The Quality Inspection of the Metal Dome

Metal dome is an important part used for membrane switch, micro switch, printed circuit boards and so on. It plays a role of conducting the electricity. Thus, it is essential to ensure the quality of the domes.

Metal Domes

But what should be paid heed to when the IQC department detects the quality of the metal domes? Here are five points.

  • Appearance: to check whether there is dust, oil stain, or spot on it.
  • Burr: it can be checked by using the A4 paper to rub the edge of the dome.
  • Force test: to test the force by force tester, and the normal range of the force is ±30%.
  • Contact resistance test: the contact resistance of the stainless steel metal dome is less than 10 Ohm, while the contact resistance of the metal dome plated with nickel, silver and gold is less than 1 Ohm.
  • Lifetime: to test whether the snap dome is up to the mustard by the lifetime tester.

To sum up, in order to guarantee the quality of the metal dome, it is necessary to pay attention to these five points, including appearance, burr, force test, contact resistance test and lifetime.

So, this is the end of this article. At Best Technology, with more than 15 years of experience, we are fully equipped to handle your metal dome or dome array manufacturing requirements. In case if you have any questions, please feel free to contact us via email at sales@metal-domes.com or call us on +86-755 2909-1601/1602/1603.

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How to Produce the 3M Adhesive Dome Array?

Namely, 3M adhesive dome array uses the 3M adhesive instead of the common adhesive used in the dome array. 3M adhesive is a little bit thick. Some of them even have the ability of high temperature resistance. So, it should be produced by opening a mold, while cannot be processed by laser. The processing steps are as follows.

The process of manufacturing the 3M adhesive dome array:

  • Cover one side of the double-side non-adhesive PET with the 3M adhesive.
  • Punch the dome holes.
  • Cover with Mylar.
  • Punch the outline.
Single and Double Layer Dome Array

And it is noteworthy that although the material used is 3M adhesive, whose viscosity is better, it is indistinguishable from appearance compared with the dome array using common adhesive on account of its transparent color.

Moreover, the model of 3M adhesive dome array can be customized depending on client’s request. But on account of the difference of the specific type and minimum order quantity, it does not necessarily fit with non-adhesive PET, hence circumstances after cases.

At Best Technology, with more than 15 years of experience, we are fully equipped to handle your metal dome or dome array manufacturing requirements. In case if you have any questions, please feel free to contact us via email at sales@metal-domes.com or call us on +86-755 2909-1601/1602/1603.

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The Structure of the Metal Dome Array

Metal dome array, generally, is double layer structure, but there is also single-layered.

For the double layer dome array, there are two layers, including Mylar, spacer and metal dome. The uppermost is the Mylar with the thickness of 0.05 mm, which is very thin. Then the thickness of the spacer is 0.075 mm with the tolerance of ±0.01 mm. And the underneath is the metal dome.

For this structure, the metal domes are connected by ventilation slots in the fabricated dome array. In this way, when you press the metal dome to conduct, the air can run along the ventilation slots. The purpose of it is to have a good click feeling and conduction ability.

Structure of Double Layer Dome Array

For the single layer dome array, the uppermost is Mylar. And its thickness is generally 0.05 mm or 0.075 mm. Besides, some of the Mylars in the single layer dome array will not have the ventilation slots, while some will make a small hole on it according to the customer’s requirements.

Structure of Single Layer Dome Array

Either the single layer dome array or the double layer dome array, there are release paper and protective film under the metal dome, aiming to protect the dome array. When the dome array has been torn down, the release paper and protective film will be the waste.

Therefore, the effect caused by the specifications of the release paper and protective film is not particularly large.

So, this is all about the introduction to the structure of the dome array. And if you have any questions about the dome or the dome array, you are welcome to contact us.

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What are the Main Applications of Different Metal Domes?

We all know that there are four types of tactile metal domes, including four-leg, circle, triangle and oblong. And these domes play different roles in various fields, even some of them can be substitute for each other. However, they virtually have their main application fields, which is more or less an unwritten rule.

Four-leg Metal Dome

In terms of structure, the height of four-leg domes is often higher than that of three other domes, hence the click feeling is also better. And four-leg domes are now mainly concentrated on the relatively large ones ranging from 5 mm to 20 mm, which is one of its advantages. With greater click feeling and longer life, this kind of snap dome is also called membrane switch dome, for which is most commonly used in membrane switch.

