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Background Statement for SEMI Draft Document 4691
NEW STANDARD: SPECIFICATION FOR HIGH DENSITY PERMANENT CONNECTIONS BETWEEN MICROFLUIDIC DEVICES
Note: This background statement is not part of the balloted item. It is provided solely to assist the recipient in reaching an informed decision based on the rationale of the activity that preceded the creation of this document.
Note: Recipients of this document are invited to submit, with their comments, notification of any relevant patented technology or copyrighted items of which they are aware and to provide supporting documentation. In this context, “patented technology” is defined as technology for which a patent has issued or has been applied for. In the latter case, only publicly available information on the contents of the patent application is to be provided.
Background
MEMS microfluidic devices must be connected to other fluidic structures in order to be useful. Machine automation of these connections will reduce the manufacturing cost and broaden the possible fields of application. Device design and interface standards are needed that will enable this automation and reduce design cycle time.
A major subset of MEMS microfluidics applications are in biology and chemistry. Many of these applications have relaxed requirements in operating and burst pressures. Plastics meet many of these needs, glass others. Plastic disposable devices are common and successful in biomedicine.
No standard presently specifies designs and methods for forming permanent seals between plastic microfluidic components where the pitch between adjacent ports of a high tube-count interface is less than 1.0mm. This is the motivation for developing the present Specification.
The results of this ballot will be discussed at the next North America MEMS / NEMS committee meeting on March 28, 2011 in conjunction with the NA Standards Spring 2011 meetings in San Jose, CA.
SEMI Draft Document 4691
NEW STANDARD: SPECIFICATION FOR HIGH DENSITY PERMANENT CONNECTIONS BETWEEN MICROFLUIDIC DEVICES
1 Purpose
1.1 This standard provides specification for interconnection dimensions and performance requirements for permanent microfluidic interfaces. It also provides guidance for interface design. This will help to enable low cost and high volume manufacturing of products having high density permanent interfaces between plastic tube adapters, plastic microfluidic cartridges, and electrofluidic devices.
2 Scope
2.1 Lab-on-a-Chip technology and microfluidics in general, have few accepted high-density standard designs and methods for interfacing multiple tubes to electrofluidic integrated circuits (EFIC) and multilayer microfluidic routing cards or manifolds. Consequently, there are few, solutions of automated assembly of these components. Currently, companies working in microfluidics development must use “fittings” and techniques which are much larger than the natural size of the tube interface. This standard will contribute to the development of miniaturized, lower cost, and mechanically robust fluidic connections in the same way that wirebonds have enabled low cost reliable integration of silicon parts with: packages, printed circuit boards, and other microchips. The scope of this standard includes applications where low cost materials and automated assembly will prevail. Though not expressly excluded, the requirements of some high performance applications such as: ultra-high purity, high vacuum, high pressure, caustic / acidic / corrosives; may not be satisfied by the limited structural and chemical stability performance requirements in this standard. Other standards exist for these applications and are referenced where possible. Devices such as “biosensors” and “bioMEMS” are intended to be addressed by this standard.
2.2 Build on Existing Microfluidics Interface Standards Work — Recent work on the published standard MS7—0708 described architectures and methods for designing microfluidic interfaces to electronic device packages. The purpose was to enable the development of new semiconductor and MEMS products that could be integrated into higher level systems. The scope includes any MEMS device that gets connected to any kind of microfluidic structure. Thus, the materials for making these devices and interfaces are unrestricted, ranging from plastics to glass and stainless steel. The corresponding bonding methods are also unlimited, and include welding, adhesive, solvent and ionic.
2.3 Design Standards and Recommendations — MS7-0708 described planar architectures that sandwich EFICs between fluidic routing cards and PCBs (see Fig. 1 below).
2.3.1 The present standard establishes design requirements that, when followed, ensure that these three types of components to fit together in a three dimensional structure.
2.3.2 It provides guidance for designing high density tube adapters that connect to these components. It provides guidance on other aspects of fabrication such as bonding, testing, and automated manufacturing.
2.4 Laminated Fluidic Routing Card Fabrication — This standard is meant for enabling connections to and from fluidic routing cards similar in structure to that shown in Fig. 1. This is distinct from connections whose mechanical dimensions are based on a method of interconnect like hose barb, luer lock, compression fitting. The nature of laminated fabrication processes allows manufacturers to publish design rules for which their process works. These rules typically include materials, layer thicknesses, x-y dimensions, hole sizes, and layer – to – layer bonding methods.
