BSI Standards PublicationLow-voltage switchgear and controlgear Part 7-4: Ancillary equipment — PCB terminal blocks for copper conductors... IEC 60068-2-20 - Environmental testing - Part
Scope
This part of IEC 60947 specifies requirements for PCB terminal blocks primarily intended for industrial or similar use
Mounting and securing components on a printed circuit board (PCB) is achieved through soldering, press-in, or similar techniques, ensuring both electrical and mechanical connections between the copper conductors and the PCB.
This standard pertains to PCB terminal blocks designed for connecting copper conductors, whether or not they require special preparation These conductors must have a cross-section ranging from 0.05 mm² to 300 mm² (AWG 30 to 600 kcmil) and are intended for use in circuits with a rated voltage not exceeding 1,000 V a.c at frequencies up to 1,000 Hz or 1,500 V d.c.
Large cross-section terminal blocks are specifically designed for high current PCBs, accommodating applications with wire sizes up to 300 mm² For further details, examples of high current PCBs and their corresponding terminal blocks can be found in Annex C.
NOTE 2 AWG is the abbreviation of “American Wire Gage” (Gage (US) = Gauge (UK)); kcmil = 1 000 cmil;
1 cmil = 1 circular mil = surface of a circle having a diameter of 1 mil;
This standard may be used as a guide for special types of PCB terminal blocks with components, such as disconnect units, integrated cartridge fuse-links and the like
If applicable, in this standard the term “clamping unit” is used instead of “terminal” This is taken into account in case of references to IEC 60947-1.
Normative references
This document references essential documents that are crucial for its application For references with specific dates, only the cited edition is applicable In the case of undated references, the most recent edition of the referenced document, including any amendments, is relevant.
IEC 60068-2-20, Environmental testing – Part 2-20: Tests – Test T: Test methods for solderability and resistance to soldering heat of devices with leads
IEC 60352-1, Solderless connections – Part 1: Wrapped connections – General requirements, test methods and practical guidance
IEC 60352-2, Solderless connections – Part 2: Crimped connections – General requirements, test methods and practical guidance
IEC 60352-3, Solderless connections – Part 3: Solderless accessible insulation displacement connections – General requirements, test methods and practical guidance
IEC 60352-4, Solderless connections – Part 4: Solderless non-accessible insulation displacement connections – General requirements, test methods and practical guidance
IEC 60352-5, Solderless connections – Part 5: Press-in connections – General requirements, test methods and practical guidance
IEC 60352-6, Solderless connections – Part 6: Insulation piercing connections – General requirements, test methods and practical guidance
IEC 60352-7, Solderless connections – Part 7: Spring clamp connections – General requirements, test methods and practical guidance
IEC 60512-2-1, Connectors for electronic equipment – Tests and measurements – Part 2-1:
Electrical continuity and contact resistance tests – Test 2a: Contact resistance – Millivolt level method
IEC 60512-4-1, Connectors for electronic equipment – Tests and measurements – Part 4-1:
Voltage stress tests – Test 4a: Voltage proof
IEC 60512-5-2, Connectors for electronic equipment – Tests and measurements – Part 5-2:
Current-carrying capacity tests – Test 5b: Current-temperature derating
IEC 60512-11-7, Connectors for electronic equipment – Tests and measurements – Part 11-7:
Climatic tests – Test 11g: Flowing mixed gas corrosion test
IEC 60512-11-9, Connectors for electronic equipment – Tests and measurements – Part 11-9:
Climatic tests – Test 11i: Dry heat
IEC 60512-11-10, Connectors for electronic equipment – Tests and measurements – Part 11-
IEC 60695-2-11, Fire hazard testing – Part 2-11: Glowing/hot-wire based test methods –
Glow-wire flammability test method for end-products
IEC 60695-2-12, Fire hazard testing - Part 2-12: Glowing/hot-wire based test methods - Glow- wire flammability index (GWFI) test method for materials
IEC 60695-2-13, Fire hazard testing – Part 2-13: Glowing/hot-wire based test methods –
Glow-wire ignition temperature (GWIT) test method for materials
IEC 60947-1:2007, Low-voltage switchgear and controlgear – Part 1: General rules
IEC 60998-2-3, Connecting devices for low-voltage circuits for household and similar purposes – Part 2-3: Particular requirements for connecting devices as separate entities with insulation-piercing clamping units
IEC 60999-1 outlines the safety requirements for connecting devices that utilize electrical copper conductors This standard specifically addresses both screw-type and screwless-type clamping units, detailing general requirements as well as particular specifications for clamping units designed for conductors ranging from 0.2 mm² to 35 mm².
