1. Common Materials for Connector Insulators

Usually, materials such as PBT, NYLON, ABS, PC, LCP, etc. are shown in Appendix 1, but in principle, materials with better flame resistance are used.

a. PBT material:

Generally, PBT materials with 20-30% glass fiber are commonly used, which have the ability to resist cracking, impact, and electricity. They have good wear resistance, low friction coefficient, good self-lubricating effect, and good oil and chemical resistance. Under high temperature and humidity, it has good dielectric strength. Its shrinkage rate is between 0.6% -3.0%, and its temperature resistance is around 230 ℃. Good formability and flame resistance. It is a commonly used adhesive for connector products.

b. NYLON66, NYLON6T, PC, LCP materials:

Its shrinkage rate is 1.0% -0.3%, and its temperature resistance is higher than PBT. Commonly used, NYLON66 has a temperature resistance of 260 ℃ -280 ℃, NYLON6T has a temperature resistance of 280 ℃ -300 ℃, and LCP has a temperature resistance of 290 ℃ -320 ℃. But its water absorption is relatively high, and it is generally used for products with high temperature resistance and less PITCH (such as SMD, HOUSING, PLCC, etc.)

C. ABS material:

It has good impact toughness, oil resistance, wear resistance, easy forming, good hardness, and rigidity, with a temperature resistance of around 100 ℃. It is generally used for auxiliary products in connectors.

2. Common defects and their causes in injection molding

Common forming defects include the following: black spots or black liquid on plastic parts, surface roughness, overflow, incomplete plastic forming, bubbles or charring, shrinkage, seam lines or plastic parts being compressed in the mold, and other defects. The main reasons are divided into three parts: the factors of the injection molding machine, the factors of the mold, and the factors of the rubber material.

3. Composition and performance of connector contacts

Connector material: The plug is made of metal connector material. Generally, brass is the main material, but there are special requirements for extremely high insertion and extraction times, and phosphorus bronze, beryllium copper, and other materials can be used for long service life. The following is an introduction to the types and properties of copper materials in the current industry

1. Brass - an alloy of copper and zinc, with a common color that varies depending on the zinc content.

a. Brass - containing 25-35% zinc, most suitable for room temperature processing.

b. Brass - containing 35% to 45% tin, most suitable for room temperature processing. Copper plates and rods sold on the market belong to this category.

2. Bronze - an alloy of copper and tin, its color varies depending on the content of tin.

Generally speaking, copper alloys other than brass are called bronze.

Phosphorus bronze - Adding phosphorus to bronze has excellent wear resistance, but excessive phosphorus makes casting difficult. Its composition is 8-12% tin and 0.5-1.5% phosphorus

Selection of contact material

The contact can be made of any one of several alloys, and the specific selection depends on the type of contact, the frequency of insertion and extraction, and the electrical and environmental conditions under which the connector operates. Some commonly used materials and their applications are as follows:

Brass - Although brass is a material with good electrical conductivity, it is prone to deformation and rapid fatigue after repeated bending. It is usually used as a fixed contact in inexpensive connectors or as other metal parts within the connectors. Connectors with brass contacts should not be used in situations where excellent elasticity is required. Of course, due to its low cost, brass can still be used competently as a contact in many places.

Phosphor bronze - Phosphor bronze has a higher hardness than brass and can maintain long-term elasticity. It is often used as a material for contacts with working temperatures below 300 ℃. For most connectors with low insertion and extraction frequency or with contacts in normal bending, the use of phosphorus bronze can ensure good reliability.

Beryllium bronze - Beryllium bronze has much better mechanical properties than brass or phosphorus bronze. Beryllium bronze parts can be shaped and hardened after annealing, and can actually maintain their shape permanently. It is also the most resistant material to mechanical fatigue. In applications with frequent plugging and high reliability requirements, it is recommended to use beryllium bronze material.

4. Local electroplating of copper sheet

Surface processing of connectors (electroplating): The surface of connectors is generally treated with electroplating to prevent corrosion and oxidation, smooth the contact surface, and ensure the mechanical properties of raw materials. Various electroplating characteristics are applied

(1) Plating thickness of 30 μ″， Ni thickness measurement of gold-plated area 50-80 μ″。

(2) Gold plating thickness 3 μ″， Ni thickness measurement of gold-plated area 30-50 μ″。

(3) Other:

Size: Accept according to the order part number size

Appearance: a. Unplated surface: No oil stains, flat material strip, non deformable, bent or stretched.

b. Electroplated surface: glossy and smooth, with fine particles and no pollution or deformation.

c. Baking: Frozen -55 ± 3 ℃ * 30 ′ Room temperature 10 ′ -15 ′ → 105 ± 2 ℃ * 30 ′ → Room temperature 10 ′ -15 ′.

d. Heat resistance: 85 ± 2 ℃ * 2hr.

(4) Copper sheet tin plating

a. Salt spray testing shall be agreed upon by both parties.

b. The baking test is as follows (item 1.3) and the tin content is below 90%.

c. Direct tin exposure accounts for over 90%.

d. Heat resistance: 85 ± 2 ℃ * 2hr.

e. Copper bottom plating, thick plating 30~50 μ″。

f. Tin lead ratio Sn/Pb90:10 or 95:5

g. The thickness of tin plating depends on the order requirements.

