www.we-online.com 0605 Circuit Board Technology · Tec Report · Issue 08 · July 2010

Niedernhall, July 2010 – PCB specialist Würth Elektronik once again demonstrates their competence

in system solutions and customer support; now offering one-stop flex-rigid PCB solutions with ZIF

contacts and custom designed ZIF connectors. Customers from diverse fields such as industry, auto-

motive, medical care and digital image processing benefit from Würth Elektronik’s particular problem

solving approach. Most notably in the two key points: quality and cost. This makes flex-rigid and

flexible PCBs an affordable and effective choice for maximum use of complex circuit technologies in

the minimum space, in particular with respect to system costs.

Flex-rigid PCBs and ZIF connectors

www.we-online.com

Würth Elektronik offers the best contact between flex-rigid PCBs and ZIF connectors

Figure 8:Semi-fl exible PCB with ZIF contact serving as connection with an optical module in a sen-

sor for measuring air quality.

Flex-rigid multilayer boards are already proving their value in daily applications. For exam-

ple, as sensors for controlling motors in roller shutters, awnings and Venetian blinds. In this

case, internal resistors and heaters were also used. Here all the typical demands are met:

high operational reliability and durability; simple assembly; resistance against oil, grease,

humidity and aggressive environmental conditions as well as simple, reliable electrical con-

nections using a fl exible limb with a ZIF contact. Wiring and solder joints were replaced,

high quality connections applied, and an assembly process for the heating resistors was

avoided.

For another application, a special design and implementation of contacts was created using

a semi-fl exible FR4 PCB with a ZIF contact for use in standard ZIF connectors. This appli-

cation was used in a module for the optical display of temperature and air quality in a sen-

sor for measuring air quality. In order to achieve large bending radii, the single-sided PCB

already had a thickness of 0.3 mm in the contact area, which means that it could be directly

plugged into the ZIF connector without the need for additional stiffeners or extra milling.

Further advantages were that cable wiring to the motherboard was no longer necessary, the

assembly process was simplifi ed and the additional benefi t that a drying process before

soldering was no longer required due to the base material used.

*) Note: ZIF connector – The term ZIF (Zero Insertion Force) originates from the socket tech-

nology of components, mainly CPU’s. In a ZIF socket, contacts are opened prior to place-

ment of the IC, e.g. by a leverage mechanism, allowing for effortless insertion of the con-

tact pins into the socket. The mechanism is then closed, fi xing the contacts to the pins in

the socket, and thus creating the electrical connection.

Particular advantages of fl ex-rigid PCBs

Flex-rigid technology is well-proven, reliable and particularly good in overcoming space and weight issues with spatial degrees of free-dom. Careful consideration of fl ex-rigid solutions and a proper as-sessment of the available options at an early stage in the design phase can return signifi cant benefi ts:

Space requirements can be minimised by applying 3D circuitry.

By removing the need for connectors and cables between the individual rigid parts the board size could be reduced and overall system weight can be brought down.

Less solder joints assure higher reliability.

Handling during assembly is easier when compared with complete fl exible boards.

Otherwise diffi cult connections can be created, thereby simplifying the assembling processes.

Integrated ZIF contacts provide simple modular interfaces to the system environment.

Test conditions are simplifi ed. A complete test prior to installation becomes possible.

Logistical and assembly costs are signifi cantly reduced with fl ex- rigid boards.

It is possible to increase the complexity of mechanical designs, whilst also improving the degree of freedom for optimised housing solutions.

Using fl ex-rigid technology to create ZIF contacts is be-coming more and more widespread, as it offers a number of benefi ts:

savings in joints/components

improved reliability

cost savings in procurement and logistics

reduced installation size

less complexity and expense in design and development

About Würth Elektronik Circuit Board Technology (CBT)

Würth Elektronik is the leading PCB manufacturer in Europe, producing a wide spectrum

of PCBs – from standard technologies through to pioneering system solutions – at manu-

facturing plants in Niedernhall, Rot am See and Schopfheim. The PCB specialist delivers

application specifi c solutions in all technologies and is a driving force behind new techni-

cal innovations, for example, in the fi eld of embedded active and passive components.

The extensive PCB portfolio ranges from double sided PCBs and multilayers in all con-

ventional technologies through to technically demanding PCBs such as HDI, fl ex-rigid and

heatsink technologies.

