[{"data":1,"prerenderedAt":66},["ShallowReactive",2],{"blog-g10-vs-fr4-material-form-procurement-en":3},{"title":4,"description":5,"date":6,"lastUpdated":6,"category":7,"image":8,"imageAlt":9,"readingTime":10,"wordCount":11,"timeRequired":12,"htmlContent":13,"faq":14,"tags":30,"slug":34,"sourceLocale":35,"availableLocales":36,"jsonld":42},"G-10 vs. FR-4: Material Forms and Procurement Evidence","Distinguish G-10 and FR-4 material forms and specify grade, construction, evidence and substitution controls before placing a PCB or insulation order.","2026-11-14","materials",null,"",11,2010,"PT11M","\u003Cp>Related woven-glass/epoxy laminate designations alone do not identify the product form, PCB construction, or flame evidence being purchased. A G-10 or FR-4 callout is a starting point for identification—not, by itself, an approved material definition or substitution decision.\u003C/p>\n\u003Cp>Before releasing an order, establish what the supplier will deliver, the manufacturer’s exact grade, and the evidence applicable to that grade in the supplied form. For a PCB, also identify the construction and determine what must be validated at board and end-product level.\u003C/p>\n\u003Cp>For broader material and fabrication context, see \u003Ca href=\"/en/blog/fr4-material/\">FR-4 material\u003C/a> and \u003Ca href=\"/en/blog/copper-clad-laminate/\">copper-clad laminate\u003C/a>.\u003C/p>\n\u003Ch2>Start with the supplied form\u003C/h2>\n\u003Ctable>\n\u003Cthead>\n\u003Ctr>\n\u003Cth>Purchased form\u003C/th>\n\u003Cth>What is supplied and what the buyer controls\u003C/th>\n\u003Cth>Evidence to request\u003C/th>\n\u003Cth>Common category error\u003C/th>\n\u003C/tr>\n\u003C/thead>\n\u003Ctbody>\u003Ctr>\n\u003Ctd>\u003Cstrong>Cured unclad industrial laminate stock or machined insulation parts\u003C/strong>\u003C/td>\n\u003Ctd>A cured sheet or other stock form, or parts machined from it. Specify the manufacturer and grade, form, dimensions, drawing requirements, intended use, and traceability. For machined parts, identify the source stock and part acceptance requirements.\u003C/td>\n\u003Ctd>Grade-specific data for the supplied stock; supplier identification and lot documentation as required; applicable scoped flame evidence when needed. For parts, add inspection and source-material traceability required by the drawing.\u003C/td>\n\u003Ctd>Treating an industrial sheet as automatically suitable for a PCB core, or treating a machined part’s source-material data as proof of finished-part performance.\u003C/td>\n\u003C/tr>\n\u003Ctr>\n\u003Ctd>\u003Cstrong>Copper-clad PCB laminate or cured core\u003C/strong>\u003C/td>\n\u003Ctd>A cured laminate with copper cladding in the specified construction. Control the exact grade, thickness, copper construction, relevant surface or treatment requirements, dimensions, and position in the approved stackup.\u003C/td>\n\u003Ctd>Manufacturer data for the grade and clad form; construction and lot identification; applicable records and test information tied to the requirements being checked.\u003C/td>\n\u003Ctd>Ordering by “FR-4 sheet” alone, without identifying the cladding or intended stackup, or assuming the core data qualifies the finished PCB.\u003C/td>\n\u003C/tr>\n\u003Ctr>\n\u003Ctd>\u003Cstrong>B-stage prepreg\u003C/strong>\u003C/td>\n\u003Ctd>Resin-impregnated reinforcement supplied in a partially cured state for subsequent lamination. Specify the manufacturer and grade, reinforcement and resin system as designated by the manufacturer, construction, supplied form, storage and handling requirements, and intended stackup use.\u003C/td>\n\u003Ctd>Grade and construction data; lot identity; storage and shelf-life documentation where required; applicable evidence for the intended construction.\u003C/td>\n\u003Ctd>Substituting a cured sheet for prepreg, or assuming prepreg and cured-core data are interchangeable.\u003C/td>\n\u003C/tr>\n\u003Ctr>\n\u003Ctd>\u003Cstrong>Finished bare PCB\u003C/strong>\u003C/td>\n\u003Ctd>A fabricated board defined by the approved fabrication data, stackup, material requirements, copper construction, features, finish, and acceptance criteria. Identify permitted materials and any restrictions on substitution.