Eurocircuits Printed circuits blog

What keeps us busy at Eurocircuits, projects we are working at, new idea's, background information and a platform where you can participate, give your opinion and guide us to what is important for you as an electronics developer

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Posted by   Dirk stans  on 24 Jun 2014  | Posted under   PCB design Hits: 4800
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How to achieve an ideal PCB Design flow by using the Eurocircuits smart menus ?

Helping our electronics design customers to define the best PCB layout flow possible and thus save time, avoid communication problems and achieve the best price and reliability for their PCB, is our goal. To achieve this goal, we have created smart menus and PCB visualization tools.

Our BLOG contains an online presentation and a movie.

Smart menus.

The Eurocircuits price calculator is based upon the technology of our PCB Configurator software - part of the PCB Visualization tools on our website. You can use the calculator with or without data. Even without attaching data, you will have the complete Eurocircuits service at your finger tips including all technical validation rules that apply when choosing different technical options for your board.

We therefore call them "smart menus". They contain:

  • Build-up wizard: including more than 700 pre-defined build-ups including blind and buried via combinations.
  • Panel editor: contains full CAM editing functionality to define a professional customer delivery panel
  • Technical validation: around 300 rules are built into the smart menus to help you to choose only those combinations of options that are viable. All violations are explained and possible corrections proposed. If these are not clear or or do not meet your requirements, you can always get help from our engineers by using the  "launch inquiry" option.
  • Classification wizard: our classification guide shows you the pattern and drill classes available for your chosen base copper foils.
  • Price guidance: on every option you choose, the smart menu informs you if there will be a slight cost increase or if the board is no longer poolable.  If the board is not poolable then the price will be calculated on the basis of production panels containing only this board. Prices calculations always include a matrix showing alternatives based upon other more favourable quantities and delivery terms. You can also define your own price matrix to show your own preferred alternative quantities and deliveries.

Visualization tools

After you have finished your PCB Layout based upon the PCB design parameters you defined using our smart menus , you can load your PCB data into the shopping basket section of your account. Our PCB Visualizer software will then start analysing your data. A few minutes later you will be able to view your board on screen and see the results of the analysis. What can you discover?

  • PCB Configurator: you can view the board and the analysis based upon the order details entered into the price calculator.  If you use the alternative pricing option "Analyse my data", PCB Visualizer will fill out the board parameters in the calculator menu and present its analysis based on our default values.  In either case, go through the order details, viewing all the comments and any possible design rule check (DRC) violations. You can then correct the data to fit the order details, or change the order details to fit the data. Other CAM data preparation functions available include:
    • Panel editor: design standard or complex customer panels interactively on screen.
    • Marking editor: add QR-code, UL-logo, text, date codes, etc... if and where you want them
  • PCB Checker: shows the results of the DRC analysis of your data against the order details. You can view all potential errors one by one and decide what to do in each case. PCB Checker also contains DFM functions including plating index, solder paste surface area, possible fiducials in a design, ....

Presentation "Your optimum PCB design flow"

Our presentation takes a tour through all Eurocircuits' smart menus and PCB Visualization tools and shows how they can help you gain time, avoid misunderstandings and save costs by defining an ideal PCB design flow.

View the Presentation - click here

The presentation is best viewed when you open the speaker notes and view them on a second screen. This can be controlled from the option button in the bottom left corner.

 

MOVIE: How to use our smart menus and PCB Visualizer

This film gives an overview of how to use our smart menus efficiently to determine your PCB layout parameters and how to then use PCB Visualizer to check your layout against your pre-set design values.

You can always view this video in full screen mode by clicking the right symbol  on the navigation bar and upgrade the resolution by clicking the setting symbol .

 
 
 
 

 
Posted by   Luc Samyn  on 14 Aug 2014  | Posted under   PCB production Hits: 3614
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What is UL?

The Underwriters Laboratory (UL) was set up around 120 years ago in the USA as an independent facility to test the safety of new products and new technologies.  Today it has a network of sites around the world focussed on product safety.  It test products, certifies manufacturers, and produces and updates safety standards across a broad range of industrial and commercial sectors. More.

