JP2013179114A - Substrate for flexible printed wiring, film for semiconductor carrier and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate for flexible printed wiring in which metal residue is suppressed after etching process while suppressing occurrence of migration, and to provide a film for semiconductor carrier and a semiconductor device using the substrate.SOLUTION: In the substrate for flexible printed wiring where a metal deposition layer is provided on one or both surfaces of a plastic film 7, and a conductive metal layer is laminated on the metal deposition layer by electric plating, the metal deposition layer consists of at least one layer containing nickel and chromium as main components and a layer (S layer) containing copper as a main component, and the summation of XY/100 is 0.9 or more and less than 5, where X (nm) is the thickness of each layer containing nickel and chromium as main components, and Y (wt.%) is the chromium content.

Description

  The present invention relates to a substrate for flexible printed wiring using a metal vapor deposition layer / conductive metal layer laminated film, a film for a semiconductor carrier having a circuit pattern formed on the substrate, and an element such as an IC or a capacitor on the film for the semiconductor carrier. The present invention relates to a mounted semiconductor device.

  Conventionally, a flexible printed wiring board having a three-layer structure in which a plastic film as a support and a copper foil as a conductor layer are bonded via an adhesive layer is known as a flexible printed wiring board. This three-layer structure type flexible printed wiring board has a problem that the dimensional change after processing is large because the heat resistance of the adhesive used is inferior to that of a plastic film, and the thickness of the copper foil used is usually 10 μm. As described above, there is a drawback that patterning for high-density wiring with a narrow pitch is difficult. On the other hand, two layers in which a metal layer as a conductor layer is formed on a plastic film by a wet plating method or a dry plating method (for example, a vacuum deposition method, a sputtering method, an ion plating method, etc.) without using an adhesive. Structural type flexible printed wiring boards are also known. The metal layer of the flexible printed wiring board of this two-layer structure type has nickel and chromium as main components between a layer mainly composed of copper as a conductor layer serving as a circuit and a plastic film serving as a support. A structure in which a layer is provided is widely used. The flexible printed wiring board of this two-layer structure type allows a high-density wiring because the conductor layer can be made thinner than 10 μm, but a severe heat load test (for example, temperature 85 ° C., humidity 85%, 1000 hours), a phenomenon called migration that becomes prominent in a high-temperature and high-humidity environment causes a problem that insulation between wires is impaired and a circuit is short-circuited. Migration is that when an electric field is applied to a metal in a high temperature and high humidity atmosphere, the metal atoms are ionized and move in the direction of the electric field.

  In order to solve this problem, an invention relating to a layer mainly composed of nickel and chromium has been implemented (Patent Document 1).

Japanese Patent No. 455080

  The invention of Patent Document 1 suppresses the occurrence of migration by increasing the chromium content in a layer mainly composed of nickel and chromium. When the chromium fraction is increased, metal residue increases between the wirings formed in the etching process for forming a circuit on the flexible printed wiring board, and the insulation between the wirings is impaired due to this residue. There was a problem that the possibility of a short circuit was increased.

  The present invention relates to a flexible printed wiring board capable of suppressing metal residues after an etching process for forming a circuit and suppressing occurrence of migration, a film for a semiconductor carrier using the substrate, and a semiconductor device. provide.

  The flexible printed wiring board of the present invention is formed by providing a metal vapor deposition layer on one or both sides of a plastic film, and laminating a layer (M layer) containing copper as a main component by electroplating on the metal vapor deposition layer. In a flexible printed wiring board, the metal vapor deposition layer is composed of one or more layers containing nickel and chromium as main components and a layer containing copper as a main component (S layer). When the film thickness is X (nm) and the chromium content is Y (wt%) (may be described as wt%), the sum of XY / 100 is 0.9 or more and less than 5. It is characterized by that.

  The flexible printed wiring board of the present invention can achieve both suppression of metal residues and suppression of migration by regulating the film thickness and chromium content of a layer mainly composed of nickel and chromium. And the reliability of the film for semiconductor carriers and a semiconductor device can be improved by using the board | substrate for flexible printed wirings of this invention.

It is an example of the circuit pattern used in the test which confirms the presence or absence of migration. It is a microscope picture which shows an example of the generation | occurrence | production state of migration.

