Performance Comparison of HSD and FAKRA Connectors

This article mainly introduces the technical requirements and test methods of audio and video transmission connectors FAKRA and HSD. So that wiring harness engineers can correctly apply and select HSD and FAKRA products.

1 Introduction
This article writes about the technical requirements and test methods of audio and video transmission connectors FAKRA and HSD. The original intention of writing is to facilitate OEMs to provide some reference opinions on the application, selection, and performance verification of HSD and FAKRA products. Everyone is familiar with the general electrical properties, mechanical properties and durability of connectors, and various companies also have mature standards. But regarding the data transmission performance of this type of connector, I think wiring harness engineers still have a lot of confusion about this, so I focused on that part and did some research. Of course, the applications of these two types of plug-ins are not limited to this. The parameters in the article are also different, and these are just some of the editor’s experiences.

Structural diagram of FAKRA and HSD connectors

2: Terms and definitions
In order to prevent anyone from not understanding the terms and definitions involved in the article, let me explain them first:
FAKRA Connector FachkreisAutomobil Connector
FAKRA is a radio frequency signal connector (hereinafter referred to as FAKRA).
HSD Connector HighSpeed Data Connector
HSD is a high-speed data connector that supports the transmission of USB2.0, LVDS, IEEE1394, and ETHERNET protocols (hereinafter referred to as HSD).
FAKRA, HSD connector structure
FAKRA and HSD connectors are composed of sheath, inner conductor, outer conductor, and crimp ring (see Figure 1).

Inner conductor and outer conductor components of FAKRA and HSD connectors

Performance comparison of HSD and FAKRA connectors

Figure 1, HSD structure diagram
The inner conductor, outer conductor, and crimp ring of FAKRA and HSD connectors are crimped to form a conductor assembly (see Figure 2).
Figure 2, FAKRA conductor assembly schematic diagram

Connector unlocking force test

Impedance
Since the impedance remains constant throughout the entire transmission line, characteristic impedance is the name that expresses this characteristic of the transmission line.

Insertion Loss
Insertion loss refers to the signal loss caused by inserting cables or components between the transmitter and the receiver, usually referred to as attenuation. Insertion loss is expressed in decibels (dB) corresponding to the received signal level.

ReturnLoss
It is the reflection caused by the impedance mismatch of the cable link, usually the reflection at the inline. Mismatches occur mainly at the connectors, but can also occur at places in the cable where the characteristic impedance changes.

3 Technical requirements
Generally speaking, the performance of audio and video transmission connectors requires attention to the following technical parameters in the table below:

Test method:
5.2.1 Appearance inspection
Under normal sight intensity and color, maintain normal viewing distance and appropriate lighting. Check terminals, jackets and connectors for deformation, damage or similar appearance.5.2.2 Dimensional inspection
Use qualified instruments and measuring tools to inspect products according to product drawings.5.2.3 Wire adhesion of conductor assemblies
After crimping the wire and conductor assembly, pull the wire axially at a speed of 50mm/min at a distance of 50 to 100 mm from the crimping part, and measure the force when the wire is pulled off or separated from the crimping part.5.2.4 Insertion force of conductor assembly into sheath
Fix the sheath and insert the conductor assembly into the sheath at a rate of 50mm/min along the axis. The conductor assembly must be properly locked, measuring the force during insertion. The wires must not be bent during the test. For waterproof parts, the measurement should be matched with the corresponding waterproof plug.5.2.5 Retention of conductor components to sheath
Insert a conductor assembly crimped onto the conductor into the sheath correctly. At a distance of 50 to 100 mm from the pressing point, pull the wire axially at a rate of 50 mm/min, and measure the force when the terminal is pulled out of the sheath. The force that has acted on the secondary locking mechanism of the conductor assembly should be recorded separately.

5.2.6 Conductor assembly insertion/extraction force
Fix one end of the conductor component, insert and pull out the matching conductor component in the axial direction at a speed of 50mm/min, and measure the force required in the process.

5.2.7 Unlocking force
As shown in Figure 3, According to the connector locking structure, apply force at the point where it is easiest to lock and unlock, and measure the force required to make the A value equal to 0.

Connector side load force

Figure 3, Schematic diagram of unlocking force test

5.2.8 Connector insertion/extraction force
Insertion force: Take a pair of assembled FAKRA/HSD connectors and secure one end. With the lock in action, insert the other end into the fixed end at a rate of 50mm/min, and measure the load during the bonding process.
Pull out force: Take a pair of assembled FAKRA/HSD connectors, plug them together and fix one end. When none of the locks work, pull out the other end from the fixed end at a rate of 50mm/min, and measure the load during the pullout process.

