Технология MIVA

Flatbed

All MIVA photoplotters are flatbed, allowing exposure of film, glass or chrome plates and eliminating any deformation of the medium during plotting. The film is fixed in place during the plotting procedure and the area of the plot is exposed by a projector mounted on a moving X-Y table which moves in a plane parallel to the film. In this way, there is no need for dynamic focussing of the projected picture. Because of this, the projected pixel size and therefore the line width or structure size is stable over the plotting area. Note: For high throughput of glass plates we recommend Premium or Sprinter class photoplotters.

Light source

Before plotting, the complete PCB image is rasterised by the plotter controller. This image is the in turn subdivided into rectangular areas which correspond to the (reduced) rectangular area of the spatial light modulator, usually a Liquid Crystal Matrix, inside the projector. Each of these images is then copied onto the film or glass plate by a single flash from a Xenon flash lamp, as the plotting head passes the flash target position. In this way, each flash transfers over one million pixels to the film in around 2 microseconds (the duration of the flash). After the flash has copied the image to the film, the next image is written into the spatial light modulator ready for the next flash target position to be reached. Exposure or flash frequency is governed by the refresh rate of the matrix and is typically 25-30 hertz. Uniquely, the light source energy is not related to the amount of energy reaching the film – imaging a large black area places no higher power demands on the lamp than imaging just a few pixels, giving a constant exposure density across the whole image. The Xenon flash lamp lifetime is more than 109 flashes – corresponding to over 100 000 full area plots. The maximum power input is only 20 Watts. MIVA Technologies guarantee the xenon flash lamp for five years regardless of plot throughput.

Resolutions, speed and plotting structure size

Resolutions available range from 3000 dpi to 128000 dpi. Each plotter has either two or three switchable resolutions. This enables optimisation of plotter speed and resolution to suit minimum structure sizes required on any one plot. The lower the plotting resolution - the higher the plotting speed and vice versa. It is important to note that on all lasers and raster photoplotters the minimum structure size is directly related but not equal to the projected spot or pixel size. This is because a line or structure is constructed from several pixels which are placed slightly offset to one another. For example, in 3000 dpi mode the specified minimum structure size is not 8,47 microns (this is the projected pixel size) but is specified by us at 70microns. This is because at least 8 pixels are needed to construct a line with high quality edge definition regardless if vertical, horizontal or oblique. Similarly, the minimum line width at 24000dpi is 20 microns and at 128000dpi 4 microns. To choose a MIVA photoplotter with resolutions to match your needs, no mathematics are necessary! Select the resolution you need in the Products table.

Plot size

The maximum film size is obviously determined by the photoplotter bed size. The minimum film size however is for some customers an important factor in reducing film wastage and is not limited on MIVA Compact and Production-class models. Film can be cut to size before plotting. For maximum plot sizes of each machine, please refer to the product overview on this site. Custom size photoplotters can be built on request to meet exceptional customer specifications. Several custom MIVA photoplotters have been installed worldwide to-date. The largest, now working in the UK, has a plotting area of 3m x 1.1m.

Environment

Since the xenon light source generates white light, red green or blue sensitive films may be exposed by this system, although green or blue light sensitive films are more comfortable to work with, as they allow red darkroom lighting to be used. Most plotter manufacturers have exposure technologies using monochromatic light, requiring film types with matching color sensitivities. A darkroom with appropriate lighting is required for loading and unloading of films. During plotting the plotter is light tight and normal working lights can be switched on.

Software

Netlink - Windows 9X, 2000 and XP compatible queue and plot manager.
Netlink runs from any PC on the same network as the plotter. The NETLINK package allows MIVA photo-plotters to be operated remotely via a local area network. NETLINK also allows plot queues to be easily set up for many different types of image and plotting media. It does this by setting up the photo-plotter automatically to work with special media requirements, thereby reducing the chance of operational errors, and minimising the operators workload. MIVA Bitmap Interpreter – for plotting of PostScript, TIFF und PCX data formats.
The MIVA Bitmap Interpreter allows photoplotters to plot bitmap data using data sources in various data formats, currently supported are:
• PCX (1 and 8 bit)
• TIFF (Uncompressed and Packbits format)
• PostScript
Other input formats can be supported as required.
This allows users to do the following:
1. Plot postscript data efficiently and cost effectively. This can convert postscript data (.PS and .EPS types) into TIFF-Packbits data on an external PC, saving processing time on the photoplotter.
2. Preview bitmaps, allowing normal CAM packages to be used to test the panelisation of bitmap data.
3. Gerber output can be generated, this allows postscript logos to be converted for use as test coupons within CAM software or with photoplotters from other manufacturers. CAM350
PCB layout design package CAM350 can be optionally delivered with the plotter. It is a CAM system which address the PCB industry specifically. These systems are generally capable of importing data from CAD systems, checking the data for manufacturing (design rule checks etc) and setting up the data for PCB production. They include functions such as panelization, etch compensation, drill and rout data export, board tester data etc.

Plotter driver and input data formats

The MIVA standard photoplotter driver is dedicated to plotter control and input data rasterization. Driver upgrades are available on request and are free of charge in the guarantee period or as part of a service contract.
Standard input formats are: Gerber, RS-274X (Extended Gerber), HP-GL, Fire 9000.
Optional input formats are: PostScript, TIFF, PCX
RS-274X, otherwise known as Extended Gerber:
This type of data format includes all of the data needed to simulate the aperture table as well as newer functions such as photo-composition (addition of negative and positive data to avoid having to make contact copies of films) etc. This type of data can be fed to MIVA photoplotters directly, requiring no further user manipulation. Postscript and bitmaps – please refer to “MIVA Bitmap interpreter” above. DXF data – several CAM systems now support DXF input, which is useful when dealing with customers who use AutoCAD for occasional designs. As with postscript, you should expect more preparation time when handling this type of file. Hewlett Packard Graphics Language (HPGL) – as with postscript and RS274X this is an easy option for customer to generate. Most CAM systems can read HPGL data. Windows programs can all use the various plotter drivers delivered with the operating system, but there are several pitfalls to be avoided:
1. There are two different scaling systems used with HPGL – the scaling difference is 0.5%, so if the correct type is not recognized immediately, it will cause big problems later on. HPGL data generated with a 74xx driver (say for a 7475 plotter) will be plotted 0.5% too large if interpreted as if the data were meant for a different type of plotter. There is no easy way to tell which system the data was generated for, the customer usually does not know either, so the safest way to process this type of data is to read it into the CAM software and measure it!
2. Some HPGL systems, such as AutoCAD produce HPGL plots which look fine on paper, but not when plotted at high resolution on film. The reason for this is the ink flow on paper – for example, a round pad is drawn as an asterisk (*) shape, making the pad look anything but round on film. Complicated filled areas can show up small missing triangles on plotted films, due to these parts being left out by the filling algorithm. The way to get around these problems, if you have to use HPGL, is to generate the data 4x larger, and reduce it within the CAM package or photoplotter.