  Examples of the plastic film as the substrate used in the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, polyethylene-α, β-bis (2-chlorophenoxyethane-4,4′-dicarboxylate) and the like. Polyester, polyphenylene sulfide, polyethersulfone, polyetheretherketone, aromatic polyamide, polyarylate, polyimide, polyamideimide, polyetherimide, polyparazic acid, polyoxadiazole, and halogen-substituted or methyl-substituted products thereof The film which consists of, etc. are mentioned. Among them, the polyimide film is most preferably used because of its high heat resistance and small dimensional change in the wet etching process for forming a circuit pattern. Moreover, said plastic film may contain these copolymers and another organic polymer. Known additives such as lubricants and plasticizers may be added to these plastic films.

  Further, regarding the plastic film, an unstretched film obtained by melt-extruding a thermoplastic polymer, or a film obtained by stretching and orienting an unstretched film obtained by solution casting is preferably used because the mechanical properties are improved.

  The thickness of the plastic film as the substrate is preferably about 6 to 125 μm, and particularly preferably 12 to 50 μm. If the plastic film is too thin, the metal strength and wiring processing become difficult due to low mechanical strength, and problems that require a reinforcing film are likely to occur, and if it is too thick, the bendability that is a feature of flexible printed wiring boards is likely to occur. It is not preferable because it is damaged.

  In the present invention, prior to forming the conductive metal layer by electroplating or the like, a metal vapor deposition layer is formed on one or both surfaces of the plastic film by vacuum vapor deposition or sputtering. This metal vapor deposition layer is composed of one or more layers containing nickel and chromium as main components and a layer containing copper as a main component (S layer). Here, when the film thickness of the layer mainly composed of nickel and chromium is X (nm) and the chromium content is Y (wt%), the sum of XY / 100 may be 0.9 or more and less than 5. is necessary. If it is less than 0.9, migration occurs, so it cannot be used for a film for a semiconductor carrier or a semiconductor device. In the case of 5 or more, a metal residue increases between the wirings formed in the etching process for forming a circuit, and the circuit is short-circuited due to this residue, so it cannot be used for a film for a semiconductor carrier or a semiconductor device. . The layer mainly composed of nickel and chromium is not limited to a single layer having a constant chromium content, and may be a plurality of layers having different chromium contents. In this case, if the sum of XY / 100 is 0.9 or more and less than 5, the effect of the present invention can be achieved.

  In order to further enhance the effect of the invention when the layer mainly composed of nickel and chromium is one layer, in addition to the above XY / 100 being 0.9 or more and less than 5, the chromium content is 3 It is preferable to set the weight to 15% by weight or more. A chromium content of 3% by weight or more is preferable because the effect of suppressing migration by chromium is increased. Further, it is preferable that the chromium content is less than 15% by weight because metal residues are reduced between the wirings formed in the etching process for forming a circuit.

  When the layer mainly composed of nickel and chromium is composed of two layers, the chromium content of one layer is 15% by weight to 30% by weight, the thickness of the layer is 5 nm to less than 7 nm, and the other layer It is preferable that the chromium content of the composition is 3 wt% or more and 10 wt% or less, and the total of XY / 100 is 0.9 or more and less than 5.

  Either of these two layers may be a layer in contact with the plastic film. In either case, the amount of metal residue after the etching process can be reduced and the occurrence of migration can be suppressed.

  On the metal vapor deposition layer thus configured, a layer (M layer) containing copper as a main component is laminated by electroplating. In order to form an electronic circuit and function as a semiconductor device, the film thickness of the copper-based layer (M layer) is preferably 5 μm to 20 μm, and electroplating is necessary to form a copper layer of this film thickness. The method is preferably used. There are copper sulfate bath, copper pyrophosphate bath, copper cyanide bath, etc. as plating baths used in the electroplating method, but copper sulfate baths that can increase the smoothness of the plating film are preferably used for wiring board applications. .

