the process of Electroforming
Learn everything about Advanced Lithographic Electroforming process, material properties and design guidelines
the Electroforming process in 6 steps
Veco's Advanced Lithographic Electroforming process is a unique combination of high precision photolithography and electrodeposition based Electroforming.
1) Cleaning
A metal sheet substrate is cleaned and degreased.
2) Coating
The substrate is coated in a light-sensitive coating/photoresist.
3) Exposing
The substrate is exposed to ultraviolet (UV) laser direct imaging (LDI), whereby the CAD part pattern is projected and transferred onto its surface. The resulting patterned surface is split into conductive areas and non-conductive areas by the photoresist material hardening in the latter.
4) Developing
The patterned substrate is developed, meaning the unexposed photoresist is removed to expose the conductive areas. It is then rinsed and dried. The patterned substrate is from here on referred to as the mandrel (part model).
5) Electrodeposition
The electrodeposition process takes place in an electrolytic bath and involves two electrodes (an anode and a cathode) and an electrolytic solution. The mandrel is placed in the bath and the electrodes pass a DC through the solution. The DC converts metallic ions into atoms that are continuously deposited on the conductive areas of the mandrel until the desired metal thickness has been achieved.
6) Harvesting
The electroformed part is harvested, or separated, from the mandrel. The electroforming process can be managed in different ways to achieve different product features. For example, if a thin photoresist is used and the metal is allowed to grow over it, resulting in the thickness of the part exceeding that of the photoresist, the outer edges will be rounded and have a bell mouth shape. Alternatively, if a thick photoresist is used and the metal is not allowed to grow over it, resulting in the thickness of the part being less than the thickness of the photoresist, the outer and inner edges will be straight and sharp.
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available processes at Veco
Overgrowth method
Thick Resist method
Surface replication
Overgrowth method
(1) Plating Defined Electroforming: the Overgrowth Method
Plating defined electroforming is also referred to as an overgrowth method. It uses a thin photoresist pattern to shield parts of the conductive substrate. A light-sensitive coating is applied to the conductive surface. By a photolithographic process a pattern is made in the coating, resulting in conducting and non conducting areas. Metal grows over the photoresist and the thickness of the product (T) exceeds the thickness of the photoresist (TR), hence the process is also known as overgrowth.
Thick Resist method
(2) Photo Defined Electroforming: the Thick Resist Method
Photo defined electroforming is also called the thick resist method. In some cases, it is desired to use the thick resist method. A thick pattern of photoresist is used during photo defined growth, such that the thickness of the product (T) does not exceed the thickness of the photoresist (TR).
Aspect ratios (TR/ WR) up to 1 can generally be achieved with ease. The exact limits depend on the size and geometry of the products .
Surface replication
(3) Surface replication with Electroforming
The electroforming process allows for extremely precise duplication of the mandrel. The high resolution of the conductive patterned substrate allows finer geometries, tighter tolerances, and superior edge definition.
This results in perfect process control, high-quality production and very high repeatability.
Electroforming is therefore perfectly suitable for high precision surface replication at low cost and in high volumes.
material properties
See below an overview of materials available for the electroforming process
The materials we offer for electroforming are Nickel and Copper. Whereas we have a variety of nickel types available:
Veco84, Sulfamate, Meta, Hr-Ni (heat-resistant), and PdNi (biocompatible).
- 1 Tensile strength, yield strength, elasticity, and elongation at failure are measured in flat tensile tests on ASTM D638 type 4 samples (thickness 75-100 µm) according to ISO 6892-1:2016 with an initial gauge length of 25 mm.
2 Stainless steel samples SS316L and SS304 are added as reference, but note that identical stainless steel types can be ordered with varying tensile properties; the measured values do not reflect the maximum capability of stainless steel 316L and 304.
3 The Vickers hardness as measured on polished cross sections with a force of 0.981 N (100p).
4 Measured at 32 °C with a vibrating-sample magnetometer.
5 Ni purity with respect to the elements Ag, Al, As, Ca, Cd, Ce, Co, Er, Eu, Ga, Gd, Ge, Hg, Ho, La, Mg, Mo, Nb, Pb, S, Si, Sn, Sr, Ti, Tm, U, Y, Zn, Zr. Based on qualitative and quantitative trace level analyses with inductively coupled plasma emission spectrometry after material dissolution in HNO3 with a final Ni concentration of ca. 1 g/L and a final HNO3 concentration of ca. 10-14 v%.
6 The Ni leaching in the standardized testing procedure for sugar sieves, i.e. leaching from 1.00 dm2 sample surface area in 170 mL DIN10531 artificial tap water at 70 °C during 24 h. All materials fulfilled the requirement of <0.14 mg Ni leaching per kg test fluid as determined for food contact applications by the European Directorate for the Quality of Medicines & HealthCare (Technical guide on metals and alloys used in food contact materials, 1st edition September 2013).
7 Temperature at which the material can be kept for 1 h while maintaining HV≥95% and Rm≥95%. Thermal treatments were done in air with instantaneous heating and cooling.
8 Measured with a four-point probe under a current of 1.000 A and at ca. 35 °C.
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