AU731328B3

AU731328B3 - Electroplating

Info

Publication number: AU731328B3
Application number: AU20622/00A
Authority: AU
Inventors: Robert Jones; Philip Timbrell
Original assignee: Tyco Electronics Pty Ltd
Current assignee: Tyco Electronics Pty Ltd
Priority date: 2000-03-02
Filing date: 2000-03-02
Publication date: 2001-03-29
Anticipated expiration: 2002-03-29

Description

AUSTRALIA

PATENTS ACT 1990

ORIGINAL

COMPLETE SPECIFICATION PETTY PATENT Invention Title: ELECTROPLATING Name of Applicant: UTILUX PTY LIMITED The following statement is a full description of this invention, including the best method of performing it known to me/us: -2-

ELECTROPLATING

The present invention relates generally to a method of electroplating a metal oxide surface of a composite glass and relates particularly, though not exclusively, to electrotinning of a tin oxide plated glass. The invention further relates to an electroplated composite glass.

In the field of photovoltaics there is the need to form an electrical connection with a panel of glass which is coated with conductive tin oxide. This electrical connection is currently achieved by either of the following techniques: i) an adhesive copper tape conductor is adhered to the tin oxide coating, the adhesive being conductive; or ii) a wire or other conductor is pressed directly against the tin oxide coating.

Although these methods are relatively effective in forming an electrical connection between the conductor and the tin oxide coating, there are energy losses in the form of heat inherent in the connection.

According to one aspect of the present invention there is provided a method of electroplating a metal onto a metal oxide surface of a composite glass panel, said electroplating being performed for a relatively short time at a relatively high current which is effective in fusing the metal to the metal oxide surface.

Typically the electroplating involves "spiking" of the current to more than twice that for conventional P37433 3 electroplating techniques, said spiking being over a fraction of the conventional electroplating period. More typically the current is "spiked" for less than about one half of the conventional period.

It is understood that the metal is "burnt" onto the metal oxide surface so as to form a molecular bond therewith.

Preferably the method of electroplating also involves ageing of the electroplated composite glass panel under ambient conditions, said ageing being performed after the electroplating.

It is understood that ageing of the electroplated panel is effective in promoting molecular bonding, including colloidal bonding, between the metal and the metal oxide surface.

According to another aspect of the present invention there is provided composite glass panel including a metal oxide surface to which a metal is electroplated, said metal being fused to the metal oxide surface by electroplating for a relatively short time at a relative high current.

Generally the metal is tin and the metal oxide surface of the composite glass is formed predominantly of tin oxide or another conductive ceramic.

Typically the electroplated composite glass is designed for use in photovoltaic applications of positive temperature coefficient (PTC) heating elements.

In order to facilitate a better understanding of the nature of the present invention a preferred embodiment of 37605 a method of electroplating a metal oxide surface of a composite glass will now be described, by way of example only, with reference to the accompanying drawing in which: Figure 1 is a graph plotting current verses time for electroplating a metal onto a metal oxide surface of a composite glass panel together with a comparative plot for conventional tin plating.

According to a preferred embodiment of the invention a composite glass in the form of a tin oxide layered glass is electroplated with a metal, in this example tin. The tin oxide layered glass is commercially available and has particular application in photovoltaics including PTC heating elements. The electroplated tin provides an effective connector for the tin oxide layered glass, the electroplated tin serving as an alternative to the adhesive copper tape or wire conductors of the acknowledged prior art.

Figure 1 illustrates a preferred embodiment of the invention where electroplating of the composite glass is performed for a relatively short time at a relatively high current. In this example the current is "spiked" to a current density of greater than double that of the conventional current used in electrotinning. This "spiked" current is applied for far less than one half the conventional period for electrotinning.