5.2.9 Connector retention force
Take a pair of assembled FAKRA/HSD connectors, plug them together and fix one end. When the lock is in effect, pull out the other end from the fixed end at a speed of 50mm/min, and measure the load required when pulling out.
As shown in Figure 4, According to the locking structure of the connector, among the five directions of the axis and the inclination of 45° with respect to each surface, select the direction in which the unlocking device is most easily released for measurement.
Figure 4 Schematic diagram of holding force test

5.2.10 Connector side load force
Take a pair of assembled FAKRA/HSD connectors (one end is soldered to the board end and the other end is connected to the wire end). After plugging, when the lock is activated, pull the wire end slowly until the pulling force reaches 75N. The direction of pulling is as follows:
Pulling direction: C1, C2, C3, C4, C5, C6, C7, C8; no visual damage is required after the test.

5.2.11 Plastic case prevents misuse and force matching
A plastic case with mismatched tooth shapes was used for testing. One end of the plastic shell is fixed, and the other end of the plastic shell is clamped (and connected to the force testing equipment), and inserted in the axial direction. When misoperation and matching force are reached, the entire plastic case will not be damaged in any way.

Performance Comparison of HSD and FAKRA Connectors

5.2.12 Sealing
This test is only applicable to waterproof FAKRA and HSD. As shown in Figure 7, Make a small hole in a pair of plugged waterproof FAKRA or HSD sheaths or insert a conduit into any hole of the sheath to inject compressed air. Before the test, the parts of the sheath other than the conduit should be sealed. Immerse the connector 100mm below the water surface, introduce 9.8 kPa compressed air each time and hold it for 30 seconds, and observe whether bubbles are generated. When bubbles occur, the test is stopped and the pressure value is recorded.

Connector sealing test

Figure 5 Sealing test

5.2.13 Contact resistance
Connect the inner conductor terminals normally and measure the resistance between the reference points. When the resistance cannot be measured directly from the reference point, the actual measurement point should be chosen as close to the reference point as possible, as shown in Figure 6. The resistance between the actual measuring point and the reference point should be subtracted. Test according to the following two methods:
a) Measured under low current and low voltage. In order to avoid damaging the insulation film of the terminal, when the circuit is connected, the voltage measurement needs to use a DC or AC voltage with a peak value not exceeding 20mV and a current of 10mA for measurement;
b) Measured under article current. Under the condition that the DC voltage does not exceed 14V, the maximum current specified in Table 3 is passed through the loop. Measurements were taken after thermal equilibrium was reached. If the wire to be measured needs to be welded at the measurement point, the welding must not affect the plugging.
Figure 6 Contact resistance test
5.2.14 Crimp metallographic analysis
Take a Fakra/HSD that only crimps the terminal, cut it off at the crimped part of the terminal, and use a grinder to grind the section flat and clear. Then use a metallographic analyzer to measure and analyze the parameters of the crimping.

5.2.15 X-ray non-destructive testing
Take a Fakra/HSD with built-in terminals, put it into the X-ray machine and fix it with a clamp, close the door for radiographic inspection. During the inspection process, the angle and position of the sample are continuously adjusted through the console outside the X-ray inspection room to completely observe the crimping condition of the crimping part. To ensure safety, X-ray inspection equipment must be operated by professional operators.

5.2.16 Insulation resistance
Take a Fakra/HSD with built-in terminals, apply a DC voltage of 500V between adjacent terminals, and on the surface of the terminal and sheath for 15 seconds through an insulation resistance meter, and measure the insulation resistance value. To ensure safety, the connector should be reliably grounded.

5.2.17 High voltage resistance
Take a Fakra/HSD with built-in terminals and apply an AC voltage of 800V (Fakra) or an AC voltage of 500V (HSD) between adjacent terminals and on the surface of the terminal and sheath for 60 seconds. To ensure safety, the connector should be reliably grounded. It is required that no flashover occurs.

5.2.18 Characteristic impedance
Use a vector network analyzer/time domain reflectometer for testing, load the characteristic impedance measurement program in the vector network analyzer, and connect the line to the calibration module for calibration. Then remove the calibration module and connect the sample to the Yanet analyzer (the connection of HSD products requires a special adapter).

5.2.19 Insertion loss
Use the Yanet analyzer for testing, call the insertion loss measurement program in the Yanet analyzer, and first connect to the calibration module for calibration. Then remove the calibration module, connect the measured sample to the Yanet analyzer (the connection of HSD products requires a special adapter), save and export the data after the signal curve on the screen is stable.

