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Eurocircuits PCB blog

Mi foglal le jelenleg minket az Eurocircuits-nél, projektek amiken jelenleg dolgozunk, új ötletek, háttér információk és egy hely ahol ön bekapcsolódhat, elmondhatja véleményét és megoszthatja velünk mi a lényeges ön számára mint elektronikai fejlesztő.

Registration is open now

From the 25th until the 28th of September of this year we will have the pleasure of meeting you at the exhibition centre, RAI Amsterdam in Holland, Hall 1 Booth B031, for “HET Instrument 2012”.

While registering for a free entry ticket, you may also choose to register for a free gadget that you can collect on the exhibition.

compass clock
 

This years gadget is the “compass clock”. The gadget is designed by our customer “YMIF engineering”. The realization and sponsoring of the gadget is again a broad cooperation between FHI member companies of which Eurocircuits sponsors and produces the PCBs.

 

Should you wish to participate, you will first need to select: “industrial electronics”.

industrial electronics
 

This editions of “HET Instrument”, our branche, Industrial Electronics is organizing 3 seminars during the exhibition. Eurocircuits is participating in the seminar Design Automation & Embedded Systems. Select the seminar you wish to attend.

seminar
 
 

And last but not least, do not forget to print out your voucher to enter the exhibition.

ticket

 

Készítette: Dirk stans
Közzétéve:
23 Mar 2012
Megtekintés:
3250

Have you ever wondered what we are doing to your data when the order status is Single Image? Here is the answer based on the instructions we give to our data preparation engineers. Many of the steps described below are automated for speed and accuracy but we have ignored this to make a clearer presentation. More information on our requirements can be found on the home page under “Technology Guidelines”.

Stage 2 - Single Image data preparation (Single Image and Single Image Cross Check)

We covered before :

  • Eurocircuits data preparation - Analysis : the initial stage, checking if the data are complete and no obvious problems are there to fulfill the order.
  • Eurocircuits data preparation - Single Image (part I) - drill data and copper layers. : Verify and clean up the drill data and the outer and inner-layers.

This current article, Eurocircuits data preparation - Single Image (part II) - other layers and outputs, is our third article in a series about frontend engineering and is about the preparation of Soldermask, Silk screen (legend), coding on PCB's, making customer panels, machine outputs: "drill layer, rout layer, V-cut layer", SMD paste layers and optional other layers.

Solder-mask preparation

  • Replace any painted pads and areas with proper flash pads and polygons as for copper layers
  • Check for missing soldermask pads on component holes or fiducials
  • Check and add soldermask clearance pads on all non-plated holes
  • Check and correct the cover between the edge of the soldermask and the adjacent copper tracks or planes (= Mask Overlap Clearance or MOC) depending on the specification of the pattern class
  • Check and correct the clearance between the copper pad and the edge of the soldermask (=Mask Annular Ring or MAR) depending on the specification of the pattern class
  • Check and correct the minimum width of the solder-mask bridge between adjacent soldermask pads (=Mask Segment or MSM) depending on the specification of the pattern class
  • Save job
  • solder-mask before corrections solder-mask after corrections

Silk-screen (Legend) preparation

  • Check and clip clearance to the board outline
  • Check and correct minimum text width to 0.17 mm
  • Clip the silk-screen data to ensure that there is no ink on component pads
    • As standard clip back 0.10 mm from the soldermask
    • If there is no soldermask clip against the copper pads, plus drill holes, plus rout layer
    • If there is no copper clip again the drill holes, plus rout layer
  • Save job
  • legend before corrections legend after corrections

PCB coding

  • Add the Eurocircuits order number on the top or bottom silk-screen layer as specified
  • Add UL marking indication and any customer-special marking indication as ordered
  • Add Barcode coding (for traceability) as per specification
  • Save job
  •  
    eurocircuits ordernumber