\u003C/td>\n\u003Ctd>Fabricator documentation tying the build to the approved data and material sources; inspection and test records required by the order; applicable construction and flame evidence.\u003C/td>\n\u003Ctd>Treating a laminate datasheet as finished-board qualification, or treating bare-board acceptance as qualification of the assembled end product.\u003C/td>\n\u003C/tr>\n\u003C/tbody>\u003C/table>\n\u003Cp>The matrix separates \u003Cem>what is delivered\u003C/em> from \u003Cem>what the designation suggests\u003C/em>. A sheet is not automatically a PCB core or a prepreg. Likewise, a manufacturer’s material data does not establish the performance or acceptance of every construction made from it.\u003C/p>\n\u003Cp>For the different roles of cured cores and B-stage material in a multilayer board, see \u003Ca href=\"/en/blog/pcb-core-vs-prepreg/\">PCB core vs. prepreg\u003C/a>. Those PCB construction details do not establish suitability for an industrial insulation part.\u003C/p>\n\u003Ch2>Define the purchase beyond the callout\u003C/h2>\n\u003Cp>A usable RFQ or purchase order should connect the designation to an identifiable item. At minimum, determine:\u003C/p>\n\u003Cul>\n\u003Cli>\u003Cstrong>Manufacturer and grade:\u003C/strong> Which exact manufacturer grade is offered, and does the manufacturer identify it for the requested form?\u003C/li>\n\u003Cli>\u003Cstrong>Form and construction:\u003C/strong> Is the item unclad stock, a machined part, a copper-clad core, prepreg, or a finished bare board? For a PCB, which stackup locations and constructions are involved?\u003C/li>\n\u003Cli>\u003Cstrong>Drawing authority:\u003C/strong> Which controlled drawing, fabrication data, or specification governs acceptance? Who may approve deviations?\u003C/li>\n\u003Cli>\u003Cstrong>Identity and traceability:\u003C/strong> What lot or batch information must accompany delivery, and how will it be retained through cutting, machining, or fabrication?\u003C/li>\n\u003Cli>\u003Cstrong>Required evidence:\u003C/strong> Which current documents, records, declarations, and test reports are required, from whom, and for what scope?\u003C/li>\n\u003C/ul>\n\u003Cp>Ask the supplier to identify gaps rather than filling them with assumptions. For example, a datasheet for a similarly named grade may be useful for initial screening, but it is not automatically evidence for the offered grade and form. A certificate of conformity should identify what is being certified against; it should not be used as a substitute for missing technical scope.\u003C/p>\n\u003Cp>For a finished PCB, the material bill may contain more than one core or prepreg construction. The fabricator should identify the materials actually proposed for each relevant stackup position, not merely repeat the broad designation from the drawing.\u003C/p>\n\u003Ch2>Match flame evidence to the actual item\u003C/h2>\n\u003Cp>Flame evidence is an \u003Cstrong>exact product, construction, and condition question\u003C/strong>. Do not infer a flame class, listing, or rating from either designation alone.\u003C/p>\n\u003Cp>When flame requirements apply, ask for the manufacturer’s grade and current applicable scoped records. Check that the record covers the offered item and the intended use, including the supplied form and construction. Request thickness and color information when relevant to the record or requirement. Establish the lot identity and how it connects to the supplied material.\u003C/p>\n\u003Cp>For a PCB, ask whether the relevant evidence addresses the proposed board construction and what additional validation is required. For a machined part, check whether the source-material evidence is applicable to the finished part and its conditions of use. The product/design owner must determine whether product-level validation is also required.\u003C/p>\n\u003Cp>Do not replace that review with a supplier’s unscoped statement such as “flame compliant.” Request enough information to verify applicability and current status, and resolve any mismatch before release.\u003C/p>\n\u003Ch2>Keep thermal and dielectric requirements separate\u003C/h2>\n\u003Cp>A substitution discussion can go wrong when unlike measurements are treated as if they answer the same question.