5.2.21 Shielding effectiveness
This test requires the use of the tri-coaxial method. Connect the sample to be measured to the triaxial equipment and connect it to the Yanet analyzer. Load the shielding effectiveness test program and start measuring. After the screen data is stable, save and export the data.

5.2.22 Time lag between groups
This test is limited to measurement of HSD products. Using a 4-interface vector network analyzer, connect the product under test to the system according to the following connection method, and transfer the time lag program in the measurement group on the vector network analyzer for measurement.

5.2.23 Near-end crosstalk
Link the test sample to Yanet Analysis for measurement, call up the near-end crosstalk program, and save and save the data after the screen data is stable.

5.2.24 Far-end crosstalk
Link the test sample to Yanet Analysis for measurement, call up the far-end crosstalk program, and save and save the data after the screen data is stable.

5.2.25 Eye diagram
PRBS generator, requires TR (100pcs, 120ps), f (bit)=800Mbit/s, sequence: 2 to the 7th power -1, amplitude (+/-500mV) high-speed oscilloscope.
Connect one end of the sample under test to the PRBS generator, and the other end to the oscilloscope to read the eye diagram. On the middle cross curve on the graph, select a segment with an amplitude of 100 mV, and read the T (Jitter) value corresponding to this segment.

5.2.26 Repeated insertion and extraction
At normal temperature, one end of a pair of connectors is fixed, and the other end is inserted and pulled out of the fixed end along the axial direction, and the cycle is repeated 10 times.

5.2.27 Combined with temperature vibration
Insert the test sample into the terminals and assemble them into two equal groups (reserve 300mm of wire length). The ends of the wires in the first group of samples are welded to each other to form a single continuous current path, which conducts 100mA current for instantaneous interruption monitoring. If the sheath has ≤10 holes, all terminals shall be monitored once. If the sheath has >10 holes, 10 terminals evenly distributed on the sheath shall be monitored in batches. The second group of samples does not monitor instantaneous interruptions. Installation methods 1 and 3 are for wire-to-wire connectors, and installation methods 2 and 4 are for device connectors.
According to the actual installation situation on the vehicle, select the test method according to Figure 11 (when the actual installation situation is unknown, give priority to methods 3 and 4)

In the picture: A – test bench; B – test piece; C – fixture
Figure 11 Installation method
Complete the vibration test in accordance with the following requirements (refer to Table 5 for vibration levels. For V2 products, sinusoidal vibration is performed first, and then random vibration is performed. For V1 and V3 products, only random vibration is performed):
a) Level V1 – installed on the body or chassis. The random vibration test was completed in accordance with the GB/T 2423.56-2006 article using a total root mean square acceleration of 20.9m/s2. The test parameters are shown in Figure 12 and Table 11. The test time for each axis (X/Y/Z) is 24 hours.

Contact resistance testing of connectors

In the figure: abscissa – power spectral density; ordinate – frequency
b) Level 2 – installed in the engine:
1) Sinusoidal vibration test. Use a scanning rate of ≤1oct/min and complete the sinusoidal vibration test in accordance with GB/T 2423.10. The test parameters are shown in Figure 13 and Table 12. The test time for each axis (X/Y/Z) is 24h;
2) Random vibration test. The total root mean square acceleration is 181m/s². The random vibration test was completed in accordance with GB/T 2423.56-2006. The test parameters are shown in Figure 14 and Table 13. The test time for each axis (X/Y/Z) is 24 hours.

5.2.28 Mechanical impact
Take a pair of connectors with embedded terminals and plug them into each other. Use the largest wire diameter that the terminal can accommodate for the wire. Connect all the holes in series and install them on the impact test bench. Use a half-sine shock wave to apply an acceleration of 100g in 6 directions: up, down, left, right, front and back, 3 times in each direction, with a pulse width interval of 10ms.
As shown in Figure 17, check whether there are instantaneous interruptions and changes in connector impedance during the test.

5.2.29 Drop test
Choose a Fakra/HSD with built-in terminals, and use the largest wire diameter that the terminals can accommodate. Put it into a low-temperature tank at -5°C and store it for 0.5h before taking it out. Drop the connector vertically from a height of 1000mm onto the concrete or steel plate, 3 times on each side, as shown in Figure 18.