About the Würth Elektronik Group

Würth Elektronik CBT is – alongside Würth Elektronik ICS (electromechanical and elec-

tronic system solutions), Würth Elektronik eiSos (passive and electromechanical compo-

nents) and Würth Solar (CIS-photovoltaic modules and solar power systems) – a division

of the Würth Elektronik Group, an internationally operating, independent subsidiary of the

Würth Group. Beside their own R&D, Würth Elektronik is also involved in numerous exter-

nal research communities, e.g. GloveNet or TIPS. In 2009 Würth Elektronik employed

around 5,900 personnel and generated a turnover of 374 million Euros.

Further information can be found at www.we-online.com.

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More informationwww.we-online.com/fl ex-rigid

Würth Elektronik GmbH & Co. KG

Circuit Board Technology

Salzstr. 21 · 74676 Niedernhall · Germany

Tel.+49 (0) 7940 946-0 

Fax +49 (0) 7940 946-55 00 00

info@we-online.de

www.we-online.com

Circuit Board Technology · Tec Report · Issue 08 · July 2010

Figure 7:ZIF contact replaces wiring in a motor control unit for roller shutters and awnings.

Figure 9:By laser cutting the fl exible ZIF contours, precise contact tolerances were achieved and an

ingenious panelisation provided a stable assembly panel.

Flex-rigid technology was also employed in the re-design of an MDE device (mobile data

entry), created for inventory administration. An adapter board with two ZIF contacts enabled

the display to be updated smoothly and securely. Additionally, by laser cutting the fl exible

ZIF contours, precise contact tolerances were achieved and an ingenious panelisation pro-

vided a stable assembly panel. In the fl exible region, the PCBs could be removed by hand,

without the needs for tools or special processing.

TEC REPORTIssue 08 · July 2010

Flexible and fl ex-rigid PCBs are being designed more and more with the prevalent ZIF inter-

face, possessing a so-called ZIF contact (ZIF = Zero Insertion Force) for connection with a ZIF

connector. Hence, appropriate one-stop system solutions make sense. For that reason, Würth

Elektronik eiSos’ designers of the new ZIF connector WR-FPC paid particular attention to

closely attuning system relevant areas. The ZIF connector WR-FPC has been specifi cally

designed for the best connection to fl exible and fl ex-rigid PCBs by respecting the tight toler-

ances and parameters applicable in PCB manufacturing in the connector design. Customers

therefore get comprehensive and systematic design support, as well as seamlessly tailored

system components. Würth Elektronik is offering a ZIF connector design-kit, particularly cre-

ated for designers and offering a range of options for design test. The ZIF connector WR-FPC

is available in different variants and for any kind of construction, either upright, horizontal,

contacts on TOP or BOTTOM.

Faithful to Würth Elektronik’s tradition of close customer ties and proximity, diffi cult and com-

plex customised solutions can be worked out as well. “We are not only service providers, but

also consultants and trouble-shooters in the entire range of fl exible and fl ex-rigid matters,”

emphasises Andreas Schilpp, product manager “3D” at Würth Elektronik, “no single job will

be released into production without full optimisation – even if in some cases that could only

be a double-check of the production panelisation for cost reduction purposes. For example,

a well-thought-out use of base materials can help reduce costs whilst, at the same time,

improving quality. At present, we are able to build about 80% of incoming jobs with Würth

Elektronik’s specifi cally qualifi ed and standardised range of base materials, a selection of the

many materials available in the market for rigid-fl ex PCB technologies. For the remaining

20%, we fi nd specifi cally tailored solutions together with our customers.”

Various options for ZIF connections

Detachable connections between displays and PCBs, or between two PCBs are often cre-

ated by using fl exible printed circuit boards or by fl exible fl at cables and ZIF connectors.

Fine pitch ZIF connectors are available, for example, on a 1.0 mm and 0.5 mm pitch. The

contact arrangement is created between the ZIF connector, which is soldered onto the PCB

and the ZIF contact, which must fi t exactly into the ZIF connector. This ZIF contact can be

simply a fl exible fl at cable, a complex fl exible PCB or a fl ex tail from a fl ex-rigid PCB.

There are various ways of creating ZIF contacts. Flex-rigid PCBs and the generally thinner

fl ex PCBs are handled in different ways to attain the required 0.3 mm PCB thickness at the

contact position: For fl exible PCBs, a stiffener is affi xed to the contact area; which means

relatively high costs due to the necessary handling required at the adhesive bonding pro-

cess. In contrast, for fl ex-rigid PCBs, Würth Elektronik utilises the simple and cost effective

method of high-precision depth milling to obtain the required thickness.

