PCB - FAQ & Co.

Here you can find several frequently asked questions and answers about our printed circuit boards. You may browse through the categories or use the search. If your question remains unanswered, please contact us by email, phone or contact form. We will reply you as soon as possible.

FAQ:

1. Mechanical Processing
2. Chemical Processing
3. Solder Mask
4. Surface Finish
5. Silk Print
6. Base Materials
7. RoHS/WEEE
8. E-Test
9. Panel Production
10. Tolerances
    1. Why is it necessary to maintain a clearance between copper areas and the routing outline?

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    2. Why is a miminum clearance needed with solder mask bridges?

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       Solder mask bridges are necessary to separate adjacent rectangular pads. If these structures are carried out to thin, they are possibly less stable and may chip off the PCB, and thus preventing a flawless soldering. This is particularly problematic concerning integrated circuits (IC), which have marginal pitches. If the pitch between two pads measures 0.20 mm to 0.25 mm only, an entire application of soldering mask onto all pads without soldering mask bridges is recommended, as the minimum size of these would already be 0.1 mm plus the diameter of the pad.

       Depending on the solder masking process, screens are used for printing, whereat the structures are limited by the mesh density. Very thin solder mask bridges cannot be printed reliably with the screen printing method. This applies particularly to all special soldering mask lacquers and printed circuit boards (PCB) fabricated in China, where this method is applied almost exclusively.

       Besides the risk of chipping off the surface, a very thin soldering mask bridge between two pads does not prevent a possible local bridging of tin. This is caused by the fact that the pads’ height measures cir. 35 µmm contrary to the 15 µmm to 20 µmm of the soldering mask layer.

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    3. Why is the solder mask required to be larger than the appropriate pads?

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    4. How do plot tolerances in films occur?

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    5. Why is the drill pad size in the inner layers required to be larger than in the outer layers?

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    6. Why is the clearance of drillings in the inner layers required to be larger than on the outside?

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Additional information about Printed Circuit Boards (PCBs):

• wikipedia.org
  Online Encyclopedia - Topic PCBs
• www.vde.com
  VDE - Verband Elektrotechnik Elektronik Informationstechnik e.V.
• www.vdi.de
  VDI - Verein deutscher Ingenieure
• www.vdlev.org
  VDL - Verband der Leiterplattenindustrie
• www.zvei.de
  ZVEI - Zentralverband Elektrotechnik- und Elektronikindustrie e.V.
• www.leuze-verlag.de
  Leuze Verlag - Literature about PCBs and PCB production
• www.elektronikpraxis.vogel.de
  Elektronik Praxis - Magazine covering electronics in general and news in the PCB production industry.
• www.elektor.de
  Elektor - Electronics Magazine with manuals and layouts for home made PCBs and PCBAs
• www.ibfriedrich.com (Target 3001)
  The Engineering office Friedrich has been developing layout and CAD software for PCB design and Application Oriented Special Integrated Circuits (ASICs) since 1989.
• www.cadsoft.de
  CadSoft offers user-friendly, powerful, and inexpensive solutions for PCB designs including circuit diagrams, layouts, and autorouting routines.
• http://news.google.de/news
  Worldwide news about Printed Circuit Boards (PCBs)