  A known method can be used as a method for producing a film for a semiconductor carrier from the flexible printed wiring board of the present invention. The wiring circuit is patterned using a photolithographic method, and pure tin is formed in a thickness of 0.15 to 0.25 μm by electroless tin plating. Then, a solder resist is formed in a required part and it is set as the film for semiconductor carriers. Thereafter, the IC is surface-mounted to obtain a semiconductor device. If necessary, resistors and capacitors may be surface mounted. Furthermore, it is possible to use underfill in order to ensure connection reliability.

  Each characteristic was evaluated by the method described below.

(1) Presence / absence of migration Comb-like electrodes 1 and 2 as shown in FIG. 1 were produced on a flexible printed wiring board by wet etching. In the part where the comb-shaped electrodes 1 and 2 are adjacent, the width 3 of the comb-shaped electrode is 15 μm, and the space 4 between the electrodes is 15 μm. The comb electrode 1 was connected to the power source from the portion 5 and the comb electrode 2 was connected to the power source from the portion 6.
A voltage of 60 V was applied between the comb electrodes 1 and 2 at a constant temperature and humidity set to a temperature of 85 ° C. and a humidity of 85%, and a thermal load test was performed. After 1000 hours, the sample was taken out and observed with an optical microscope using transmitted light (magnification 200 times). FIG. 2 shows the state of occurrence of migration. If there was no migration at a load time of 1000 hours, no problem occurred in practice, but a test with a load time of 2000 hours was also conducted to compare the suppression effect.

(2) Metal residues between wiring Etching the copper layer (M layer) and metal deposition layer of the flexible printed wiring board using a ferric chloride aqueous solution (37% by weight) at a liquid temperature of 30 ° C. and a processing time of 35 seconds. The amount of the metal residue between the wirings was evaluated by the following method.
The sample was immersed in heated aqua regia (a liquid in which 35% hydrochloric acid and 60% nitric acid were mixed at a volume ratio of 3: 1) to dissolve the metal layer. The solution after standing to cool was introduced into an ICP emission analyzer (OPTIMA4300DV manufactured by PerkinElmer), and nickel and chromium were quantified. If nickel was less than 5 μg / cm ² and chromium was less than 1 μg / cm ² , it was judged as “good” and the others were judged as “bad”.

(3) Thickness of Nichrome Layer and Ratio of Constituent Elements The plastic film, which is a support for the flexible printed wiring board, was dissolved and removed to expose the plastic film side interface of the metal vapor deposition layer mainly composed of nickel and chromium. For example, in the case of a substrate for flexible wiring using a polyimide film as a plastic film, the polyimide film can be removed with a heated ethylenediamine / hydrazine mixed solution.
The constituent element ratio of the metal surface mainly composed of nickel and chromium thus exposed was measured by Auger electron spectroscopy.
The measuring device was PHI-670 manufactured by PerkinElmer. The measurement conditions were an acceleration voltage of 10 kV, a sample current of 20 nA, a beam diameter of 80 nmφ, and a sample tilt angle of 30 degrees. Moreover, the ion etching conditions for performing the analysis of a depth direction used argon ion, and performed it with the acceleration voltage of 2 kV and the sample angle of 30 degree | times. The measurement result is a graph in which the number of electrons having energy attributed to the target element is plotted against the sputtering time. The etching rate was calculated | required with the sample of the same composition as the vapor deposition layer to measure, and the film thickness of the metal vapor deposition layer was calculated | required from sputtering time and the etching rate.

Example 1
Plasma treatment was performed on one side of a polyimide film “Kapton” EN (registered trademark of DuPont, USA) having a thickness of 38 μm and a width of 524 mm. The plasma treatment was performed with a RF power of 2.0 kW by introducing nitrogen gas to 0.3 Pa in a vacuum chamber having a vacuum degree of 2 × 10 ⁻³ Pa. Next, using a target of 5% by weight of chromium and 95% by weight of nickel, sputtering deposition is performed on the plasma-treated surface of the polyimide film to form a nickel chromium deposited layer having a film thickness of 25 nm. did. Furthermore, copper having a purity of 99.99% by weight was sputter-deposited on a layer containing nickel and chromium as main components to form a copper layer having a thickness of 80 nm, thereby forming a metal vapor-deposited layer. Thereafter, electroplating was performed to form a copper layer having a thickness of 8 μm on the metal vapor-deposited layer, and a flexible printed wiring board was produced.
The metal layer of this flexible printed wiring board was etched to produce a wiring pattern with a pitch of 30 μm (width 15 μm, space 15 μm), which was used as a migration observation sample. Etching was performed using a ferric chloride aqueous solution (37% by weight) as the etching solution at a liquid temperature of 30 ° C. and a treatment time of 35 seconds. The metal residue quantification sample was etched under the same conditions without producing a wiring pattern.

