Selection problem of surface mount technology of PCBA

- Nov 03, 2018-

The PCBA surface mount connector undoubtedly offers many advantages, including reduced assembly costs, double density and improved integrity for high-speed performance.However, the PCBA surface connector also contains some perceived shortcomings - from reliability problems (such as the connector falling off from the circuit board) to assembly problems caused by the coplanarity.In fact, these so-called cognitive defects are no longer a problem if design engineers carefully consider and review the process of selecting the appropriate connector.

Therefore, when you choose the PCBA surface mount connector, you may want to consider the following: which PCBA surface mount pin design is adopted and the reason for using this design;Which measures are used to eliminate the mechanical stress;Whether the problem of coherence can be solved;Easy access to sample boards and test reports.All of the above questions should be raised and decisions made on a factual basis rather than on the presentation provided by the salesperson.Keep in mind that the design of the PCBA surface mount connector is not exactly the same.

Pin design

After carefully observing the PCBA surface pin of the connector you are considering, ask the connector engineer what methods are used to ensure that the solder remains at the key junction between the PCBA surface pin and the pad.In addition, is the connector pin vertical, J, or otherwise?Ask your company's salespeople why they use this pin type.If they do not know the answer, report to you after they find out the reason, and then consider their products further.

The design elements of the PCBA surface-mounted connector are not randomly implemented.Once the design is complete, no reliability problems or weak junctions can occur.Engineers who design PCBA surface connectors choose specific design elements for specific reasons, and it is important for you as a design engineer to understand the reasons.For example, the vertical PCBA surface mount pin is most reliable when using the solder well design.The so-called welding well is a hole in the center of the pin to prevent the solder from being sucked into the terminal and away from the pad.Another key design feature is the j-shaped terminal, which has a curved Angle designed to limit the drift of solder flow.If the PCBA surface mount connector you are considering is not one of the above two types, be sure to make sure its signal terminals take other precautions to provide reliable welding.Nowadays, signal terminals are no longer the only type of terminals using PCBA surface mount technology. In fact, more and more power terminals are also using PCBA surface mount technology.Although power terminal requirements are not as demanding as high-speed signal terminals, some design elements need to be retained to ensure connector reliability.Even if the area of PCBA surface mount pin is large, the details of PCBA surface mount technology cannot be ignored.Also, if you don't know exactly how the solder joint is maximized, ask the salesperson to describe the details of the connector design explicitly.Reliable pin design is necessary in all industrial applications.

Stress relief measures

Even if the signal and the power pin design are sufficient to increase the integrity of the welding process, do not stop your price on the connector.After all, you don't want all the plugging to depend entirely on the adhesion of the signal pin to the PCB.It cannot fail to mention the lateral force caused by well-intentioned but insufficient information of the field technicians.In fact, the mechanical stress on these boards must be minimal, however, many connector companies overlook this key detail, resulting in a negative reputation for PCBA surface connectors not only for durability, but also for general I/O applications.

As the saying goes, "there will be no pie in the sky, and there will be no such thing as something good for nothing", so will the PCBA surface patch connector.You cannot expect the mechanical durability of the PCBA surface-mounted connector to be comparable to that of the through-hole reflux connector.This is unfair to both the PCBA surface mount connector and your design.Note that the PCBA surface patch connector with very small contact with the PCB surface occupies only half of the PCB pad area of the standard through-hole reflux connector.

In some cases, a very reliable PCBA surface connector can actually compete with a through-hole reflow connector.For example, PCBA surface-mounted d-sub connectors do not fall off the board because they are not designed to be ultra-thin and slim.However, we must actually understand that the stress that a PCBA surface-mounted d-sub connector can withstand is ultimately limited.In some cases, the overall size of the PCBA surface-mounted connector shall be the same as that of the through-hole backflow connector to ensure a reliable connection.For larger stress relief pads used daily in harsh environments, the physical and structural dimensions of the pads need to be similar to those of the through-hole reflux connectors.Although the PCB does not provide substantial savings, the PCBA surface mount version provides double card density, simplifies assembly, and potentially reduces manufacturing costs.In I/O applications, consider using a PCBA surface connector.If the design board space is limited, there are many PCBA surface connectors for your choice.

If the PCBA surface connector you are considering for use does not have an attachment that ensures a reliable PCB connection, it is recommended that you forgo the option.The PCBA surface mount connector must have a sturdy mechanical attachment to withstand multiple attachment cycles and rough handling.Just because you respect the choice of connectors as a design engineer doesn't mean that the person who always assembles them will.Keep in mind that PCBA surface connectors will never fall off the board unless they have design problems.At the same time, you need to carefully and thoroughly assess all possible scenarios when the connector is designed into the system.For example, can the PCBA surface mount connector withstand the usual interfacing with I/O cables or heavy sandwich CARDS?Can you withstand the back-and-forth motion that you might face when unplugging the connector?

Carefully check the PCBA surface connector you are considering using.Does the connector have an additional pad or anchor for reliable connection?Make sure you are satisfied with any additional measures taken by the connector company.Can you truly feel the durability of the connector?Are manual test boards available?Can the supplier provide a test report on shear data at the X and Y levels?

All PCBA surface connectors must be equipped with some form of stress relief.Some connector companies achieve stress relief by using screws to lock circuit boards or accessories onto the panels.While these concepts may increase mechanical strength, some solutions can provide the necessary and reliable PCB support without even secondary assembly or manual intervention.

The through-hole reflux technology enables the PCBA surface mount connector to pass through the extractor and provide a stronger circuit board connection than the PCBA surface mount technology.Similar to the through-hole needle, the through-hole reflow soldering or pin soldering paste requires the fine-mesh to be partially drilled into the PCB, enabling these fine needles to pass through the reflow soldering.These through-hole pins are used in conjunction with the PCBA surface-mounted signal pins and are often supplied with double loads through increased mechanical strength and grounding.However, there will be some disadvantages when the through-hole reflux pins are applied to high-speed applications.

Although PCBA surface mount pins are used for signal performance, through-hole reflux pins provide a stronger connection on the circuit board.Furthermore, the backflow through the hole provides superior stiffness and strength in the case of the height of the interlayer connector and the continuous increase in the weight of the sub-clip.Pasting technology has been the DE facto standard for backplate connectors for the past 40 years. PCBA surface mount/through hole reflux backplate solutions often exceed the compression signal performance while providing excellent durability.If executed correctly, there is no doubt that the PCBA surface mount technology is suitable for any application.

Coplanar sex

As more and more circuit boards are compressed into smaller and smaller chassis, resulting in the current demand for interlayer connectors.The need for more stitches and smaller pads drives connector companies to quickly and mass-produce many unique designs for designers to choose from.However, the biggest question lurking is: which PCBA surface mount connector will provide the most reliable connection after assembly, testing, or even installation after application?

Nearly every systems manufacturing engineer has experienced problems with PCBA surface mount connectors, and it's not hard to know why.Minimal contact terminals and an increasingly thin printed circuit board under economic license make the coplanar almost impossible to achieve.It is assumed that although the ultra-thin sandwich card is twisted to meet the IPC standard, the pin design of the PCBA surface mounted connector is not good, which eventually leads to the pin being unable to connect with the circuit board.Again, design engineers must question and assess all aspects of PCBA surface connector design.