JPS60230993A - Copper pyrophosphate solution for anisotropic plating - Google Patents

Abstract

PURPOSE:To obtain a copper pyrophosphate soln. capable of giving plating with high anisotropy and favorable surface properties by specifying the concn. of copper ions, the ratio of the concn. of pyrophosphate ions to the concn. of copper ions, and the concn. of ammonia. CONSTITUTION:Potassium pyrophosphate and copper pyrophosphate are added to a copper pyrophosphate plating soln., and an aqueous ammonia soln. is further added to obtain a copper pyrophosphate soln. for anisotropic plating having 25- 38g/l concn. of copper ions [Cu<2+>], 6.5-7.5 weight ratio of the concn. of pyrophosphate ions [P2O7<4->] to the concn. of copper ions [Cu<2+>], and 0.05-0.20mol/l concn. of ammonia [NH3]. The soln. is adjusted to about 8.2-9.0pH with KOH, polyphosphoric acid or the like, and additives and a stabilizer are added to the soln. as required.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a copper birophosphate solution for anisotropic plating. The anisotropy here refers to the elongation A of plating in a direction parallel to a certain plating surface, and the elongation B of plating in a direction perpendicular to it.
It is represented by A.

[Conventional technology]

Photolithography has traditionally been frequently used to produce precision printed circuit boards, but additive methods in particular have been shown to be a highly advantageous manufacturing method, as they can produce circuit boards with high wiring density.

However, in printed circuit boards using this manufacturing method, it is difficult to manufacture thick and fine patterns because the anisotropy value does not exceed /.

For example, when plating a pattern arranged in a line, the line spacing of the pattern before plating is /θθμm′,
If a plating with a thickness of θμm is applied to it, the anisotropy K will be 7.
Therefore, the plating width also increases by 508m, resulting in short circuits between the lines. On the other hand, the present inventors have already developed
/Otsu 66/G revealed that the value of K can be increased by increasing the current density of plating. This has made it possible to plate fine printed circuit boards thickly. However, in order to produce printed circuit boards with even finer patterns, it is desirable to increase the value of K and further improve the surface properties.

Therefore, the present inventors conducted a detailed study on the compositional conditions of the copper birophosphate solution, and as a result, they discovered a composition that has a higher K value and allows plating with good surface properties.

〔composition〕

That is, the present invention provides at least (N copper ion concentration (Cu") 23 to 3 g?/L
(B) Pyrophosphate ion concentration (P20 knee) / copper ion concentration [:Cu”] weight ratio B, j ~ 2. evening IC) ammonia concentration [NH3] θ, θj ~ θ0.2. θmol/
This is a copper pyrophosphate solution for anisotropic plating consisting of:

To explain further, to make this composition, first add potassium pyrophosphate and steel pyrophosphate to a commercially available steel pyrophosphate plating solution, and then add ammonia water to adjust the composition to the above conditions, or add potassium pyrophosphate and steel to the above composition. A method may also be used in which copper birophosphate is dissolved in water at a predetermined tg and then aqueous ammonia is added.

Incidentally, commonly used additives and stabilizers may be added as necessary.

In the present invention, the value of the ratio (P) of the weight concentration of birophosphate ion p, ony to copper ion Cu'1 is 6.J' to 7.51, preferably 6.J' to 7.5g. It is desirable that the P ratio be lower, and copper with strong internal stress and extremely low malleability will be produced, and if the P ratio is higher than 7.0, tree-like abnormal protrusions will be formed on the surface of the plated steel layer.

In addition, the steel ion concentration [Cu” average is 2tf/l~3♂
2A, preferably 26 to 35 f/l. If the copper ion concentration is lower than 2 s t/l, tree-like abnormal protrusions will appear on the surface of the plated copper, and if the copper ion concentration is lower than 3.
When the value is higher than /f/l, copper with strong internal stress and extremely low malleability is produced, and in some cases, tree-like abnormal protrusions are formed on the plating surface.

Furthermore, the ammonia ion concentration (NH3) is θ, θj~
θ, 2θmOho/1, preferably O6θ♂~θ, /
t molA is desirable, and the ammonia concentration is θ, θj
When the ammonia concentration is lower than mol/l, the value of K is low and the anisotropy is weakened, and when the ammonia concentration is higher than θ and 2θ mol/l, the malleability of copper is significantly deteriorated and the internal stress is also considerably high.

Under the above composition conditions, 'C' has a pH range of 2 to 9;
It should be between θ, but if the pH is lower than this, if the KOH1 is high, use polyphosphoric acid, citric acid, or a pH adjuster commercially available from each plating solution manufacturer.
2-9. θ, preferably pH ♂, y to ♂, 1.

The current density of the cathode is 3~jθA/d m", preferably J--, 20ν. In order to increase the value of K,
The higher the current density of the cathode, the better. The upper limit is determined by the fading phenomenon.