For PCBs the main standards are UL 796, the specific PCB standard, and UL 94 for flammability testing of all plastics.  These specify a number of performance tests to measure the long-term reliability and fire safety of the PCB.  If a board is released to these standards, it is marked with the UL logo, the fabricator’s logo and the board type.  So here for Eurocircuits, we see on the left the UL logo, then Eurocircuits’ UL trademark, and last ML for “multilayer”.

 
UL on the PCB

When is UL marking used?

UL marking is required whenever safety, especially flammability, is a critical issue.  For European OEMs it is often required on any boards that go into equipment that will be imported into the USA.  The requirement may be set by the OEM or by the end customer.

What does UL marking mean?

  1. The base material meets the specified flammability level laid down in UL94.  For FR4 the level required is UL94 V0.  This means that when a vertical sample of the material is introduced into the test flame and then removed, it will self-extinguish within 10 seconds.  It will not drip flaming particles.
    All Eurocircuits FR4 materials meet the requirements of UL 94 V0.  For boards requiring UL marking we use Isola and Nan Ya materials
    • For STANDARD pool multilayer boards we use IS400 Mid Tg 150°C (this Tg is higher than standard FR4 to ensure full compatibility with lead-free soldering).
    • For all high Tg (170° - 180° C) requirements we use Isola PCL-FR4-370-HR.
    • For one and two layer boards we use IS400 Tg 150°C or Nan Ya NP-155F Tg 150°C
      => For more information on their properties see UL Certificate E41625 for Isola materials and E98983.
  2. The base material meets the specified level for ability to resist ignition from electrical sources.  For the values see E41625 and E98983.
  3. The base material meets the specified electrical breakdown (tracking) or Comparative Tracking Index (CTI) value.  This is the voltage difference at which the insulation properties of the base material may break down, causing safety and performance issues.  The Isola and Nan Ya FR4 materials meet the requirements of Class 3 (175 – 249 V).
  4. The base material meets the performance profile levels specified for direct support of current carrying PCBs (DSR).  These are specified in UL Standard ANSI/U/796A.
  5. The boards meet the other specifications set out in the table under UL marking in STANDARD pool below.

Eurocircuits UL specs

Our UL certificate E142920 can be found on the UL website

Abbreviations used.

  • Cond = conductor
  • Edge: this is explained below
  • Thk = thickness
  • SS = One copper-clad side
  • DS = Two copper clad sides including single-sided and multilayer
  • DSO = Double-sided only
  • Max Area Diameter: this is explained below
  • Meets UL796 DSR requirement.  See item 4 above.
  • CTI = Comparative Tracing Index.  See item 3 above.

TIPS.

  1. UL marking is free of charge.
  2. To add UL marking to your order, click on “Advanced options” at the bottom of the Price calculator menu, and then tick the “UL marking” box.  The smart Price calculator menu will flag any options that are not UL-compatible.
  3. When data has been uploaded, the Marking editor can be used to define the UL logo position.

General.

  1. All boards requiring UL marking are made in our factory in Eger, Hungary.
  2. We offer UL marking in STANDARD pool only.
  3. We have 3 active board classes, each with its own UL marking:
    1. i. Multilayer boards: designator ML; marking:

       
      UL ML
    2. ii. 1- and 2-layer boards with minimum thickness 0.63 mm: designator DV; marking:

       
      UL DV
    3. iii. 1- and 2-layer boards with thickness 0.38 mm – 0.62 mm: designator DS; marking:

       
      UL DS

The other classes listed in the certificate are no longer used.

UL marking in STANDARD pool

UL marking is only available for PCBs which are conform to the parameters listed here (the numbers in brackets indicate more information below). This includes poolable and non-poolable options.

