Photo-Chemical Machining - The Hong Kong Polytechnic University

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Photo-Chemical Machining (PCM)Item PCM Metal StampingMinimum aperture size, for 0.15 – 0.3 mm 0.5 – 1.0 mmmetal thickness 0.1 mm –0.2 mmPitch tolerance, for 10 mm ± 0.005 mm ± 0.013 mmcentre-to-centre dimensionMetal readily processedCopper alloysFerrous alloysNickel alloysMolybdenumAluminiumTungstenCopper alloysFerrous alloysNickel alloysMolybdenumAluminiumIn conclusion, PCM is most suitable for thin gauge, high accuracy and small tomedium quantity job orders. Metal stamping is more appropriate for theproduction of very large quantity. Consequently, PCM serves as the best methodto produce prototypes in sheet metal industry. It has definite advantages overmetal stamping in photo tooling cost, lead time and ease of incorporate designchanges.5. Typical Applications of PCMA wide range of functional products can be made by PCM in electronic,computer, metal working and precision engineering industries. Some typicalapplications worthy of mentioning are as follows:1. Colour TV receiver tube aperture mask, commonly known as shadowmask, normally comprises of some 300,000 perfectly etched slots. PCM isthe only feasible method for the shadow mask manufacturing.2. Integrated circuit lead fame, an electronics component with a complexgeometry, is broadly fabricated by PCM because of the rapid change in ICdesigns and also the geometry becomes more and more complex.3. Stainless steel spring and magnetic head for floppy diskette drive arecommonly fabricated by PCM.4. Metal stencils for SMT can only be made by PCM as accurate dimensionsare strictly required.5. Metal mesh screen, used in juice extractor, is another major PCMapplication.6. Metal toy models, a small batch production of great number of differentdesigns, are typical products made by PCM.Page 6IC Professional Training
Photo-Chemical Machining (PCM)7. Prototypes for precision sheet metal engineering industry, e.g. watch dials.8. Decorative and graphic products are commonly made by PCM due to thelow volume and normally complex pattern design.6. Types of Sheet Metal Suitable to be Etched by FeCl 3Table 6.1Metal(composition)Aluminium (Al) &Aluminium AlloysEtchants FormulationTemperature (°C)40° Bé FeCl 3 43Chromium 42° Bé FeCl 3 : conc.HCl (2:1) 32Constantan (55% 36-42° Bé FeCl 3 49Copper (Cu), 45%Nickel (Ni)Copper & Copper 30-42° Bé FeCl 3 43-49AlloysMoly Permalloy 42° Bé FeCl 3 : conc.HCl (9:1) 54(Ni,13%Fe,5%Cu,4%Mo)Nickel (Ni) 38-42° Bé FeCl 3 49Nickel-iron (Ni-Fe)alloys42Bé FeCl 3 (with HNO 3additions if necessary)Stainless steels 35-48° Bé FeCl 3 35-5549Stainless steels(containingmolybdenum)36-42° Bé FeCl3 with HNO 3additions35-55Steels(mild, spring,silicon and tool)36-42° Bé FeCl 3 52Tin (Sn) 42° Bé FeCl 3 54Page 7IC Professional Training
Page 1 and 2: IC LEARNING SERIESPhoto-ChemicalMac
Page 3 and 4: Photo-Chemical Machining (PCM)Photo
Page 5 and 6: Photo-Chemical Machining (PCM)Fig.
Page 7: Photo-Chemical Machining (PCM)5. Th
Page 11: ReferencesPhoto-Chemical Machining

Photo-Chemical Machining - The Hong Kong Polytechnic University

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