Agitation is necessary, and air agitation, pump agitation, cathode rocking, or a combination of these may be used. For example, in air agitation, the air flow rate is θ, θj~ko, θθM ψ
Minutes (the volume under standard conditions of the amount of air flowing in 7 minutes per unit plating layer liquid area) is preferable. Further, the bath temperature during plating is preferably 50 to 60°C, as is generally practiced.

Anything can be used as the base for plating as long as it is conductive.
For example, for metals, copper-nickel, aluminum, etc. can be considered.

As for the plating equipment, there is no particular problem as long as it is a commonly used one.

EXAMPLES Below, in order to further clarify aspects of the present invention, examples will be given and explained.

Examples 7-6 Insulating polyimide film (manufactured by DuPont [Kapton]
, thickness 2254 m), and a jμm thick copper foil using Bostik's phenolic resin adhesive (product name: XA-J-gQ).
-4t) to adhere. Next, a negative resist [Microresist] 74t7-// manufactured by Eastmango Duck Co., Ltd.
θcst j was applied to the copper surface so that the resist thickness after drying was 3~j/Jm, and after prebaking, it was exposed to light with a high-pressure mercury lamp through a circuit pattern mask, and a special developer (
The resist was developed with a rinsing solution (Microresist Developer, manufactured by Eastman Kodak Company) and a rinsing liquid (Microresist Rinse, manufactured by Eastman Kodak Company), and post-baked to form a resist in the shape of a circuit pattern. Subsequently, the copper foil was removed by etching with a ferrous chloride and tOq6 solution. As a result, film thickness jμm, width/3θμm, array pitteco θθ
A linear pattern of μm was obtained.

Next, add Barshaw Murata's pyrophosphate steel plating solution.
Add appropriate amounts of potassium pyrophosphate, steel pyrophosphate, and water to adjust the composition to a copper ion concentration of 3 tl tll, P = 7, and further convert ammonia water with a concentration of J1 to ammonia to obtain θ, θJ'mol. After adding the plating solution to a concentration of Plating was carried out on a shaped copper pattern under the following conditions: current density T, ♂ irradiation, air stirring θ, /M3/M2 minutes, bath IMs s °C. From the width and thickness of the copper wire pattern obtained as a result, =/, Wa? , and a deep anisotropy was exhibited. Furthermore, using a plating bath in which the copper ion concentration, P, and ammonia concentration shown in Table 1 were changed and the pH was adjusted, plating was performed on the same copper wire pattern as described above under the same conditions. The results obtained are shown in Table 7.

Table -/ Notes: (1) Surface quality: Good means that the entire plated surface is dense and glossy, and there are no tree-like abnormal projections.

(2) Physical properties of the pot: A good condition is one in which the internal stress is strong and there is no peeling off from the substrate or significant decrease in malleability.

(3) Dactality: It indicates how many times a sorted test piece must be bent at θ0 seven times to the left and right, and how many times it has to be bent to cause cracks to enter the copper layer. It is one.

Comparative Example/~j A copper foil with a thickness of j μm was placed on an insulating substrate using Bostic Co., Ltd. [XA
-J-gg-gJ Adhere using phenolic resin adhesive. Next, use Eastmango Duck's negative resist [
After drying the microresist 7'17-//θcst J, the resist thickness is 3~! ; After pre-baking, it is applied to the copper surface to a thickness of 11 m, exposed to light with a high-pressure mercury lamp through a circuit pattern mask, developed with a special developer and rinse solution, and post-baked to form a resist in the shape of a circuit pattern. Subsequently, the copper foil was removed by etching with a ferric chloride jθIIG solution.

As a result, the film thickness was 311 m, the width was 30 μm, and the arrangement pitch was 2.
A linear pattern of θθμm was obtained. Next, appropriate amounts of potassium pyrophosphate, steel pyrophosphate, and water were added to a copper pyrophosphate plating solution manufactured by Versho Murayama Co., Ltd. to obtain a composition with a copper ion concentration of 34 tff/l and a P ratio of 6. θ, then add an appropriate amount of ammonia water at a concentration of 2, adjust the concentration to θ, θJ' mol/l in terms of ammonia, and then adjust the plating solution's p)l ratio to , 7. KOH Tati solution or Versho Murayama's pH:A adjustment solution was added.

Using such a plating solution, the above-mentioned linear steel pattern was plated under the following conditions: current density 31 A/d, air agitation θ/M "7M" minutes, and bath temperature J/C. When K was calculated from the width and thickness of the copper wire pattern obtained as a result, ? llt, and highly anisotropic plating was performed, but the timing performance was as shown in Table 2.

(Leaving space below) Table - No [Effects] Using the pyrophosphate steel solution of the present invention, it is possible to produce plated products with high anisotropy K and excellent surface properties. It has become possible to manufacture printed circuit boards with fine patterns.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] At least, the captive copper ion concentration [:CLl''), 2, t ~ 3♂1
/1.1B) Pyrophosphate ion concentration CP2Oney)
/Copper ion concentration [C, 2+] weight ratio, j~7. j,
(C) Ammonia concentration (NHs: lθ, OS~θ, 2θ
mol/l. Copper birophosphate solution for anisotropic plating consisting of