JPS5816592A - Printed circuit board and metal-lined laminated board preformed product and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to lamination technology. More particularly, the present invention relates to novel printed circuit boards and metal clad laminate intermediate products, and to novel methods of manufacturing such printed circuit boards and intermediate products.

The present invention was made by Eric Lifshin, Joseph Dee Carcioli, Steven Jay Schroeder, and Joe Wong.
Joseph D, Cargioli, 5tep
hen J, 5chroner & Joe W
No. 180,341 entitled Transfer Lamination of Vapor Deposited Foils, Methods and Products, filed on August 22, 1980, in the name of Co., Ltd. . This patent application discloses the idea of creating an extremely smooth, virtually pinhole-free, ultrafine-grained copper surface on a copper-clad laminate by applying an ultra-thin initial copper coating according to a vapor deposition technique. .

The present invention was also made in 1980 in the name of the above four co-inventors.
Also related to the invention is U.S. patent application Ser. This patent application discloses the idea of providing chemically bonded copper clad laminates using thin films of materials selected from several metals, aluminum oxide and silicon oxide.

As used herein, the term "carrier" refers to aluminum sheet materials and other metals and plastics having a thickness such that they can withstand a series of processing steps and can be rolled up for storage or transportation. Similarly, consisting of
It covers all kinds of sheet materials. Examples of the above plastics include '? DuPont products known as MVlar and Apton and the present invention are associated with resistance to processing humidity and strength in the deposition humidity of the copper layer and in peeling the copper-clad laminate product from the carrier sheet. Other organic polymeric materials of equivalent flexibility may be mentioned that have the necessary inertness and bonding properties to the release agent coating to ensure adhesion to the coating.

Similarly, [Removal agent! &R means an oxide in which the diffusivity of copper atoms is negligible under temperature and time conditions corresponding to 175° C. and 1 atm. It also shows that copper and other metals deposited as coatings do not exhibit as strong adhesion to aluminum and other carrier sheet materials as they do to aluminum and other carrier sheet materials, and under manufacturing or use conditions, copper coatings and aluminum sheets or other carrier sheet It also refers to substances that help prevent interdiffusion or reaction with.

“Polar IJ refers to a thickness of less than about 16 microns.

"Membrane" and "foil" refer to an ultra-thin coating and a combination of a darning coating and one or more ultra-thin coatings, respectively.

"Vapour deposition" refers to sputtering, physical vapor deposition (i.e. electron beam evaporation, induction heating evaporation and resistance heating evaporation)
, chemical vapor deposition and ion plating.

The term "substrate" as used herein means
Refers to the part of the copper-clad laminate product or other product of the present invention that serves as a means of physical support for a metal film or metal foil, and which is in contact with the copper or other metal film or foil. Suitably, it is constructed of curable glass fiber epoxy pre-brig. Other materials useful for such purposes include materials commonly referred to as "phenolic papers," i.e., paper sheet products impregnated with a resin that upon curing provides adhesion between the substrate of the laminate and the metal film or foil. can be mentioned. Furthermore, other materials include polyimide and polyester resins.

As used herein, the term "background layer" refers to a film or foil of copper or other metal onto which a desired circuit pattern of copper or other metal can be placed. .

One of the starting materials used to manufacture printed circuit boards on a commercial scale is copper-clad laminates. Such intermediate products consist of a substrate and a copper foil affixed thereto, and the printed circuit board manufacturer forms the desired circuit pattern by various methods. The most common method today is known as subtractive processing, in which the desired circuit pattern is masked by placing photoresist or screen-printed masking material on the copper-clad laminate, and then etched away the unwanted copper layer. consists of removing.

Another method of circuit patterning involves the use of a very thin copper clad intermediate product. Masking is applied as described above, exposing the copper layer in areas where it is desired to form a circuit pattern. Then,
After increasing the thickness of the circuit lines by electrodeposition, the masking material and thin background layer are removed by etching.

In the industry, this method is known as the half-add method.