IEC 60999-2 outlines the safety requirements for connecting devices that utilize electrical copper conductors This standard specifically addresses screw-type and screwless-type clamping units, detailing particular requirements for clamping units designed for conductors ranging from 35 mm² to 300 mm².
IEC 61210, Connecting devices – Flat quick-connect terminations for electrical copper conductors – Safety requirements
ISO 6988, Metallic and other non-organic coatings – Sulfur dioxide test with general condensation of moisture
For the purposes of this document, the terms and definitions given in IEC 60947-1, as well as the following, apply
PCB piece of insulating material with fixed metal traces to connect electronic components
Note 1 to entry: Printed circuit boards are typically subdivided according to:
– their structure (e.g single- and double-sided, multilayers);
– the nature of the base material (e.g rigid, flexible)
A PCB terminal block is designed for mounting on a printed circuit board, featuring one or more insulated contact units It facilitates both electrical and mechanical connections between copper conductors and the printed circuit board.
The rated current is the continuous current value specified by the manufacturer that a PCB terminal block can carry through all its poles, considering the maximum cross-section This rating is typically applicable at an ambient temperature of 40 °C, ensuring that the upper limiting temperature is not exceeded.
2.4 contact unit conductive part establishing the connection between printed circuit board and connectable conductor(s)
Note 1 to entry: See Annex A
The ULT maximum temperature of a PCB terminal block is determined by the sum of the ambient temperature and the temperature rise caused by current flow, ensuring that the terminal block remains operable under these conditions.
Note 1 to entry: At ambient temperature = ULT the available temperature rise due to current flow is zero, thus the current carrying capacity of the PCB terminal block is zero
LLT minimum temperature of a PCB terminal block assigned by the manufacturer, at which a PCB terminal block is intended to operate
Various types of PCB terminal blocks can be distinguished based on several criteria: the type of clamping unit, the ability to accept prepared conductors as per IEC 60947-1:2007, the type of electrical contact to the printed circuit board, the method of mechanical fastening to the board, the number of poles, the pitch or center-to-center pin spacing, the configuration of contact units with identical or dissimilar clamping units, the number of clamping units per contact unit, and the specific service conditions.
Summary of characteristics
The characteristics of a PCB terminal block are as follows:
– type of PCB terminal block (see 4.2);
– rated and limiting values (see 4.3).
Type of PCB terminal block
The following shall be stated:
– type of clamping units (see 7.1.1);
– type of contacting on the printed circuit board;
Rated and limiting values
Rated voltages
Subclauses 4.3.1.2 and 4.3.1.3 of IEC 60947-1:2007 apply.
Rated current
Verification of the rated current specified by the manufacturer is made according to 8.4.5
When defining the rated current at an ambient temperature different from 40 °C, manufacturers must specify the ambient temperature used for the rating in the technical documentation Additionally, they should reference the derating curve outlined in IEC 60512-5-2, Test 5b, if applicable.
The derating curve is obtained by applying a reduction factor of 0,8 according to IEC 60512-5-2, Test 5b If another reduction factor is used, this shall be stated in the technical documentation.
