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.
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 PCB’s 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 marking is required whenever safety, especially flammability, is a critical issue. For European OEM’s 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.
Our UL certificate E142920 can be found on the UL website here.
Abbreviations used.
TIPS.
The other classes listed in the certificate are no longer used.
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 |
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).
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.
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).
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)
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 |
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.
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:
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.
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).
This is not permitted under UL rules (risk of exposed or torn copper).
We do not offer UL marking for Via Fill for boards less than 0.63mm thick.
We do not offer UL marking for heatsink paste.
All colours that we offer are covered.
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
or use our online Chat.
|
Recently, Eurocircuits introduced a spray coating process for Soldermask, this brings many advantages including a thinner and more unified coating which helps us to meet today’s technology challenges.
The Soldermask is imaged using a Dai Nippon Ledia Direct Imaging system; this improves registration accuracy and eliminates the need for Photo-tools.
The spray coating of Soldermask is only achievable due to the low viscosity of the ink. Due to this low viscosity however, there may also be Soldermask ink in the barrel of the Via Hole. This may or may not remain after final curing depending upon the data provided by the customer.
The Soldermask data we receive for Via’s (holes and pads) varies from customer to customer, the Via’s may have no Soldermask Opening, meaning they are to be completely covered with Soldermask, also known as Tented Via’s.
Fully Tented Via Holes cannot be guaranteed with spray coating due to the viscosity of the ink. There may be a small opening in the Soldermask above the Via Hole and there may be Soldermask residue in the barrel after curing. To avoid this we strongly recommend using our Via Filling option when ordering PCB’s with Tented Via’s.
If the data shows untended Via Holes or Pads we follow our standard design rules, as below:
Additionally, we ensure that our other design rules for Soldermask are also met, as below:
Please also see our:
RoHS regulations are designed to limit or eliminate substances that are dangerous to the environment and to people. Inadequately treated e-waste poses environmental and health risks. The RoHS directive is also meant to increase the amount of e-waste that is appropriately treated and to reduce the volume that goes to disposal.
RoHS (Restriction of Use of Hazardous Substances) regulations limit specific substances – lead, cadmium, polybrominated biphenyl (PBB), mercury, hexavalent chromium, and polybrominated diphenyl ether (PBDE) flame retardants – in electrical and electronic equipment.
RoHS is not a quality standard, and the simple fact that boards are RoHS compatible does not add to the quality of the board. RoHS, or more familiar ‘lead-free’ does have serious effect on PCB fabrication and soldering. The fact that boards are soldered at higher temperatures requires changes in the PCB manufacturing process. New FR-4 materials are developed to withstand the higher temperatures without reducing the lifetime of the final product. More info can be found in our article about lead-free soldering
The European Parliament and the Council of the European Union created a program that standardizes the restriction and use of hazardous substances within the EU while contributing to the protection of human health and the environment. The EU has published Directive 2002/95/EC of the European Parliament and of the Council of 27 January 2003 on the restriction of the use of certain hazardous substances in electrical and electronic equipment and Directive 2011/65/EU of the European Parliament and of the Council of 8 June 2011 on the restriction of the use of certain hazardous substances in electrical and electronic equipment (recast). These directives are commonly referred to as the RoHS and RoHS2 directives.
RoHS compliance means acting in full accordance with RoHS regulations.
DECLARATION
We certify that all components and all homogeneous subcomponents manufactured by Eurocircuits are in compliance with the directive 2011/65/EC of the European Parliament and of the council of 8 June 2011 on the restriction of the use of certain hazardous substances in electrical and electronic equipment (RoHS Directive), amended by Directive (EU) 2015/863
According to supplier’s information we certify the non-use of:
We deem that our products are also compliant with the China RoHS (the Administration on the Control of the Pollution caused by Electronic Information Products).
We certify the non-use of:
A certificate, signed by two directors that are authorised to represent Eurocircuits, can be found here.
For Eurocircuits ,
Lengyel Norbert
Quality Assurance manager
|
|
|
during office hours. We will be more than happy to help.
Eurocircuits meets students
