Silvia Borjabad Copper Electroforming 7th JRA-1 Meeting Zaragoza (November 2007) Status Report.

Silvia Borjabad

Copper Electroforming

7th JRA-1 Meeting Zaragoza (November 2007)

Status Report

OUTLINE

Copper Electroforming Process

Review of objectives and work progress

Summary and prospects

S. Borjabad 7th JRA-1 Zaragoza Nov´07


Electroforming is a method of producing pieces by the deposition of a metal onto a mold (mandrel) which is subsequently removed

PUMP

ENGINE

FIL

TE

RTANK

SOCuSO4

H2 4

Copper Electroforming Overview

PUMP

ENGINE

FIL

TE

RTANK

SOCuSO4

H2 4SOCuSO4

H2 4

CuSO4

H2 4

Copper Electroforming Overview

• High-purity copper parts

• Accurate surface reproduction

• Underground process

• Chemical & electrolitic improvements


Process Parameters & Key Elements

Constituent Concentration

CuSO4 . 5H2O 188 g/l

H2SO4 75 g/l

HCl 30 mg/l

Thiourea 3 mg/l

• Mandrel turns during the whole process producing a homogeneous deposition

• Electrolyte circulates with continuous filtration to eliminate impurities

• Covered bath avoids air and dust contamination

• Plating is done over polished and cleaned stainless steel mandrels with the same shape of the relevant copper parts

• H2SO4 improves the electric conductivity

• HCl and Thiourea affect copper crystal nucleation and grain size

Constituents of the Electrolyte

(Brodzinski et al.,A292 (1990) 337)



Filter and Pump

Electrolitic Bath

Voltage SupplyElectronic

Control System

Temperature and pH sensors

Electroforming Set-Up


• Electrolyte circulation

• Inert cover gas (N2)

• Rotation Speed & Direction

• Plating modes

• Temperature & pH sensors

• Parameters DAQ system



Electroforming process parameter tuning

Electroformed copper parts with complex geometry

Monitorization of parameters during the electroforming process

Radiopurity measurements of electroformed copper parts

Chemical & electrolytic improvements

Electroforming in steps to fabricate cryostat copper components


Electroforming Process Parameter Tuning

Optimum parameters: 3 A/dm2, 2 rev/s, forward-reverse rotation

Parameters: Current Density, Speed Rotation and Direction Rotation


Goals

Smooth surface

Homogeneous copper distribution

Without periodic machining process


• Electroformed copper part for PMT encapsulation (collaboration ANAIS)

• Hexagonal & cylindrical electroformed copper parts

Isolated areas with Teflon, parafine or

silicone

• Smooth surface

• Accurate surface reproduction (corners)

1.5 mm of thickness



Complex mandrel

• Smooth surface

• Homogeneous distribution

• Final machining process


Auxiliary anode

Isolated areas with

Teflon

1.5-2 mm of thickness

Soldering tests with

electroforming in progress

Parameters monitorization during the electroforming



Temperature & pH sensors DAQ software

Parameters measurement system

Electroforming Parameters

Current (I)

Voltage between electrodes (ΔV)

Electrolyte Temperature & pH

Evolution during the process

Electrolyte properties

Radionuclide Units (mBq/kg)

Th series 212Pb ≤ 16

228Ac ≤ 25

U series 234Th ≤ 32

234Pa ≤ 90

226Ra ≤ 24

214Pb ≤ 3

214Bi ≤ 6

235U ≤ 1.4

137Cs ≤ 7

40K ≤ 90

60Co ≤ 7

56Co ≤ 3

57Co ≤ 8

58Co ≤ 5

Preliminary radiopurity measurement of electroformed copper The levels of radiopurity in an electroformed copper part were previously measured with a HPGe detector (1Kg Ge) at the Canfranc Underground Laboratory (LSC).

Copper mass: 161 g

Measuring time: 5 d

Copper part into a Marinelli container

Copper around the HPGe detector

A standard- electroformed copper part (commercial chemicals & at sea level)

(Data Analysis courtesy J. Puimedon)



New measurement in progress









In progress

Next steps

Summary and Prospects

Electroformed copper parts with smooth surface and without machining can be manufactured by means of the tuning of process parameters.

Copper parts with different geometry (hexagonal, cylindrical) can be achieved by easy modifications.

Radiopurity measurements of electroformed copper parts are in progress.

Soldering tests to join copper parts with electroformed copper are in progress.

SUMMARY

PROSPECTS Chemical & electrolitic improvements: CuSO4 purified by recrystallization,

high- purity acids and anodes, CoSO4 and BaSO4 to reduce Co and Ra isotopes.

Electroforming in steps to fabricate different copper parts such as cryostat components.

This facility will be installed at the new (enlarged) Canfranc Underground Laboratory as soon as the clean room is ready.


Silvia Borjabad Copper Electroforming 7th JRA-1 Meeting Zaragoza (November 2007) Status Report.

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