It has long been recognized in the industry that high-definition circuit patterns, that is, circuit patterns that reproduce minute line widths and line spacings with high precision, are extremely desirable.
It has not been previously possible to consistently produce printed circuit boards with such characteristics. In other words, as a result of the fact that the platform of the subtraction method inevitably has noticeable side etching of the circuit lines,
A reduction in circuit padding metal and a change in the surface topography of the circuit lines occur. There are also significant restrictions on the spacing between circuit lines. On the other hand, in the case of the half-additive method, the thickness of the circuit lines and the required line spacing are significantly reduced, which is achieved, among other things, by achieving a smooth, pinhole-free, ultra-thin adhesion coating based on this invention. be done. however,
A drawback of circuits formed using this method is that the extremely thin circuit lines, about 1 mil wide, are brittle and are therefore susceptible to damage if the metal protruding above the board is subjected to external forces while energized. It will be done.

Now, in accordance with the present invention, it is possible to overcome the limitations of the prior art which hindered the integrity and high definition characteristics of the through-circuit pattern. Moreover, such results are achieved without substantial sacrifice in other respects.

In summary, the present invention provides a novel idea to eliminate the side etching of circuit lines, which is more or less unavoidable in conventional methods, and to form metal circuits on a background layer consisting of a substantially pinhole-free vapor-deposited metal film. It is based on the novel idea of installing patterns. The merging of these two ideas in accordance with the present invention makes it possible to produce extremely high definition circuit boards, which is a highly desirable and unique advantage in the highly developed art. be.

More particularly, side etching is avoided by embedding the circuit pattern into the substrate of the circuit board prior to etching away any unwanted metal present on the surface of the board. In other words, etching is performed after laminating the circuit pattern structure with the substrate of the circuit board and after separating and removing the carrier sheet from such assembly. As a result of this modification of the basic process sequence, the metal layer defining the circuit pattern is embedded in the substrate. On the other hand, since the unnecessary metal film (ie, the back L1 layer) is exposed on the substrate surface, it is easy to selectively dissolve and remove it. By severely limiting the thickness of the background layer, the time and caustic agent requirements for such removal steps are significantly reduced. Also, by rapid deposition of the background layer, the above-mentioned U.S. Pat.
As described in the specification of No. 1, the state without pinholes, which is essential for high-definition circuit patterns, can be achieved in ultra-thin metal films.

Briefly, the method of the present invention provides a method for depositing a substantially pinhole-free deposited metal film (as defined by the removal of the photoresist after the application of the photoresist and the application of an additional metal layer) onto a substantially pinhole-free vaporized metal film forming a background layer. ) embedding the circuit pattern metal layer in the substrate by placing an additional metal layer with the desired circuit pattern and laminating the metal body thus obtained with the substrate; It consists of steps in which the background layer is removed from the substrate while leaving the .mu. According to a preferred embodiment, both the background layer and the circuit pattern metal layer are made of copper. As an optional step, the copper or loose metal layer defining the circuit pattern may be electrolytically treated to produce nodular surface features to improve adhesion to substrates laminated with such assemblies. It will be done. As another option, a chemically bonded interface as described in Application No. 189,003 can be formed in the background layer after the photoresist is removed. Then,
If lamination and etching are performed as described above, the circuit pattern will be exposed. During this process, the adhesive layer is removed together with the background layer, but the adhesive layer is not removed from the embedded circuit pattern.

Particularly when forming very high definition circuit patterns with line widths and line spacings of less than 1 mil, it is important to place the circuit pattern defining metal on the deposited background layer.

Only in this way can a pinhole-free background layer with a required thickness of less than 16 microns be formed, thereby ensuring the integrity of the final printed circuit board!
It is possible.

Similarly briefly, the novel laminate product of the present invention includes a substrate and a metal body, the metal body comprising a deposited background layer in contact with the substrate and a circuit j-turn defined metal embedded in a surface portion of the substrate. Consists of layers. As described above in connection with the method of the present invention, the circuit pattern-defining metal layer is mechanically adhered by electrodepositing nodules on its surface. Alternatively, chemical bonding can be achieved by placing ultra-thin coatings of bent lead, aluminum, tin or chromium and ultra-thin coatings of silicon dioxide or aluminum oxide on the metal layer located on the background layer.

