US 20160372276A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2016/0372276 A1 HAN et al. (43) Pub. Date: Dec. 22, 2016 (54) A PRECIOUS METAL SWITCH CONTACT C2.5D 5/48 (2006.01) COMPONENT AND ITS PREPARATION C2.5D 3/48 (2006.01) METHOD C2.5D 3/46 (2006.01) C2.5D 5/02 (2006.01) (71) Applicant: NANTONG MEMTECH HIH II/04 (2006.01) TECHNOLOGIES CO., LTD, C23C 8/42 (2006.01) Nantong (CN) (52) U.S. Cl. CPC ................ H01H I/02 (2013.01); H0IH II/04 (72) Inventors: Huisheng HAN, Nantong (CN); (2013.01); C23C 18/1605 (2013.01); C23C HONGMEI ZHANG, NANTONG 18/1689 (2013.01); C23C 18/42 (2013.01); (CN); YANG DING, NANTONG (CN); C25D 3/48 (2013.01); C25D 3/46 (2013.01); ZHIHONG DONG, NANTONG (CN); C25D 5/022 (2013.01); C25D 5/48 (2013.01) CHENG HUANG, NANTONG (CN) (57) ABSTRACT (21) Appl. No.: 14/896,403 This invention discloses a preparation method for precious metal Switching contact components by means of plating (22) PCT Filed: Sep. 15, 2014 masking, plating and etching processes. The plating masking PCT/CN2014/090913 process is performed by using a plating mask ink with or (86). PCT No.: without a photo exposure machine. Plating of precious S 371 (c)(1), metals is performed by electroless plating or electro plating (2) Date: Dec. 7, 2015 methods. Etching is carried out with etching solutions con taining weak organic acids, weak inorganic acids or acidic (30) Foreign Application Priority Data buffering agents. Improvement of the etched Surface gloss and prevention of the side etching are realized with the Sep. 15, 2014 (CN) ......................... 2014 10467.116.6 Sulfur-contained compounds. The dust- and oil stain-resis Publication Classification tances of the Switch contacts are improved by increasing the etching depth. The Switch contacts made by this invention (51) Int. Cl. are featured with the advantages of good reliability, good HIH IM02 (2006.01) resistance to dust and oil stain, short contact bounce time, C23C 8/6 (2006.01) long service life, low cost of raw materials and so on. Patent Application Publication Dec. 22, 2016 Sheet 1 of 2 US 2016/0372276 A1 Fig. 1 Patent Application Publication Dec. 22, 2016 Sheet 2 of 2 US 2016/0372276 A1 Fig. 2 US 2016/0372276 A1 Dec. 22, 2016 A PRECIOUS METAL, SWITCH CONTACT exposure machine. U.S. Pat. No. 4,077,852 “Selective Gold COMPONENT AND ITS PREPARATION Plating discloses selectively electroplating gold on metallic METHOD Surfaces containing copper using a chromate film as a plating mask. This procedure permits reduced use of gold FIELD OF THE INVENTION without adversely affecting device performance. In addition, chromate films may be patterned with relatively high dimen 0001. This invention relates to a switch contact compo sional resolution so as to achieve gold plating patterns useful nent used for circuit Switch-on or Switch-off and its prepa in electronic and integrated circuits. The chromate film is ration method, which falls into the technical field of the made by the cathodic deposition of potassium dichromate. Switch contact manufacturing. However, when chromate is used as a plating mask, the gold electroplating conditions must be milder than the commonly BACKGROUND used gold plating condition. Lower plating bath tempera 0002 Precious metals such as gold and silver have good tures and lower Voltage or current density, for example, must electrical conductivity and chemical stability, and thus they be used for the plating. or their alloys can be used as contact materials in the 0005. The Applicant's Chinese Patent Application No. Switches, but their expensive prices limit their application 201310748955 “A Switch Contact Component and Its Scope. Base metals such as iron, cobalt, nickel, aluminum, Preparation Method discloses a three-layer laminated copper, titanium, etc., as well as their alloy, including switch contact component: the substrate is rubber, the inter stainless Steel, have good chemical stability in the atmo layer is a continuous base metal sheet, and the upper layer spheric conditions, but their electrical conductivity when is discontinuous precious metal plating, or discontinuous used as contact materials is usually less ideal than precious binary metal composite layer of base metal plating and metals, their conductivity is usually less than gold and silver, precious metal plating. The structure, which has good elec and their chemical stability is poorer than precious metals tric conductivity and stability, dust-resistance and oil stain such as gold and silver. Furthermore, their electrical wear resistance when used as a Switch contact component, is resistance is generally worse than gold, silver and other formed by printing a partial plating mask and plating. precious metals. In comparison with precious metals, base However, the contact component made by this preparation metals are usually cheap, readily available and in abundant method has limited plating thickness. The plating thickness Supply. As conductive materials or as contact materials, they is restricted by the thickness