Menu

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.

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.

 

This blog is also available in following languages
Készítette: Luc Samyn
Közzétéve:
14 Aug 2014
Megtekintés:
3565