UL type Designator

ML

DV

DS

Usable for

Multilayer

Single and Double sided

Single and Double sided

Base Materials

IS400

PCL-FR-370HR

IS400

NP-155F

PCL-FR-370HR

IS400

NP-155F

PCL-FR-370HR

UL 94 Flame Class

V-0

V-0

V-0

Min. build-up thickness (mm) (1)

0,63

0,63

0,38

Min. bonding sheet (prepreg) thickness (microns) (2)

126

Minimum outer layer conductor thickness (microns) (3)

18

18

18

Maximum inner layer conductor thickness (micron) (4)

70

Minimum track width (mm) (5)

0,10

0,10

0,10

Minimum edge track width (mm) (6)

0,15

0,15

0,15

Maximum conductor area diameter (mm) (7)

76,20

76,20

76,20

Surface finishes:

Leadfree HAL

Immersion NiAu (ENIG) (8)

Immersion Ag

 

Yes

Yes

Yes

 

Yes

Yes

Yes

 

Yes

NO

Yes

Hard gold edge connector

Yes

Yes

Yes

PTH on the board edge

Yes

Yes

Yes

Round-edge plating

Yes

Yes

Yes

Copper up to board edge (9)

NO

NO

NO

Carbon paste

Yes

Yes

Yes

ViaFill (10)

Yes

Yes

NO

Heatsinkpaste (11)

NO

NO

NO

Soldermask types (12)

ELPEMER 2467

XV501T Screen XV501T-4 Screen

ELPEMER 2467

XV501T Screen XV501T-4 Screen

ELPEMER 2467

XV501T Screen XV501T-4 Screen

Hole plugging material (ViaFill)

XV501T-4 Screen

XV501T-4 Screen

Peelable soldermask

Yes

Yes

Yes

Carbon ink

SD 2841 HAL *IR

SD 2841 HAL *IR

SD 2841 HAL *IR

Solder limit

Maximum temperature (°C) (13)

265

265

265

Solder limit

Maximum time (sec) (13)

20

20

20

Maximum operating temp (°C)

130

130

130

1. Minimum build-up thickness (mm)

This is the thickness of the PCB measured over the laminate where there is no internal or external copper.

The minimum  STANDARD pool thicknesses which can be UL marked are:

 

UL-ML

UL-DV

UL-DS

UL min. build-up thickness (mm)

0,63

0,63

0,38

Min. STANDARD pool thickness (mm)

0.80

0.80

0.50

TIP

For UL marking of UL-DS PCBs the surface finish must be Che Ag or No surface finish (leadfree/leaded HAL is not possible due to the min board thickness requirement of 0.80mm for HAL and Che Ni/Au is not available for UL-DS-marked PCBs due to the fact that we always use  a via-fill in combination with Che Ni/Au).

2. Minimum bonding sheet (prepreg) thickness (microns)

Minimum prepreg thickness in a multilayer. This may be one prepreg or a combination of different prepreg.

 

UL-ML

UL-DV

UL-DS

UL min. bonding sheet (prepreg) thickness (microns)

126

In STANDARD pool most of the 700+ pre-defined builds meet this requirement. The smart Price calculator menu will flag any pre-defined build that is not UL-compatible.

3. Minimum outer layer conductor thickness (microns)

Specifies the minimum END copper thickness for the outer layers.

 

UL-ML

UL-DV

UL-DS

UL min. outer layer conductor thickness (microns)

18

18

18

For 2-layer and multilayer boards all start copper foil thicknesses may be used: 12µm (end +/-30µm), 18µm (end +/-35µm), 35µm (end +/-60µm), 70µm (end +/-95µm) and 105µm (end +/-130µm).

For 1-layer boards the start copper foil is the same as the end copper thickness, so following start copper foils are available: 35µ (end +/-35µm), 70µm (end +/-70µm) and 105µm (end +/-105µm).

4. Maximum inner layer conductor thickness (micron)

Specifies the maximum END copper thickness for the inner layers.

 

UL-ML

UL-DV

UL-DS

UL max. inner layer conductor thickness (micron)

70

On inner layers start copper foil is the same as end copper thickness.  UL marking is available only for 12µm, 18µm, 35µm and 70µm (not 105 µm)

5. Minimum standard track width (mm)

The minimum width of any track on any layer placed more than 0.40mm from the edge of the board.

 

UL-ML

UL-DV

UL-DS

UL min. standard track width (mm)

0,10

0,10

0,10

eC PCB Classification pattern class

Class 8

Class 8

Class 8

6. Minimum edge track width (mm)

The minimum width of any track on any layer placed less than 0.40mm from the edge of the PCB-board.

