Wiring Harness Process Design for Automotive Electronics

Stripping length

When all terminals are crimped for the first time, a reasonable stripping length must be set to avoid inadequate crimping and excessive exposure of the core wire.

The design of the stripping length is set according to the actual structural dimensions of the terminal. Sometimes it is also necessary to consider whether the exposed core wire will affect the matching pin seat.

How to set the terminal stripping length:

Cut length and finished length

The setting of tangent length should be based on actual production, and attention should be paid to the tolerance of tangent length and finished product length.

In the process documents, the general length tolerance is explained. When the finished product length exceeds 1000mm, the positive tolerance of the finished product length should be set according to 1% of 1000±10. When the finished product length is 50000, the tolerance should be set to: +500/-100, and the tolerance of the tangent length also needs to be adjusted appropriately. It cannot be set to ±2 regardless of the length.

Tail processing

The tail treatment of the wire can be divided into: tinning, twisting tinning, half stripping, and other special treatments (such as bending the tail).

After the client tail is processed, there are two possible uses:

1. Insert directly into the hole of PCB board. At this time, there are requirements for OD after tinning; the size of PCB board needs to be determined;

2. It may be welded with other components, in which case the OD requirement after enameling can be appropriately relaxed.

Before drawing, if the tail is stripped and tinned, the following three points must be confirmed with the customer:

①Which method does the customer prefer? Directly insert into the PCB hole or solder with other components?

② If the wire is directly inserted into the PCB hole, what is the specific size of the PCB hole? This will determine whether the wire needs to be twisted.

③ In principle, the stripped ends below 3mm are not twisted because it is not conducive to half-stripping. When processing such tail stripping ends, it is necessary to confirm with the customer the OD size of the core wire after the tail is tinned. If the customer has no requirements for the OD size after the tail is tinned, directly mark the size after tinning on the drawing according to the required tail tinning standard.

Shielded wire processing method

1. For shielding wire processing methods for regular customers, please refer to the "Shielding Wire Trimming Technical Standards".

2. When the shielding layer structure of the shielded wire exceeds the crimping range of the terminal, the shielding layer needs to be trimmed. When trimming, it should be done according to the maximum wire standard of the terminal crimping.

3. Shielded wires with aluminum foil cannot be boiled in water to avoid shrinkage.

Wire arrangement processing method

1. If the customer has no special requirements, the length of the branch line of the finished product below 100mm shall be controlled within 20±5m, and the length of the branch line of the finished product above 100mm shall be controlled within 30±5mm.

2. For UL2651 TS cable and UL20080 flexible flat cable, the tail should not be twisted and tinned, because the PVC insulation layer and copper wire of UL2651 and UL20080 wires are not completely round, and it is not easy to perform half-stripping and leaving glue operation, so it is not suitable to perform twisting and tinning operation; if the customer needs to insert the PCB board at the tail, it is recommended to use UL2468 UL2651 TC cable.

3. TC flat cable with spacing can replace pointed terminals such as SAN and SCN after the tail is peeled.

LVDS line tangent length setting method

Because LVDS lines generally use small-pitch, multi-P-position plastic shells, the hanging neck phenomenon must be considered when designing the length of the scattered line tangent.

Take the 30P plastic shell as an example, where the finished product length is 300mm and both ends enter the plastic shell by 3mm.

Considerations for double row plastic case design

1. When choosing wires, try to use flat wires;

2. If the customer must use a single line, try to design it in different colors to facilitate assembly;

3. The drawings of double-row plastic shells need to be in a relatively unified format;

4. When drawing, pay attention to the arrangement method of the double-row plastic shell pins provided by the customer, and confirm the arrangement method with the customer first to avoid pin mismatch (especially DuPont double-row).

Considerations when designing circuit board terminals

1. Circuit board terminals refer to terminals, tubular terminals, pin terminals, etc. that are directly inserted into the PCB board;

2. When designing the circuit board terminal drawing, the size of the PCB board must be confirmed with the customer;

3. When designing the circuit board terminal drawing, the crimping width after crimping must be marked. This width is related not only to the hole size of the terminal suitable for the PCB board, but also to the customer's actual PCB board hole size. Therefore, before drawing, confirm the size of the PCB board hole size with the customer and mark it on the drawing;

4. When designing this type of terminal, do you need to confirm with the customer whether there are any requirements for its appearance? Some are samples provided by the customer, and you need to confirm with the customer whether its appearance after crimping needs to be the same as the customer's.

Wire clamp terminal design considerations

The wire clamp terminals at the same position must be staggered by more than 20mm to prevent short circuits.

Terminal crimping design considerations

The terminals are matched with the wires, which are generally set according to the crimping range of the terminals, and attention should be paid to the outer diameter of the wire insulation that the terminals are suitable for.

When the terminal selection exceeds the standard, there are four solutions:

1. Change the terminal model and select terminals suitable for wire specifications;

2. Change the wire specifications to suit the crimping range of the terminal;

3. If the wire is too small, the core wire can be folded in half and then pressed, which will result in high processing cost;

4. If the wire is too large, remove the rubber from the insulation, press it and wrap it with heat shrink tubing.

Any of the above options needs to be confirmed with the customer.

Terminal sections are made in the following cases:

1. When requested by the customer;

2. When selecting new terminals;

3. After the new die is made;

4. High current terminals;

5. All terminals on the vehicle wiring harness;

6. Other special terminals.

The judgment criteria for profiles generally refer to the company's internal standards (i.e., AMP standards). When customers have different standards, it is necessary to discuss with them the potential risks that may be caused by the differences in standards.

Injection molding design considerations

Common materials of rubber

Note when designing:

1. The selection of rubber materials should meet the requirements of customer products (such as temperature resistance, wear resistance, corrosion resistance, etc.);

2. The size of the injection molded parts must be provided by the customer, or a sample must be provided;

3. Dimension control after injection molding;

4. Selection of injection molding machines;

5. Process control of injection molded parts (such as the ratio of new materials and recycled materials, the ratio of masterbatches, baking time, molding temperature, cooling time, etc.).

Notes on handling technical document change notifications

Please note the following points when changing ECN:

1. Have complete and clear ECR requirements (including change method, order number, and material investigation).

2. The "in use" mark on the ERP drawing must be removed immediately, and the reason for the change, date, and work number must be noted in the remarks. When "in use" is turned on, it must be turned on by the person who deactivates the system in principle, or the details must be confirmed with the person who deactivates the system before it can be turned on.

3. For ECR that is changed immediately, the drawings and ECN must be issued to the workshop within 2 hours.

4. The implementation date of ECN should be written according to the requirements of ECR, and cannot simply be written as "natural change" or "immediate change".