Introduction to general structure of communication connectors

 

High density and low spacing characteristics of communication connectors determine thin walls, long flow, complex shapes, and easy deviation of wiring of its housing and wafer plastic parts
Communication connector injection mold quality concerns
Module wafer (Insert Molding) category:
Molding type:
>Filling problems: short shot, trapped air, poor exhaust, rib position hysteresis...
>Ejection problems: insufficient ejection force, unbalanced ejection...
>Warping deformation: fiber orientation, uneven wall thickness...
>End guard weld line position and strength

 

>Insert sealing problems
>Insert deformation and offset problems
>Ranking problems-filling balance

 

Moldflow application process introduction

 

Case 2: Analysis of warpage and weld line strength of end guards
XX series connector end guard warpage optimization design

 

The first version has too much deformation in simulation, exceeding 0.15. Left picture is second version after optimization design. Simulation flatness is reduced to 0.09. Due to thin wall, considering that fz does not calculate ejection deformation, actual value may exceed this value. From simulation results, this solution also has a big problem.

 

Analysis of warpage and weld line strength of end guards
Case 2: xx series connector first version end guard
Problem: excessive warping, assembly difficulty increased, occasional cracking due to bending stress during assembly, cracking of electroplating
After finalization, mass production process plan: the entire series of products automatic assembly line assembles all other parts, leaving this one part, and assembles it to another automatic machine dedicated to assembling end guards (hot clamp, clamp flat first), cost of this automatic line is 1 million yuan.

 

 

xx series connector expanded end guard
1. Reduce bone flow rate and adjust filling speed
2. Optimize its contact structure with terminal,
3. Reduce bone clamping force (mold removal, partition, etc.)
Due to optimization of its contact structure with terminal, some holes in new structure need to be stressed, and quality requirements of weld line become higher.

 

 

Glue feeding method on the right side can avoid more weld line positions and appear at stress position

 

Analysis of weld line and temperature coincidence
Temperature drop at the front edge of both directions is low, and risk of weld quality being affected by temperature is not high

 

Analysis of coincidence between weld line and shear stress
Shear stress slightly exceeds upper limit (0.5) and weld line position does not basically coincide

 

Analysis of weld line and pressure overlap
Electroplating cracking and blistering mostly occur in places with high internal stress and high shear stress near gate

 

1. Temperature drop at the front of glue feeding direction 1 and direction 2 is relatively low, and weld line strength is less affected by temperature drop of material
2. Direction 2 can avoid more weld lines than direction 1, but weld line in the high pressure area is in force direction, while weld line in high pressure area of direction 1 avoids hand direction
In summary: considering glue feeding direction, it is better to choose direction 1

 

 

Summary
Summary of processability of end guard molding
Design of end guard parts should meet impedance and assembly requirements, try to balance filling during injection molding to prevent "ear-shaped" flow and reduce warping.
Flexibly use "flow diversion/blocking" principle to adjust filling speed
Reasonably design wall thickness to prevent excessive filling pressure and over-pressure near gate
Leave a reasonable ejector position to balance ejection and avoid ejection deformation.
Mechanism of base warping
Base products
Communication connector plastics are generally thin-walled, relatively uniform, and almost all of them are fiber-reinforced materials. From actual experience, main cause of its deformation is uneven shrinkage caused by fiber orientation, which causes internal stress. Internal stress and strength verification win, resulting in warping and low dimensional accuracy.
When structural plan has been determined, method to optimize fiber orientation is mainly pouring direction and process hole design.

 

Base warping Fiber orientation anomaly
Base products
Orientation issues:
Change flow in structure, change intersection position in mold, reduce shear stress in process.

 

Case 3: Analysis of warpage and dimensional accuracy of base
Analysis of impact of fiber orientation on product quality
Both solutions can fill smoothly without thin wall retention and short shot

 

Inlet 2 achieves a more consistent front temperature
Results also show that neither feed has cold spots nor excess shear heat

 

Glue injection 2 has a more consistent fiber orientation, with less shrinkage in orientation direction and more shrinkage in perpendicular orientation direction. This result has a great impact on warpage
Combined with filling animation reference orientation, Scheme 2 is more conducive to mold shrinkage value.

 

 

Solution 2: Warping is a little bigger. Both solutions need to do pre-deformation compensation. Warping in this direction is easy to do pre-deformation

 

 

Other base series: High side wall of base is stretched outward and cannot be pulled back after assembly, resulting in an increased risk of shelling

 

Summary
Base products
Orientation issues
Structural changes in flow (process holes, local wall thickness changes)
Change gate position on mold
Reduce shear stress in process
Try to make plastic part have an orientation that is easy to capture, which is convenient for mold shrinkage value
Case 4: Plastic encapsulation and secondary plastic encapsulation: wiring deviation
Wafer parts
Plastic sealing and secondary plastic sealing: wiring deviation
Affects reliability, changes in spacing affect SI

 

Plastic encapsulation and secondary plastic encapsulation: wiring deviation
Affects reliability, and changes in spacing affect electrical performance
Non-hollow wiring design requires addition of "pressing material" and "material bridge" structures to design anti-drift inserts for mold, or set holes at easily deflected positions to clamp mold inserts
MF simulation finds position in advance to avoid under-design or over-design (designs such as material bridges and press grooves will affect electrical performance. If remedied afterwards, it often costs more).

 

Summary
Module category:
>Insert sealing problem: Insert structure design should be easy to seal mold under premise of meeting electrical performance - more straight surfaces, less curved surfaces, and burrs are easy to generate when pressure is exceeded
>Insert deformation offset problem: MF simulation finds position in advance to avoid insufficient or over-design of material bridge and pressure material
>Ranking pouring problem: MF simulation multi-cavity filling balance to prevent overfilling, over-pressure point, and burrs.
Sharing of practical experience - problem of blocking mold cavities or unbalanced expansion of mold cavities

 

Due to influence of reed strip structure, feeding pitch, etc., 24-bit solution cannot be completely balanced in design. Design balance needs to meet power-of-2 module numbers such as 2, 4, 8, 16, and 32.

 

 

 

Summary: There are following risks when expanding cavity to 24 positions:
1. Filling of 8 positions at both ends and 16 positions in the middle is unbalanced, resulting in the risk of stagnation of 8 positions at both ends and over-pressure maintenance of 16 positions in the middle
2. There are large burrs and risk of spring offset deformation in 16 positions in the middle
3. Filling pressure required for 24 positions is about 140mp, clamping force is 53t, and equipment in factory is not matched
4. At the same time: mold life is reduced and mold cost is increased due to high pressure
5. Risk of automatic feeding mechanism changes and process problems in expansion design
6. Although expansion of cavity to 32 positions can balance glue feeding, mold size is increased, and there are some problems such as strength verification
Practical experience sharing of actual and simulation matching of single-stage injection molding process of micro connectors
Tricks of actual and simulation matching of single-stage injection molding process of micro connectors
(Product segment mold flow generally does not draw runners)

 

Analysis of long-term application benefits of Moldflow in enterprises
Project cost
Product segment MF simulation: reduce "wiring deviation, base warping/precision, end guard" core parts improvement product design and mold modification at least once.
A product is about 25-50w, a series of products is generally multiplied by 3, and cycle is about 15-30 days.
Avoiding the overall reliability plan caused by plastic parts problems (including process plan): about 100w (backplane connector)
Mold modification mold cost:
Wiring deviation: involving plastic sealing, terminals, cutting 3 sets of molds (one part once) about 10-15w
Base warping and precision: about 3-8w (one part once)
End guard: about 2-5w (one part once)
Total: one product single mold repair cost 30W