Tolerances in production

Very small geometrical tolerances must be maintained in manufacture, so that the ZIF con-

tact fi ts optimally in the ZIF connector. Due to this reason, only fl at solderable surfaces are

possible. For increased reliability and a longer lifespan, the solderable surface fi nish electro-

less nickel/immersion gold has proved itself favourably in practice.

The profi le of a simple ZIF contact, with the technical requirements of a PCB profi le with a tol-

erance range of ±0.1 mm, is created through routing. However, enhanced tolerances such

as ±50µm can only be realised through the use of camera controlled routing or laser cutting.

Drawing specifi cations in the manufacturing documents

Without the corresponding specifi cations on the drawing and/or without dimensioning in the

gerber data, a fl exible tail is not recognisable as a ZIF contact. Therefore, the following details

should be contained in the manufacturing drawing according to the data sheets of the connec-

tor manufacturer:

length and width of the contact area

thickness of the contact (stiffening material + fl ex material + copper) including the

tolerance. Standard is 0.3 mm ± 0.05 mm

lenght of the stiffener. The stiffener must overlap with the fl exible solder mask/coverlay

toleranced distance of the fi rst contact to the profi le

ideally an indication of the possible areas for connecting tabs in the delivery panel

Figure 1:Würth Elektronik eiSos’ ZIF connectors are ideally suited for connecting fl ex-rigid PCBs.

Figure 2:For fl exible PCBs, a stiffener is affi xed to the contact area, resulting in a higher operating

expense. For fl ex-rigid boards, Würth Elektronik utilises cost-effective precision depth milling

to meet the required thickness.

Figure 3:A combination of precise laser cutting and depth milling leaves a stable assembly support at

the underside of the PCB. Conventional milling (see PCB in the background) removes this

extra support, and the assembly panel becomes less stable.

Figure 5:An idea originating from PCB technology: “Ears” behind the ZIF contact improves handling:

The contact can be easily inserted into the connector by holding it at these “ears”.

Figure 4:Tabs can be set in various ways: The upper variant has tabs in the fl exible area directly beside

the stiffeners (see option two). The method shown at the bottom leaves material in the original

PCB thickness offering many advantages (see option three).

There are many ways to set connecting tabs in fl ex-rigid boards

In order to allow the insertion of the contact into the ZIF connector, the specifi ed contact area

in its length must not have any tabs at its side edges. Connection tabs must be placed beyond

the connection area. There are a number of options here:

1) If the customer agrees to extend the contact stiffener into the fl exible area, stable tabs can

be set in the stiffened area (FR 4 depth milling).

2) If an extension of the stiffened area is not suitable, the tabs in the fl exible area must be set

directly beside the stiffener.

3) Intermediate tabs: Here, the entire PCB’s material thickness remains unchanged, offering

various advantages.

4) Laser-cut micro tabs in the fl exible area: Micro tabs can be applied for laser-cut fl exible out-

lines. Rigid material underneath the fl exible limb enhances the delivery panel’s stability and

allows for easy manual de-panelisation.

5) Ease of handling with “ears”: An idea originating from PCB technology; highly effi cient and

cost saving.

Further options with a stable intermediate tab

Usually, for fl ex-rigid boards with an internal fl exible layer, the ZIF contact is also located on

the fl exible core. That would require some complex special operation steps during the pro-

duction process. For fl ex-rigid with the fl exible layer located as external layer, a change of

the contact side could become necessary. Such a change is made possible by via holes in

the rigid area in between.

Flex-rigid boards in practice

“Making quality manufacturable and cost effective is Würth Elektronik’s top priority”, high-

lights the fl ex-rigid PCB specialist Andreas Schilpp, “an essential prerequisite is as much

standardisation as possible. Through our internal, cross-departmental coordination of sys-

tem solutions, we are in a position to almost standardise innovative technologies such as

fl ex-rigid and open up more and more areas of application. We have been able to prove this

in many projects”.

Furthermore, Schilpp points out: “As it’s also the case in many other areas: the earlier cus-

tomers involve their suppliers in the design and development stages, the higher the

chances of benefi ting from system solutions become. Namely, this is because we are able

to introduce our PCB production know-how at the right time. A fact that often proves advan-

tageous and cannot necessarily be recognised by customers at the early stage of design”.

02 Circuit Board Technology · Tec Report · Issue 08 · July 2010 www.we-online.com 04

Figure 6:For fl ex-rigid boards with a fl exible internal layer, the ZIF contact is usually also located on

the fl exible core. For fl ex-rigid boards with a fl exible external layer, a change of the contact

face can be necessary sometimes. Such change of sides is realised by via holes in the rigid

area in between.

