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.