How to improve the metal dome assembly efficienc?

As the labor cost increase every year, more and more customer pursue the assembly efficiency of metal dome. So how to increase the assembly efficiency?

There are many methods for metal dome assembly, such as the triangle with legs is fixed with the pin hole of the boards, for this kind metal dome we need manually place the dome one by one, the assembly efficiency is very low, cost many labor.

triangle-metal-dome-insert-in-PCB

And some customer might manually place the metal dome on PCB boards one by one and then stick adhesive tape to fix the dome with PCB board, although save material cost but this methold also has the disatvantage of low assembly efficiency and high labor cost.

stick-adhesive-tape-to-fix-the-dome-with-PCB-board

Currently the most popular assembly method is customorize a dome array according customer’s PCB boards, put several kinds metal dome or several quantity metal dome on one dome array sheet, customers only need to stick a board one times. Not only the assembly efficiency increased and saved labor cost but also improved the functional stability.

dome-array-with-many-metal-domes

Furthermore, if you want improve the assembly efficiency on the basis of this method, we can design the layout of dome array sheet according customer’s PCB panel layout, put several or dozens dome array in an specific layout thus we can assemble several or dozens dome array on PCB boards at one time, this method can greatly increase the assembly efficiencyof metal dome.

dome-array-with-many-different-metal-domes

In addition, we have other method to improve the assemble effiency, such as make many dome sheets in one entire sheet according the PCB panle and then assemble the entire sheet on PCB panel at one time. More details you can refer to another blog

Best Technology, as the top 5 metal dome & dome array manufacturer in China, we have more than 15 years experience in snap dome, metal dome sheet and tactile membrane switch industrial, our metal dome is equivalent with Snaptron & Nicomatic metal dome,we can always provide you the best solution for your dome switch project. If you have any doubt or inquiry about the snap dome please kindly call us or email us at any time.

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What’s air vent hole and function of it on dome array?

The hole on PET around metal dome or the slot between dome and dome is called the “vent hole” or “vent slot”, which is very important for the normal operation of metal dome. It will result in poor feel and affect the function of the switch if without the vent hole. Although this design may not be used in every applicable product, it is desirable in almost all applications. When you press on metal dome, the air is trapped underneath it. So when we press on snap dome, in order to prevent the air from being compressed underneath, we have to make a vent slot for dome switch.

There are different ways to make vent holes of dome array, for example:

  1. the vent holes can be designed between metal dome and the spacer;
Dome array
  • A small opening hole can be made on the top layer of dome retainer;
Dome array drawing

pcb

In a word, the improper design of the vent hole of Dome array will seriously affect the feel of metal dome when pressed. Please pay attention for this issue.

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Can metal dome be weld on PCB board?

We know there are different assembly methods for metal dome, such as metal dome with legs can insert in PCB’s pin hole to fix, similar like below picture. Most of the dome switch with legs are triangle type. It has several leg specifiication: 0.8*0.8mm, 0.8*1.5mm and 0.8*3.0mm. Usually we can choose the metal dome with the appropriate leg length according to the PCB’S thickness. If you want know further information about how to assemble it please refer to another article “How to assembly triangle series metal dome on PCB”.

triangle metal dome insert in pcb
triangle metal dome with different size legs pcb

Another method is making metal dome with adhesive tape to be dome array and stick on PCB to conduct with it, we also call it as dome sheet, peel dome. The advantage of making dome array is that its assembly efficiency will be faster than insert one by one, especially when the number of metal domes on a dome array is relatively large, and one dome array can contain different types metal dome but only assemble one time.

dome array with many different metal domes pcb

Beside those two methods, some clients chose to weld metal dome on PCB board directly, normally we don’t suggest to do it so . Because the metal dome has a little arc with a certain ductility, when we pressing it the metal dome will extend around, if welding it on PCB board, the metal dome can’t extend around when you pressing it, as we pressing for a long time it will easily cause the metal dome to be concave, so it is not recommended to weld metal dome directly.