Standard cross-sections
The standard values for cross-sections of copper conductors to be used are given in Table 1
Table 1 – Standard cross-sections of copper conductors
Metric size ISO Comparison between AWG/kcmil and metric sizes
Size Equivalent metric area mm 2 AWG/kcmil mm 2
Maximum cross-section
The maximum cross-section shall be selected from the standard cross-sections given in Table 1.
Connecting capacity
For PCB terminal blocks with a cross-section range of 0.05 mm² to 35 mm², the specifications in Table 2 must be followed Conductors can be either rigid (solid or stranded) or flexible The manufacturer is required to specify the types of conductors, along with their maximum and minimum cross-sections, and indicate how many conductors can be connected to each clamping unit Additionally, any necessary preparation for the conductor ends must be provided by the manufacturer.
Table 2 – Relationship between maximum cross-section and connecting capacity of PCB terminal blocks
Maximum cross-section Connecting capacity mm 2 AWG/kcmil mm 2 AWG
Marking
A PCB terminal block must be clearly and durably marked with the manufacturer's name or trademark for easy identification, along with a type reference that allows for the retrieval of relevant information from the manufacturer or their catalog.
Small PCB terminal blocks with unmarked surfaces should only be labeled as specified in section a) In such instances, all required information must be displayed on the smallest packaging unit.
Additional information
Manufacturers must provide specific information in their data sheets, catalogs, or on packaging, including compliance with IEC 60947-7-4 if applicable, the maximum cross-section, the connecting capacity (if it differs from Table 2), the number of conductors that can be connected simultaneously, and the rated current along with the reduction factor for the derating curve if it is not 0.8.
The rated current is ideally assessed using four-pole contact units Additionally, it is important to consider the rated insulation voltage (U_i) and the rated impulse withstand voltage (U_imp) when applicable Service conditions that differ from those outlined in Clause 6 should also be noted, along with any special preparation required for the end of the conductor.
6 Normal service, mounting and transport conditions
Constructional requirements
Clamping units
The clamping units shall allow the conductors to be connected by means ensuring that a reliable mechanical linkage and electrical contact is properly maintained
Insulating materials, excluding ceramics or equally suitable alternatives, must not transmit contact pressure unless the metallic components possess adequate resiliency to accommodate potential shrinkage of the insulation.
The corresponding test is under consideration
Clamping units and connecting methods listed in Table 3 fulfil the requirements of this standard
Table 3 – Standards for clamping units and connecting methods
The article outlines various reference standards for clamping units and connecting methods, including screw-type clamping units compliant with IEC 60999-1 or IEC 60999-2, screwless-type clamping units adhering to IEC 60999-1, IEC 60999-2, or IEC 60352-7, and wrapped connections as per IEC 60352-1 Additionally, it covers crimped connections following IEC 60352-2, insulation displacement connections (accessible) according to IEC 60352-3 or IEC 60998-2-3, and insulation displacement connections in general.
The article discusses various connection methods as outlined in international standards, including press-in connections (IEC 60352-5), insulation piercing connections (IEC 60352-6), and flat quick-connect terminations (IEC 61210) It also mentions soldered connections in accordance with IEC 60068-2-20 Additionally, it emphasizes that the selected test method must be clearly stated in the test report, ensuring compliance with IEC 60998-2-3.
NOTE The relevant standard applies for the preconditioning of prepared conductors.
Mounting and installation
PCB terminal blocks must be designed for secure mounting on printed circuit boards through methods such as soldering, pressing-in, or screwing It is essential that the connection to the printed circuit board remains intact and undamaged when connecting the conductors.
Tests shall be made in accordance with 8.3.2.
Clearances and creepage distances
For PCB terminal blocks, the manufacturer specifies the rated impulse withstand voltage (U imp) and rated insulation voltage (U i), with minimum clearance and creepage distance values provided in Tables 13 and 15 of IEC 60947-1:2007, Amendment 1 (2010).
For PCB terminal blocks for which the manufacturer has not declared a value of rated impulse withstand voltage (U imp ), guidance for minimum values is given in Annex H of IEC 60947-1:2007
Electrical requirements are given in 7.2.2.