Figure 2:Figure 2:Figure

Flex-rigid PCBs and ZIF connectors

Flexible and fl ex-rigid PCBs are being designed more and more with the prevalent ZIF inter-

face, possessing a so-called ZIF contact (ZIF = Zero Insertion Force) for connection with a ZIF

connector. Hence, appropriate one-stop system solutions make sense. For that reason, Würth

Elektronik eiSos’ designers of the new ZIF connector WR-FPC paid particular attention to

closely attuning system relevant areas. The ZIF connector WR-FPC has been specifi cally

designed for the best connection to fl exible and fl ex-rigid PCBs by respecting the tight toler-

ances and parameters applicable in PCB manufacturing in the connector design. Customers

therefore get comprehensive and systematic design support, as well as seamlessly tailored

system components. Würth Elektronik is offering a ZIF connector design-kit, particularly cre-

ated for designers and offering a range of options for design test. The ZIF connector WR-FPC

is available in different variants and for any kind of construction, either upright, horizontal,

contacts on TOP or BOTTOM.

Faithful to Würth Elektronik’s tradition of close customer ties and proximity, diffi cult and com-

plex customised solutions can be worked out as well. “We are not only service providers, but

also consultants and trouble-shooters in the entire range of fl exible and fl ex-rigid matters,”

emphasises Andreas Schilpp, product manager “3D” at Würth Elektronik, “no single job will

be released into production without full optimisation – even if in some cases that could only

be a double-check of the production panelisation for cost reduction purposes. For example,

a well-thought-out use of base materials can help reduce costs whilst, at the same time,

improving quality. At present, we are able to build about 80% of incoming jobs with Würth

Elektronik’s specifi cally qualifi ed and standardised range of base materials, a selection of the

many materials available in the market for rigid-fl ex PCB technologies. For the remaining

20%, we fi nd specifi cally tailored solutions together with our customers.”

Various options for ZIF connections

Detachable connections between displays and PCBs, or between two PCBs are often cre-

ated by using fl exible printed circuit boards or by fl exible fl at cables and ZIF connectors.

Fine pitch ZIF connectors are available, for example, on a 1.0 mm and 0.5 mm pitch. The

contact arrangement is created between the ZIF connector, which is soldered onto the PCB

and the ZIF contact, which must fi t exactly into the ZIF connector. This ZIF contact can be

simply a fl exible fl at cable, a complex fl exible PCB or a fl ex tail from a fl ex-rigid PCB.

There are various ways of creating ZIF contacts. Flex-rigid PCBs and the generally thinner

fl ex PCBs are handled in different ways to attain the required 0.3 mm PCB thickness at the

contact position: For fl exible PCBs, a stiffener is affi xed to the contact area; which means

relatively high costs due to the necessary handling required at the adhesive bonding pro-

cess. In contrast, for fl ex-rigid PCBs, Würth Elektronik utilises the simple and cost effective

method of high-precision depth milling to obtain the required thickness.

Tolerances in production

Very small geometrical tolerances must be maintained in manufacture, so that the ZIF con-

tact fi ts optimally in the ZIF connector. Due to this reason, only fl at solderable surfaces are

possible. For increased reliability and a longer lifespan, the solderable surface fi nish electro-

less nickel/immersion gold has proved itself favourably in practice.

The profi le of a simple ZIF contact, with the technical requirements of a PCB profi le with a tol-

erance range of ±0.1 mm, is created through routing. However, enhanced tolerances such

as ±50µm can only be realised through the use of camera controlled routing or laser cutting.

Drawing specifi cations in the manufacturing documents

Without the corresponding specifi cations on the drawing and/or without dimensioning in the

gerber data, a fl exible tail is not recognisable as a ZIF contact. Therefore, the following details

should be contained in the manufacturing drawing according to the data sheets of the connec-

tor manufacturer:

length and width of the contact area

thickness of the contact (stiffening material + fl ex material + copper) including the

tolerance. Standard is 0.3 mm ± 0.05 mm

lenght of the stiffener. The stiffener must overlap with the fl exible solder mask/coverlay

toleranced distance of the fi rst contact to the profi le

ideally an indication of the possible areas for connecting tabs in the delivery panel

Figure 1:Würth Elektronik eiSos’ ZIF connectors are ideally suited for connecting fl ex-rigid PCBs.

Figure 2:For fl exible PCBs, a stiffener is affi xed to the contact area, resulting in a higher operating

expense. For fl ex-rigid boards, Würth Elektronik utilises cost-effective precision depth milling

to meet the required thickness.