Figure 1
MEMS EFIC connected by fluidic routing card and printed circuit board.
Note 1: The Electrofluidic Integrated Circuit Device (EFIC) is designed to be compatible with existing printed circuit board technology. The Fluidic Routing Card is made out of multi-layer fluidic structures. Several architectures exist for fabricating Fluidic Routing Cards, including plastic + adhesive, glass + bonding, and stainless steel + welding. This is Figure 4 from MS7-0708.
Figure 2
Interface planes shown using cross section of MEMS EFIC connecting to microfluidic routing card.
Note 1: A cross section of the fluid interface between a “Chip-on-Board” (COB) style MEMS sensor and a multilayer fluidic routing card. The fluid path is from left to right in the fluidic card, turns down into and across the MEMS device, and then back up the outlet into the fluidic routing card. The [MEMS device + MEMS fluidic adapter] make up the Electrofluidic Integrated Circuit device (EFIC). The “Sealing Plane” and “Support Plane” are separated by a distance called the “Fluidic Interface Height”. Specifying this height ensures that the electrofluidic device and fluidic routing card can fit together. The sealing plane is where glue or a gasket is placed to keep the liquid from leaking. The support plane may provide mechanical support as well as additional bonding area, but no fluid is passing through it. The fluidic routing card is constructed by aligning and bonding together multiple cut layers of material.
2.5 MEMS-Microfluidics Architectures are Evolving — The architectures in Standard MS7-0708 are based around MEMS silicon-based products, their known properties and manufacturing methods. The packaging around the Si chips, and electrical connections from the chip to printed circuit boards are described in realistic detail; Fig. 1 here is taken directly from that Standard. Connections to external microfluidic structures, while described at the same level of detail, are more speculative due to the newness of MEMS – Microfluidics interfaces.
2.6 Biochemical Compatibility Restricts Manufacturing Path — Many assembly methods that have been developed for Si chip packaging, such as injection molding around an Si die that is bonded to a Cu lead frame, are incompatible with applications where some biochemical material like DNA must be placed on chip and survive subsequent packaging, storage, and handling. A standard is needed for applications with these additional biochemical survivability requirements.
2.7 Low-cost high-quantity Manufacturing is Needed — The commercialization of MEMS-based biosensor technologies is limited, in part, by the lack of mass manufacturing methods and infrastructure. This standard will help enable mass manufacturing by defining interfaces and requirements for a narrow area of use.
2.8 Permanent Tube to Fluidics Interface — This standard focuses on interfaces that are permanent (adhesive, bonding, welded) and not designed to be removable or re-usable.
2.9 Enable Technologies — These technologies will be enhanced or enabled by this Standards activity: MEMS, microfluidics, Lab-on-a-Chip (LOC), biosensors, Point-of-Use and Point-of-Care diagnostic products, bioanalytical instrumentation, and clinical chemistry analysis.
2.10 Applications — This standards activity will describe architectures, materials, and methods that are fully compatible with consumer-oriented biosensor products. Biomaterials, such as DNA, proteins, and antibodies, are added during the manufacturing process. These biomaterials are present in the final product, and must perform a biochemical function for the end user. For example, a DNA chip carries single stranded DNA, which must be “active” when the final user of the product runs their analytical test.
2.11 Materials — The scope is narrowed significantly by the range of materials that are appropriate for biosensor products. Some of the current detection means include: visual, micro-optical, electrochemical, fluorescence, and magnetic. Clear materials are desirable, as are non-conducting materials. Plastics, particularly those with sufficient optical properties in the relevant spectrum, are most desirable due to their low cost and ease of forming.
2.12 Manufacturing Process Environment — Survival of on-chip biomaterials places severe constraints on fabrication process temperatures, and the presence of harsh chemicals. Water and solvents like ethyl and isopropyl alcohol are compatible.
2.13 Manufacturing Methods for High-Quantity — Architectures in this Standard are compatible with mass-manufacturing methods. Robotic and automated assembly is the ideal method. However, some scale-up through lower volume methods is inevitable and necessary.
NOTICE: SEMI Standards and Safety Guidelines do not purport to address all safety issues associated with their use. It is the responsibility of the users of the documents to establish appropriate safety and health practices, and determine the applicability of regulatory or other limitations prior to use.