 

UL-ML

UL-DV

UL-DS

UL min. edge track width (mm)

0,15

0,15

0,15

eC PCB Classification pattern class

Class 6

Class 6

Class 6

This is a UL requirement to prevent damage to fine tracks near the edge of the PCB.

TIPS.

  1. Eurocircuits’ standard specifications still apply.  If a PCB is break-routed, there can be no copper on the outer layer within 0.25 mm of the edge of the board or 0.40 mm on the inner layer.  For V-cut scoring the clearance must be 0.45 mm on all layers.
  2. Copper up to the board edge is not allowed under UL rules – see (9) below.

7. Maximum conductor area diameter (mm)

This specifies the maximum solid, unpierced conductor area on any layer of a PCB-board, measured by the diameter of the largest circle that can be inscribed within the conductor pattern.

 

UL-ML

UL-DV

UL-DS

UL max. conductor area diameter (mm)

76,20

76,20

76,20

A “solid, unpierced copper area” is defined as any “full” or “solid” copper plane that does not have any PTH or NPTH holes in it.  This rule has been introduced by UL to reduce the thermal mismatch between a large solid copper plane and the laminate.

The diameter is measured thus:

 
UL maximum copper area

TIP

In most cases copper planes will include clearances for drill holes and so are not solid.  Otherwise if UL marking is required for designs with very large unbroken copper areas, consider using cross-hatching.

8. Surface finish - Immersion NiAu (ENIG)

To ensure optimum quality on immersion nickel-gold PCBs with closed vias we use ViaFill. As we do not offer UL marking on ViaFill for boards less than 0.63 mm thick, we cannot offer UL marking on type UL-DS PCBs (less than 0.63 mm).

9. Copper up to board-edge

This is not permitted under UL rules (risk of exposed or torn copper).

10. ViaFill

We do not offer UL marking for ViaFill for boards less than 0.63mm thick.

11. Heatsinkpaste

We do not offer UL marking for heatsinkpaste.

12. Soldermask types

All colours that we offer are covered.

13. Solder limit – temperature and time

These are the values that we use in our quality checks.

 

If you have any questions, please contact us by email at euro@eurocircuits.com This e-mail address is being protected from spambots. You need JavaScript enabled to view it or use our online Chat.

 

Posted by   Lengyel Norbert  on 21 Oct 2014  | Posted under   PCB quality Hits: 1031
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Quality assurance -  Microsection analysis

Introduction

Microsectioning or cross-section analysis is a destructive sample testing procedure, used throughout the PCB fabrication industry. We make regular microsections each day, as they allow us to see inside the PCB and make precise measurements to check our production processes and to confirm the quality of the finished PCBs.

We use microsectioning to check the quality of:

  • PCB base material
  • inner structure of multilayer boards
  • plating in plated-through holes
  • thickness and registration of external and internal conductors
  • connection between the layers
  • soldermask cover
  • surface finish thickness

Microsectioning procedure

  1. Select the appropriate PCB or quality-control test coupon
  2. Cut out a piece for sample
  3. Embed the sample in resin
  4. Grind down to a flat surface
  5. Polish and etch back if needed

Multilayer build checking

We check the build-up of the multilayer PCB, the thickness of the cores, copper foils and prepregs, and the effectiveness of the bonding process. We also look for any defects in the laminate after thermal stress (delamination, blistering, voids or cracks etc.)

We inspect the registration of inner copper lands to the holes. The next picture shows the same PCB as the last one, but when we measure the registration of the hole to the inner layer copper we see that there is some misalignment (in this case within tolerance).  We also use a special test coupon on all multilayer production panels to confirm the position of the drilled holes relative to the (already printed) inner layers.

 

 

There should be a robust connection between the wall of the plated through hole and the inner layer copper as shown in the next picture.  A poor or broken connection points to process issues in drilling or hole-wall cleaning.  A broken internal connection on a finished board would be caught by electrical test.

 

Through hole plating

We make 5 non-destructive measurements of the thickness of the plated copper in the holes on every production panel.  We back this up with regular microsectioning to get more information about process quality. For this we use the test coupon which we put on every production panel.