5.2.30 Heat resistance
Choose a Fakra/HSD with built-in terminals, and use the largest wire diameter that the terminals can accommodate. Use the working temperature specified in Table 4 as the test temperature and test in a high temperature box for 120 hours. After the test, take out the connector and adjust it to room temperature.
5.2.31 Cold resistance
Take a pair of connectors with embedded terminals and plug them into each other. Use the largest wire diameter that the terminals can accommodate. Place the connector in a thermostat with a temperature of -40°C for 120h. After the test, immediately repeat the insertion and extraction actions 5 times, and then return it to normal temperature.
5.2.32 Thermal shock
Impact tests should be performed between the highest and lowest ambient temperature values applicable to the connector in Table 4 (Operating Temperature).
The matched samples will undergo 100 thermal shock cycles. Each thermal shock cycle includes the following steps:
a) 30 minutes at (-40±2)℃;
b) 10s maximum transition time;
c) 30 minutes at the maximum ambient temperature corresponding to the test samples listed in Table 4;
d) 10s maximum transition time.
5.2.33 Temperature and humidity cycle
5.2.33.1 When conducting temperature and humidity cycle tests, the wires should be the minimum and maximum size values within the crimpable range.
5.2.33.2 Carry out 10 cycles of testing in the following order, each cycle is 24 hours:
a) Maintain room temperature t (23±5)℃ and relative humidity (70~75)% for 4 hours;
b) When the relative humidity is (95~99)%, raise t to (55±2)℃ within 0.5h;
c) Keep the result b for 10h;
d) Reduce t to (-40±2)℃ within 2.5h and keep it for 2h;
e) Within 1.5h, raise t from (-40±2)℃ to the classification test temperature and keep it for 2h;
f) Allow to return to room temperature (23±5)°C within 1.5h.
5.2.33.3 After the end of a test cycle, the test is suspended for 2 hours. During the suspension period, the test samples will be stored under the conditions described in a).
5.2.33.4 If it takes more than 1.5 hours for the laboratory to reach the graded test temperature, the process e) can be extended and the process a) can be shortened appropriately.
5.2.33.5 Follow the test cycle shown in Figure 19.
5.2.33.6 For the classification test temperature, see Table 4 Environmental Temperature.

Table 1, technical requirements

project			skills requirement	experiment method
Basic features	Appearance and size	Appearance and size	1. FAKRA’s interface should comply with the requirements of ISO20860-1 2. The interface of HSD should comply with the requirements of 10.2 in TS 2008001 3. The rest of the requirements must be consistent with those of ordinary connectors.
	Mechanical strength	Conductor Assembly Wire Adhesion	≥110N
		Insertion force of conductor assembly into sheath	≤30N
		Retention of conductor assembly to jacket	≥110N
		Insertion/extraction force of conductor components	Insertion force＜20N Pullout force: 2N-20N
		unlocking force	Just have the same requirements as ordinary connectors
		Connector insertion force and extraction force	Just have the same requirements as ordinary connectors
		Connector retention	≥110N
		Connector side load force	≥75N
		Matching force of plastic case to prevent misoperation	≥80N
		Sealing	Just have the same requirements as ordinary connectors

 

project			skills requirement	experiment method
Basic features	Electrical characteristics	Data transfer performance	Product Contact Resistance Initial test After durability test FAKRA ≤5mΩ ≤40mΩ HSD ≤15mΩ ≤40mΩ
		Crimp metallographic analysis	Crimp wing gap: not less than 1/10 of terminal wall thickness Crimping wing difference: not less than 1/2 of the terminal wall thickness Burr height: no greater than terminal wall thickness Burr width: no more than 1/2 of terminal thickness Base thickness: not less than 3/4 of the terminal thickness
		X-ray non-destructive testing	There is no free shielding wire or short circuit between the core wire and the shielding wire.
		Insulation resistance	Just have the same requirements as ordinary connectors
		High voltage resistance	FAKRA：800V   AC  HSD：  500V   AC
	Contact resistance	Characteristic impedance	FAKRA should ensure that the characteristic impedance is 50±6Ω and the line is 50±3Ω. HSD should ensure that the characteristic impedance is 100±15Ω and the line is 100±6Ω.
		Insertion loss	See table below
		return loss	FAKRA：≤ -15.6dB  0 to 2 GHZ  ≤ -14 dB   2 to 3 GHZ HSD：≤ -20 dB    0to 1.0 GHz ≤ -17 dB   1to 2.0 GHz
		Shielding performance	FAKRA should meet the requirement of ≤-45dB at 3GHZ HSD should meet 0 – 1 GHz ≤ -65 dB, 1 – 2 GHz ≤ -60 dB
		Intra-group lag (HSD only)	90° plug-in ≤ 25ps 180° plug-in ≤ 5ps Line≤25ps/m
		Inter-group time lag (HSD only)	Plug-in≤5ps Line≤25ps/m
		Near-end crosstalk (HSD only)	＜-30dB to 1GHz
		Far-end crosstalk (HSD only)	＜-35dB to 1GHz
		Eye diagram (HSD only)	Adaptation chip manufacturers provide eye diagram requirements