HÁ ÔÅÍÕ ÓÁÂÖÁ... þÔÏÂÙ ÎÅ ÂÙÌÏ ÎÅÐÏÎÑÔÏË, ÓÁÂÖ - ÜÔÏ Hå ÍÁpËÁ ÍÁÔÅpÉÁÌÁ, Á ÓÔÁÎÄÁpÔÎÙÊ ËÌÁÓÓ ÍÁÔÅpÉÁÌÏ× Ó ÎÅËÏÔÏpÙÍ ÏÂÝÉÍ ÎÁÂÏpÏÍ Ó×ÏÊÓÔ×. ëÏÎËpÅÔÎÙÅ ÍÁpËÉ ÚÁ×ÉÓÑÔ ÏÔ ÐpÏÉÚ×ÏÄÉÔÅÌÑ, É ÇÕÇÌ ÎÁ ×ÏÐpÏÓ 'FR4 + "PCB laminate"' ÚÁ×ÁÌÉÔ ×ÁÓ ÓÓÙÌËÁÍÉ.
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FR4 Laminate
FR4 laminate is the usual base material from which plated-through-hole and multilayer printed circuit boards are constructed. "FR" means Flame Retardant, and Type "4" indicates woven glass reinforced epoxy resin.
The laminate is constructed from glass fabric impregnated with epoxy resin (known as "pre-preg") and copper foil, which is commonly supplied in thicknesses of "half-ounce" (approx 18 microns) or "one-ounce" (approx 35 microns). Foil is generally formed by electrodeposition ("ED Foil"), with one surface electrochemically roughened to promote adhesion. A typical 1.6 mm rigid laminate is made by bonding together eight plies of heavyweight pre-preg, with half-ounce copper foil either side, in a hot hydraulic press.
FR4 laminate displays a reasonable compromise of mechanical, electrical and thermal properties. Dimensional stability is influenced by construction and resin content. Generally, heavyweight glass fabric gives a more dimensionally stable material, although it is necessary to use lightweight fabrics for high layer count multilayer circuits.
Dielectric constant, typically in the range 4.4-5.2, depends on glass-resin ratio. It decreases with increasing resin content and increasing signal frequency. At microwave frequencies, dielectric losses make FR4 unsuitable and materials such as PTFE are more appropriate.
Expansion coefficient of FR4 laminate in the xy plane is approximately 16 ppm per degree C (copper 17-18ppm, glass fibre 5-7ppm, resin 40 ppm). The glass transition temperature (Tg) of FR4, at which the resin changes from a glassy to a plastic state, ranges from 120œC to 180œC depending on resin chemistry. Above Tg, the expansion coefficient of epoxy resin in the z axis (which is not reinforced) is approx 330 ppm per degree C. Continuous operating temperature for FR4 is typically 130œC.
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Fels Company - The PCB Laminates FAQ Last update: 4.01.2001
- Whatever you want to know about PCB laminates *
-------------------------------------------------------------------------- Q.: What is FR4? A.: FR4 is a glass fiber epoxy laminate. It is the most commonly used PCB material. 1.60mm FR4 uses 8 layers of (7628) glassfiber material. The red UL/manufacturers logo is in the middle (layer 4).
-------------------------------------------------------------------------- Q.: Isn't FR4 green in color? A.: No, it is usually transparent. The green color comes from the solder mask in the PCB finished product.
-------------------------------------------------------------------------- Q.: Does the color of the logo has a meaning? A.: Yes, there are red and blue logos. Red is UL94-V0, blue is UL94-HB. If you have a blue logo material, it is either XPC (phenolic) or G10 (glass epoxy). In 1.50/1.60mm FR4 the logo is in the middle layer (layer 4) of the common 8 layer construction.
-------------------------------------------------------------------------- Q.: What is G10? A.: G10 is out of fashion now for standard PCBs. It is woven glass fabric with a different epoxy from FR4. It is only UL94-HB. The main usage nowadays is for thin watch circuit - since it is very punchable.
-------------------------------------------------------------------------- Q.: What is CEM-3? A.: CEM-3 is very similar to FR4. Instead of woven glass fabric a 'flies' type is used. CEM-3 has a milky white color and is very smooth. It is a complete replacement for FR4 and has a very large market share in Japan.
-------------------------------------------------------------------------- Q.: What is CEM-1? A.: CEM-1 is a paper based laminate with one layer of (7628) woven glass fabric. It is not suitable for PTH.
-------------------------------------------------------------------------- Q.: What does FR or CEM mean? A.: CEM - Composite Epoxy Material FR - Fire Retardent
-------------------------------------------------------------------------- Q.: What is: PF-CP-Cu? IEC-249? GFN? A.: Here are a list of the common laminate standards: ANSI-LI-1 DIN-IEC-249 part 2 MIL 13949 BS 4584 JIS XPC - - PF-CP-Cu-4 PP7 FR1 2-1 - PF-CP-Cu-6 PP7F FR2 2-7-FVO - PF-CP-Cu-8 PP3F FR3 2-3-FVO PX - PE1F CEM-1 2-9-FVO - - CGE1F CEM-3 - - - CGE3F G10 - GE EP-GC-Cu-3 GE4 FR4 2-5-FVO GFN EP-GC-Cu-2 GE4F Attention: This data might not be complete. Many manufacturer produce also laminates which fall not into a clear ANSI spec. That means that the actual DIN/JIS/BS etc. specification might differ. Please check with the actual manufacturer what standard will fit your request most.
