| When designing a keypad it is important that you | | | | required through a process of laser etching the |
| have an understanding of how the production | | | | keypad or if the keypad needs epoxy resin tops |
| costs of producing the keypad are calculated as | | | | then these extra operations are expensive and |
| this will have an impact on what features you can | | | | again will add increased cost to the parts if the |
| include. | | | | quanties are not high. |
| Silicone keypads are typically produced using a | | | | On many keypads Carbon contact pills are used |
| compression moulding method in a high | | | | to create the switch connection between the |
| temperature 200T press. This method of | | | | keypad and the PCB. The carbon pills are |
| production is slow compared to injection moulding | | | | assembled during the moulding process and do not |
| as the cycle time can be up to 15 minutes per | | | | have any major effect of the unit cost but do |
| shot. Due to this lengthy cycle time it is important | | | | help with reducing the overall assembly cost as |
| to have as many impressions in the tool as | | | | much cheaper than using mechanical switches. |
| possible. For example a small keypad size of 50 x | | | | An example of reducing costs, when several |
| 50mm could have 49 impressions and produce | | | | mouldings are required it is sometimes possible to |
| 196 parts per hour but a larger keypad size of | | | | have several designs in the same mould tool |
| 100 x 150 would only have 6 impressions so only | | | | rather than having separate tools, this keeps the |
| produce 24 parts per hour. This output is the | | | | initial tooling costs low and can save several |
| main driver of price when producing keypads. | | | | thousands of pounds. |
| As well as output in moulding you should also be | | | | It is difficult to give clear guide lines on how to |
| aware of set up costs. Set up costs are applied | | | | reduce costs. The easiest process to follow is to |
| when producing small quantities, there are costs | | | | design the keypad to suit your requirements and |
| involved in preparing the silicone material, setting | | | | then look at the alternative methods available if |
| up the moulding press, printing and spraying. This | | | | the costs are too high. This way of developing |
| means that if the quantity is low and you have | | | | the project often allows the manufacturer of the |
| extra operations such as prints and spray | | | | keypad to suggest alternatives that may not |
| coatings then the unit cost for the keypad will be | | | | before have been considered without sacrificing |
| high. | | | | design and quality. |
| When designing keypads it is often the case that | | | | The most important issue to remember is not to |
| multiple print colours are requested, this can | | | | compromise your design where possible as the |
| enhance the value of the product but also adds to | | | | keypad is often the most important item in your |
| the cost, if the order quantities are high enough | | | | instrument and can add value far in excess of the |
| then printing is a small addition to the unit cost as | | | | cost in making it. |
| is spray coating. If however backlighting is | | | | |