The plating thickness is the average of six measurements taken three on each side of the hole roughly a quarter, a half and three-quarters down.

 

Our standard tolerance for component holes is +/- 0,1 mm. We measure the finished hole diameters at final inspection using a tapered gauge.  Microsectioning backs this up and provides more detailed information on the quality of our processes.  The next picture shows the actual width of a plated hole with nominal diameter of 250 microns.

 

Copper thickness

Inner layers

Inner layers are not plated so the copper thickness is that of the copper foil used.  However, some copper is lost during the cleaning processes.  The IPC A 600 Class 2 standard gives the following values for the minimum acceptable copper foil thickness after processing:

Start copper

Minimum thickness after processing

12 µm

9,3 µm

18 µm

11,4 µm

35 µm

24,9 µm

70 µm

55,7 µm

 

This image show the copper thickness after processing for an inner layer with 35 µm start copper:

 

Outer layers.

Outer layers are plated up when we plate through the holes, so that the final copper thickness is the start copper foil less any copper lost during cleaning plus the plated copper.  IPC A 600 Class 2 gives the minimum acceptable finished copper thickness after processing as:

Start copper

Minimum thickness after processing

12 µm

29,3 µm

18 µm

33,4 µm

35 µm

47,9 µm

70 µm

78,7 µm

 

Microsectioning shows the thickness of an outer layer track with 18 µm start copper:

 

We can also measure separately the thickness of the base copper and of the plated copper.  The base copper foil in this case was 12 microns.

 

Solder mask

The minimum solder mask thickness over the copper conductors should be 8 µm.

 

Surface finish

We can use microsectioning to measure the thickness of Leadfree Hot Air Levelling (HAL). For electroless gold over nickel (ENIG or Che Ni/Au) we can only use microsectioning to measure the nickel thickness (as shown in the picture) as the gold thickness is under 0.1 µm. For measuring the thickness of the gold and for Immersion silver we use non-destructive X-ray measurement.

 

Posted by   Lengyel Norbert  on 24 Apr 2014  | Posted under   PCB quality Hits: 2956
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Quality assurance - Part 2 : After Production

Final inspection steps

1. Check the quantity of boards received.

If we lose boards during manufacture, we immediately launch a top-up order. We push this through production to try to meet the original delivery date. The new order has the extension –E1, so you can see if there’s been a reload on your order by checking the Running orders menu. If we lose boards at final inspection, then we immediately reload. Depending on the type of PCB, a remake is typically completed in 2 working days.

2. Check the dimensions of the PCB against the drawing.

Sample check.

For each sample check, the number of samples to be tested is laid down by our QA department. This number is based on the size of the order and more than 30 years of manufacturing experience.

We use Eurocircuits’ standard tolerances unless the customer has requested special tolerances. For standard tolerances see our blog “PCB design tolerances” ( coming soon).

3. Check the board thickness against the drawing.

Sample check.

The standard tolerance based on the laminate manufacturers’ specifications is +/- 10%. If there is a gold edge-connector, the measurement is always taken there

 

4. Check the finished hole diameter.

Sample check.

We measure the finished hole size using a measuring microscope or a tapered probe with a read-out dial. The hole size tolerances depend on the type and size of the hole – see our blog “PCB design tolerances

5. Check hole positions

Sample check

We check the position of the holes relative to the edge of the PCB and to each other using a measuring microscope.

100% visual check.

We check all boards to ensure that there is no drill breakout on outer or inner layers.

6. Bow and twist.

We check where needed.

If any boards are not flat, then we measure the bow and twist. For more information and some hints on designing to avoid bow and twist, go to our dedicated blog http://www.eurocircuits.com/eurocircuits-printed-circuits-blog/bow-and-twist-in-printed-circuits and eC-Glossary.

7. Cosmetic appearance.

Sample tape test.

We use tape tests to test the adhesion of legend ink, soldermask, surface finish and copper. We press a strip of pressure-sensitive tape across the test area and then pull it off sharply. There should be no bits of legend ink, soldermask, surface coating or copper adhering to the tape.