-------------------------------------------------------------------------- Q.: What is FR3? A.: FR3 is mainly a europaen product. It is basically FR2 - but instead of phenolic resin it uses a epoxy resin as binder. The basic layer is paper.
-------------------------------------------------------------------------- Q.: What is FR2? A.: Paper material with phenolic binder. It is UL94-V0.
-------------------------------------------------------------------------- Q.: What is the difference between FR1 and FR2? A.: It is basically the same. FR1 has a higher TG of 130oC instead of
105oC for FR2. Some laminate manufacturer which produce FR1 will not produce FR2, since cost and usage are similar and there is no advantage for having both.
-------------------------------------------------------------------------- Q.: What is 'CTI'? A.: Comparative Tracking Index Indicates the highest usable voltage for that laminate. It becomes important in application with high humidity, such as washing machines or cars. A higher index means a better protection. Similar is 'PTI' and 'KC'.
-------------------------------------------------------------------------- Q.: What are 'prepregs'? A.: A 'prepreg' is an epoxy coated glassfabric. It has two usages: as a dielectricum in multilayer PCBs, and as the raw material for FR4.
8 layers of '7628' prepregs are used in one sheet of 1.60mm FR4. The central layer (no. 4) usually carries the red company/UL logo.
-------------------------------------------------------------------------- Q: Can I make my own FR4? A: Sure, it's quite easy too. You just need: Prepregs & copper foil - and a (multilayer)press. The copper foil should be red or brass treated for best results.
-------------------------------------------------------------------------- Q.: What does '7628' mean? And what other numbers are there? A.: Here we go... Type Weight [g/m^2] Thickness [mm] Warp/Weft
106 25 0.050 22 x 22
1080 49 0.065 24 x 18.5
2112 70 0.090 16 x 15
2113 83 0.100 24 x 23
2125 88 0.100 16 x 15
2116 108 0.115 24 x 23
7628 200 0.190 17 x 12
-------------------------------------------------------------------------- Q.: How can I replace laminates? A.: XPC >>> FR2 >>> FR1 >>> FR3 >>> CEM-1 >>> CEM-3 or FR4.
-------------------------------------------------------------------------- Q.: What laminates are good for PTH? A.: CEM-3 and FR4 are best. FR3 and CEM-1 is not recommended. Below that PTH is not possible. (Of course you can still do 'Silver Paste TH')
-------------------------------------------------------------------------- Q.: Are there alternatives to PTH? A.: The hobby user can use rivets (or eyelids) which are available in electronic shops. There are a few other solution for low density PCBs, such es simple wiring etc. A more professional approach to making double sided connections is to use 'silver through hole' techniques. A silver paste is silk screened on the PCB, making the through hole connection. This procedure can be used on all types of laminates, including paper phenolics like XPC etc.
-------------------------------------------------------------------------- Q.: What is 'Pre-Sensitized' laminate? A.: This is for hobby applications. It is standard laminate, coated with a (liquid) image photoresist. Just tear off the light protection, expose, develop, etc.
-------------------------------------------------------------------------- Q.: What are 'Off-Cuts'? A.: Since nowadays many PCB factories prefer to get there laminate already in panel sizes there are often 'left over' sizes. This are sold at a lower price. The quality is mostly absolute A-grade.
-------------------------------------------------------------------------- Q.: What are 'Strips'? A.: Stripes are usually long pieces of laminate with a width of 50-150mm. Some laminate manufacturer (mainly Japanese) do cut there B-grade laminate to strips for the secondary market. For paperphenolics there is no real problem with the size. Where CNC drilling is required the panel size is critical since the througput will be lower.
-------------------------------------------------------------------------- Q.: What is 'Core Thickness'? A.: Core Thickness means the laminate base thickness without copper. This is relevant for multilayer PCBs which have a defined layer construction. It's mainly used for thincore FR4 laminate.
-------------------------------------------------------------------------- Q.: What quantity do I need to make import worthwhile? A.: It depends where your location is. We usually ship to the 'nearest container port'. For the USA this would be the West Coast. All european ports are possible too. The shipping charge is usually about US$30-70 per CBM (m^3). On top of this you have some import charges and duties in your own country. The smalles lots we usually ship is 2 pallets or about 2000kg.
FELS COMPANY
617, 6/F., Advanced Technology Centre 2 Choi Fat St., Sheung Shui, N.T. Hong Kong Tel.: +(852) 2423-1812 Fax : +(852) 2423-1899 e-mail: snipped-for-privacy@felsweb.com
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