\u003C/p>\n\u003Cp>\u003Cstrong>Glass transition temperature, or Tg\u003C/strong>, describes a transition in material behavior under a defined measurement method. It is not, by itself, an approved continuous operating limit or an assurance that an assembly process is acceptable.\u003C/p>\n\u003Cp>\u003Cstrong>Continuous service temperature\u003C/strong> concerns the intended long-term use and the criteria used to establish suitability. Ask what property or acceptance criterion supports the claimed service condition and whether it applies to the actual part and environment.\u003C/p>\n\u003Cp>\u003Cstrong>Assembly thermal exposure\u003C/strong> is a separate review of the proposed manufacturing profile: temperatures, time at temperature, number of exposures, handling, and acceptance criteria for the board and assembly. Evaluate the proposed material and construction against that profile rather than comparing Tg alone.\u003C/p>\n\u003Cp>For PCB stackup considerations, the \u003Ca href=\"/en/blog/high-tg-fr4-guide-pcb-stackup-materials/\">high-Tg FR-4 material and stackup discussion\u003C/a> provides additional context. Its PCB examples are not a qualification of an industrial sheet or machined part.\u003C/p>\n\u003Cp>\u003Cstrong>Dielectric data\u003C/strong> also depends on test conditions. Identify the property, method, frequency, temperature, conditioning, orientation or geometry where relevant, and the specimen construction. Compare data generated under compatible conditions; a number without those conditions is not a complete basis for approval.\u003C/p>\n\u003Ch2>Fictional RFQ: count the forms before comparing them\u003C/h2>\n\u003Cp>The following is a \u003Cstrong>fictional ordering example\u003C/strong>, not product data or test results.\u003C/p>\n\u003Ctable>\n\u003Cthead>\n\u003Ctr>\n\u003Cth>RFQ line\u003C/th>\n\u003Cth>Request\u003C/th>\n\u003Cth>Initial disposition\u003C/th>\n\u003C/tr>\n\u003C/thead>\n\u003Ctbody>\u003Ctr>\n\u003Ctd>A\u003C/td>\n\u003Ctd>\u003Cstrong>G-10 callout; one cured unclad sheet\u003C/strong> for a drawing-controlled insulation part. The RFQ specifies the manufacturer grade, dimensions, and required documentation.\u003C/td>\n\u003Ctd>Continue to normal document and drawing review; release is not automatic.\u003C/td>\n\u003C/tr>\n\u003Ctr>\n\u003Ctd>B\u003C/td>\n\u003Ctd>\u003Cstrong>FR-4 callout; one copper-clad cured core\u003C/strong> for a PCB stackup. The manufacturer grade, copper construction, and applicable evidence are not identified.\u003C/td>\n\u003Ctd>Hold pending clarification.\u003C/td>\n\u003C/tr>\n\u003C/tbody>\u003C/table>\n\u003Cp>The arithmetic is \u003Cstrong>two RFQ lines: one continuing to review and one held\u003C/strong>. The count does not compare properties or test outcomes. The two requests concern different ordered forms; even a complete answer for the sheet would not define the PCB core.\u003C/p>\n\u003Ch2>Control a proposed substitution\u003C/h2>\n\u003Cp>A proposed alternate is a change to evaluate, not an equivalence to assume. Use a documented workflow:\u003C/p>\n\u003Col>\n\u003Cli>\u003Cstrong>Confirm drawing authority.\u003C/strong> Identify the owner of the controlled requirements and obtain that authority’s approval before purchasing or building with a deviation. Record the affected part numbers, documents, and effective scope.\u003C/li>\n\u003Cli>\u003Cstrong>Identify form and grade.\u003C/strong> Record the original and proposed manufacturer, exact grade, supplied form, and supplier. Verify that the evidence provided applies to the offered item, not just to a related designation.\u003C/li>\n\u003Cli>\u003Cstrong>Review stackup and construction.\u003C/strong> For a PCB, compare the affected core and prepreg positions, copper construction, thickness requirements, and other controlled stackup features. For a machined part, review the stock and finished-part requirements.\u003C/li>\n\u003Cli>\u003Cstrong>Align test methods and conditions.\u003C/strong> Identify the required properties, methods, specimen forms, conditioning, and acceptance criteria. Resolve incompatible or missing data instead of comparing isolated values.