INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

 

Case Study #279

1. Headline: Material substitution in the fabrication of

printed circuit boards reduces use of solvents.

2. Background: In anticipation of the new measures aiming to

strongly reduce the use of chlorinated solvents, BULL S.A.

altered their tool for stripping and developing films for

printed circuits, in order to work in an aqueous phase.

3. Cleaner Production Principle: Process modification

4. Description of Cleaner Production Application:

Information about the process and wastes

The manufacturing of multilayered printed circuits uses

dry chlorinated photosensitive films, developed with

trichloroethane and stripped with methylene chloride. The

photosensitive film is placed on the printed circuit, it

is exposed to the ultraviolet rays. The unexposed zones

are developed with trichloroethane. The circuits are

rinsed with water. Once the circuits are engraved, the

exposed zones are stripped with methylene chloride.

This process generates chlorinated wastes and aqueous

effluents with traces of solvents.

Aqueous effluents with trichloroethane:

11 000 m3/year, 1250 mg/l of COD

Chlorinated wastes :

21 tons/year with 78 % of trichloroethane

41 tons/year with 92 % of methylene chloride

Aqueous wastes :

2 tons/year containing 30 % of solvent

Gaseous discharges :

47 tons/year of trichloroethane

121 tons/year of methylene chloride

The law about CFCs prohibits using trichloroethane from

the end of 1995.

BULL S.A. adopted alkaline sensitive films developed with

sodium carbonate and stripped with potassium hydroxide, in

an aqueous phase. The sequence of operations is the same

but only generates an aqueous effluent/1850 m3/year, 8 to

12 g/l of COD.

These effluents are treated by ultrafiltration. The

filtrate (free from metal, COD lower than 1.8 g/l, BOD5 of

180 mg/l) is biodegradable, and the concentrates (30

t/year) are incinerated in a collective centre.

The new lines of developing and stripping are designed to

minimize the water consumption tanks to 5 rinsers in series.

Matters / energy balance and substitution

BEFORE AFTER

(base 1992)

Aqueous discharges 7040 m3/year 1170 m3/year

Trichloroethane 28 kg/day 0

Metals 0 0.088 kg/day

COD 60 kg/day after 14.4 kg/day

settling

BOD5 0 1.44

Chlorinated discharges 168 t/year 0 t/year

Chlorinated solvents 62 t/year 0 t/year

Water and chlorinated 2 t/year with o t/year

solvents 30% of solvent

Aqueous wastes 0 t/year 30 t/year

Rinsing water 11 000 m3/year 1760 m3/year

5. Economics:

Cost of direct investment

4 cascades rinsing with 5 posts 740 000

Ultrafiltration, storage and buildings 1 440 000

Studies

309 000

Treatment plant adaptation 156 000

Total amount

2 645 000FF (1993)

Operation and maintenance costs

Ultrafiltration operation : 85 000 FF/year.

Period of amortization: 2.5 years.

6. Advantages: Water savings : 8800 m3/year. No more need

for chlorinated solvents. No risk of accidental

pollution. No wastes nor chlorinated discharges.

Decrease in the discharged COD flow.

7. Constraints: The ultrafiltration concentrates are sent to

a collective centre for evapo-incineration.

8. Contacts:

Agence de l'Eau Loire-Bretagne

Mlle ROSSI

TEL: 33 38.51.73.73

BULL S.A.

331, avenue Patton

B.P. 428

49004 ANGERS CEDEX - France

TEL: 33 41.73.76.32

FAX: 33 41.73.73.20

M. MENARD

Environmental Chief

TEL: 33 41.73.76.32

M. Maton

M. Chatenet

Office International de l'Eau

Direction de la Formation et des Etudes

rue Edouard Chamberland

87065 Limoges Cedex, France

TEL: 33 55114770

FAX: 33 55777115

9. Keywords: France, printed circuit board, process

modification, material substitution, chlorine, solvent,

stripping, trichloroethane, ultrafiltration, COD, BOD,

water saving, incineration, ISIC 3825, ISIC 3692, ISIC

5000, filtration

10. This case study was submitted to UNEP IE in 1994 by the

French Office International de l'Eau. It has not undergone

a formal technical review.