Component soldering becomes more and more complex as electronic gadgets get smaller. This also works with the circuit boards getting more compact. The built board has a number of difficulties and flaws as a result of this intricacy. This solder mask bridge is a frequent problem when assembling these components.
The phrase “bridge” typically refers to a passageway or connecting two previously inaccessible locations. In the context of wireless communications, the provision of internet connections in-between both wired networks via a Wi-Fi connection is referred to as “bridging”. In this scenario, the wireless bridge performs the role of a client. It achieves this by connecting to the router and sharing Internet connectivity with the connected devices.
Yet, the word “bridging” inside the PCBA field refers to a completely other process when used in tandem with soldering. One form of problem that might happen while soldering is called solder bridging. It is a problem that could have an effect on production, call for reworks. This could possibly lead to irregular functioning in this field. It is important to know how to avoid solder bridging for the best board fabrication and performance. Therefore let’s examine solder bridging’s root causes in further detail and suggest ways to prevent it.
Let’s examine a solder mask bridge in more detail, along with its causes, the prevention, as well as its remedies.
How your PCB is impacted by the solder masking process
After delving into the process of solder mask, let’s look at how it impacts your PCB. This solder mask affects PCB assembly as well as board quality, as was previously mentioned. The most noteworthy effects of the solder mask are explained below, please let’s explain them below.
Prevents solder mask bridges: Creates the solder dam in-between the solder joints as well as other areas of your board that are conductive, which could cause board damage or short circuits.
Reduced solder paste consumption: Makes it possible to utilize fewer solder paste during the soldering operation. Serves like an insulator in-between the board components, providing additional isolation of the PCB’s components.
Safeguarding the PCB: This prevents the introduction of pollutants that could be caused by handling this board. Resists oxidation, which could reduce the device’s operational lifetime.
Raising its breakdown voltage: may improve the value of breakdown voltage that the dielectric material of the board holds and offer further protection against corona or arcs that are frequently found on high voltage (over 1 kV) boards.
Preventing the development of the metal whiskers: aid in avoiding the development of tin whiskers, which are typically linked to lead-free solder and tin plating for different electronic components.
It goes without saying that the procedure for the solder mask has a significant impact on how easily your board may be manufactured and how it will perform in use. However, there are some circumstances in which a solder mask might not be feasible or desirable, such as with small parts as well as fine pitches present on the BGAs (ball grid array). It is advisable to consult your CM in order to make sure there won’t be any negative consequences on the performance or dependability.
What does a PCB solder mask bridge represent?
Two points are joined by a bridge. The solder mask bridge forms on circuit boards whenever extra solder links at least two pads that ought to be separated above your solder mask.
Because of this problem, electrical shorts are created that, depending on how the bridging points are used, might result in various types of harm.
Causes of Solder Bridging
Solder bridging can occur under various circumstances. These can be defective machinery, subpar manufacturing techniques, or bad designs. The most common causes include:
- Using too much solder on the SMT pads because the stencil specifications were wrong;
- Defective seals in-between the stencil and bare board during printing;
- Relatively large designs for solder pad compared to that gap present between the pads;
- Incorrect component placement;
- Relatively small component lead sizes in comparison to pad size; insufficient solder resistant layers found between the pads.
The fact that the liquid solder usually wicks toward heated metal or melted solder must be remembered (a large part of this PCB assembly procedure relies heavily on that factor).
This phenomena happens due to the fact that reflowing solder features strong surface tension, thus it remains balled up wherever it ought to be when holding items in it. Bridging can be brought on by anything that alters the system’s normal behavior.
Commonly Known Issues of Soldering Bridging
Solder bridging could cause these problems.
Dewetting and Non-Wetting
Molten solder deciding to leave exposed copper on its pad is referred to as non-wetting. This problem typically arises when brass components have not yet been adequately plated or when the flux needs to be changed. On the contrary, dewetting indicates that molten solder covers a pad, then retreats, leaving the solder mound.
Pin Holes and Blow Holes
Both of these holes arise when the board has either poor plating of copper or an excessive amount of moisture.
Lifted Pads
Whenever the soldered component is removed from the joints with a worn-out soldering surface or one having an uneven layer of copper plating, lifted pads may appear.
Tombstone
Whenever the component is lifted all through wave soldering, it creates the tombstone problem and looks like one. Component lifting can be caused by using parts having different measurements for solderability or using leads of the wrong length.
Excess Solder
High solder accumulation could arise due to the improper lead size compared to the pad ratio. Additionally, it might be because of the conveyor belt’s rapid movement.
What You Must Do To Avoid Solder Mask Bridges?
While it’s not possible to ensure that there won’t be any solder mask bridges, one can avoid the problem by taking these precautions.
