DE1807414A1 - Process for etching copper and copper alloys, especially copper-clad laminates - Google Patents

Description

SABA, Schwärzwälder Apparate-Bau-Anstalt August Schwer Söhne GmbH
7730 Villingen / Black Forest
Hermann-Schwer-Strasse

PA 250

Patent registration

Description;

Process for etching copper and copper alloys, especially of copper-clad laminates.

The invention relates to a method for etching printed circuit boards in immersion and spray etching systems. En with consistently high etching speed by controlling the etchant rate with a redox electrode. There are various options for etching printed circuit boards, for example printed circuits. Aqueous solutions of ferric chloride (P Cl-,) of anaonium persulfate (NH ^) ₂ S ₂ ⁰ H ^ * sodium chlorate and hydrochloric acid (KaCl 0-, + HCl), sodium chloride (KaCl O ₂ ) are known as etching agents. , Hydrogen peroxide and sulfuric acid (H _? Op + H ₂ SO,), copper-II-chloride (CuCIp) with various Bajensrationsrmittelern such as air and oxygen. Etching is carried out in immersion or spray-etching systems, the latter in particular in the form of a continuous system being suitable for circuit board production according to the assembly line principle. A prerequisite for an 'economical assembly line production is the highest possible and constant throughput speed. In most of the etching methods known up to now, the etching time becomes increasingly longer due to the increasing copper content of the etchant and the decreasing effect of the etchant. For example, when the Ou content increases from 0 to 50 g Cu / ltr, the etching time in the ammonium persulfate bath increases from 6 minutes to 33 minutes and in the water

009825/1650

- 2 -

BATH ORIGINAL

1807AU

- 2 PA 250

stoffperox'yä / Jehweic acid bath of 5 luin. to 21.5 minutes (DAS 1 253 008, Degussa). In some other process with hydrogen peroxide and sulfuric acid with the addition of a catalyst, jitz times of 1.5 min. at the beginning and 3 .. in. at approx. 35 g Cu / ltr. reached, as the copper content increases, the etching time is lengthened and becomes uneconomical. The initial speed with ferric chloride as the etching agent is approx. 1 minute. Aue! ': If iron III chloride is used as an etching agent, the initially high etching rate decreases with increasing copper content, continuously, uni in spray heating systems with a copper content of approx. 50 g, uneconomical long. e etching times (= curdling flow rate).

According to the new method, it is _elun ~, en to significantly exceed the mean etching time achieved by Elrenchlor ij (ui.i approx. 40 ", o), which brings economic advantages in various respects, including all Opening sentence .-, öcc v.inaigkeit of the new procedure somewhat less than that- in the case of etching: η ^ it user. — Ill-chlorid., J-jdocL i-: 3ni- .LT consuming luainahr he ^. during .eiteren Ätzverlaufes, unabnän _o i _±, SVON, 7 / ow much aurcr plates. aie etcher gelau ^f e are :. v and / ie much copper was etched thereby reciit, v uniformly adhered / ground .

The described disadvantages of all processes are avoided by the inventive etching process, some of which is characterized by the fact that the generation of etching agents within the etching system is controlled by a redox electroae and thus a consistently high etching speed is achieved.

009825/1650

BAD ORIGffviÄt

PA 250

After a; further Llerkraal aes erf indun ^ y. e;: iätex. Procedure, the dosage of the Regenerierun £ seheii; ikalieri is controlled according to the measured potential of the etching solution by the redox electrode _f ; e.

The method according to the invention is also characterized in that that as a caustic copper-II-chloride and for Kegenerati on the copper-I-chloridee formed during the etching process Hydrogen peroxide and hydrochloric acid are used and that the copper-I-ion concentration is below 4 gr / itr. is held.

Thereby v. earth according to the invention, the supply lines of the ceiden He. enerierungschenakalien to de: i. Etching agent filters are made of ele ^ t, that for the dosage curtain aas quantity ratio of. both Regeneration chemicals is optimal.

On the basis of the figure, which shows the course of the Gu ⁺ ion concentration in the etching solution as a function of the potential of the Kectox electrode, the process should be described in more detail.

Etching n: it copper-ll-c: u.orjd creates i _t aci. άβν j'ieichui.g Cu + CuGIp = 2 CuGx i.upier-I-ct.i ^ rid, wotti ao. l · :. eli> relatively very small amount of Kuj-fer-I-chloride (4 he Gu / Itrj in the Ätfclösung, the CPU 12r gr Gu / ltr may contain as Καμίer-ll-onlorid that Ätzgesci Winai _f; ness very nerKlich slowing . Femerkenawert is, Yes: he abs _ute "i \ ert the courier -.. ehaltes cur Einiifiltun": ΐΐ a r.oher _Λ · - c: i <\ inJi.vKeit i.icni particularly constant _f reiialten v.erdex: i: .uc - he kai.r. zwiscr .n 80 gr Gu / l and 130 _r r Gu, itr se :: · * ar-.en - make:... it rather dai What matters is to keep the cei ::: '^ zzvcTfur.j. resulting Cu-I-chloride-lienge nöglic :: st t-iea ^ rif- venter 2.-rr / Itr; and

009825 / USO

BATH ORIGINAL

180741A

- 4 PA 250

to copper (II) chloride again as quickly as possible oxidize. The regeneration is purely stoichiometric considered, n-I from the following reaction equation:

2 CuGl + H ₂ O ₂ + 2 HCl- ^ 2 CuCl ₂ + 2

The mechanism of action that takes place between these reactants is much more complicated than this equation suggests; it will not be discussed here.