of the plating mask printed are much less expensive than precious metals. In short, thereon. As we know, it is difficult to obtain a very thick independent use of any of metals results in both advantage printed ink layer. The thickness of printed inks is usually no and disadvantages. more than twenty microns. Therefore, the thickness of 0003 Precious metal plating (particularly gold plating) plating made by this method is less than twenty microns. on contacts made from stainless steel and other base metal 0006. The insufficient thickness means the height of the substrates is an effective method to improve contact perfor conducting contact Surface of the convex dots protruding out mance. Technical personnel have made a lot of efforts to of the Substrate is not enough, and therefore, the contacts improve gold plating methods and the gold plating quality of dust resistance and oil stain resistance shall be impacted. the contacts. For Example, Chinese Patent Application No. When the plating thickness exceeds the thickness of the 201310564337 “Process Method of Gold Plating on Mini plating mask, the plating mask will be submersed in the sized Relay Contacts and Reeds' discloses the solutions to plating. When Submersed in the plating, the plating mask, instability of contacting resistance and statistic bonding which is electrically insulated, may spill to the contact function by using specific plating fluid formulas and improv Surface and lead to an increase of contact resistance, even to ing the density and purity of the gold plating. USA Patent a failed conductivity function. In addition, the contact angle Application 20140045352 “Connector with Gold-palladium of the printed ink on the base metal substrate is difficult to Plated Contacts' discloses a method for controlling the color be controlled to 90°. That is, it is very difficult to make the of the binary metal alloy by adjusting the gold and palladium edge of the printed ink perpendicular to the surface of the concentration in the binary metal alloy. Japanese Kokai base metal Substrate, and thus the edge of the plating is Tokkyo Koho 2003-0571 11 discloses a technique to elimi hardly perpendicular to the base metal substrate. nate the pinholes in the plating and improve the corrosion 0007 Steel, stainless steel, copper or copper alloy, nickel resistance of silver-based contacts, by the use of a sputtering or nickel alloy are common base metals for the preparation method to coat a 1 um thick gold layer, and then by the use of contacts. For the etching on these metals, etching solu of electroplating method to coat a 1 um thick gold layer on tions containing relatively strong inorganic acids such as the silver-based contacts. The So-prepared contacts have HC1+HNO+FeCl+caprolactam (used for stainless steel good reliability even in highly corrosive gas environments. etching) (Chinese Patent Application No. 201010160309.9). 0004 Chinese Patent Application No. 201010557154.2 HNO+FeCl+NaCl (used for stainless steel etching) (Chi “Fabrication Process of Partial Gold Plating Sheets” and a nese Patent Application No. 201310100019.9), fluoboric series of patent documents filed by the same applicant and acid or fluosilicic acid-methyl sulfonic acid or amino Sul applied on the same date disclose a method to implement fonic acid-water soluble ferrous salt (used for the etching of partial gold plating, wherein a protective dry membrane is tin without corrosion to copper and nickel) (Chinese Patent photo-exposed selectively, so as to shelter the non-plating Application No. 2013 101871607), nitric acid or sulfuric Zone. An alkaline-dissolved protective dry membrane and an acid-hydrogen peroxide+specific polymers (China Patent exposure machine must be used in this method. Chinese Application No. 2009 10023466.2), nitric acid and/or sulfu Patent Application No. 2009 10023466.2 “A Spare Part ric acid-hydrogen peroxide+ammonium--aromatic amine-- Laminating Method before Partial Gold Plating on Reeds” nitro compounds (Chinese Patent Application No. discloses a method of one-side gold plating, also using an 201110110116.7), nitric acid--nickel nitrate--iodic acid-- US 2016/0372276 A1 Dec. 22, 2016 amino acid (U.S. Pat. No. 4,556,449), sulfuric acid-perox uncured photosensitive ink, so as to make a dotted, striped ide+low molecular weight carboxylic acid (used for copper or latticed base metal surface exposed from the substrate; etching) (U.S. Pat. No. 4.462,861), sulfuric acid-nitrate-- 2) precious metal plating: on the areas of the Substrate hydrogen peroxide (JP2004-52001), Ferric chloride-l-hydro Surface without plating masks printed, a coating in thickness chloric acid-high molecular compound (JP2000-336491), of 0.05-5 um of precious metals is applied by electroplating phosphoric acid-hydrogen peroxide (JP2006-294797), and or electroless plating; or one coating of 0.1-20 um thick perchloric acid-ceric ammonium nitrate (JP2004-59973), non-precious metal is plated by electroplating or electroless are used as etching solutions.