Figure 3:A combination of precise laser cutting and depth milling leaves a stable assembly support at

the underside of the PCB. Conventional milling (see PCB in the background) removes this

extra support, and the assembly panel becomes less stable.

Figure 5:An idea originating from PCB technology: “Ears” behind the ZIF contact improves handling:

The contact can be easily inserted into the connector by holding it at these “ears”.

Figure 4:Tabs can be set in various ways: The upper variant has tabs in the fl exible area directly beside

the stiffeners (see option two). The method shown at the bottom leaves material in the original

PCB thickness offering many advantages (see option three).

There are many ways to set connecting tabs in fl ex-rigid boards

In order to allow the insertion of the contact into the ZIF connector, the specifi ed contact area

in its length must not have any tabs at its side edges. Connection tabs must be placed beyond

the connection area. There are a number of options here:

1) If the customer agrees to extend the contact stiffener into the fl exible area, stable tabs can

be set in the stiffened area (FR 4 depth milling).

2) If an extension of the stiffened area is not suitable, the tabs in the fl exible area must be set

directly beside the stiffener.

3) Intermediate tabs: Here, the entire PCB’s material thickness remains unchanged, offering

various advantages.

4) Laser-cut micro tabs in the fl exible area: Micro tabs can be applied for laser-cut fl exible out-

lines. Rigid material underneath the fl exible limb enhances the delivery panel’s stability and

allows for easy manual de-panelisation.

5) Ease of handling with “ears”: An idea originating from PCB technology; highly effi cient and

cost saving.

Further options with a stable intermediate tab

Usually, for fl ex-rigid boards with an internal fl exible layer, the ZIF contact is also located on

the fl exible core. That would require some complex special operation steps during the pro-

duction process. For fl ex-rigid with the fl exible layer located as external layer, a change of

the contact side could become necessary. Such a change is made possible by via holes in

the rigid area in between.

Flex-rigid boards in practice

“Making quality manufacturable and cost effective is Würth Elektronik’s top priority”, high-

lights the fl ex-rigid PCB specialist Andreas Schilpp, “an essential prerequisite is as much

standardisation as possible. Through our internal, cross-departmental coordination of sys-

tem solutions, we are in a position to almost standardise innovative technologies such as

fl ex-rigid and open up more and more areas of application. We have been able to prove this

in many projects”.

Furthermore, Schilpp points out: “As it’s also the case in many other areas: the earlier cus-

tomers involve their suppliers in the design and development stages, the higher the

chances of benefi ting from system solutions become. Namely, this is because we are able

to introduce our PCB production know-how at the right time. A fact that often proves advan-

tageous and cannot necessarily be recognised by customers at the early stage of design”.

02 Circuit Board Technology · Tec Report · Issue 08 · July 2010 www.we-online.com 04

Figure 6:For fl ex-rigid boards with a fl exible internal layer, the ZIF contact is usually also located on

the fl exible core. For fl ex-rigid boards with a fl exible external layer, a change of the contact

face can be necessary sometimes. Such change of sides is realised by via holes in the rigid

area in between.

Figure 2:Figure 2:Figure

Flex-rigid PCBs and ZIF connectors

Flexible and fl ex-rigid PCBs are being designed more and more with the prevalent ZIF inter-

face, possessing a so-called ZIF contact (ZIF = Zero Insertion Force) for connection with a ZIF

connector. Hence, appropriate one-stop system solutions make sense. For that reason, Würth

Elektronik eiSos’ designers of the new ZIF connector WR-FPC paid particular attention to

closely attuning system relevant areas. The ZIF connector WR-FPC has been specifi cally

designed for the best connection to fl exible and fl ex-rigid PCBs by respecting the tight toler-

ances and parameters applicable in PCB manufacturing in the connector design. Customers

therefore get comprehensive and systematic design support, as well as seamlessly tailored

system components. Würth Elektronik is offering a ZIF connector design-kit, particularly cre-

ated for designers and offering a range of options for design test. The ZIF connector WR-FPC

is available in different variants and for any kind of construction, either upright, horizontal,

contacts on TOP or BOTTOM.