Another novel product of the present invention is, also briefly stated, a carrier, a back layer disposed on such a carrier t, and a circuit pattern defining metal placed on such a background layer and protruding on the surface thereof. It is a metal-clad laminate consisting of layers. Also in this case, the background layer and the circuit pattern defining metal layer are preferably made of copper. Additionally, photoresist or other masking materials used in installing the circuit pattern-defining metal layer may remain on the background layer if, for example, there is a risk of damage to the circuit pattern-defining structure during handling of such products. Just let it happen.

The printed circuit board of the present invention comprises a substrate and a metallic circuit pattern embedded in such a substrate and exposed on its surface. Special adhesive means can be used. However, even without the use of special adhesive means, the circuit pattern remains secure during operation due to the frictional force between the boundary surface of the embedded circuit pattern and the inner wall of the cavity of the substrate that houses it. can be done.

The present invention will now be described in more detail with reference to the accompanying drawings.

The main product of the present invention is a high definition printed circuit board 10 as shown in FIG. This circuit board 10 includes a sheet-like substrate 12 and a copper [114
It consists of A major feature of this new product is that the top surface 15 of the substrate is substantially planar, and that the exposed portion of the copper layer 14 and the top surface 15 of the substrate are substantially in one plane. As a result of the fact that none of the metal making up the circuitry of such circuit boards protrudes from the top surface 15 of the board, side etching caused by caustic agents used to remove background layers (not shown) during circuit board manufacture is eliminated. Ru. This unique relationship, as mentioned above, allows printed circuits to be manufactured with significantly smaller line widths and line spacings than in the prior art.

The novel circuit board product of the present invention can be manufactured in three different configurations as shown in FIGS. 4.5 and 6. These forms differ mainly only in the bonding state of the circuit pattern to the substrate. That is, in the product of FIG. 4, all surface areas of copper layer 14 except for the top surface 'are in direct contact with substrate 12. However, in the products shown in Figures 5 and 6, the copper layer substrate interface is interrupted by mechanical or chemical adhesive means consisting of a layer or coating placed on the copper layer after the circuit pattern deposition step and before the substrate lamination step. . More specifically, the product of FIG. 5 includes a nodular or dendritic copper coating 30 disposed at the lower end of a copper layer 31 defining a circuit pattern, such copper coating 30 being within a substrate 32. I'm in face-to-face contact with it.

Similarly, the circuit board product 40 of FIG. 6 includes an ultra-thin zinc coating 41 disposed at the lower end of the copper layer 42 defining the circuit pattern and an ultra-thin 5fO2 coating 43 disposed on the zinc coating 41.
・Contains and takes sho.

! A coating 43 is in surface contact with the interior of the substrate 44.

These three products according to the present invention (represented by dashed lines) when carrying out the method shown in the process flow diagram of FIG.
Manufactured by selecting any of the optional steps to achieve the desired copper layer substrate adhesion effect. As another optional step, a release layer such as that described in the aforementioned U.S. Pat. Also, Eric L Hshin & Margo, Jill
U.S. Patent Application No. 227,290 entitled "Transfer Lamination of Copper Sheets and Films, Methods and Articles" filed on January 22, 1981 in the name of Mar (la G11l) and assigned to the assignee of the present invention. As described in the specification, a similar release function can be obtained without the use of a release layer. The portions of these three patent applications in which the problem of carrier peeling and means for achieving it are discussed in detail are incorporated herein by reference.

In the next step, a copper coating 50 (FIG. 1) is deposited as a Vg layer on the aluminum carrier sheet 51 itself or on the carrier sheet provided with a release layer as in F. A suitable circuit pattern mask (eg, conventional photoresist) 52 is then applied to the copper coating 50. The metal selected for the circuit pattern is electroplated onto the assembly to the desired thickness. Copper is preferred for this purpose, and the circuit pattern copper layer 53 is formed as a result of copper being deposited through openings in a mask in a predetermined pattern.

At this stage, as shown in FIG. 2 and represented by a solid line in the center of the process diagram, the mask 52 is immediately
may be removed and the substrate 54 may be laminated. Next, as shown in FIG. 3, after carrying out a carrier sheet removal process, the copper coating 1150 forming the background layer is appropriately corroded away (that is, dissolved and removed). As a result, the circuit pattern copper layer 5
3 remains embedded in the substrate 54 and exposed flush with the substrate surface. The product thus obtained is as shown in FIG. The circuit-patterned copper layer embedded in the substrate is secured to a sufficient degree for the desired purpose by the frictional forces between the interfaces of the circuit-patterned elements and the inner walls of the substrate.