Drill drawing preparation

  • Assign standard hole-size symbols to the drill holes and provide the key
  • Check that all required dimensions and tolerances are indicated
    • For slots, indicate width, length, plated or non-plated
  • Add any additional information required:
    • Special routing or depth routing
    • Press fit holes
    • Other useful information
  • Save job
  •  
    drillmap

Rout layer preparation

  • Copy outline to rout layer
  • Check for any customer special instructions for board profile and prepare accordingly
    • Special rout shapes and tolerances
    • Non standard tooling (radius, ...)
    • Specific requirements for a customer panel
    • Separate outer (profile) routing from inner routing (cut-outs and slots) and apply proper tool sizes and numbering
  • Convert drill holes larger than 10 mm into inner routing
  • Check and set rout directions
  • Apply tool compensation
  • Add break tabs according to specifications
  • Check and set correct tool sequences for pre-drills, routing stage drills, inner/outer routings
  • Save job
  •  
    routing- prepared

V-cut ( scoring) layer preparation

  • Create V-cut layer with 0.90 mm V-cut draws as per specifications
  • Save job

Paste layer preparation

  • If solder paste data is supplied by the customer use it without modifications
    • convert any painted pads to flash pads.
  • If no solder paste is supplied prepare the paste layer from the board data. Select all non-drilled, flashed pads that are free of soldermask and copy to a paste layer.
  • Save job

Special layers preparation

These layers will be prepared only when ordered.

  • Gold Finger Layer Preparation
    • Create the gold finger connections according the specifications
    • Add specific routing for the gold edge-connectors
    • Check the connections widths and positions and the bus bar width and position against the modified mechanical layers
  • goldfinger before preparation goldfinger after preparation
  • Peel-off Layer Preparation
    • Create the peel-off layer as specified by the customer
    • Check that it is conform to our production requirements and resolve any errors.
  • Via-Fill Layer Preparation
    • Create the via-fill layer as specified by the customer
    • Check that via-fill is only applied on 1 side of the PCB. This cannot be the side with any BGA on it
    • Check that the via-fill layer is conform to our production requirements and resolve any errors
  • Carbon Layer Preparation
    • Create the carbon layer as specified by the customer
    • Check that it is conform to our production requirements and resolve any errors

Make a customer panel

The Single Image (the “deliverable”) may be a customer-specified panel or array. There are three options here:

  • Panelisation done by Eurocircuits according to the Eurocircuits standard panel rules
    • Create a Eurocircuits standard panel using automated panelisation routines in accordance with the order details:
      • Step X and Y
      • Panel border width
      • Distance between the individual circuits
    • Check for panel stability
      • Check routing or V-cut positions
      • Check break-tab positions and add more if needed for panel stability
  • Panelisation done by Eurocircuits to the customer’s specification
    • Prepare the panel to the customer’s panel drawing
    • Check for panel stability
      • Check routing or V-cut positions
      • Check break-tab positions and add more if needed for panel stability
  • Panelisation done by the Customer
    • the customer supplies fully panelised Gerber data
      • Check for panel stability
      • Check routing or V-cut positions
      • Check break-tab positions and add more if needed for panel stability
  • Save job

 customer panel prepared
 

Final Check

  • Build a new netlist from the current data and check it against the reference netlist saved immediatly after the customer data was loaded.
  • If there are any differences between the two netlists, find the reason for it and correct when necessary.
  • Check each copper layer against its original data
  • Some differences are caused by our actions to make the board easier to produce, ignore them and find out where all other difference originate from and repair if needed.
  • If there are no more errors:
    • zip the job data
    • upload it to the system to allow for the next stage in the preparation process to begin

A second engineer now runs a series of checks to confirm that the production data matches:

  • the customer’s order and his other instructions
  • the specifications of the chosen Eurocircuits service

If there are any errors, these must be corrected. When the data is confirmed as correct, it is passed on to the next stage where it will be placed on a production pooling panel. We will bring this story shortly.

