film 16 so as not to contact the bank 15b.

  A cover film 17 is formed on the via protection film 16 as described later. It is preferable to make the thickness of the via protection film 16 smaller than the thickness of the bank 15b so that the upper surface of the cover film 17 and the upper surface of the bank 15b are substantially the same height. For this purpose, the amount of metal ink applied per unit area when forming the via protection film 16 may be made smaller than the amount of metal ink applied per unit area when forming the wiring 15a and the bank 15b.

  In this step, the metal ink soaks into the gaps between the metal particles in the via 14 and the density of the metal particles in the upper portion of the via 14 increases. In FIG. 6B, the portion of the via 14 where the density of metal particles is high is indicated by reference numeral 14a.

  The via protection film 16 may be of a size that covers the entire upper side of the via 14, but may be slightly larger than the via 14 in consideration of misalignment, as shown in FIGS. 6A and 6B. preferable.

  Next, in step S17, metal ink is applied to the entire inner surface of the bank 15b using an ink jet printer. Thereafter, the metal ink is dried to form a cover film 17 as shown in FIGS. Via protection film 16 and bank 15b communicate with each other through cover film 17.

  Next, in step S18, for example, heat treatment (baking of the metal ink) is performed at a temperature of 150 ° C. for about 30 minutes. By this heat treatment, the metal particles in the wiring 15a, the bank 15b, the via protective film 16 and the cover film 17 are combined to give good conductivity.

  Next, in step S19, it is determined whether or not the formation of a predetermined number of wiring layers is completed. When it is determined that the formation of the predetermined number of wiring layers has not been completed (in the case of NO), the process returns to step S12 and the processes up to step S18 are performed. On the other hand, in step S19, when the formation of the predetermined number of wiring layers is completed (in the case of YES), the process ends.

  In this way, a wiring board having a multilayer wiring structure is completed. FIG. 8 is a schematic perspective view showing an example of a wiring board 20 having a multilayer wiring structure formed by the method of the present embodiment.

  In FIG. 7, the first layer wiring is indicated by reference numeral 12, and the second and subsequent wirings are all indicated by reference numeral 15a. Further, the first and second insulating layers are both denoted by reference numeral 13.

  In the present embodiment, when forming the via protective film 16, the metal ink soaks into the via 14, and the density of the metal particles on the via 14 increases (see FIG. 6B). For this reason, when applying the metal ink to be the cover film 17, the metal ink is not easily absorbed by the via 14, and a good electrical connection is obtained between the cover film 17 and the via 14.

  In the present embodiment, the wiring 15a, the bank 15b, the via protective film 16 and the cover film 17 are fired simultaneously. Therefore, the bonding of metal particles between the via 14 and the via protective film 16, between the via protective film 16 and the cover film 17, between the cover film 17 and the bank 15b, and between the bank 15b and the wiring 15a. High strength.

  Furthermore, in this embodiment, the via 14 and the wiring 15b are connected via the via protective film 16, the cover film 17, and the bank 15b. For this reason, the width and thickness of the wiring 15a do not change depending on the size of the via 14 and the state of the metal particles, and the shape stability of the wiring is high.

  Combined with these, according to the method for forming a multilayer wiring structure of the present embodiment, a multilayer wiring board with high reliability of electrical connection between vias and wiring and high wiring shape stability. Is obtained.

  The following additional notes are disclosed with respect to the above embodiments.

(Appendix 1) forming a first wiring on a substrate;
Forming an insulating layer having a contact hole on the substrate and the first wiring;
Filling the contact hole with metal ink to form a via;
Metal ink is deposited on the insulating layer, and a second wiring and a via that is spaced apart from the via and surrounds the via and connected to the second wiring; and
Attaching a metal ink on the via to form a via protective film separated from the bank;
Forming a cover film connecting the via protective film and the bank by attaching metal ink to the inside of the bank.

  (Additional remark 2) After the process of forming the said cover film, it has the heat processing process which bakes the metal particle in the said 2nd wiring, the said bank, the said via | veer protective film, and the said cover film, A method for forming a multilayer wiring structure as described.

  (Supplementary note 3) The method for forming a multilayer wiring structure according to supplementary note 1 or 2, wherein the via protective film covers not only the via but also the insulating layer around the via.

  (Additional remark 4) The formation method of the multilayer wiring structure of any one of Additional remark 1 thru | or 3 characterized by the thickness of the said via protective film being thinner than the thickness of the said bank.

  (Appendix 5) The step of forming the via, the step of forming the second wiring and the bank, the step of forming the via protective film, and the step of forming the cover film all dry the metal ink. The method for forming a multilayer wiring structure according to any one of appendices 1 to 4, further comprising a step.

  (Appendix 6) Any one of appendices 1 to 5, wherein the via, the second wiring, the bank, the via protective film, and the cover film are all formed using an ink jet printer. A method for forming a multilayer wiring structure according to the item.

(Appendix 7) An insulating layer provided with a contact hole;
A via made of a conductor filled in the contact hole;
Wiring formed on the insulating layer;
A bank disposed around the via and electrically connected to the wiring;
A conductive via protective film formed on the via;
A wiring board comprising: a cover film formed on the via protective film and electrically connecting the via protective film and the bank.

  (Additional remark 8) The said via | veer, the said wiring, the said bank, the said via protective film, and the said cover film | membrane are all what baked metal ink, The wiring board of Additional remark 7 characterized by the above-mentioned.

  DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 12 ... Wiring, 13 ... Insulating layer, 13a ... Contact hole, 14 ... Via, 15a ... Wiring, 15b ... Bank, 16 ... Via protective film, 17 ... Cover film, 20 ... Wiring board.

Claims (4)

Forming a first wiring on a substrate;
Forming an insulating layer having a contact hole on the substrate and the first wiring;
Filling the contact hole with metal ink to form a via;
Metal ink is deposited on the insulating layer, and a second wiring and a via that is spaced apart from the via and surrounds the via and connected to the second wiring; and
Attaching a metal ink on the via to form a via protective film separated from the bank;
Forming a cover film connecting the via protective film and the bank by attaching metal ink to the inside of the bank.   2. The multilayer according to claim 1, further comprising a heat treatment step of firing metal particles in the second wiring, the bank, the via protective film, and the cover film after the step of forming the cover film. A method for forming a wiring structure.   3. The multilayer wiring structure according to claim 1, wherein the via, the second wiring, the bank, the via protective film, and the cover film are all formed using an inkjet printer. Forming method. An insulating layer provided with contact holes;
A via made of a conductor filled in the contact hole;
Wiring formed on the insulating layer;
A bank disposed around the via and electrically connected to the wiring;
A conductive via protective film formed on the via;
A cover film formed on the via protective film and electrically connecting the via protective film and the bank ;
The via, the wiring, the bank, the via protective film, and the cover film are all baked with metal ink, and the via and the via protective film are separated from the bank. Wiring board.

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