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Knowledge Base

Assembly Knowledge Base: Saving time through knowledge transfer

Thanks to our many years of EMS experience, we have compiled tools to support you. For further technical information or additional topics, please contact us, we still have a lot of further information material available.

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Project data

For the processing of your data should be included:

  • Parts list, BOM (Bill Of Materials)
    • Ideally as Excel (XLSX) but can also be processed as TXT or PDF
  • Assembly plan
    • As PDF or as image (JPG, PNG etc.) to check the directions of rotation
  • CAD data
    • As Gerber (RS-274-D), Extended Gerber (RS-274-X), ODB++, Eagle etc.
  • Pick & place file (center point coordinates)
    • As a TXT file in ASCII or as an Excel file

Required project data

Bill of Materials (BOM)

  • Designation (C1, U33, R104 etc.)
  • Value, type or manufacturer's designation (100nF, BAV99, AD8033ARZ etc.)
  • Type (e.g. 1206, SOT-23, SO-8 etc.)
  • Optional columns:
    • Additional component information (tolerance, dielectric, etc.)
    • Supplier article number (Digi-Key, Mouser, etc.)
    • Quantity (quantity per value item)
    • Explicit component manufacturer links
    • Delivery by customer of a component (yes/no)
    • Assembly (yes/no)
    • SMT or THT

Assembly plan

  • Position with designation matching the parts list (C1, U33, R104 etc.)
  • Polarity marking (pin 1, cathode, etc.)

CAD data:

  • Gerber
  • Layerstackup

Pick & Place Data:

  • Designation (C1, U33, R104 etc.)
  • X and Y coordinates of the component center point
  • Rotation angle (0°, 90°, 180°, 270°)
  • Placement side (top or bottom)

SMD assembly - Fiducial marks

In order to ensure the necessary accuracy in today's miniaturized component world, the application of reference points in the form of fiducials is essential.

These are required for automatic solder paste printing as well as for SMD assembly. The machines measure the fiducials with their camera system and can thus precisely determine whether there is an offset in X/Y as well as in theta and correct the offset.

If no fiducials are available for SMD assembly, this increases the set-up process and alternative points such as feed-through holes must be used, which can never guarantee the same accuracy.

PCB Assembly - Best practices for using fiducials in PCB design

If you want to get the most out of automated assembly, you need to set your fiducials correctly. There are some key guidelines for setting fiducials in your design.

  • The fiducial is created by placing an undrilled round copper layer. There must be no solder mask on the fiducial.
  • The optimum size of a fiducial is between 1.0 mm and 3.0 mm. A zone around the mark that corresponds approximately to its diameter must remain free.
  • In the interest of maximum accuracy, three marks must be placed on the edge of the blanks for global fiducial marks. If there is not enough space for this, at least two global fiducials are required.
  • For local reference points, at least two fiducial marks are placed diagonally opposite each other on the outer edge of the SMD component.
  • The larger the PCB, the smaller the angular offset during production. This is because a small angular deviation is easier to detect if the distance between the reference points is greater.

Professional PCB design

Würth's Design Rules and Design Guides are very comprehensive and are used by many as an aid for the various PCB technologies.

read more

Board assembly: Quality standards

Working in accordance with internationally recognized standards is a matter of course for us:

  • IPC-A-600 (acceptance criteria for printed circuit boards)
  • IPC-A-610 (acceptance criteria for electronic assemblies)
  • IPC-7711/7721 (Rework, modification and repair of electronic assemblies)
  • IPC-JSTD-001 (Requirements for soldered electrical and electronic assemblies)
  • IPC-T-50 (Terms and definitions for the printed circuit board and assembly industry)
  • IPC-JSTD-020 (Classification of moisture/reflow sensitive non-hermetic semiconductor components for surface mounting)
  • IPC-JSTD-033 (Handling, packaging, transportation and use of moisture/reflow and/or process sensitive components)

Additional criteria can of course be agreed in individual cases.

Further information

We will be happy to provide you with further information on all topics related to electronic assembly production, saving you valuable time during development. Just ask us!

Common abbreviations

AOI Automated Optical Inspection
ASCII American Standard Code for Information Interchange

BGA Ball Grid Array

CAD Computer-Aided Design
CAM Computer-Aided Manufacturing
CAN Controller Area Network

DIL Dual In-Line (siehe auch DIP)
DIN Deutsches Institut für Normung
DIP Dual in-line package
DFN Dual flat no-lead

EOL End of Life
EDV Elektronische Datenverarbeitung
EMS Electronic Manufacturing Services
EMV Elektromagnetische Verträglichkeit
ERP Enterprise-Resource-Planning
ESB Express Service Bestückung
ESD ElectroStatic Discharge
EXA Express Assembling

FPGA Field Programmable Gate Array
FPT Flying-Probe-Test
FPA Fast Prototyp Assemby


HDI High Density Interconnect

IC Integrated Circuit
ICT In-Circuit-Test
IoT Internet of Things
IPC IPC - Association Connecting Electronics Industries
ISO International Organization for Standardization



LCD Liquid Crystal Display
LCR Inductance (L), Capacitance (C), Resistance (R)
LED Light-emitting diode
LGA Land Grid Array
LTB Last Time Buy

MBB Moisture Barrier Bag
MLF Micro Lead Frame
MLPQ Micro Leadframe Package Quad
MLPM Micro Leadframe Package Micro
MLPD Micro Leadframe Package Dual
MOI Manual Optical Inspection
MSD Moisture Sensitiv Devices


OEM Original Equipment Manufacturer

PBGA Plastic Ball Grid Array
PCB Printed Circuit Board
PCBA Printed Circuit Board Assembly
PCN Product Change Notification
PLCC Plastic Leaded Chip Carrier

QFN Quad Flat No Lead
QFP Quad Flat Package
QM Qualitätsmanagement

REACH Registration, Evaluation, Authorisation and Restriction of Chemicals
RoHS Restriction of Hazardous Substances

SMD Surface Mount Device
SMT Surface Mount Technology
SPI Solder Paste Inspection
SQL Structured Query Language

THR Through-Hole Reflow
THT Through-Hole Technology
TDFN Thin Dual Flat No-lead Package
TQFN Thin Quad Flat No-lead Package

UL Underwriters Laboratories
UTDFN Ultra Thin Dual Flat No-lead Package
UFQFPN Ultra thin Fine pitch Quad Flat Package No-leads

VIA Vertical Interconnect Access
VQFN Very Thin Quad Flat No Leads Package


XDFN eXtreme thin Dual Flat No-lead Package


Contact details

Schaffner GmbH
Rickenbacherstrasse 29
CH - 4460 Gelterkinden

  061 985 94 94
  061 985 94 98

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