100% visual inspection

The PCB must be clean and free from any damage, scratches, fingerprints, dust etc. All design features must be present (holes, pads, tracks, slots and cut-outs, profiling for panels etc.)

8. Base material.

100% visual inspection

The base material must be correct to specification and show no defects (delamination, measling (white spots), inclusions etc.). More.

9. Copper pattern.

100% visual inspection.

All copper tracks, pads, planes must be present and of correct size to IPC specifications, and not over- or under-etched. To ensure that track widths are correct we use etch-compensation, that is, we increase the track widths on the phototools used to print the boards by the amount that the track will be reduced when it is etched (see further http://www.eurocircuits.com/eurocircuits-printed-circuits-blog/eurocircuits-data-preparation-make-production-panels) . Any nicks (“mousebites”), pinholes or scratches must also be within IPC specifications. More.

The isolation distance track to track (TT), track to pad (TP), and pad to pad (PP) must be correct to IPC specifications. There must be no shorts between copper features or open circuits (these will have been detected by electrical test). The inner layers must be correctly aligned to the outer layers. This has been checked at electrical test. There must be no inner layer copper exposed at the board edge (we normally cut back copper planes to ensure adequate clearance).

10. Copper surface.

Sample check

  1. The principal thickness measuring checks are made immediately after plating, but we check a further sample at final inspection.
  2. The operator makes a tape test to check the adhesion of the surface finish, soldermask and legend to the surface of the PCB. We press a strip of pressure-sensitive tape across the test area and then pull it off sharply. There should be no bits of copper, surface coating, soldermask or legend ink adhering to the tape.

100% visual inspection.

The copper surface under the soldermask must be free of any damage, pitting, oxidisation, staining or burning.

11. Plated through holes.

Sample check

We measure copper thickness using specialist measuring instruments. We have separate probes to measure the copper thickness on the surface of the PCB and through the holes. The copper on the hole walls must be minimum 20 microns thick. The main inspection is immediately after plating (see Part 1). At final inspection we measure a further sample.

100% visual inspection

Plated-through holes must be drilled right through and clear of any obstruction (glass fibres from the laminate, trapped dirt etc.). There must be no defects in the plating through the holes (voids, cracks, plating detached from the wall of the hole etc.). A complete break in the plating will have been detected at the electrical test stage and the board scrapped. More.

12. Non-plated holes.

100% visual inspection.

They must be clean and clear of any obstructions or contamination (glass fibres, plating etc.).

13. Via fill.

100% visual inspection.

Holes specified for via-filling must be completely closed, though the soldermask need not completely fill the hole.

14. Soldermask.

Sample test.

Poor soldermask adhesion or curing is detected by the sample tape test described under Para 10

15. Legend.

Sample test.

Poor legend adhesion or curing is detected by the sample tape test described under para 10.

100% visual inspection.

The colour must be correct and the text legible without smearing. The marking should be cut back from the edge of the soldermask window by 0.1 mm. The legend must be correctly registered. More.

100% visual inspection.

The soldermask must be of the correct colour and free of dirt or damage (some minor repairs are allowed). There must be no soldermask or soldermask residue contaminating pads to be soldered. It must be correctly registered - see eC-Glossary.

16. Peelable soldermask.

100% visual inspection.

The peelable soldermask must be a continuous layer 0.25 mm thick, free from dirt or damage and with no visible separation from the board surface. There must be no residual contamination elsewhere on the PCB.

17. Markings.

100% visual inspection.

Eurocircuits’ order number, UL marking and any other special marking requested by the customer must be in the designated location and on the designated layer (typically the legend layer) as specified in the customer’s order.

18. Surface finishes.

Sample check on all finishes.

Poor surface finish adhesion is detected by the sample tape test described under Para 10.

18.1. Lead-free hot-air solder levelling.

100% visual inspection.

The surface must be flat and even across the PCB without any non-wetting. Component holes must not be narrowed or blocked. A few via holes may be blocked if they are not covered by soldermask.

18.2. Electroless gold over nickel.

Sample checks.

  • Thickness measurements.
  • Solderability test
  • Tape test.

100% visual inspection.

The finish must cover all exposed copper and have the same colour across the PCB. There must be no discolouration even in the holes

18.3. Chemical silver.

Sample check.