Terminal identification and marking
Subclause 7.1.8.4 of IEC 60947-1:2007 applies with the following addition
A PCB terminal block must include space for identification marks or numbers for each clamping or contact unit associated with its circuit, unless physical constraints prevent such markings.
If such marking is not possible the information shall be stated by the manufacturer, e.g in the manufacturer's data sheet or his catalogue or on the packing unit
Such provision may consist of separate marking items, such as marking tags, identification labels, etc.
Resistance to abnormal heat and fire
The insulation materials of PCB terminal blocks shall not be adversely affected by abnormal heat and fire
Compliance is checked by: a) the glow-wire test on the complete product according to 8.5 or b) verification of the insulating material in accordance with
1) IEC 60695-2-12, method GWFI at a temperature of 850 °C or
2) IEC 60695-2-13, method GWIT at a temperature of 775 °C
This verification is not necessary for small parts (see IEC 60695-2-11)
NOTE 1 The relevant test method is specified by the manufacturer
NOTE 2 For some applications it may be mandatory to check compliance by the glow-wire test on the complete product according to 8.5 only The need is either defined in the end-product standard or by agreement between manufacturer and users See B.1.
Maximum cross-section and connecting capacity
PCB terminal blocks shall be so designed that conductors of the maximum cross-section and the connecting capacity, if applicable, can be accepted
Compliance is checked by the test described in 8.3.4
The verification of the maximum cross-section may be performed by the special test according to 8.3.5.
Performance requirements
Temperature rise
PCB terminal blocks must undergo testing as specified in section 8.4.5 It is essential that the combined ambient temperature and the temperature rise of the PCB terminal block do not surpass the upper limiting temperature (ULT).
Dielectric properties
If a manufacturer specifies the rated impulse withstand voltage (U imp) as per IEC 60947-1:2007, the stipulations outlined in sections 7.2.3 and 7.2.3.1 of the same standard, along with Amendment 1 (2010), must be adhered to Additionally, if relevant, the impulse withstand voltage test should be conducted in accordance with section 8.4.3 a).
For the verification of solid insulation the power-frequency withstand voltage test shall be carried out in accordance with 8.4.3 b)
Verification of adequate clearances and creepage distances must comply with section 8.4.2 For PCB terminal blocks lacking a declared rated impulse withstand voltage (U imp) by the manufacturer, minimum value guidance is provided in Annex H of IEC 60947-1:2007.
Short-time withstand current
A PCB terminal block shall be capable of withstanding the short-time withstand current which corresponds to 120 A/mm² for 1 s, in accordance with 8.4.6
The test shall be performed using the smallest cross-section in the current path of the contact unit as declared by the manufacturer.
Contact resistance
The change in contact resistance of a PCB terminal block, as measured by standard 8.4.4, must remain within the allowable limits due to conductor connections and mounting on the printed circuit board.
Ageing test (climatic sequence and corrosion test)
For the verification of the resistance of connections against the influence of temperatures and corrosive atmospheres the climatic sequence test shall be carried out
Compliance is checked by the test described in 8.4.7.
Electromagnetic compatibility (EMC)
Subclause 7.3 of IEC 60947-1:2007, Amendment 1 (2010) applies
Kinds of test
Subclause 8.1.1 of IEC 60947-1:2007 applies with the following addition
No routine tests are specified The verification of the maximum cross-section according to 8.3.5 is a special test All other tests are type tests.
General
Unless otherwise specified, PCB terminal blocks are tested in new and in clean condition, and installed as for normal use (see 6.3 of IEC 60947-1:2007) at an ambient temperature of
The tests are carried out in the order described in the subclauses
Each test is conducted on new individual specimens featuring a minimum of four contact units (one set), with each multipole PCB terminal block accommodating the necessary number of contact units.