The applicant observed that electroplating under the conditions of this embodiment of the invention "burnt" the metal or tin onto the tin oxide surface of the composite glass panel. This is evidenced in blackening of the interface between the tin and the tin oxide. Importantly, P37433 the preferred method of electroplating further involved ageing of the electroplated composite glass panel under ambient conditions. This ageing process is understood to further promote molecular bonding between the tin and the tin oxide surface. It was found that ageing for a period of at least 24 hours was sufficient to bond the tin to the tin oxide layer in preparation for the application of current. This ageing allowed the electrolyte to evaporatively dry from the electroplated tin and the tin oxide layer. Without this ageing the electroplated tin did not bond with sufficient strength to the tin oxide layer.

In order to test the effectiveness of the "contact" between the tin and the tin oxide layer of the composite glass, the applicant set up a test fixture. The test fixture comprised a 35 amp DC Power supply in series with a digital multimeter (set to amperes) which is in series with an electrode. The electrode consisted of a copper (tin plated) wire slid over a silicone former. A thermocouple was inserted inside the silicone former. The current was taken from the composite glass sheet by another electrode laying on the tin oxide coating of the composite glass. This assembly was suspended onto metal blocks with the area tested being exposed to free air on all sides by approximately 2cm.

The temperature rise for the following samples was noted when a DC current of 500 mA was passed through the circuit. The current was adjusted back to 500 mA when the heat caused the current to drop due to an apparent PTC effect of the tin oxide.

P37433 -6- Sample 1 a thin tin plating on the tin oxide layer of the composite glass, the tin plating being applied according to the preferred embodiment of the invention.

Sample 2 another thin tin plating applied to the tin oxide layer of the composite glass, the thin tin plating being applied according to a variation on the preferred embodiment of the invention using less current over a longer period.

I0 Sample 3 an adhesive copper tape conductor adhered to the tin oxide coating according to the acknowledged prior art.

Sample 4 involved application of the electrode to the tin oxide layer of the composite glass according to the acknowledged prior art.

The following table details the approximate temperature rise above ambient for each of the samples. In each instance the temperature increase was not recorded until it had stabilised after a certain period of time.

Generally, the temperature had stabilised after about 1 hour. The results indicated i'n bold type are for the acknowledged prior art techniques.

Sample No. Temperature Increase Above Ambient 1 6°C 2 3 18"C 4 17"C P37433 It is clear from the data obtained that electroplating of the tin oxide layered composite glass according to the described embodiment, shows a significantly reduced temperature increase from that of the prior art. Samples 1 and 2 of this embodiment of the invention displayed a temperature increase of about one third to a half that of the prior art of samples 3 and 4.

Now that a preferred embodiment of the present invention has been described in some detail it will be apparent to those skilled in the art that the method of electroplating the metal oxide composite glass has at least the following advantages: energy losses in the form of heat are significantly reduced; and (ii) an effective electrical connection is provided on the metal oxide layered glass.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modification other than those specifically described.

For example, the current and period over which it is applied during electroplating may vary provided the metal is adequately fused to the metal oxide surface of the composite glass. The metal oxide coating on the glass need not be limited to tin oxide but rather may extend to other conductive metal oxide coatings. Similarly, the metal oxide composite glass may be electroplated in practically any conductive metal.

All such variations and modifications are to be considered within the ambit of the present invention the nature of which is to be determined from the forgoing description.

P37433

Claims

1. A method of electroplating a metal onto a metal oxide surface of a composite glass panel, said electroplating being performed for a relatively short time at a relatively high current which is effective in fusing the metal to the metal oxide surface.

2. A method of electroplating as defined in claim 1 also involving ageing of the electroplated composite glass panel under ambient conditions, said ageing being performed after the electroplating.

3. A method of electroplating as defined in claim 1 or 2 wherein the metal is tin and the metal oxide surface of the composite glass is formed predominantly of tin oxide or another conductive ceramic. :Dated this 1 3 th day of September 2000 UTILUX PTY LIMITED By their Patent Attorneys GRIFFITH HACK 37605