Four-leg Dome Sheet

Circle Metal Dome

Contrary to four-leg snap dome, circle metal dome, or round dome, focuses on the relatively small ones like 2.5 mm-5 mm. Thus, when there is only a small space on the PCB, the circle snap dome is the best option. And because most of the domes used in the phone are round dome, it is also named mobile phone dome.

Round Domes on FPC

Triangle Metal Dome

The advantage of triangle snap dome is that it can get the maximum force under the same diameter in comparison with other domes, which means it needs to be pressed hard to be conductive, so as to avoid misoperation especially in industrial control. Therefore, triangle dome metal is extremely suitable for industrial controls, like control panel.

Triangle Domes on PCB

Oblong Metal Dome

Oblong dome is seldom used. Because of its shape, oblong dome metal, also called rectangle snap dome, can be used in a long and narrow space compared with other three domes. And it is mainly used to be mounted on printed circuit boards, and other products such as membranes, panels, and so forth.

In a word, although it is not stipulated that only one of these snap domes can be used in a field, which indicates that they may be alternatives for each other in accordance with the specific uses and requirements, they generally still have their main application fields. And we, Best Technology, are an experienced electronic company so that if you would like to know more about metal domes or snap domes, you are welcome to contact us.

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How to assemble metal dome on PET adhesive sheet?

Normally we have three method to assemble metal dome on PET adhesive sheet. Please check details below:

  1. Assembly jig: this is the assembly method we use often currently. According to the drawing of PET adhesive sheet (dome array) to make a fixture, material is aluminum plate. The dome holes on plate is base on shape of different metal domes and qty. Like below photos, place with 8.4mm four legs metal dome with qty 69 keys.
Assembly jig (plate)
Place PET adhesive (dome array) on assembly Jig (plate)
Stick metal dome on PET adhesive
  • Through the assembly of tube fixture, this method has small tolerance and fast speed, but the cost is relatively high, suitable for relatively large quantity of production. Like below photos.
Collect metal domes in tube
Dome switch Tube in assembly machine
  • Place snap dome or metal dome on PET adhesive by manual. Usually if the customer only requires few prototype and samples, and does not want to pay the fixture fee, we will manually place metal domes of the sample. The disadvantage of this fitting method is that the fitting tolerance is relatively large, and some may tilt more severely.
Place metal dome on PET adhesive by manual

This video you will know more clearly.

If you still have any question after read, please feel free to contact us, we are here always and would solve your issue and provide our help to you.

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How to measure the diameter of triangle metal dome?

Are you wondering how to measure the diameter of triangle metal dome? If you are interesting, let me introduce it brifely.

various triangle metal dome

Method one: We know there are three vertices on each sideline of traingle dome, so we can draw a circle along the three vertices and emasure the diameter of circle to get a result, which is diameter of triangle metal dome as well.

method two to measure the diameter of triangle metal

Method two: Measure the distance from one vertice to the oppsite side to get a result and take an integer, this integer is diameter of triangle dome. For example, if you test like this and get a result as 6.51mm, then the diameter of triangle dome is 7mm.

draw a circle to measure the diameter of triangle dome

Method three: If the triangle metal dome with legs, we can simple measure the distance between two legs, and this distance is also the diameter of triangle metal dome.

metal dome

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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Do you know the differences of tooling types that making metal dome?

Normally we will use two types punching toolings to make metal dome: high speed tooling and low speed tooling, see below photos. Is there any difference in metal dome they produce? The answer is ” Yes”, there are many differences, please see below for more details.

  1. The stability of quality of dome switch is better with high speed tooling.
  2. The stamping speed is faster with high speed tooling, so lead time will be shorter. Normally 3-5 days for high speed tooling, 7-10 days for low speed tooling. Of course, we also need to depend on the production schedule and order quantity at that time.
  3. The life time is higher with high speed tooling. For example, for same diameter dome 12.2mm, 350g, the life times could be more than one million with high speed tooling, but only around 0.1 million times with low speed tooling.
  4. The high-speed molding line is on the outside and the low-speed molding line is on the inside.
  5. The burr is smaller (around 0.3mm) with high speed tooling than low speed tooling (above 0.5mm).
  6. The cost of high speed tooling is around 10,000 USD-20,000USD, but the cost of low speed tooling is around 1,000 USD-5,000 USD
  7. The price of metal dome with high speed tooling is higher than low speed tooling, because of better quality.