(Example 2)
The same plasma treatment as in Example 1 was performed, and then, using a 20 wt% chromium 80 wt% target, sputtering deposition was performed on the plasma treated surface of the polyimide film to form a 6 nm thick nickel chromium vapor deposition layer. On this nickel chromium vapor deposition layer, sputter deposition was continuously performed using a target of 5 wt% chromium and 95 wt% nickel to form a nickel chromium vapor deposition layer having a film thickness of 11 nm, and further copper having a purity of 99.99 wt%. Was sputter-deposited on a metal vapor deposition layer mainly composed of nickel and chromium to form a copper vapor deposition layer having a thickness of 80 nm. Thereafter, similarly to Example 1, electroplating with a thickness of 8 μm was performed, a copper layer was formed on the metal vapor-deposited layer, and a flexible printed wiring board was produced.

(Example 3)
The same plasma treatment as in Example 1 was performed, and then a nickel chromium vapor deposition layer having a thickness of 11 nm was formed by sputtering deposition on the plasma treatment surface of the polyimide film using a target of 5 wt% chromium and 95 wt% nickel. On this nickel chromium vapor deposition layer, sputter deposition was continuously performed using a target of 20 wt% chromium and 80 wt% nickel to form a nickel chromium vapor deposition layer having a film thickness of 6 nm, and further copper having a purity of 99.99 wt%. Was sputter-deposited on a metal vapor deposition layer mainly composed of nickel and chromium to form a copper vapor deposition layer having a thickness of 80 nm. Thereafter, similarly to Example 1, electroplating with a film thickness of 8 μm was performed, a copper layer was formed on the metal vapor-deposited layer, and a flexible printed wiring board was produced.

Example 4
The same plasma treatment as in Example 1 was performed, and then a nickel chromium vapor deposition layer having a film thickness of 22 nm was formed by sputtering deposition on the plasma treatment surface of the polyimide film using a target of 5 wt% chromium and 95 wt% nickel. Thereafter, a nickel chromium vapor deposition layer having a film thickness of 6 nm, a copper vapor deposition layer having a film thickness of 80 nm, and a copper plating layer having a film thickness of 8 μm were formed in this order in the same manner as in Example 3 to produce a flexible printed wiring board. .

(Example 5)
The same plasma treatment as in Example 1 was performed, and then a nickel chromium vapor deposition layer having a film thickness of 6 nm was formed by sputtering deposition on the plasma treatment surface of the polyimide film using a target of chromium 20 wt% nickel 80 wt%. Furthermore, copper having a purity of 99.99% by weight was sputter-deposited on a metal vapor deposition layer mainly composed of nickel and chromium to form a copper vapor deposition layer having a thickness of 80 nm. Thereafter, similarly to Example 1, electroplating with a film thickness of 8 μm was performed, a copper layer was formed on the metal vapor-deposited layer, and a flexible printed wiring board was produced.

(Example 6)
The same plasma treatment as in Example 1 was performed, and then a nickel chromium vapor deposition layer having a thickness of 25 nm was formed by sputtering deposition on the plasma treatment surface of the polyimide film using a target of 14 wt% chromium and 86 wt% nickel. Furthermore, copper having a purity of 99.99% by weight was sputter-deposited on a metal vapor deposition layer mainly composed of nickel and chromium to form a copper vapor deposition layer having a thickness of 80 nm. Thereafter, similarly to Example 1, electroplating with a film thickness of 8 μm was performed, a copper layer was formed on the metal vapor-deposited layer, and a flexible printed wiring board was produced.
(Example 7)
The same plasma treatment as in Example 1 was performed, and then a nickel chromium vapor deposition layer having a thickness of 50 nm was formed by sputtering deposition on the plasma treatment surface of the polyimide film using a target of 2 wt% chromium and 98 wt% nickel. Furthermore, copper having a purity of 99.99% by weight was sputter-deposited on a metal vapor deposition layer mainly composed of nickel and chromium to form a copper vapor deposition layer having a thickness of 80 nm. Thereafter, similarly to Example 1, electroplating with a film thickness of 8 μm was performed, a copper layer was formed on the metal vapor-deposited layer, and a flexible printed wiring board was produced.