3 Referenced Standards and Documents
3.1 SEMI Standards
SEMI F1 — Specification for Leak Integrity of High-Purity Gas Piping Systems and Components
SEMI MS7 — Specification for Microfluidic Interfaces to Electronic Device Packages
SEMI MS8 — Guide to Evaluating Hermeticity of MEMS Packages
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
4 Terminology
4.1 Abbreviations and Acronyms
4.1.1 bioMEMS — a MEMS device that performs a function in a analytical instrument or laboratory procedure.
4.1.2 CAD — computer aided design.
4.1.3 COB — chip on board.
4.1.4 EFIC — Electrofluidic Integrated Circuit (EFIC) - the integration of semiconductor electronics and microfluidics on a common substrate
4.1.5 PCB — printed circuit board.
4.2 Definitions
4.2.1 EFIC — Electrofluidic Integrated Circuit (EFIC) - the integration of semiconductor electronics and microfluidics on a common substrate
4.2.2 Lab-on-a-Chip — is a miniaturized version of a laboratory instrument for performing, typically, a clinical or biochemical analysis.
4.2.3 Fluidic component types — Fluidic interfaces can be formed between three types of “fluidic components”: microfluidic routing cards, tube adapters, and EFICs (MEMS electrofluidic integrated circuit components). This standard describes the structural features that a given “fluidic component” must have on its exterior for the purposes of forming a fluidic connection with another fluidic component. Some optional features are also included in the standard.
4.2.4 Planar Fluidic Interface geometry types — An interface between two fluidic components whose sealing contact takes place in a plane is a planar fluidic interface. Non-planar sealing interfaces such as chamfered or spherical are not addressed in this Standard.
4.2.4.1 Single level Planar Interface — The fluidic sealing between two fluidic components takes place in a single plane called the “sealing plane”. No additional planes are used for structural support.
4.2.4.2 Two-level Planar Interface — The fluidic sealing between two fluidic components takes place in a single plane called the “sealing plane”. One additional plane, the “support plane,” parallel to the sealing plane, is used to provide support and alignment.
4.2.5 Recessed or Extended — If the support surface is closer to the mating piece than the sealing surface, it is a “recessed sealing plane”. If the support plane is further away from the mating piece than the sealing plane, it is called an extended sealing plane.”
4.2.6 Exclusion Area — The “exclusion area” is additional space in the sealing plane that is reserved for non-mating functions of the fluidic component.
4.2.7 Fluidic Mating Surface — The “mating surface” is the face of one fluidic component that is bonded to other fluidic components, and through which fluids pass.
4.2.8 Fluidic interface height — This is the vertical separation of the sealing surface and the support surface. If the support surface is closer to the mating piece than the sealing surface, it is a “recessed sealing surface”. If the support surface is further away from the mating piece than the sealing surface, it is called an extended sealing surface.”
5 Requirements
In order to indicate compliance to this standard, all elements listed within this section A or B shall be performed.
5.1 Section A: Specification for minimum required elements on a product data sheet
5.1.1 Product details that shall be on component specification sheet of a fluidic component for a 1-level planar interface are:
5.1.1.1 Material composition — The material of the fluidic mating surface shall be specified (e.g. PMMA, polycarbonate, glass ,…) and all materials comprising the wetted flow path shall be specified.
5.1.1.2 Any bonding or sealing methods used shall be specified.
5.1.1.3 Maximum Allowable Working Pressure — The manufacturer’s maximum allowable working pressure (MAWP) shall be specified.
5.2 Section B: In order to indicate compliance to this part B of this standard, all elements listed within this section shall be performed.
5.2.1 The product shall have the following dimensions:
5.2.1.1 The pitch from center to center of ports shall be [select one: 0.050mm, 0.100mm, 0.200mm, 0.400 mm, 0.500mm, 0.800mm or 1.000mm]
5.2.1.2 The pitch-to-port diameter ratio shall be [select one: 1.5, 2, 3 or 4]
5.2.1.3 The height of sealing plane shall be same as device package [for example: 1.00mm as used MSOP 8 JEDEC MO-187]
5.2.1.4 The alignment hole diameter shall be 1.0mm.
5.2.1.5 The exclusion zone perimeter shall be 1.0mm beyond edge of sealing surface.
5.2.1.6 Alignment hole spacing, shall be center-to-center of 8.0mm.
5.2.1.7 Exclusion zone height shall be the same as height of sealing plane.
6 Guide for Interface Design