Verify the design of the circuit board again
Make sure that the design of the boards meets the best levels of producibility for the surface mount and through hole components. Also, you may work with the standards for the IPC industry for both the design as well as assembly of the PCB, which defines the A level as the best level for general productivity. In general, the most effective practice involves avoiding the tiny spacings or parts.
Asides that, check the design rules of the mask relief for areas which do not require the applications of the solder mask. We advice setting the relief to between 0.003 to 0.008 inches in the SMT components. However, you may need to adjust the value when the pads get extremely close together. Also, the color of the solder mask affects the relief.
Alter its Reflow Profile
By lengthening the period just above your liquid solder, the pads as well as component leads will have enough time to reach that same temperature. The solder would wet both once it reaches the desired temperature and moves there.
Leave Solder Mask Dams Between Pads
The solder mask dams are needed between the SMT pads due to the fact that it serves as the isolation wall, which prevents spillovers.In general, the minimum size of the dam should be about 0.004 inches.
For through-hole components, use the appropriate lead lengths.
The board’s thickness and size, the mass and size of the components, and the soldering type all affects the proper lead length.
This PCB manufacturer must assist you in determining the exact length needed for that application because long leads could result in bridging.
Minimize the Volume of the Solder Paste
One reason for solder mask bridges is the overuse of solder paste. Therefore, significantly less bridging can be achieved by reducing the volume of the solder paste or altering the stencil in order to change the location of the application.
Employ Solder Mask Specified Pads for the Tight Regions
You can choose the solder-mask-defined pad for protecting the surface for soldering if there isn’t enough space available for barrier and mask relief and you do not require the solder mask dams.
Use the Proper Pad Diameter and Hole Size
A solder mask bridge is more likely to form when there are big copper pads or through holes between the adjacent surfaces for soldering.
Apply the Solder Masking Properly
Any areas of the PCB which do not require soldering have a solder mask placed as its top layer. Molten solder won’t stick to epoxy, which is a common type of mask material. Therefore, you have to apply that mask in-between the component pins so as to stop the solder from forming the solder mask bridge.
Utilize Fiducials on the PCB
The fiducials are the markets placed on the circuit board design, which allows the automated machine to locate your PCB, and then align it properly. It will also place these components perfectly. The misplaced parts would also increase the solder mask bridges chances and then the marks will aid in the elimination of the problem.
Team up with a well-known PCB Manufacturer
Once you are done sending the files for the design to your manufacturer, then you have no control over the processes of fabrication, as well as assembly.
How You can Fix the Solder mask bridges
Before you can solve the solder mask bridge issue, you must have a solder flask, solder wick, as well as a soldering iron that is heat adjustable. Having all these, you can get rid of the problem using the steps below.
Monitor Its Temperature
The tip of the soldering iron must transfer the required heat for your solder wick to be able to melt as well as absorb that solder. Therefore, there’s a need to keep monitoring the temperature as well as ensure that it surpasses the temperature for soldering by some degrees. Take for instance, soldering at 250°C, increase your temperature to about 270°C. The higher temperature would cover for the heat absorption of the wick from its solder joint.
Make use of Surface Tension
The surface tension of molten solder can be used to detach the bridge with no need for a wick. Make use of a soldering iron having a clear top, but take care not to overheat the ICs or pads.
Make use of the Solder Wick
To absorb this melted bridge, we suggest utilizing solder wick. Add solder flux, position the wick well over bridge, and carefully heat with an iron. To transfer heat, lightly press your iron over that wick. Remember to replace the wick when it gets clogged.
It is essential to prevent overheating the PCB or the components. Additionally, removing this bridge may result in the removal of the solder joint; if this occurs, apply additional flux then solder that part neatly back to the board.
Frequently Asked Questions
What exactly are Solder mask bridge Jumpers?
Solder mask bridge jumpers are pairs of pads on the trace of a circuit board that can be bridged by a solder balls. To make the bridge, you may additionally utilize the 0-ohm resistor. Certain bridges, however, do not require soldering or joining and should stay open for various uses.
How Do You Solder Pads Together?
As previously indicated, you may bridge the solder pads with the solder ball or the 0-ohm resistor.
What does a faulty solder junction imply?
A poor solder joint indicates one with insufficient solder. Inadequate solder makes that joint weak, increasing the likelihood of cracking and failure. This flaw can be corrected by warming the junction and applying extra solder. This strengthens the joint sufficiently.
What exactly are disturbed joints?
Disturbed joints are usually caused by movement even during the alloy solidification. The final joint appears frosted and has a ripple structure on its surface. The movement might be manual or automatic. You can fix this issue by reheating these joints and allowing them to cool properly.
Conclusion
In summary, solder mask bridges could be harmful to the circuit boards owing to shorting. Therefore, you ought to take the precautions outlined above to prevent them. Nonetheless, if they do develop, a quick solution is possible.