For a PCB terminal block family with the same design and comparable form, tests need only be performed on specimens representing the most unfavourable case
The surface of the conductors shall be free of contamination and corrosion which degrades performance
Care shall be taken when stripping conductors to avoid cutting, nicking, scraping or otherwise damaging the conductors
In cases where the manufacturer has stated that special preparation of the end of the conductor is necessary, the test report shall indicate the method of preparation used
The tests are carried out with the type of conductors (rigid or flexible) as stated by the manufacturer
If a PCB terminal block fails a test, the test will be conducted again on a second set of terminal blocks, which must all pass the retest Additionally, if the test is part of a sequence, the entire sequence will need to be repeated.
Verification of mechanical characteristics
General
The verification of mechanical characteristics includes the following test:
– attachment of the PCB terminal block on its support (see 8.3.2);
– verification of the maximum cross-section and connecting capacity (see 8.3.4);
– verification of maximum cross-section (special test with gauges) (see 8.3.5).
Attachment of the PCB terminal block on its support
Testing should be conducted on a minimum of two poles of a PCB terminal block, installed on a suitable support, such as a printed circuit board, in accordance with the manufacturer's guidelines For terminal blocks intended for soldering onto printed circuit boards, the tests must be performed on boards featuring plated-through holes.
The wiring of the PCB terminal blocks for this test shall be carried out as shown in Figure 1 with the maximum cross-section as specified by the manufacturer
Following the verification of contact resistance as outlined in section 8.4.4, the conductor must be connected and disconnected five times in accordance with the manufacturer's instructions, using a new end of the conductor for each connection.
The tightening torque for screw-type clamping units in PCB terminal blocks must comply with Table 4 of IEC 60947-1:2007, or it may follow a higher value specified by the manufacturer.
At the conclusion of the test, the PCB terminal blocks must meet the contact resistance requirements outlined in section 8.4.4 Additionally, the terminal assembly should remain undamaged to ensure its continued usability.
Verification of the maximum cross-section and connecting capacity
The verification of the maximum cross-section and connecting capacity shall be carried out according to the standard for clamping units to be used (see 7.1.1)
NOTE The mechanical properties of clamping units are tested according to the applicable connecting methods listed in Table 3.
Verification of maximum cross-section (special test with gauges)
Subclause 8.2.4.5 of IEC 60947-1:2007, Amendment 1 (2010) applies with the following addition
The test shall be carried out on each clamping unit of one PCB terminal block.
Verification of electrical characteristics
General
The verification of electrical characteristics includes the following:
– verification of clearances and creepage distances (see 8.4.2);
– verification of the contact resistance (see 8.4.4);
– short-time withstand current test (see 8.4.6);
Verification of clearances and creepage distances
Verification is conducted between two adjacent PCB terminal blocks or insulated contact units of a multipole PCB terminal block, ensuring that all live parts and accessible metal components of the PCB terminal block are properly assessed.
Clearances and creepage distances must be measured under specific conditions: a) PCB terminal blocks should be connected using the least favorable conductor types and cross-sections as specified by the manufacturer, or without a conductor if that presents the worst-case scenario; b) conductor ends must be stripped to the length indicated by the manufacturer, if necessary.
The method of measuring clearances and creepage distances is described in annex G of IEC 60947-1:2007
Clearance measurements must exceed the values specified in Table 13 of IEC 60947-1:2007 for case B – homogeneous field, as outlined in section 7.2.3.3 of the same standard This requirement is based on the rated impulse withstand voltage (U imp) and the pollution degree indicated by the manufacturer.
The impulse withstand voltage test must be conducted as specified in section 8.4.3 a), unless the measured clearances meet or exceed the values listed in Table 13 of IEC 60947-1:2007 for case A – inhomogeneous field, as referenced in section 8.3.3.4.1, item 2 of the same standard, including Amendment 1 (2010).
Creepage distances must meet or exceed the values specified in Table 15 of IEC 60947-1:2007, Amendment 1 (2010), in accordance with sections 7.2.3.4 a) and b) These requirements are determined by the rated insulation voltage (U i), the material group, and the pollution degree as indicated by the manufacturer.
