Conversation with Miraco… Strategies for Successful Flex Circuit Assembly

Estimated reading time: 3 minutes

Miraco Inc. offers design, sourcing and value-added assembly of flexible interconnect products, including flex circuits, flat cables and wire/cable assemblies. The company services its diverse customer base from multiple locations—including headquarters in Manchester, New Hampshire, and its principal manufacturing site, Miraco South facility, in Tijuana, Mexico. The company also has additional satellite offices in the north and southeastern parts of the United States.

Jason Michaud, a 19-year veteran at Miraco, is the company’s new vice president of sales. In an interview with SMT007 Magazine, Jason speaks about the challenges in flex circuit assembly, and the best practices to address those issues.

Stephen Las Marias: Are you seeing increasing demand for flexible circuits?

Jason Michaud: Yes, with packaging sizes getting smaller, the need for creative flex solutions is growing. Overall, we are seeing an increase in demand for flexible printed circuits.

Las Marias: What factors are driving this?

Michaud: What’s driving a good portion of new business for Miraco is the redesign and sourcing of flexible printed circuits for customers who had gone directly offshore with their flexible circuit requirements previously and have experienced problems doing so. We are seeing a lot of flex circuits that were underdesigned or improperly designed to meet their intended use.

Las Marias: What are the top three challenges when it comes to flexible circuit assembly?

Michaud: The challenge for flexible circuit assembly is balancing electrical, mechanical, environmental and cost requirements with the material availability of suppliers and the manufacturability of the complete interconnect system. Pressure sensitive adhesive is a good example of something that is simple in relative terms compared to the flexible circuit layers; however, it drastically complicates the assembly process by limiting handling and cleaning options post soldering. However, if you process the soldering and cleaning of the assembly first, it is labor intensive and costly to apply the pressure-sensitive adhesive in piece form. It’s a double-edged sword.

Las Marias: Which parts of the assembly process are greatly impacted when doing flex circuit assemblies?

Michaud: When considering assembly, panelization and fixturing during design become important, as to panel size and panel stability. The number and type of components will dictate these parameters. These are important to facilitate the proper oven location during reflow. Oversized panels or unstable panels can greatly affect reflow and profile results in turn affecting yield and cost. Singulation post assembly is always a concern that is flexible circuit- and component-specific.

Las Marias: What strategies do you employ to address these challenges?

Michaud: Understanding the capabilities of the assembly equipment and its limitations is vital. Having calibrated equipment and a known repeatable process is key. Outlining post assembly can be accomplished through steel rule die, hard punch dies or lasering. Depending on the components that are assembled, the number you are outlining, and the required outline tolerance determine the best and most cost-effective route.

Las Marias: How different is the assembly of flex circuits from rigid- or rigid-flex circuits? What are the critical factors to consider?

Michaud: Flex circuits are typically more sensitive to assembly processes than their rigid-flex counterparts. In either case, as both products are hydroscopic, pre-bake cycles are a critical precursor to any assembly. In flex assembly, consideration must be given to added support for solder pad and/or through-hole areas with stiffening materials, preventing stress from transitioning to the soldered joint as, of course, flex circuits want to flex. In rigid-flex, you are more typically assembling to the rigid area and it provides self-stress relief. Proper pad sizing and thermal relief during design helps optimize reflow and hand solder assembly.

To read the full version of this article, which appeared in the June 2018 issue of SMT007 Magazine, click here.