  • Thickness measurement
  • Tape test.

100% visual inspection.

Must not be tarnished or blackened. Finished boards are wrapped in “silver save” paper to avoid any oxidisation of the silver.

19. Thermal shock test

Sample test.

A sample is taken from every multilayer job and immersed in molten solder for a defined length of time. It is then checked for any delamination, blistering, solder-mask lifting etc.

20. Solderability test.

Sample test.

A sample is immersed in molten solder for a short time. The surface must be completely coated with solder with no de-wetting or non-wetting.

Calibration

All measuring equipment is regularly calibrated back to national standards

Posted by   Lengyel Norbert  on 15 Apr 2014  | Posted under   PCB quality Hits: 2981
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Quality assurance - Part 1 : During Production

Introduction

Quality is not something that is inspected into your PCB. We build it into your boards from the moment you open the price calculator. Our smart menus guide you towards optimum manufacturability. Then PCB Visualizer checks the manufacturability of your specific data-set. We back the quality of your data by preparing the right tooling, using the right equipment, buying in the right materials, designing and implementing the right processing, and hiring and training the right operators. There’s more on this in our video: “How to make a PCB.” Operator training is critical. It is the duty of every operator to check the boards as they go through their process, and we make sure that they have the training and the expertise.

Of course, our fabrication process also include specific inspection and test steps. We use these to make sure that our processes are running correctly. These steps give you the added re-assurance that the board you receive is correct to your design and will perform correctly over the lifetime of your product. These steps are described below.

Standards

We inspect all boards to IPC-A-600 Class 2 This is the standard used for most PCBs, and is the standard most often specified by our customers. The IPC, or Institute for Printed Circuit Boards, is “a global trade association representing all facets of the industry including design, printed circuit board manufacturing and electronics assembly.” The IPC-A-600 standard “describes the preferred, acceptable and non-conforming conditions that are either externally or internally observable on printed boards”. It divides PCBs into 3 product classes. Class 2 includes “products where continued performance and extended life is required, and for which uninterrupted service is desired but not critical.” Class 3 (where uninterrupted service is critical) is used for aerospace, defence and medical applications. For more information visit www.ipc.org.

Customers, especially those supplying the US market, may also specify UL marking. In this case, we further inspect to UL796. The Underwriters’ Laboratory (UL) is “an independent global safety science company …. dedicated to promoting safe living and working environments, UL helps safeguard people, products and places in important ways, facilitating trade and providing peace of mind.” For PCBs, the most important criterion highlighted by UL marking is flammability. All our FR4 material meets UL 94 V0 plastics flammability test. For more on UL visit www.ul.com.

Inspection steps during production.

Front-end Engineering

The first step is to make sure that the data that we will use to make your PCBs is correct. To find out how we do this, go to our blog “Front-end Data Preparation

Fabrication tests

We run 3 types of test during fabrication, visual, non-destructive measurements and destructive tests. The destructive tests are used to check our processes. They are made on actual PCBs or on the test coupons which we put onto every production panel. After more than 30 years of PCB manufacturing experience, we have developed test coupons on the production panels which provide simple, non-destructive tests for more complex parameters.

Each fabrication step can be seen in our video “How to Make a PCB”. The sequence below is based on a multilayer PCB. Single- and double-sided boards do not use all these steps, but are tested in the same way.

Passport

The results of these checks are summarised for each job in its Passport which contains information on the materials used, measurements made and tests passed. You can access the Passport via the blue book icon with each job under View Running Orders once it has been inspected or under Order repeats/View history.

Traceability

If you need more information on a job, we have full traceability back to material batches etc. Contact euro@eurocircuits.com or your local sales channel for this service.

Step 1. Base material.

This is automatically checked against the order details using a data-matrix. The material data (type, manufacturer, laminate and copper foil thickness) is entered into the job history and will appear in the final Passport.

 

 

2. Print and Etch inner layers.

Visual checks.

This step includes 3 visual checks:

  1. After printing and stripping to make sure that the unwanted etch resist has been stripped away cleanly
  2. After etching to make sure that all the unwanted copper has been etched away.
  3. At the end of the process to make sure that all the etch resist has been stripped from the board.