\u003C/li>\n\u003Cli>\u003Cstrong>Check assembly thermal exposure.\u003C/strong> Review the actual planned exposure and handling against the proposed construction, including the criteria for accepting the board after processing.\u003C/li>\n\u003Cli>\u003Cstrong>Verify traceability and scoped evidence.\u003C/strong> Link the proposed material and relevant records to the lots supplied. Check current applicability, including construction and conditions for flame evidence where required.\u003C/li>\n\u003Cli>\u003Cstrong>Define qualification and disposition.\u003C/strong> The design owner determines the necessary material, board, assembly, or end-product validation. Record results and approval when completed; quarantine or reject affected material if required evidence or acceptance is missing.\u003C/li>\n\u003C/ol>\n\u003Cp>The checklist may lead to a request for more information, a trial under controlled conditions, approval within a defined scope, or rejection. It should not produce an open-ended permission to exchange all materials bearing a familiar designation.\u003C/p>\n\u003Cp>For a proposed change in a board construction, the \u003Ca href=\"/en/blog/pcb-material-substitution/\">PCB material substitution checklist\u003C/a> provides a related stackup and approval workflow.\u003C/p>\n\u003Ch2>Who owns which evidence?\u003C/h2>\n\u003Cp>The \u003Cstrong>material manufacturer\u003C/strong> identifies its grade and supplied forms and provides the applicable technical and product documentation. It can clarify the scope of its records and how the material is identified by lot. Its documentation does not, on its own, approve the buyer’s finished design.\u003C/p>\n\u003Cp>The \u003Cstrong>fabricator or parts supplier\u003C/strong> identifies what it proposes to use and deliver. For a PCB, that includes the relevant stackup materials and construction, traceability, and the build and inspection records required by the order. For machined insulation parts, it includes the relationship between source stock and delivered parts. The supplier must disclose a proposed deviation rather than silently replacing the specified item.\u003C/p>\n\u003Cp>The \u003Cstrong>product or design owner\u003C/strong> controls the requirement and decides whether evidence supports the intended use. That includes approving substitutions and defining any board-, assembly-, or end-product qualification. Procurement and NPI teams can coordinate the evidence package and hold the order, but should not assume design authority.\u003C/p>\n\u003Cp>A useful RFQ makes these responsibilities visible: name the drawing authority, list required deliverables, and state that a proposed alternate requires approval before use. To begin a scoped purchasing discussion, use the \u003Ca href=\"/en/quote/\">quote page\u003C/a>.\u003C/p>\n\u003Cp>When the project also includes board assembly, the \u003Ca href=\"/en/blog/pcb-assembly-quote/\">PCB assembly quote guide\u003C/a> explains which fabrication files, BOM, sourcing, and testing assumptions help suppliers prepare comparable quotes.\u003C/p>\n\u003Cdiv data-component=\"BlogQuickQuoteInline\">\u003C/div>\n\n\u003Ch2>Frequently asked questions\u003C/h2>\n\u003C!-- faq:start -->\n\n\u003Ch3>Is an FR-4 callout enough to order a PCB core?\u003C/h3>\n\u003Cp>Not usually by itself. Identify the manufacturer grade, cured-core form, copper construction, stackup position, and governing acceptance requirements. Ask for evidence applicable to that exact item and use.\u003C/p>\n\u003Ch3>Can a cured G-10 sheet replace prepreg?\u003C/h3>\n\u003Cp>Do not treat it as a direct replacement. A cured sheet and B-stage prepreg are different supplied forms with different roles. Any proposed construction change requires review and approval by the drawing authority.\u003C/p>\n\u003Ch3>Does a material datasheet establish flame compliance for a finished PCB?\u003C/h3>\n\u003Cp>No. A datasheet may be part of the evidence package, but flame applicability must be checked against the exact product, construction, and conditions. Finished-board and end-product validation may also be required.