Faithful to Würth Elektronik’s tradition of close customer ties and proximity, diffi cult and com-

plex customised solutions can be worked out as well. “We are not only service providers, but

also consultants and trouble-shooters in the entire range of fl exible and fl ex-rigid matters,”

emphasises Andreas Schilpp, product manager “3D” at Würth Elektronik, “no single job will

be released into production without full optimisation – even if in some cases that could only

be a double-check of the production panelisation for cost reduction purposes. For example,

a well-thought-out use of base materials can help reduce costs whilst, at the same time,

improving quality. At present, we are able to build about 80% of incoming jobs with Würth

Elektronik’s specifi cally qualifi ed and standardised range of base materials, a selection of the

many materials available in the market for rigid-fl ex PCB technologies. For the remaining

20%, we fi nd specifi cally tailored solutions together with our customers.”

Various options for ZIF connections

Detachable connections between displays and PCBs, or between two PCBs are often cre-

ated by using fl exible printed circuit boards or by fl exible fl at cables and ZIF connectors.

Fine pitch ZIF connectors are available, for example, on a 1.0 mm and 0.5 mm pitch. The

contact arrangement is created between the ZIF connector, which is soldered onto the PCB

and the ZIF contact, which must fi t exactly into the ZIF connector. This ZIF contact can be

simply a fl exible fl at cable, a complex fl exible PCB or a fl ex tail from a fl ex-rigid PCB.

There are various ways of creating ZIF contacts. Flex-rigid PCBs and the generally thinner

fl ex PCBs are handled in different ways to attain the required 0.3 mm PCB thickness at the

contact position: For fl exible PCBs, a stiffener is affi xed to the contact area; which means

relatively high costs due to the necessary handling required at the adhesive bonding pro-

cess. In contrast, for fl ex-rigid PCBs, Würth Elektronik utilises the simple and cost effective

method of high-precision depth milling to obtain the required thickness.

Tolerances in production

Very small geometrical tolerances must be maintained in manufacture, so that the ZIF con-

tact fi ts optimally in the ZIF connector. Due to this reason, only fl at solderable surfaces are

possible. For increased reliability and a longer lifespan, the solderable surface fi nish electro-

less nickel/immersion gold has proved itself favourably in practice.

The profi le of a simple ZIF contact, with the technical requirements of a PCB profi le with a tol-

erance range of ±0.1 mm, is created through routing. However, enhanced tolerances such

as ±50µm can only be realised through the use of camera controlled routing or laser cutting.

Drawing specifi cations in the manufacturing documents

Without the corresponding specifi cations on the drawing and/or without dimensioning in the

gerber data, a fl exible tail is not recognisable as a ZIF contact. Therefore, the following details

should be contained in the manufacturing drawing according to the data sheets of the connec-

tor manufacturer:

length and width of the contact area

thickness of the contact (stiffening material + fl ex material + copper) including the

tolerance. Standard is 0.3 mm ± 0.05 mm

lenght of the stiffener. The stiffener must overlap with the fl exible solder mask/coverlay

toleranced distance of the fi rst contact to the profi le

ideally an indication of the possible areas for connecting tabs in the delivery panel

Figure 1:Würth Elektronik eiSos’ ZIF connectors are ideally suited for connecting fl ex-rigid PCBs.

Figure 2:For fl exible PCBs, a stiffener is affi xed to the contact area, resulting in a higher operating

expense. For fl ex-rigid boards, Würth Elektronik utilises cost-effective precision depth milling

to meet the required thickness.

Figure 3:A combination of precise laser cutting and depth milling leaves a stable assembly support at

the underside of the PCB. Conventional milling (see PCB in the background) removes this

extra support, and the assembly panel becomes less stable.

Figure 5:An idea originating from PCB technology: “Ears” behind the ZIF contact improves handling:

The contact can be easily inserted into the connector by holding it at these “ears”.

Figure 4:Tabs can be set in various ways: The upper variant has tabs in the fl exible area directly beside

the stiffeners (see option two). The method shown at the bottom leaves material in the original

PCB thickness offering many advantages (see option three).

There are many ways to set connecting tabs in fl ex-rigid boards

In order to allow the insertion of the contact into the ZIF connector, the specifi ed contact area

in its length must not have any tabs at its side edges. Connection tabs must be placed beyond

the connection area. There are a number of options here:

1) If the customer agrees to extend the contact stiffener into the fl exible area, stable tabs can

be set in the stiffened area (FR 4 depth milling).

2) If an extension of the stiffened area is not suitable, the tabs in the fl exible area must be set

directly beside the stiffener.

3) Intermediate tabs: Here, the entire PCB’s material thickness remains unchanged, offering

various advantages.

4) Laser-cut micro tabs in the fl exible area: Micro tabs can be applied for laser-cut fl exible out-

lines. Rigid material underneath the fl exible limb enhances the delivery panel’s stability and

allows for easy manual de-panelisation.