5. Electrical performance

a. Voltage and current rating: Voltage rating involves spacing, while current rating involves contact area and pin cross-sectional area. When using, it should be used according to specifications and standards.

b. Contact resistance: When the connector is correctly connected, a current of DC 0.1A is applied between each terminal and the PIN. The contact impedance should be as shown in the attached table. However, when testing with a current of 1KHZ and 1mA in general circuit use, the testing includes the pressing part between the wire and the connector.

c. Insulation impedance: When a voltage of DC500V is applied between terminals and between terminals and grounding points, the insulation resistance value should be as shown in Table 6.

d. The voltage time test between the voltage resistant terminals and between the terminals and the grounding point, as shown in the attached table, should show no abnormalities.

6. Mechanical properties

(1) Insertion force: at a combined speed of 25mm ± 3mm/min. The insertion force obtained from inserting should meet the specifications of the insertion and extraction force.

(2) Pullout force: at a pulling out speed of 25 mm ± 3mm/min. The pull-out force obtained by pulling it out should meet the specifications of the insertion and pull-out force.

(3) Durability: After conducting a 30 ohm insertion and extraction test at a speed of (10 ohm/min), the following requirements should be met.

a: The contact impedance is within two digits of the initial value.

b: The extraction force should meet the specification value.

(4) Terminal retention force: Pull the terminal out of the HSG at a speed of 5 mm ± 3mm/min, and the tensile force should meet the specified value of the tensile force.

(5) PIN retention force: Push the PIN out of the BASE at a speed of 5 mm ± 3mm/min, and its thrust should meet the thrust specification value.

(6) Terminal riveting force: Pull the terminal out of the wire at a speed of 5 mm ± 3mm/min, and its tensile force should meet the riveting specification value

7. Environmental performance

(1) Temperature rise of the terminal: After applying the maximum rated current of AC to any junction until thermal equilibrium, the temperature rise value should be below 30 ℃.

(2) Vibration resistance: Under the energized state of DC 0.1A, the test shall be conducted with an amplitude of 1.5m/m and a frequency of 10Hz-55Hz/min. After three times and two hours each time on the X, Y, and Z axes, the following requirements shall be met:

a: The contact impedance should be within two digits of the initial value;

b: Discontinuous conduction time at 1 μ Below sec;

C: The appearance should be free from abnormalities.

(3) Impact resistance: Under DC 0.1A power on condition, test the X, Y, and Z axes three times with an acceleration of 50g. After the test, the following requirements should be met: a: I discontinuous conduction time of 1 μ Below SEC., b: The appearance should have no abnormalities

(4) Tin adhesion: Immerse 1.2mm from the base plane of the terminal, in a tin bath at 230 ± 50 ℃ for 3 ± 1 second, and there should be more than 95% tin adhesion on the immersion surface

(5) High temperature resistance: After 96 hours in a constant temperature bath at 85 ± 2 ℃, it should be abnormal and the contact resistance should be within twice the initial value

(6) Solder heat resistance: Immerse the terminal body at a reference plane of 1.2mm in a tin bath at a temperature of 260 ± 50 ℃ for 5 ± 1 second, and the insulation should have no abnormal states such as cracks or deformation. The terminal strength should be within the specifications.

(7) Humidity resistance: Place in a constant temperature and humidity bath with a temperature of 85 ± 2 ℃ and a humidity of 90%~95% for 96 hours. After wiping with small droplets, the test should meet the following requirements within 30 minutes:

a. The contact impedance should be within two digits of the initial stage;

b. The insulation resistance should be above 10M Ω;

c. The appearance should be free from abnormalities;

d. It should meet the requirements for voltage resistance.

(8) Salt water spray test: put the sample in a salt water spray with a ratio of 5 ± 1% and a temperature of 35 ± 2 ℃, turn on for 16 hours, turn off for 8 hours, and clean it with clean water after 3 cycles. The following requirements shall be met: a: the contact impedance shall be within two times of the initial value, c: there shall be no cracks or obvious corrosion on the appearance.

(9) Sulfide gas test: After placing the sample in a sulfide gas with a concentration of 50 ± 5ppm at 40 ± 2 ℃ for 24 hours, the contact impedance should be within twice the initial value.

8. Copper conductor related testing items

(1) Line diameter tolerance:

When 0.10mm ≤ d ≤ 0.40mm, the allowable deviation is ± 0.004mm;

When 0.40mm ＜ d ≤ 1.0mm, the allowable deviation is ± 1% d (d represents the outer diameter of the line)

(2) Difference between maximum outer diameter and minimum outer diameter (f)

When 0.10mm ≤ d ≤ 0.40mm, the allowable difference f<0.004mm;

When 0.40mm ＜ d ≤ 1.0mm, the allowable difference f ＜ 1% dmm (d represents the outer diameter of the wire).

