Insight Technology – Finished Hole Size Tolerances

Definition of Tolerance for Manufacturing

Manufacturing tolerances are the amount of variation that is allowed in a measurement

or other characteristic of an object.

Ref: Collins English Dictionary

Tolerances are everywhere, they are applied to everything that is manufactured whether it is a simple screw, a mobile phone or a spacecraft, they are all affected by tolerances and PCB’s are no different.

Even our domestic electricity has a tolerance, for example in Europe it is approx. +/- 6%.

When you design a new product, you do so with a specific set of dimensions in mind, these are known as the nominal dimensions.

However, these must have a tolerance, no matter how small (or large) they must exist to allow for cost effective manufacture.

We should all know that the smaller (tighter) the tolerance the higher the cost of manufacture will be.

For industrial PCB production there are international standards for these tolerances. We produce all our boards according to the “IPC-A-600 Acceptability of Printed Boards” version F (http://www.ipc.org/TOC/IPC-A-600F.pdf) Class II (Industrial products).

Using the Eurocircuits Insight Technology platform together with Eurocircuits TV we have created a series of informative guides that help explain these manufacturing tolerances.

Our first guide in this series is:

Finished Hole Size Tolerances

The finished hole size on a PCB is affected by the following factors:

  • Type of Hole – Plated, Non-Plated or Via.
  • Nominal Hole Size vs available Drill Bit Sizes.
  • Drill Bit Size Tolerance.
  • Drill Bit Wear during use.
  • Hole Cleaning (Desmear).
  • The Plating Process and Copper Balance.
  • The Final Surface Finish of the PCB.

To read more on how and why these factors influence the finished hole size on a PCB simply click on the button below.

 

 

 

Eurocircuits Introduces – PCB Prototype 3+3 Service

Eurocircuits Introduces – PCB Prototype 3+3 Service

 

Eurocircuits understands that Time-to-Market is crucial for developers as they need to meet shorter lead-times to maximise the potential of their new products.

Since the beginning of 2019 we have developed and introduced new software, manufacturing processes and equipment that allows us to reduce the manufacturing and assembly time of your PCB prototypes.

Using these new tools we are very excited to introduce you to our new

PCB Prototype 3+3 Service

Fast & Easy

Your PCB Prototypes manufactured in 3 working days and Assembled in 3 working days as standard, helping you to meet your Time-to-Market challenges.

Reducing our standard delivery term from 12 working days to 6 working days……….that’s 50% faster!

 

Have your Prototypes Manufactured & Assembled

In Europe by Eurocircuits

………………..Why Wait!!………………..

 

 

Direct Imaging – Boosting the Quality of PCB’s and SMD Soldering

 

 

After Directing Imaging (DI) of copper layers, Direct Imaging of Soldermask redefines the boundaries for the soldering of SMD components.

Direct Imaging is the biggest technological advancement for the manufacturing of PCB’s in the last decade.

Since we introduced the Ledia Direct Imaging system (DI) for Soldermask exposure at Eurocircuits, we have been working hard to find its optimum registration capabilities.

As a result we can now offer improved registration capabilities for Soldermask and we are now able to reduce the minimum required clearances for DI compatible Soldermask as below:

MAR to 0.030mm…from 0.060mm
MSM to 0.070mm…from 0.100mm
MOC to 0.060mm…from 0.100mm

Due to the improved registration it is possible to have Soldermask between the pads of fine pitch components and this helps to protect against solder bridging as below.

 

 


DI Soldermask Conventional Soldermask

Smaller Soldermask openings give designers another big advantage, as it allows for tracks to be routed closer to pads.

From a manufacturing point of view, using DI for Soldermask has many advantages. For example, we can switch from one job to another in a matter of minutes as there is no need for films which is a timely process as used on conventional exposure systems.

DI Soldermask demands a premium price from our supplier, however, Eurocircuits believe the benefits out-way this additional cost and does not charge extra for the use of DI Soldermask.

We want our customers to benefit from using DI Soldermask and we see it as a win-win for everyone.

Available colours for DI exposure, at present, are Green, Red, Black and Blue.

For more information please see our PCB Design Guidelines – Soldermask Section.

 

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Tolerances on PCB – Blog

What tolerances should I design into my PCB?

Where possible design your PCB to meet industry standard mid-range tolerances. Eurocircuits use these specifications and tolerances as the basis of our lowest-cost pooling services.

For more detailed information on our Manufacturing Tolerances please see our Tolerances on a PCB page.

 

 

What About Underwriters Laboratory?

What is the Underwriters Laboratory (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 focused 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 printed circuit boards 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 Underwriters Laboratory logo, the manufacturers 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 the Underwriters Laboratory Marking Used?

UL marking is required whenever safety, especially flammability, is a critical issue.  For European OEM’s (original equipment manufacturers) 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 Underwriters Laboratory 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 the properties see UL Certificate E41625 for Isola materials and E98983 for the Nan Ya material.

  1. The base material meets the specified level for ability to resist ignition from electrical sources.  For the values see E41625 and E98983.
  2. 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).
  3. 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.
  4. The boards meet the other specifications set out in the table under UL marking in STANDARD pool below.

Eurocircuits Underwriters Laboratory Specifications

Our UL certificate E142920 can be found on the Underwriters Laboratory website here.

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 PCB’s 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:

Lead-free 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

Via Fill (10)

Yes

Yes

NO

Heatsink Paste (11)

NO

NO

NO

Soldermask Types (12)

ELPEMER 2467

XV501T Screen XV501T-4 Screen

Electra EMP110

ELPEMER 2467

XV501T Screen XV501T-4 Screen

Electra EMP110

ELPEMER 2467

XV501T Screen XV501T-4 Screen

Electra EMP110

Hole Plugging Material (Via Fill)

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 PCB’s the surface finish must be Che Ag or No surface finish (lead-free/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 PCB’s 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 PCB’s with closed vias we use Via Fill. As we do not offer UL marking on Via Fill for boards less than 0.63 mm thick, we cannot offer UL marking on type UL-DS PCB’s (less than 0.63 mm).

9. Copper up to Board-e

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

10. Via Fill

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

11. Heatsink Paste

We do not offer UL marking for heatsink paste.

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

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or use our online Chat.