5) Ease of handling with “ears”: An idea originating from PCB technology; highly effi cient and

cost saving.

Further options with a stable intermediate tab

Usually, for fl ex-rigid boards with an internal fl exible layer, the ZIF contact is also located on

the fl exible core. That would require some complex special operation steps during the pro-

duction process. For fl ex-rigid with the fl exible layer located as external layer, a change of

the contact side could become necessary. Such a change is made possible by via holes in

the rigid area in between.

Flex-rigid boards in practice

“Making quality manufacturable and cost effective is Würth Elektronik’s top priority”, high-

lights the fl ex-rigid PCB specialist Andreas Schilpp, “an essential prerequisite is as much

standardisation as possible. Through our internal, cross-departmental coordination of sys-

tem solutions, we are in a position to almost standardise innovative technologies such as

fl ex-rigid and open up more and more areas of application. We have been able to prove this

in many projects”.

Furthermore, Schilpp points out: “As it’s also the case in many other areas: the earlier cus-

tomers involve their suppliers in the design and development stages, the higher the

chances of benefi ting from system solutions become. Namely, this is because we are able

to introduce our PCB production know-how at the right time. A fact that often proves advan-

tageous and cannot necessarily be recognised by customers at the early stage of design”.

02 Circuit Board Technology · Tec Report · Issue 08 · July 2010 www.we-online.com 04

Figure 6:For fl ex-rigid boards with a fl exible internal layer, the ZIF contact is usually also located on

the fl exible core. For fl ex-rigid boards with a fl exible external layer, a change of the contact

face can be necessary sometimes. Such change of sides is realised by via holes in the rigid

area in between.

Figure 2:Figure 2:Figure

Flex-rigid PCBs and ZIF connectors

www.we-online.com 0605 Circuit Board Technology · Tec Report · Issue 08 · July 2010

Niedernhall, July 2010 – PCB specialist Würth Elektronik once again demonstrates their competence

in system solutions and customer support; now offering one-stop flex-rigid PCB solutions with ZIF

contacts and custom designed ZIF connectors. Customers from diverse fields such as industry, auto-

motive, medical care and digital image processing benefit from Würth Elektronik’s particular problem

solving approach. Most notably in the two key points: quality and cost. This makes flex-rigid and

flexible PCBs an affordable and effective choice for maximum use of complex circuit technologies in

the minimum space, in particular with respect to system costs.

Flex-rigid PCBs and ZIF connectors

www.we-online.com

Würth Elektronik offers the best contact between flex-rigid PCBs and ZIF connectors

Figure 8:Semi-fl exible PCB with ZIF contact serving as connection with an optical module in a sen-

sor for measuring air quality.

Flex-rigid multilayer boards are already proving their value in daily applications. For exam-

ple, as sensors for controlling motors in roller shutters, awnings and Venetian blinds. In this

case, internal resistors and heaters were also used. Here all the typical demands are met:

high operational reliability and durability; simple assembly; resistance against oil, grease,

humidity and aggressive environmental conditions as well as simple, reliable electrical con-

nections using a fl exible limb with a ZIF contact. Wiring and solder joints were replaced,

high quality connections applied, and an assembly process for the heating resistors was

avoided.

For another application, a special design and implementation of contacts was created using

a semi-fl exible FR4 PCB with a ZIF contact for use in standard ZIF connectors. This appli-

cation was used in a module for the optical display of temperature and air quality in a sen-

sor for measuring air quality. In order to achieve large bending radii, the single-sided PCB

already had a thickness of 0.3 mm in the contact area, which means that it could be directly

plugged into the ZIF connector without the need for additional stiffeners or extra milling.

Further advantages were that cable wiring to the motherboard was no longer necessary, the

assembly process was simplifi ed and the additional benefi t that a drying process before

soldering was no longer required due to the base material used.

*) Note: ZIF connector – The term ZIF (Zero Insertion Force) originates from the socket tech-

nology of components, mainly CPU’s. In a ZIF socket, contacts are opened prior to place-

ment of the IC, e.g. by a leverage mechanism, allowing for effortless insertion of the con-

tact pins into the socket. The mechanism is then closed, fi xing the contacts to the pins in

the socket, and thus creating the electrical connection.

Particular advantages of fl ex-rigid PCBs

Flex-rigid technology is well-proven, reliable and particularly good in overcoming space and weight issues with spatial degrees of free-dom. Careful consideration of fl ex-rigid solutions and a proper as-sessment of the available options at an early stage in the design phase can return signifi cant benefi ts:

Space requirements can be minimised by applying 3D circuitry.