Another product of the invention, shown in FIG. 5, results from an optional step that provides a mechanical bonding effect as shown in the process diagram of FIG. This process involves electrodepositing a copper coating on an initial copper layer as described in the aforementioned US patent application Ser. No. 1803.41. The dendritic or nodular surface properties thus obtained result in the creation of a mechanical adhesive effect in the final product. Regarding the detailed method for realizing such adhesion surface characteristics, the patent application specification of -F is incorporated into the water IO document by reference. - Similarly, the product of FIG. 6 requires another optional step as shown in the process diagram of FIG. It is the result of an optional process that produces adhesive properties. In this case, the aforementioned U.S. Patent Application No. 1890
As described in the '03 specification, a very thin zinc coating is applied over the copper layer electrodeposited on the background copper coating, followed by a very thin silicon dioxide coating.

The application of these coatings is carried out according to vapor deposition techniques after removing the mask. The portions of the above patent applications relating to means for producing chemical adhesive properties and methods of use thereof are incorporated herein by reference.

In order that those skilled in the art may more clearly understand the novel features and advantages of the present invention, the following examples are presented. These examples are intended to be illustrative of the practice of the invention and are not intended to limit the scope of the invention.

Example 1 A 1-5 micron thick copper coating was deposited by sputtering on an aluminum carrier sheet previously coated with a release layer of thermal silicon dioxide. It takes m tall! A photoresist was placed over the layer and the desired circuit pattern was developed in the usual manner. Copper was electroplated through a photoresist mask to a thickness of approximately 25 microns. In the final step of the plating process, copper was electrodeposited on the circuit lines and pads to create nodules that provided good mechanical adhesion to the substrate. After washing off the photoresist, the circuit pattern was transferred to a substrate for a circuit board using a press pan.

This substrate was a glass fiber epoxy prepreg sheet, commonly known as FR4 board in the cured state. Since the circuit pattern was thicker than the background layer, it was embedded directly into the substrate. In the copper-clad laminate thus obtained, there were areas where the copper layer thickness was 5 microns or less and areas where the copper layer thickness was greater (mainly areas where the circuit pattern was installed). When such a laminate was contacted with a very mild copper etchant, the thin copper coating rapidly undissolved, leaving a circuit pattern embedded in the surface of the substrate. Upon such etching of the T-culm, the circuit pattern did not receive any side etching. .

Example 2 A 1-2 micron thick copper coating was deposited by electron beam evaporation onto a clean aluminum carrier sheet that was maintained at about 120<0>C throughout the deposition process.

A photoresist was placed on the background layer and a test circuit pattern containing 125 1/8 inch squares, each having a line width of 10 microns and a line spacing of 1 mil, was developed in the conventional manner.

A copper layer approximately 10 microns thick was then deposited over the circuit pattern by electroplating.

