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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New product launch in line

Good news, we developed and new prouct and lauched in line now! An special square metal dome with Ø 3.0 hole in center,  which allow you place an LED on the PCB board directly. The dome dimension is 7.4*7.4mm, standard trip force from 220gf to 350gf, 0.1mm SUS301 material. Except the standard stainless steel product, nickel plated or gold plated both optional.

Technical drawing

This unique square metal dome is durable and reliable while maintianing good click feeling. There are four “ball shape” leg in all four corners to enhance the contuctivity between metal dome and PCB board.  

Product picture
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What problem or issue would have if the metal dome height and PET adhesive size are not suitable?

Recently, we got feedback fron one of our customers that found Plastic of Dome Switch bulge and peel off as below photo when production after assembly dome array on PCB, we could see the place from the red arrow. Why will have such issue happened? See the following analysis.

PCB with dome array

This is due to the product design flaws, it’s not the problem of the PET adhesive, two reasons below that lead to this issue:

  1. The height of dome switch that used is around 0.75-0.80mm, it’s very high height.
  2. The adhesive tape area from metal dome to edge is only 0.40-0.60mm, you could see from above photo, and only cover a layer of PET with 0.05mm glue, viscous tension is not enough to support for a long time; It will inevitably jack up the material with such high dome height.

We can use the schematic diagram below to understand above issue. If we want to achieve the ideal, we need to use the right height of snap domel and the suitable adhesive tape size. If we want to solve this issue above, we could do below based on the actual situation:

  1. Drecease the height of metal dome, keep original adhesive tape size.
  2. Increase the adhesive tape size, keep the original height of metal dome
  3. Drecease the height of metal dome and Increase the adhesive tape size.
structure analysis
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What the difference between metal dome with dimple and without dimple?

We had knew that metal dome has different types, without dimple and with one or several dimples, but do you know what the difference between with dimple and without dimple?

the metal dome without dimple

The biggest difference is the difference in conduction stability, the metal dome with dimple has better conduction stability than no dimple metal dome.

Because in the using process, once there are dust on the contact side of metal dome, the no dimple metal dome is surface-surface contacting with PCB pad, and the dust will block the conduction.

the metal dome with dimple

For the metal dome with dimple, there are dimple to surface contact with PCB pad, as long as the dust didn’t exsit on the dimple, it will not affect the conduction, even the dust is on the dimple as long as you press the dome several times the dust will fall off. So the conduction stability is more better.

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 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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