According to the stoichiometric equation, it is therefore necessary to add the regentration chemicals HpO ₂ (34 gr) and 2 HCL (2 36.5 gr) to the specified ratio of the etching solution. If, for example, a 35% HpOp solution and 37.5 % hydrochloric acid are used, the chemicals have to be added in a ratio of 1: 2, which can be met by a suitable design of the drains from the storage vessels. From aer de. The energy reaction equation shows that: During regeneration, hydrochloric acid is consumed, and the pH of the etching solution must change. It would be obvious, by controlling the pH ψ V.ertes with a IJH electrode, the addition of Re-enerationsmittel xu control, but is reflected in the Traxis, file no optimum etching conditions can be ersielt. If, however, a redox electrode is used to control the addition of chemicals, the desired goal is achieved with great accuracy. During the etching process, Cu ions and Cu ⁺ ions are present in the solution. The potential of the electrode depends on the concentration ratio (correct; activity ratio)

^ V aer * ormel E = E + ψ- ^ln SÜ

09825/1650

V ^na ^ h aer ormel E = E + ψ Ss Cu ⁺ ° ^P C ⁺

- 5 ORIGINAL BATHROOM

Pi 250

The potential of the electrode becomes positive when the concentration of the higher oxidation level increases and reaches a maximum value when the Cu ion concentration is zero. With an increasing Gu ion content, the potential of the solution changes, in the range of a lower Cu ion concentration (0-4g / ltr), relatively much more strongly than with further increases in Cu ⁺ ions (see diagram). This change in potential is displayed via a verse barker on a measuring device and 'written down on a recorder. The measuring device is provided with two adjustable sensors, which adjust the external potential accordingly _; y in the etching solution are passed by the pointer of the measuring device and, when the pointer moves from the area of higher potential with increasing Cu ion concentration in the etching solution to the area of lower potential and thereby passes the sensor, solenoid valves are opened and this means that the itegenerating chemicals (HpOp + HCl) can run from storage containers via the etching system into the etching solution. To achieve a consistently high etching rate, the two sensors are set so that a potential difference of approx. 100 mV is not exceeded during the control process, the Cu ion content remaining below 2 g / l and the two sensors being ao far apart separately, that when the valves are opened, the 1st valve, which regulates the hydrochloric acid flow, is opened well before the 2nd valve, which controls the HoOp flow, and, in the opposite direction of movement of the pointer, the hydrochloric acid valve is closed again well after the HpOp valve will. This setting is intended to ensure that there is always a slight excess of HCl LT in the solution.

009825/1650 - 6 -

BATH ORIGINAL; rv r->

1807A Η

PA 250 ■

Another advantage of this process is that the re ^ energizing chemicals during the etching process added and used etching solution can be removed during the etching, i.e. an interruption in production this is avoided.

Moreover, the spent etching solution has a high V / iederverwertungswert, since it consists of a hydrochloric acid-containing Cu-II-chloride solution (without other salt impurities) and may be used for the preparation of copper compounds of various kinds, womix also because ^r _ always tedious and cost-incurring Abwaaserüroblem at etchers is fixed.

00 9 8 25/1 6 50

BATH ORIGINAL

Claims (4)

"■■■ '■ - .- ■■ .." .. ■. ■ ■■■ Γ '-' ■■> ■: ■■ ■: -, '«" I "! -I- * »! ... J - 7 PA 250 patent claims 1. A process for etching copper and copper alloys, especially copper-clad laminates for producing printed circuit boards in diving and Sprühätzanlagen, characterized in that the regeneration of the etchant made within the Atz-anla / re, electrode ORP is controlled by a and a consistently high itzgeschwin-. | age is achieved. 2 »Method according to claim 1, characterized in that that the Hedox electrode regulates the dosage of the regeneration chemicals measured according to de ^ i Controls the potential of the etching solution. 3. The method according to claim 1 , 2 dt jurci: characterized in that the Hedox electrode aie dosage of He. ex.e- acer !!. a-jnetventile controls, 4. The method according to claims 1 to 5 * d: -. Lurch characterized in that the etching agent used is Kupier-11-cr.J.cria and e \ XT regeneration of the Kupier-I-chloriaea ". Hydrogen oxide and hydrochloric acid the copper ion concentration is kept below 4 g / xtr. 009825/1650 BAD ORtGINAU PA 250 Process according to Claims 1 to 4, characterized in that the feed lines for the two regeneration chemicals to the etchant container are designed so that for the loosening process da "ratio of the two regeneration chemicals is optimal. GC9825 / 1,650 BAD ORfGIMAL