Dielectric tests
If the manufacturer specifies a rated impulse withstand voltage (U imp), the impulse withstand voltage test must be conducted as outlined in Table 4 Additionally, the power-frequency withstand verification of solid insulation, in accordance with IEC 60512-4-1, should follow the test voltages provided in Table 5 During this test, PCB terminal blocks are connected using the least favorable conductor configuration (excluding a printed circuit board), with a test duration of 1 minute The test voltage is applied between each pole that may have different potentials in the application.
NOTE The relationship between nominal voltages and of the rated impulse withstand voltage (U imp) are given in Annex H of IEC 60947-1:2007 (see also 7.1.3)
A voltage dip of the test voltage or a disruptive discharge or flashover is not allowed
Table 4 – Impulse withstand test voltages
Impulse withstand voltage a for a height of 2 000 m above sea level at sea level kV kV (1,2/50 às) kV (1,2/50 às)
12 12 14,8 a If the testing laboratory is situated at a height between sea level and 2 000 m, interpolation of the impulse voltage is allowed
Table 5 – Dielectric test voltages corresponding to the rated insulation voltage
Rated insulation voltage A.C test voltage (r.m.s.) a
U i Overvoltage category III Overvoltage category II
500 < U i ≤ 1 000 4,2 3,1 a R.M.S test voltages are based on 6.1.3.4 of IEC 60664-1:2007 and are higher than those of IEC 60947-1:2007, Table 12A in order to be in line with requirements of end-product standards.
Verification of contact resistance
The verification of contact resistance is essential and should be conducted at several key stages: prior to and following the attachment test of the PCB terminal block on its support, before and after the temperature rise test, before and after the short-time withstand current test, and throughout the ageing test, including before, during, and after the process.
The verification is made as specified in 8.3.2, 8.4.5, 8.4.6 and 8.4.7
Contact resistance must be measured between the connected conductor and the interconnection on the printed circuit board (PCB) at each contact unit of a PCB terminal block, as illustrated in Figure 1 This measurement follows the procedure outlined in IEC 60512-2-1 Following tests a), b), c), and d), the contact resistance should not increase by more than 50% of the initial measurement value.
If the measurement value exceeds 1,5 times the initial measurement value, the clamping units and the connecting methods may be evaluated separately
I Test current mV Voltmeter n Number of connections to the printed circuit board per contact unit
CC Trace on the printed circuit board for interconnection
A max Maximum cross-section in mm 2
Figure 1 – Test assembly for the measurement of contact resistance and temperature rise
Temperature rise test
The test assesses the PCB terminal block's capacity to continuously handle the rated current without surpassing the upper limiting temperature (ULT) Unless stated otherwise, this evaluation follows the IEC 60512-5-2 standards under specified test conditions.
The test involves an assembly of PCB terminal blocks arranged side by side, ideally featuring four contact units per level, as illustrated in Figures 1 and 2 These terminal blocks are to be mounted on a printed circuit board (PCB) in a manner consistent with standard usage, connected in series with insulated conductors of maximum cross-section Additionally, the interconnections on the PCB should utilize solid bare conductors of equal cross-section or similar materials, ensuring they are as short as possible.
Figure 2 – Example of wiring structure of a multi-tier PCB terminal block
The tightening torque for screw-type clamping units in PCB terminal blocks must comply with Table 4 of IEC 60947-1:2007, or it may follow a higher value specified by the manufacturer.