Best Technology, as the top 5 metal dome & dome array manufacturer in China, we have more than 15 years experience in snap dome, metal dome sheet and tactile membrane switch industrial, our metal dome is equivalent with Snaptron & Nicomatic metal dome,we can always provide you the best solution for your dome switch project. If you have any doubt or inquiry about the snap dome please kindly call us or email us at any time.

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Can metal dome sheet go through high temperature furnace?

Some customers could ask whether metal dome array or dome sheet can pass high temperature furnace? The answer is no.

Why some customers would have such a request? That’s because they need to do the welding and soldering process after place the dome switch into the print circuit board, thus they need to go over a high temperature stove. But the maximum temperature of the PET adhesive material can withstand is around 125 degrees (suitable working temperature is around 60-80 degrees), and the temperature in a high-temperature furnace is more than 200 degrees. The material melts when it enters a high temperature furnace, so it’s definitely not going to work.

If the customer must do as that, then need to change to use a material that can withstand high temperatures. However, there are many improvements in the difficulty of the production process and the cost of materials is very high. Therefore, we will suggest that the customers assemble the dome array 

after welding the high-temperature furnace, which is very reasonable and convenient.

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How to increase the click feeling of metal dome?

We know the click feeling of metal dome largely affects the use of the whole products, so how should we do to improve the click feeling of metal dome?

Here are the answers:

  1. Choose the high-height metal dome, such as four leg metal dome, metal dome with dimple on center or metal dome with dimple on side. Their has relatively strong touch feeling itself, can remian better click feeling after assembly.
  • Adjust the click ratio directly. We know click feeling (CC) has a equation to define: CC(%)=(CP-CL)/CP*100%, the higher the CC score, the better click feeling. But we don’t suggest to make CC score exceed 70%, because if the click feeling is too high then it will affect the life cycle of snap dome.
  • Make UV plunger on the surface of dome array, position on the center of switch dome to improve the click ratio, this kind products we called UV plunger dome array.
  • Don’t make thecontact silicon botton too large, large silicon botton will affect the click feeling as well.
  • Make the dome array accurately aligned with PCB pad during assembly. Becasue the click feeling in center of metal dome is the best, the deviation will also affect the click feeling.

Best Technology, as the top 5 metal dome & dome array manufacturer in China, we have more than 15 years experience in snap dome, metal dome sheet and tactile membrane switch industrial, our metal dome is equivalent with Snaptron & Nicomatic metal dome,we can always provide you the best solution for your dome switch project. If you have any doubt or inquiry about the snap dome please kindly call us or email us at any time.

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Why need to add an plunger (actuator) on metal dome array?

Why the customer want to make an plunger or actuator  on the top layer of metal dome array?

There are two main functions:

1. Increase the total height of overall product;

2. Increase the touch and click feeling of dome switch.

The height and diameter of the plunger or actuator should be based on the diameter of the tactile dome, and need to make a tooling for plunger making.

But at the same time, we need to pay attention for below issues when making plunger or actuator.

  1. It’s better to make the height of plunger or actuator under 1mm, then the defect rate is very low.
  2. If the height of plunger is larger than 1.0mm, the defective rate will be 20% to 30% more than the usual 1mm.
  3. The poor performance is mainly a small bubble inside a, can be seen by visual.
  4. There are also some bubbles around edge, this will cause the plunger to fall off with a gap.
  • The plunger itself can not be straight, showing a cone, because the plunger plastic molding curing, need to be pulled out of the mold, there will be a drawing Angle. 
  • The plunger is made on the top layer (MYLAR or dome retainer) and then transferred to spacer, there will be tolerance.
  • In addition, the assembly of dome switch (metal dome) on PET adheisve also has tolerances, so Plunger and tactile swithch (metal dome) can not be completely concentric.
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What the reasons for poor conduction of metal dome?

We all know that the metal dome is very important for the conduction of electronic product, if the metal dome has problem, the whole product will be affected. Then whether a product has conduction problem and its must caused by the metal dome? Sure, it isn’t.

Let’s briefly introduce several situations of poor contact of metal domes.

