•A good storage and correct handling will help to preserve the useful life of the printed circuit board, and also will avoid future problems when its time to assemble. •Eliminating the possible humidity content of the circuits, we can avoid some of the most serious assembling quality faults.
The impedance control system is done using some test coupons, the SI6000 soft and the CITS 500s equipment from POLAR INSTRUMENTS.
The equipment measures the impedance on a representative track configuration coupon of which the client has given us a determinate value and tolerance.
When generating files to manufacture a printed circuit board we need to bear in mind some observations:
With the help of the CAD software all the needed layers have to be generated (soldermask, external layers, drilling, solder paste, etc.). We should not leave to the manufacturer the accomplishment of any of the layers. This will decrease the margin of error between the circuit we want and the manufactured circuit.
All files must ideally be made with the same measurement systems (millimetres, inches, tenths of inch) and place all layers in the same working position. The most usual one is to see the printed circuit board from the component side (top layer).
The output format of the different layers, if possible, should be done with Gerber274x and the drilling one in an ASCII code with no extended characters (ACII NONE).
The Gerber files output resolution for the different layers, is advisable to be done in a 5 whole number and 5 tenths format. This format will assure a correct resolution when the Gerber format files have to be translated to the manufacturer’s format.
The drilling or Excellon file, is advisable to be done at least in a hundredth of millimetre resolution and enclose a drilling report were the number of holes and their plating choice can be seen
It is preferable to enclose a file the kind of “read-me. txt”, to explain any extra operations to bear in mind at the moment of. manufacturing the printed circuit board.
To make work easier and protect different files, it is preferable to create a compressed file with all that’s needed to make the printed circuit board.
They are ASCII files with coordinates and simple instructions that allow us to interpret the printed circuit board to be manufactured with independency of the design CAD system used. The different shapes that appear in the printed circuit board (circles, rectangles, oblongs, etc.) and the correspondent diameter are identified with the name “Dcodes” (D10, D15…). Each Dcode has one or more coordinates assigned. At first, the definition of the diameters and shapes of the Dcodes came in a file a part, therefore the Gerber 274x file, which is a developed version of the Gerber, has the advantage of including in one single file the diameter rand the shape definition of each Dcode together with the coordinates. The result is the visualization of the wanted image, that will match with the original in the CAD . Definitively, it is preferable to use the Gerber274x output because we have all the information we need in one single file and, therefore, the mistake at the moment of translating to other formats is minimum.