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Application: Design guidelines to improve the flexibility and reliability of flexible circuits.
Many of the issues that arise when using a flex circuit come from a lack of knowledge about how to properly design one, especially when the circuit is required to bend. Many novices will design a circuit that calls for bending the flex in too tight of a bend radius, which can cause damage to the circuit and lower the reliability of the end product. This series of articles will focus on the seven key aspects to consider when designing for maximum durability and maximum “flexibility”. It is important to know that because flexibility is a relative term this study will instead use the term reducing bend radius. Below are two of the seven design strategies. Please see Part I and Part III for more tips!
3. Do not allow electroless copper as a seed layer prior to plating vias.
- Also, an area to be concerned about is the type of plating your vendor uses. Some copper plating requires a seed layer of electroless copper. This seed layer becomes an ED copper layer and can lead to conductor cracking. For a tight bend radius direct metallization is the preferred plating method.
4. Use only Polyimide covers in the flexing area.
- There are two options for applying dielectric material over copper:
A. Polyimide cover material: This is the preferred material in areas where parts will be bent. As a general rule, you will want to specify a dielectric thickness and adhesive thickness separately. A rule of thumb is that for every 1 ounce of copper thickness there is 1 mil of adhesive thickness.
B. Flexible Solder Mask: Flexible solder mask has a minimum bend radius of 0.4” and is not recommended for any dynamic flexing application or application where the bend radius will be tighter than 0.4”
12/28/2020 | Pete Starkey, I-Connect007
For the third in a series of Technical Snapshot webinars, EIPC chose to focus on PCB surface finishes, comparing specific properties, examining corrosion behaviour and discussing selection criteria for low-loss, high frequency applications.
12/18/2020 | I-Connect007 China Team
Forces within and outside the PCB industry have led to concerns over rising prices for raw materials of copper-clad laminates (CCL). Recently, two major explosions at epoxy resin plants in China had a great impact on domestic resin suppliers. Prices have risen steadily in 2020, with leading CCL manufacturers announcing price increases of 20-30% recently. As the cost of raw materials such as electronic copper foil, resin and glass fiber have risen, the cost for manufacturing CCL has taken off as well.
12/15/2020 | Happy Holden, I-Connect007
This is the first Electronic Circuits World Convention that I have not attended in person since 1978. To refresh your memory, these are held every three years on a rotating basis. The HKPCA hosted this year’s conference and they kept up the fine tradition of collecting outstanding keynotes, nearly 60 technical presentations and myriad poster papers. HKPCA was also kind enough to provide English slides and translations. It is still possible to sign up and view the presentations. I have listened to 20 of the presentations, and hope to attend even more in the coming days as they are all worth watching.