  1. When there are some dirts on contact side of metal dome and PCB boards, they will all affect the normal conduction of metal dome.
pads with adhesive
metal dome with dirts
  • If the PCB pad layout is incorrect, its will affect the metal dome conduction as well. For example, if the external diameter of PCB pad is 5mm, but the snap dome size is 6mm, when pressing down the metal dome, it will exceed the pad and can’t connecting so it won’t work.

Normally we suggest that the external diameter of PCB pad should exceed at least 1mm than metal dome.

metal dome and pads
  • If your product has a silicon keypad and the gap between silicon keypad and PCB boards is too large then it will result poor conduction problem. As we are pressing the silicon kepad to make metal dome down to connect with PCB board, if the gap is too large we can’t make the dome down on PCB pad, then it’s no conduction.
  • If the deviation of metal dome assembly is too big that may also affect the conduction, because normally we press the center of metal dome to make product connected, if the assembly is deviated too much, when we press the center of product it may acutally working on the side of metal dome but not on the center, and that means the dome can’t down on the PCB pad to make conduction.
assemble deviation

Best Technology, as the top 5 metal dome & dome array manufacturer in China, we have more than 15 years experience in snap dome, metal dome sheet and tactile membrane switch industrial, our metal dome is equivalent with Snaptron & Nicomatic metal dome,we can always provide you the best solution for your dome switch project. If you have any doubt or inquiry about the snap dome please kindly call us or email us at any time.

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How to distinguish quickly the suface of Nickel plated, gold plated, silver plated, stainless steel, phosphor bronze silver plated from metal dome?

The color appearance of Nickel-plated and stainless steel is relatively indifference, so need to distinguish through the multimeter, adjusted the multimeter to the diode gear, the two pens moved on the metal dome at the same time, if the sound is continuous and crisp, it is nickel-plated, if it’s intermitten, then the surface is stainless steel.
The material is gold plated, silver plated, and phosphor bronze, which can be distinguished by appearance, gold plating is usually single plated, contact surface is gold. Silver plated is usually single side silver plated, contact surface is silver. And phosphor bronze is silver plated, the surface is copper, the contact surface is silver.

metal domes
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Can different shapes and size of metal domes be placed on a dome array?

Different metal dome shapes (four legs snap dome, triangle metal dome, round and oblong tactile dome) and diameter can be done on a dome array, we could do as the customer request. Why does the customer have such a request? The reasons as below:

  1. It may be the design problem of the customer’s circuit board.
  2. Different keys with different requirements, only use different domes, then could meet the requests. Such some keys require higher force, some keys require good click feeling;
  3. The size of the keys is different, so we have to use different diameters of metal domes.
    Although this kind of metal dome array can be made, the process of making is a little more complicated. It needs to make two or more laminate (assembly) fixtures and assemble them twice or more, it bases on the dome types. So the assembly time is twice or more as much as that of a single shape and specification, so the price will be higher.
    Recommendation: Use a shape and size of metal dome if no special requirements are required.
Plunger (actuator) dome array
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What performance should we learn about metal domes?

Do you know what is the force, rebound force and click ratio means in metal dome product?
Those are some basic performance we should know if you are going to buy metal dome, hereby we will tell you.

CP means compression peak force, we usually use it to define the operation force of metal dome, Its means the biggest force you pressed on the snap dome and make dome from a short opening status to the conductive status. CL means the compression low force, we also call it as rebound force. Its means the biggest force when the dome back from conductive status to opening status. Generally people use G(gram )or N (Newton force) to define all kinds force concepts. Please also refer to our blog how to test the life of metal dome .

Curve machine for force testing

And click ratio, someone also name it click feeling (CC) has a equation to define: CC(%)=(CP-CL)/CP*100%, this CC result(click ratio) is commonly required at 35%~6o%, if the click ratio is too high then it will affect the life cycle of metal dome. Briefly, you can also refer to the below chart to understand these concepts.

Fore test report for example
Best Technology, your best partner in Asia, is professional for dome sheet and dome switch more than 15 years in China. Please feel free to contact us if you have any question about snap dome.

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