Készítette: Luc Samyn
Téma:
PCB Design
Közzétéve:
01 Mar 2012
Megtekintés:
3965

Surface Finishes on printed circuit boards

Then finally, you have finished your design and the moment has come to order the PCB.  You have considered all the important aspects. The DRC check is done and you are relieved: no errors remaining.

The online calculator shows you the default pooling options and offers you the possibility to adjust some of them to your specific need.  En there you bump onto the Surface Finish.  What is Surface Finish and how to make the right choice?

treatment - surface finish

Since all finishes have advantages and disadvantages, it is important to stand still by their application and to check how your boards will be treated during assembly.   The different finishes we offer are Lead-free HAL, Electroless Nickel/Immersion Gold (known as ENIG) and Immersion Silver (ImAg).  All of these are Lead-free and can be used for a RoHS design but also in a SnPb assembly.  Edge connectors can be covered with hard Gold (electroplated Ni/Au).

Leadfree-HAL

The use of HAL as a finish results in PCBs with the highest level of solderability and solderability robustness with regards to multi-step assembly and storage and all this for a reasonable price.  On the other hand, the HAL process requires the submerging of the complete PCB in liquid solder and is responsible for extra thermal load on the PCB.  For that reason, it isn’t the best choice if your board requires small via holes or the board exceeds a normal thickness (when the aspect ratio is high).  Another aspect is the less flat surface it may create.  Although we try to achieve a flat surface, the variety of the amount of solder present on the solder-pads can make this finish less suitable for small sized components with small pad sizes.

ENIG (chem. Ni/Au)

Many customers choose this finish because of the flat surface, the good solderability and the acceptable shelf live, but also because they are already familiar with this finish from before the introduction of the Lead-free assembly.  At least, this parameter could remain unchanged and gave at that time some confidence.  However, the ENIG process is a complicated one with a higher risk of defects (skip plating, black pad or interface embrittlement).  When using ENIG, the solder-joint is formed between the solder and the Ni layer of the NiAu surface, not with the underlying Cu.  The Au is completely dissolved in the solder-joint. This interface is considerably more brittle than a SnCu interface and therefore not recommended for applications where shock, bending or strong vibrations are part of the picture. And last, but not least: it is the most expensive surface finish of the list.  For some applications, like key pads or wire bonding, it is the better choice.

Immersion Silver (chem. Ag)

This surface finish is often a bone of contention, some love this finish, and some hate it. It offers a flat surface, a very good solderability and a long shelf life.  The solder-joint is created with the underlying Cu, since the Ag is dissolved during soldering.  Sounds good, but the ImAg is susceptible to sulferdioxide (SO²) which tarnishes the surface and creates the AgS² layer.  This layer affects adversely the surface solderability. To avoid this tarnish, we pack the PCBs in silver saving paper and require hermetic sealing to avoid moisture and atmosphere SO² coming in.  In case of multi step assembly, the partially assembled boards should better be stored in a sulfur-free atmosphere. If all this handling is not a problem and taken into account, it is the best choice and… the cheapest.

Any lead free

If you don’t choose a finish, your board will be produced on a production panel where the finish is lead-free HAL or chem. Ag or chem. NiAu.  The choice is defined by other PCBs appearing on the same panel.

Gold for edge connectors

Due to the need of abrasive resistance of edge connectors we can finish these connectors with a layer of electroplated NiAu (hard gold).  This finish is processed in a special sized bath construction and only used for these connectors.  It is not possible to have this hard gold processed on other locations of the PCB.

Carbon

Carbon combines a high mechanical strength with a good electrical conductivity and can often be used as a substitute for gold on contacts.  It is applied directly on the Cu and used for switch contacts, foil keyboards and can enable the creation of cross-over conductors.  It is resistant to HAL and soldering processes without showing practically any change in resistance.  Carbon is printed (conductive ink) and the accuracy in position and image is therefore limited by the printing process.

Summary table

eurocircuits surface finish.jpg

 

Készítette: Marianne De Wolf
Téma:
Technology
Közzétéve:
09 Mar 2012
Megtekintés:
4517