(Comparative Example 1)
The same plasma treatment as in Example 1 was performed, and then a nickel chromium vapor deposition layer having a film thickness of 12 nm was formed by sputtering deposition on the plasma treatment surface of the polyimide film using a 5 wt% chromium 95 wt% target. And a metal vapor deposition layer mainly composed of chromium. Furthermore, copper having a purity of 99.99% by weight was sputter-deposited on a metal vapor deposition layer mainly composed of nickel and chromium to form a copper vapor deposition layer having a thickness of 80 nm. Thereafter, similarly to Example 1, electroplating with a film thickness of 8 μm was performed, a conductive metal layer was formed on the metal vapor-deposited layer, and a flexible printed wiring board was produced.

(Comparative Example 2)
The same plasma treatment as in Example 1 was performed, and then a nickel chromium vapor deposition layer having a film thickness of 25 nm was formed by sputtering deposition on the plasma treatment surface of the polyimide film using a target of 20 wt% chromium and 80 wt% nickel. And a metal vapor deposition layer mainly composed of chromium. Furthermore, copper having a purity of 99.99% by weight was sputter-deposited on a metal vapor deposition layer mainly composed of nickel and chromium to form a copper vapor deposition layer having a thickness of 80 nm. Thereafter, similarly to Example 1, electroplating with a film thickness of 8 μm was performed, a conductive metal layer was formed on the metal vapor-deposited layer, and a flexible printed wiring board was produced.

1, 2 Comb electrodes.
3 Width of electrode 4 Space between electrodes 5 and 6 Portion connected to power supply
7 Plastic film 8 Migration

Claims (6)

In a substrate for flexible printed wiring, in which a metal vapor deposition layer is provided on one or both sides of a plastic film, and a layer mainly composed of copper (M layer) is laminated on the metal vapor deposition layer by electroplating. The layer is composed of one or more layers containing nickel and chromium as main components and a layer (S layer) containing copper as a main component (S layer). ), A flexible printed wiring board, wherein the total of XY / 100 is 0.9 or more and less than 5 when the chromium content is Y (% by weight). The layer of nickel and chromium as main components of the metal vapor deposition layer is composed of one layer, and the chromium content of the layer of nickel and chromium as main components is 3 wt% or more and less than 15 wt%. 2. The flexible printed wiring board according to 1. The metal-deposited layer composed mainly of nickel and chromium consists of two layers, and the chromium content of the layer composed mainly of nickel and chromium in contact with the plastic film (N1 layer) is 15 wt% or more and 30 wt% or less, The N1 layer has a film thickness of 5 nm or more and less than 7 nm, and the chromium content of the layer mainly composed of nickel and chromium (N2 layer) in contact with the layer mainly composed of copper (S layer) is 3% by weight or more. The flexible printed wiring board according to claim 1, wherein the substrate is 10% by weight or less, and is laminated in the order of N1, N2, S, and M layers from the layer in contact with the plastic film. The metal vapor deposition layer is composed of two layers composed mainly of nickel and chromium, and the chromium content of the layer composed mainly of nickel and chromium (N1 layer) in contact with the plastic film is 3 wt% or more and 10 wt% or less. And the chromium content of the layer mainly composed of nickel and chromium (N2 layer) in contact with the layer mainly composed of copper (S layer) is 15 wt% or more and 30 wt% or less, and the film thickness of the N2 layer is The flexible printed wiring board according to claim 1, wherein the substrate is laminated in the order of N1 layer, N2 layer, S layer, and M layer from a layer that is 5 nm or more and less than 7 nm in contact with the plastic film. The film for semiconductor carriers formed using the board | substrate for flexible printed wiring in any one of Claims 1-4. A semiconductor device using the semiconductor carrier film according to claim 5.