The length of connectable conductors and conductor loops shall be taken from Table 6
Table 6 – Length of connectable conductors and conductor loops
Cross-section Length mm 2 mm
For PCB terminal blocks having/providing several connections to the printed circuit board the cross-section of interconnections A B shall be calculated according to the following equation:
A B is the cross-section of interconnections in mm 2
A max the maximum cross-section in mm 2 and n the number of connections to the printed circuit board per contact unit
The sum of cross-sections of interconnections (A B × n) shall not exceed the cross-section of the connectable conductor Examples are given in Table 7
Table 7 – Examples of cross-sectional distribution of interconnections on printed circuit boards
Number of connections to printed circuit board (n)
Cross-section of interconnections ( A B ) mm 2 mm 2
The test assembly must be organized according to the test conditions outlined in IEC 60512-5-2, Test 5b, as illustrated in Figure 1 Unless specified otherwise, the printed circuit board (PCB) size should extend beyond the base area of the PCB terminal block on all sides by a distance equal to five times the spacing of the terminal block Additionally, the specific printed circuit board utilized in the test must be detailed in the test report.
After verification of the contact resistance as described in 8.4.4, the test shall be carried out with single-phase alternating or direct current as described in IEC 60512-5-2, Test 5b
As described in IEC 60512-5-2, the measuring points for measuring the temperature shall be located on the hottest spot above the printed circuit board (component side)
Where applicable it may be necessary to determine the hottest spot by carrying out pre-tests
The reduction factor to determine the derating curve is 0,8 If this is not adhered to, the derating factor used shall be indicated in the technical documentation
After the test and subsequent cooling to ambient temperature, the PCB terminal block must meet the contact resistance requirements outlined in section 8.4.4, without any alterations to the assembly.
Short-time withstand current test
The purpose of this test is to verify the ability to withstand a thermal shock
The test is conducted on two adjacent contact units featuring the longest and most unfavorable current paths of either one PCB terminal block or two adjacent PCB terminal blocks During this test, the PCB terminal block is installed according to the manufacturer's guidelines and connected using conductors with the maximum cross-section A max and interconnections A B, as specified in section 8.4.5 (refer to Figure 3).
The tightening torque for screw-type clamping units in PCB terminal blocks must comply with Table 4 of IEC 60947-1:2007, or it may follow a higher value specified by the manufacturer.
At the end of the test, the test (circuit) assembly shall show no interruptions and the PCB terminal blocks shall be free from cracks, ruptures or other critical damage
After cooling down to room temperature the contact units shall comply with the contact resistance test according to 8.4.4
I Test current mV Voltmeter n Number of connections to the printed circuit board per contact unit
CC Trace on the printed circuit board for interconnection
A max Maximum cross-section in mm 2
Figure 3 – Test assembly for the measurement of short-time withstand current
Ageing test (climatic sequence and corrosion test)
The purpose of this test is to verify that clamping units and connections to the printed circuit board are able to withstand environmental conditions and ageing
The test sequence involves a series of evaluations on PCB terminal blocks, each linked with conductors of both minimum and maximum cross-sections Proper attachment of the terminal block to the PCB must adhere to the manufacturer's guidelines.
The tests are carried out on prepared specimens in the indicated test sequence (see Figure 4)
Following each test step, excluding the contact resistance measurement, a visual inspection of the specimens is required to ensure that the PCB terminal blocks are free from any cracks, ruptures, or significant damage.
Verification of thermal characteristics
The thermal characteristics are checked by the glow wire test
NOTE The tests are not carried out on parts of ceramic material alternative alternative
Cold storage in accordance with IEC 60512-11-10, Test 11j Test temperature: lower limiting temperature of the specimen Test duration: 2 h
Test: sulphur dioxide with general condensation in accordance with ISO 6988 Severity: KFW 0,2 S Test duration: 24 h
Dry heat in accordance with IEC 60512-11-9, Test 11i Test temperature: upper limiting temperature of the specimen Test duration: 168 h
Test: flowing mixed gas in accordance with
Test: impulse withstand voltage (8.4.3 a)) Test: dielectric strength
The test is carried out according to IEC 60695-2-10 under following conditions:
– on parts of insulating materials necessary to retain current-carrying parts in position and on parts of the protective conductor circuit at a test temperature of 850 °C;
– on parts of insulating materials necessary for the proper functioning of the PCB terminal block at a test temperature of 650 °C
When conducting tests on the same sample at multiple locations, it is essential to ensure that any damage from prior tests does not impact subsequent evaluations.