Sample check.

Each production panel has a specially developed test coupon which indicates that the board has been correctly etched and that the track widths and isolation distances are correct. The type of etch resist used and the values for track width, isolation distances and annular ring are entered into the Passport file.

3. Inspect inner layer copper patterns.

We use Automatic Optical Inspection equipment to scan the inner layer copper and compare it to the design data. The machine checks that all track widths and isolation distances correspond to the design values and that there are no short or open circuits which will cause the finished board to malfunction.

A Pass is entered into the Passport.

4. Multilayer bonding.

Material.

This is automatically checked against the order details using a data-matrix. The material data (type, manufacturer, pre-preg and copper foil) is entered into the job history and will appear in the final Passport.

Thickness after bonding.

This is measured on each production panel and the result entered into the Passport.

5. Drilling.

The drilling machines automatically check drill diameters to ensure that the size of the holes will be correct. A special test coupon on multilayer boards confirms the position of the drilled holes relative to the (already printed) inner layers.

 

The smallest finished hole size is entered into the Passport.

6. Hole-wall preparation.

We deposit a layer of carbon on the walls of the holes to make them conductive for electroplating. We enter the process into the Passport.

7. Apply plating resist

Visual checks.

After printing and stripping to make sure that the unwanted plating resist has been stripped away cleanly

Type of resist is entered into the Passport.

8. Copper and tin plating.

Non-destructive sample check.

The operator measures the copper thickness in the holes at 5 or more locations on one panel from every flight bar. The result is entered into the Passport .

9. Outer layer etching

Visual checks.

After etching to make sure that all the unwanted copper has been etched away.

Sample check.

Each production panel has a specially developed test coupon which indicates that the board has been correctly etched and that the track widths and isolation distances are correct. The type of etch resist used and the values for track width, isolation distances and annular ring are entered into the Passport file.

10. Soldermask.

During process.

Visual checks:

  1. Each panel is evenly coated with soldermask ink (laquer)
  2. Alignment of soldermask phototool to the PCB

Sample checks:

The operator uses a projection microscope to check every panel to ensure that the soldermask is correctly aligned and that there are no solder-mask traces on pads.

The adhesion of the soldermask to the surface of the PCB is checked by the tape test used after legend printing.

The type of soldermask ink used is entered into the Passport data.

11. Surface finish

Sample checks on all surface finishes:

  1. The thickness is measured using an X-ray scope.
  2. We check the adhesion of the surface finish to the surface of the PCB using the tape-test after legend-printing.

100% visual inspection.

1. Lead-free hot-air levelling.

The surface must be flat and even across the PCB without any non wetting. Component holes must not be narrowed or blocked. A few via holes may be blocked if they are not covered by soldermask.

2. Electroless gold over nickel.

The finish must cover all exposed copper and have the same colour across the PCB. There must be no discolouration even in the holes

3. Chemical silver.

There must be no tarnishing or blackening.

The surface finish used is entered into the Passport, even where the order is for “Any leadfree”.

For gold and silver finishes we also enter the actual values measured.

12. Component legend.

Sample checks after curing:

The operator makes a tape test to check the adhesion of the surface finish, soldermask and legend to the surface of the PCB. We press a strip of pressure-sensitive tape across the test area and then pull it off sharply. There should be no bits of copper, surface coating, soldermask or legend ink adhering to the tape.

Visual check.

The operator checks that the legend on every board is clean and legible without blurring or smudging.

13. Electrical test.

All boards are electrically tested except single-sided boards where electrical testing is an option.

  1. Shorts and open circuits.

We build a netlist from the Gerber and drill data. We use this as a reference netlist to test all nets are tested for shorts and open circuits. A pass is recorded in the Passport. As an extra precaution, if your design system outputs IPC-D-356A netlist format include the file in your data-set. We can then use this to check the Gerber netlist against your design netlist.

  1. Inner layer registration.

A special test coupon allows us to confirm that the inner layer registration is correct.

14. Profiling and milling.

We check the size and position of the board profile and internal milling using special test coupons.

15. Final inspection.

See Part 2.