In a word, when we choose a metal dome, we should not only pursue the price, but also look at other aspects, such as production technology, quality, delivery time and so on.

If you want to know more about metal dome, please don’t hesitate to contact us, Best Technology. We are always here, waiting for you.

High speed tooling
Low speed tooling

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What’s light guild film and what function of it?

LGF, also known as light guide film , is a new product designed to improve the existing light guide film. It is to add a layer of LGF to the current common double layer metal dome structure, so as to achieve good light distribution effect.

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double layer metal dome structure

Using LGF( light guide film) on PCB (print circuit board), such as POS machine light source only need 1-4 LED lights, the use of light reflection and refraction principle, combined with special optical software design, do microstructure processing on the fiber film, so that the “point light source” expanded to “surface light source”.The beam propagates from the medium at the right Angle and density, so as to achieve the excellent effect of uniform softness and high brightness.

LGF dome array

Various parameters and advantages of light guide film (LGF) are as follows:

  1. Light guide film (LGF) has two types material: PC and PU; Both materials have the same light guiding effect; Comparatively speaking, PU material is softer and feels better. And PC material in the price advantage.

2. LGF thickness of light guide film has two kinds: 0.125mm and 0.1mm, both of which are the same. Thick light guide film has good light guide effect, strong light spot and concentrated light.And the light guide film of thin point has the advantage on feel.

3. Good luminous effect, uniform brightness, high light intensity.

4. Light, soft, thin thickness.In the use of mobile phones, different from the light guide plate takes up a large space.

5. Save LED qty, save power consumption, save cost.

6. Simple structure, does not affect the overall product design (does not affect the click sound of metal dome) and feel good.

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What’s caused the poor click feeling when pressing metal dome?

The click feeling of metal dome is very important for the using of whole product, a good click feeling not only need the metal dome has very good click feeling, but also related with the assembly of whole product, if you find a product with poor click feeling, you might analyze from below aspects:

  1. Click feeling of the metal dome is not good, we can test the metal dome by load curve tester and get the test result for height, force and rebound force, when the height is too low or rebound force is too high, it’s easy to cause bad click feeling. For this aspect, we can improve the click feeling by adjusting the height or rebound of the metal dome.
Dome array assembled with another overlay
  • Whether the silicon button which contacted with metal dome is too big? If this silicon botton is too large it will also affect the metal dome’s click feeling. For this problem we can improve the click feeling by reduce the diameter of silicon button.
dome array with silicon button
  • Whether the space between silicon button and PCB board is appropriate? The space too large or too small will both affect the press feeling.
  • Metal dome assembly deviation. Usually the metal dome was assembled on PCB borad by manual, so there is some deviation, and large deviation will cause bad click feeling. For this problem, we suggest to make assembly by jig and located position to reduce the deviation and improve click feeling.
  • There is another condition that some clients may put another coverlay on the surface of metal dome after assembly, if the coverlay is too thick then it will affect the click feeling as well.
Curve test performance

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 factors will influence the click feeling of the metal dome after assembly on PCB

We always get feedback from customers that the click of dome switch or metal dome is not good after assembly on PCB, what reasons cause this issue? That’s what they care about most. Today I will analyze it from the following reasons.

  1. There is an 0.15mm assembly tolerance when assemble metal dome onto PET adhesive
  • If place four legs or triangle metal dome, there will also be a 5 percent angular tilt tolerance.
  • If place round metal dome, the diameter of hole on spacer would be 0.3mm larger than metal dome, then could ensure unilateral tolerance of 0.15mm
  • There is a assembly tolerance when customer place dome array on PCB (print circuit board)
  • The press key or press rubber key is very large, exceed 30% of contact surface of metal dome from center, lead to hard to press and influence the click.

All above factors would influence the click of snap dome, so we need to take these factors into account when we produce. Avoid trouble in next step.

If you still have any question after read, please feel free to contact us, we are here always and would solve your issue and provide our help to you.

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