\u003C/p>\n\u003Ch3>Is a higher Tg sufficient to approve a substitute?\u003C/h3>\n\u003Cp>No. Tg is only one material characteristic measured under a method. The review must separately address the applicable requirements, construction, assembly thermal exposure, traceability, and qualification criteria.\u003C/p>\n\u003Ch3>Who approves a supplier’s alternate grade?\u003C/h3>\n\u003Cp>The drawing or design authority approves the change within a documented scope. The supplier identifies the proposed material and provides supporting evidence; procurement should hold an unapproved substitution rather than authorize it by purchase-order wording alone.\u003C/p>\n\u003C!-- faq:end -->\n\u003Csection class=\"related-links\" aria-label=\"Related\">\u003Ch3>Related links\u003C/h3>\u003Cul>\u003Cli>\u003Ca href=\"/en/blog/fr4-material/\">FR4 PCB Material Guide: What It Is, When It Works, and When to Choose Something Else\u003C/a>\u003C/li>\u003Cli>\u003Ca href=\"/en/blog/copper-clad-laminate/\">Copper Clad Laminate (CCL): Types, Grades and How PCB Laminates Are Specified\u003C/a>\u003C/li>\u003Cli>\u003Ca href=\"/en/blog/pcb-core-vs-prepreg/\">PCB Core vs Prepreg: Differences and Stackup Selection\u003C/a>\u003C/li>\u003Cli>\u003Ca href=\"/en/blog/high-tg-fr4-guide-pcb-stackup-materials/\">high tg fr4 guide: materials and stackup strategy whitepaper\u003C/a>\u003C/li>\u003Cli>\u003Ca href=\"/en/blog/pcb-material-substitution/\">PCB Material Substitution: What Changes, What to Check, Who Approves\u003C/a>\u003C/li>\u003Cli>\u003Ca href=\"/en/quote/\">quote page\u003C/a>\u003C/li>\u003Cli>\u003Ca href=\"/en/blog/pcb-assembly-quote/\">PCB Assembly Quote Guide: Files, Cost and Comparison\u003C/a>\u003C/li>\u003C/ul>\u003C/section>",[15,18,21,24,27],{"question":16,"answer":17,"answerText":17},"Is an FR-4 callout enough to order a PCB core?","Not usually by itself. Identify the manufacturer grade, cured-core form, copper construction, stackup position, and governing acceptance requirements. Ask for evidence applicable to that exact item and use.",{"question":19,"answer":20,"answerText":20},"Can a cured G-10 sheet replace prepreg?","Do not treat it as a direct replacement. A cured sheet and B-stage prepreg are different supplied forms with different roles. Any proposed construction change requires review and approval by the drawing authority.",{"question":22,"answer":23,"answerText":23},"Does a material datasheet establish flame compliance for a finished PCB?","No. A datasheet may be part of the evidence package, but flame applicability must be checked against the exact product, construction, and conditions. Finished-board and end-product validation may also be required.",{"question":25,"answer":26,"answerText":26},"Is a higher Tg sufficient to approve a substitute?","No. Tg is only one material characteristic measured under a method. The review must separately address the applicable requirements, construction, assembly thermal exposure, traceability, and qualification criteria.",{"question":28,"answer":29,"answerText":29},"Who approves a supplier’s alternate grade?","The drawing or design authority approves the change within a documented scope. The supplier identifies the proposed material and provides supporting evidence; procurement should hold an unapproved substitution rather than authorize it by purchase-order wording alone.",[31,32,33],"G-10","FR-4","PCB materials","g10-vs-fr4-material-form-procurement","en",[35,37,38,39,40,41],"de","it","cn","fr","ru",{"blog":43,"breadcrumb":52},{"@context":44,"@type":45,"headline":4,"description":5,"url":46,"datePublished":6,"dateModified":6,"timeRequired":12,"keywords":47,"articleSection":7,"author":48,"publisher":51},"https://schema.org","BlogPosting","https://hilpcb.com/en/blog/g10-vs-fr4-material-form-procurement/","G-10, FR-4, PCB materials",{"@type":49,"name":50},"Organization","HILPCB",{"@type":49,"name":50},{"@context":44,"@type":53,"itemListElement":54},"BreadcrumbList",[55,60,64],{"@type":56,"position":57,"name":58,"item":59},"ListItem",1,"Home","https://hilpcb.com/",{"@type":56,"position":61,"name":62,"item":63},2,"Blog","https://hilpcb.com/en/blog/",{"@type":56,"position":65,"name":34,"item":46},3,1794758597555]