1 / 7

PCB specs

PCB specs. Single-strip defects. The issue. We have observed some defects in the readout strips (metallic) in a number of boards delivered by ELTOS for the MMSW chambers (as presented by Fabian Kuger , e.g., in the Würzburg Meeting) Defects are Interconnected lines (shorts)

george
Download Presentation

PCB specs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. PCB specs Single-strip defects Joerg Wotschack

  2. The issue • We have observed some defects in the readout strips (metallic) in a number of boards delivered by ELTOS for the MMSW chambers (as presented by Fabian Kuger, e.g., in the Würzburg Meeting) • Defects are • Interconnected lines (shorts) • Interrupted lines (resulting in partly dead strips) • Questions • How many defects of each type can we accept? • Shall we specify limits for these defects in the specs for the PCB producers and, if yes, which? Joerg Wotschack

  3. QC on PCBs • Besides systematic dimension deviations local defects on the PCBs are a QC issue: Repaired lines are straight, width variations are small Defect: Interconnected strips Damaged strip, huge width variation Strip is broken  dead channel Joerg Wotschack

  4. Considerations for the discussion • Tracks from the IP have inclinations between 7 and 35 degrees • Typical cluster sizes (track projection onto readout strips) are 10 – 28 mm or 3(4) to 8(10) strips. • A missing or interconnected strip will lead to a missing or wrong strip signal and thus to a larger position error • Comparable effects are created by the pillars (1% inefficiency) • Proposal: accept defects at a similar level as the inefficiency created by the pillars • ≤10 interconnected lines (shorts) as long as they are distributed; minimum distance between defects: 10 strips • ≤ 10 interrupted lines/PCB (1024 channels) as long as they are distributed; minimum distance between defects: 10 strips • The sum of interconnects and shorts: ≤10/PCB; minimum distance between defects: 10 strips Joerg Wotschack

  5. What to do with defects • Quality control to detect defects • Accept defects as long as below threshold? • Record defects; do not do anything further • Repair, where possible (e.g., shorts) • Centrally (e.g. CERN) • Construction site • Ask for repair (where possible) in PCB industry? • Extra costs? Joerg Wotschack

  6. What to write into specs? • No limits, but ask PCB industry to deliver a protocol with each PCB listing the number and address of defect strips • Define max number of defects (as specified above) • Accept repairs ? • Require repairs ? Joerg Wotschack

  7. What about spares? • How many PCBs of each type do we want to order? Minimum is 64 PCBs of each type • To cope with defects • To allow for selection of PCBs • To allow for accidents during panel construction • Is it cheaper to accept defects and to produce 10–20% more boards? • Option on re-processing after full delivery Joerg Wotschack

More Related