The test is carried out on a single specimen In case of doubt the test shall be repeated on two other specimens which shall then comply with the repeated test
The test is being carried out by applying the glow-wire for one time for 5 s with a tolerance of – 0/+1 s
During testing, the specimen must be positioned in the least favorable orientation for normal use, with the surface to be evaluated held vertically The glow-wire tip should be applied to the designated surface of the specimen, considering the normal use conditions where a heated or glowing object may come into contact with it.
A test specimen passes the glow-wire test if there is no flaming or glowing, or if it meets specific conditions: a) any flames or glowing must extinguish within 30 seconds after the glow-wire is removed (i.e., \$t_e \leq t_a + 30 \, \text{s}\$); and b) the specified layer of wrapping tissue must not ignite.
Verification of EMC characteristics
General
Subclause 8.4 of IEC 60947-1:2007 applies with the following addition.
Immunity
PCB terminal blocks within the scope of this standard are not sensitive to electromagnetic disturbances and therefore no immunity tests are necessary.
Emission
PCB terminal blocks within the scope of this standard do not generate electromagnetic disturbances and therefore no emission tests are necessary
Structure of a PCB terminal block
The structure of a PCB terminal block consists of an insulation body and one or more contact units (see also Figure A.1)
Solder pin/pad or equivalent Current bar(s)
Figure A.1 – Structure of a PCB terminal block
Additional Information to be specified between manufacturer and user
B.1 Additional information available on request of the user
In addition to the product information as described in Clause 5, the following items are subject to agreement between manufacturer and user:
• additional derating curves according to IEC 60512-5-2, test 5b;
• glow-wire flammability test method for end-products according to IEC 60695-2-11;
• glow-wire flammability index (GWFI) of PCB terminal block materials according to IEC 60695-2-12;
• needle flame test according to IEC 60695-11-5;
• ball pressure test according to IEC 60695-10-2
NOTE For the purpose of this annex, the word “agreement” is used in a very wide sense and the word “user” includes testing stations
B.2 Information for testing additional to those mentioned above
• Insulating material group (CTI value) of the insulating material
It is recommended to check the insulating material group by the PTI value;
• Relevant detail specification, if available, for example loaded temperature according to IEC 60512-9-5, Test 9e;
• Tests for T-classified PCB terminal blocks according to IEC 60998-1:2002, Clause 12
Examples of PCBs and PCB terminal blocks for high current application
C.1 Layout of high current PCBs (schematic diagram)
PCB terminal blocks designed for high current applications are typically utilized alongside compatible high current printed circuit boards Connection methods to the PCB include soldering and screwing.
Figure C.1 – Structure of a high current PCB C.2 High current PCB terminal blocks
Figure C.2 – PCB terminal block with soldered connection to the PCB
Figure C.3 – PCB terminal block with screwed connection to the PCB
IEC 60512-5-1, Connectors for electronic equipment – Tests and measurements – Part 5-1:
Current-carrying capacity tests – Test 5a: Temperature rise
IEC 60512-9-5, Connectors for electronic equipment – Tests and measurements – Part 9-5: Endurance tests – Test 9e: Current loading, cyclic
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60664-1:2007, Insulation coordination for equipment within low-voltage systems – Part 1: Principles, requirements and tests
IEC 60695-2-10, Fire hazard testing – Part 2-10: Glowing/hot-wire based test methods – Glow-wire apparatus and common test procedure
IEC 60695-10-2, Fire hazard testing – Part 10-2: Abnormal heat – Ball pressure test
IEC 60695-11-5, Fire hazard testing – Part 11-5: Test flames – Needle-flame test method –
Apparatus, confirmatory test arrangement and guidance
IEC 60998-1:2002, Connecting devices for low-voltage circuits for household and similar purposes – Part 1: General requirements
IEC 61984, Connectors – Safety requirements and tests