After washing and removing the photoresist, lamination was carried out in the same manner as in Example 1. When the carrier sheet was peeled off from the composite thus obtained, it was removed cleanly. Thickness 1-2
After removing the micron background layer by etching,
It was found that 85% of the 178 inch square circuits were formed without defects.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing a metal-clad laminate product according to the present invention, FIG. 2 is a schematic cross-sectional view similar to FIG. is a schematic cross-sectional view similar to FIG. 1 showing yet another metal-clad laminate product (i.e., circuit board intermediate product) based on the present invention, and FIG. 4 is a schematic cross-sectional view similar to FIG. FIG. 5 is a schematic cross-sectional view showing another circuit board of the present invention in which an embedded circuit pattern-defining copper layer is mechanically bonded to the substrate. 6 are schematic cross-sectional views showing yet another circuit board of the present invention in which an embedded circuit pattern-defining copper layer is chemically bonded to the substrate, and FIG. 6 is a diagram illustrating the method of the present invention, including optional processes for manufacturing the circuit boards shown in FIGS. 5 and 6. FIG. In the figure, 10 is a printed circuit board, 12 is a substrate, 14 is a circuit pattern copper layer, 15 is the upper surface of the substrate, 30
31 is a circuit pattern copper layer, 32 is a substrate, 41 is a zinc coating, 42- is a circuit pattern copper layer, 43 is S! 02 coating, 44 the substrate, 50 the deposited copper coating, 51 the aluminum carrier sheet, 52 the photoresist, 53 the circuit pattern copper layer, and 54 the substrate. Attorney for patent applicant General Electric Company (76
30) Iku Numa Toku 2 Showa year month
Kazuo Wakasugi, Commissioner of the Japan Patent Office1, Indication of the case, Patent Application No. 055231 of 19812, Name of the invention: Printed circuit boards, metal-clad laminate intermediate products, and manufacturing methods thereof3, Person making the amendment. Relationship to the case Applicant address 1-4 River Road, Schenectaday, New York, 12305, United States of America Address of agent 4th floor, No. 35 Kowa Building, 1-14-14 Akasaka, Minato-ku, Tokyo 107

Claims (1)

[Claims] 1. An additional metal layer with a desired circuit pattern is provided on the vapor-deposited metal film that is substantially free of pinholes and forms the background layer, and the metal body thus obtained is laminated with the substrate to form the previous circuit. A printed circuit board comprising the steps of embedding a patterned metal layer in the substrate and then removing the background layer from the substrate while leaving the circuit pattern metal layer embedded in the substrate. manufacturing method. 2. The method of claim 1, wherein the background layer and the circuit pattern metal layer are both made of copper. 31. 3. A method as claimed in claim 2, in which as a final step the background layer is removed by selective etching, so that the negative side of the circuit pattern metal layer is exposed. 4. includes a preliminary step of depositing said background layer on a carrier, electrodepositing said circuit pattern metal layer, and then placing an adhesive layer on said composite to increase adhesion to said substrate, and 4. The method of claim 3, including the additional step of removing the carrier from the background layer attached to the substrate. 5. A vapor-deposited background layer comprising a substrate and a metal body, with the metal body in contact with a part of the surface of the substrate, and a circuit pattern defining layer embedded in 8 parts of the surface of the substrate and integral with the background layer. A metal-clad laminate product characterized by: 6. The product according to claim 5, wherein the background layer and the circuit pattern defining layer are both made of copper. 7. The product according to claim 5, further comprising adhesive means for fixing the circuit pattern defining layer and the substrate together. 8. The product according to claim 7, wherein the adhesive means is an adhesive layer electrodeposited between the substrate and the circuit pattern defining layer. 9. The background layer and the circuit pattern defining layer are both made of copper and are selected from the group consisting of zinc, aluminum, tin and chromium and are made of an ultra-thin metal coating located on the body and of aluminum oxide and silicon dioxide. 8. A product according to claim 7, wherein said adhesive means is constituted by a very thin oxide coating selected from the group and located on said metal film on said body. 10. A high-definition printed circuit board comprising a substrate and a metal circuit pattern embedded in the substrate and exposed on one surface of the substrate. 11. The printed circuit board of claim 10, wherein the line width and line spacing of the circuit pattern is less than about 1 mil. 12, disposed between the circuit pattern and the substrate;
11. The printed circuit board of claim 10, further comprising adhesive means for securing said circuit pattern to said substrate. 13. Claim 12, wherein the circuit pattern is made of copper, and the adhesive means is constituted by an extremely thin zinc coating located on the shell and an extremely thin silicon dioxide coating located on the zinc coating. Section, Printed Circuit Boards as described. 14. The printed circuit board of claim 12, wherein said circuit pattern is made of copper and said adhesive means comprises a nodule-like or dendritic copper coating electrodeposited on said circuit pattern. 15. A metal-clad laminate product comprising a carrier, a substantially pinhole-free vapor-deposited metal film forming a background layer, and a circuit pattern-defining metal layer. 716. The article of claim 15, wherein said background layer and said circuit pattern defining metal layer are both comprised of copper. 17. The article of claim 16 including a photoresist circuit pattern mask located on the surface of the background layer and surrounding the circuit pattern defining metal layer.