(3) Elongation (soft state): The total length of the wire is 20mm

When 0.10mm ≤ d ≤ 0.25mm, the elongation is ≥ 12%; When 0.25mm ＜ d ≤ 0.40mm, the elongation is ≥ 15%; When 0.40mm ＜ d ≤ 1.0mm, the elongation is ≥ 20%;

-----Elongation rate=(fracture duration -20)/20

9. Copper conductor related properties

The most commonly used conductor in wires and cables is copper, which has comprehensive properties such as high conductivity and thermal conductivity, high ductility, good strength, and can form alloys with various other metals or be coated with other metals.

Copper wires used at temperatures up to 300 ℉ (or 400 ℉ for a short period of time) are coated with tin, tin lead, or pure lead, with a coating thickness of 40-70 micro inches. These coatings are not only used to minimize oxidation, but also to increase weldability and anti-corrosion effects.

Copper wires used continuously at temperatures up to 400 ℉ (or for short periods at 500 ℉) are plated with a minimum of 40 micro inches of silver, which can withstand higher temperatures well. When the frequency is high enough and the skin effect becomes obvious, the conductivity of the silver coating is better than that of the tin coating.

Copper alloys or copper clad steel conductors are used to increase strength, but the use of these materials always comes at the expense of conductivity. For example, cadmium copper, a copper alloy containing 0.5-1.0% cadmium, has a tensile strength of 150% of copper, but a conductivity of only about 80% of copper. In addition, the tensile strength of copper clad steel wires is 150-200% of copper, but the conductivity is usually only 30-40% of copper.

Aluminum alloy is lighter than copper conductors of the same specification, but its conductivity is only about 60% of that of copper. In addition, when exposed to air, aluminum generates a surface oxide that can form unwanted high resistance connections. Therefore, copper is often used as the material for conductors in wires and cables. According to the current industry classification of conductors, there are generally three forms: solid conductors, stranded conductors, and braided conductors.

a. Solid conductor - Use solid (single stranded) conductors when wires and cables have minimal movement and do not require bending. Its advantage is its low cost compared to equivalent stranded wires. Wires and cables with solid conductors are typically used for the installation of small instruments, backplane wiring, or any similar fixed equipment.

b. Stranded conductor - Stranded conductor is used in most wires and cables to provide good flexibility and longer bending life. From a practical perspective, stranded conductors have a longer service life than solid conductors. If there are small V-shaped cracks or similar damages, they will break after only a few bends. However, in the same operation, only a few stranded conductors have scratches or damage, and the remaining undamaged stranded wires can still provide appropriate service life.

c. Braided conductors - Flat or circular (tubular) braided conductors are sometimes used in certain applications, where they are more suitable than round solid cables or stranded cables. Braided conductors rarely have insulation, as the insulation layer hinders high deflection and the ability to slightly expand and contract the length due to axial pushing and pulling of the cable.

10. Insulation materials for wires and cables

The insulation materials for wires and cables can be divided into the two most basic categories - thermosetting and thermoplastic, but there are so many types, compounds, and mixtures within each category that the available insulation materials are almost unlimited. At present, most insulation materials in the industry are composed of compounds made of synthetic rubber polymers (thermosetting) and compounds made of synthetic materials to provide special physical and electrical properties.

(1) Thermosetting insulation material:

The characteristic of thermosetting materials is that they can be stretched, compressed, or deformed (within reasonable limits) under mechanical stress, and when this mechanical stress is eliminated, they can "bounce back" to their initial state and shape. Due to the susceptibility of thermosetting insulation materials to thermal softening, they will not melt, flow, or deform during the applied heat and electrical overload (which causes internal heating).

(2) Thermoplastic insulation materials

Thermoplastic insulation materials are known for their excellent electrical properties and lower costs. Thermoplastics are widely used as insulation materials, especially in high-voltage cables, due to their thin insulation thickness, which can achieve good electrical properties. In addition, cables with thinner insulation layers are usually smaller in size than cables made of thermosetting insulation materials with the same electrical properties.

Several modified thermoplastic insulation materials can be prepared using various basic thermoplastic materials. Sometimes the main change is color, but most thermoplastic plastics have different grades to meet the requirements of special usage temperature, strength, and environmental resistance factors. Naturally, these materials are thermally formed, softening and flowing under mechanical pressure, and then maintaining their deformed shape and state after cooling and/or removing mechanical strain.

PVC insulation materials are widely used in wires and cables because they have high dielectric strength and mechanical strength, high flexibility and flame retardancy, water resistance, oil resistance, and wear resistance. They also have the advantages of low cost and easy processing. This makes it attractive to both cable manufacturers and users. However, recent data shows that PVC processing is harmful to health.

Nylon is mainly used as a cover or sheath on other insulation materials to provide mechanical, thermal, and chemical protection. These sheaths are generally very thin because even thin-walled nylon is very tough. Thick nylon or insulation can make the cable very hard. Nylon is generally not used as the main insulation because of its poor moisture absorption resistance, which reduces its electrical performance under high humidity usage conditions.

Polyethylene and polypropylene are used for many applications that require excellent electrical properties