By removing the need for connectors and cables between the individual rigid parts the board size could be reduced and overall system weight can be brought down.

Less solder joints assure higher reliability.

Handling during assembly is easier when compared with complete fl exible boards.

Otherwise diffi cult connections can be created, thereby simplifying the assembling processes.

Integrated ZIF contacts provide simple modular interfaces to the system environment.

Test conditions are simplifi ed. A complete test prior to installation becomes possible.

Logistical and assembly costs are signifi cantly reduced with fl ex- rigid boards.

It is possible to increase the complexity of mechanical designs, whilst also improving the degree of freedom for optimised housing solutions.

Using fl ex-rigid technology to create ZIF contacts is be-coming more and more widespread, as it offers a number of benefi ts:

savings in joints/components

improved reliability

cost savings in procurement and logistics

reduced installation size

less complexity and expense in design and development

About Würth Elektronik Circuit Board Technology (CBT)

Würth Elektronik is the leading PCB manufacturer in Europe, producing a wide spectrum

of PCBs – from standard technologies through to pioneering system solutions – at manu-

facturing plants in Niedernhall, Rot am See and Schopfheim. The PCB specialist delivers

application specifi c solutions in all technologies and is a driving force behind new techni-

cal innovations, for example, in the fi eld of embedded active and passive components.

The extensive PCB portfolio ranges from double sided PCBs and multilayers in all con-

ventional technologies through to technically demanding PCBs such as HDI, fl ex-rigid and

heatsink technologies.

About the Würth Elektronik Group

Würth Elektronik CBT is – alongside Würth Elektronik ICS (electromechanical and elec-

tronic system solutions), Würth Elektronik eiSos (passive and electromechanical compo-

nents) and Würth Solar (CIS-photovoltaic modules and solar power systems) – a division

of the Würth Elektronik Group, an internationally operating, independent subsidiary of the

Würth Group. Beside their own R&D, Würth Elektronik is also involved in numerous exter-

nal research communities, e.g. GloveNet or TIPS. In 2009 Würth Elektronik employed

around 5,900 personnel and generated a turnover of 374 million Euros.

Further information can be found at www.we-online.com.

DIE

NECK

ARPR

INZE

N 07

10. E

rrors

and

om

issi

ons

exce

pted

.

More informationwww.we-online.com/fl ex-rigid

Würth Elektronik GmbH & Co. KG

Circuit Board Technology

Salzstr. 21 · 74676 Niedernhall · Germany

Tel.+49 (0) 7940 946-0 

Fax +49 (0) 7940 946-55 00 00

info@we-online.de

www.we-online.com

Circuit Board Technology · Tec Report · Issue 08 · July 2010

Figure 7:ZIF contact replaces wiring in a motor control unit for roller shutters and awnings.

Figure 9:By laser cutting the fl exible ZIF contours, precise contact tolerances were achieved and an

ingenious panelisation provided a stable assembly panel.

Flex-rigid technology was also employed in the re-design of an MDE device (mobile data

entry), created for inventory administration. An adapter board with two ZIF contacts enabled

the display to be updated smoothly and securely. Additionally, by laser cutting the fl exible

ZIF contours, precise contact tolerances were achieved and an ingenious panelisation pro-

vided a stable assembly panel. In the fl exible region, the PCBs could be removed by hand,

without the needs for tools or special processing.

TEC REPORTIssue 08 · July 2010

www.we-online.com 0605 Circuit Board Technology · Tec Report · Issue 08 · July 2010

Niedernhall, July 2010 – PCB specialist Würth Elektronik once again demonstrates their competence

in system solutions and customer support; now offering one-stop flex-rigid PCB solutions with ZIF

contacts and custom designed ZIF connectors. Customers from diverse fields such as industry, auto-

motive, medical care and digital image processing benefit from Würth Elektronik’s particular problem

solving approach. Most notably in the two key points: quality and cost. This makes flex-rigid and

flexible PCBs an affordable and effective choice for maximum use of complex circuit technologies in

the minimum space, in particular with respect to system costs.

Flex-rigid PCBs and ZIF connectors

www.we-online.com

Würth Elektronik offers the best contact between flex-rigid PCBs and ZIF connectors

Figure 8:Semi-fl exible PCB with ZIF contact serving as connection with an optical module in a sen-

sor for measuring air quality.

Flex-rigid multilayer boards are already proving their value in daily applications. For exam-

ple, as sensors for controlling motors in roller shutters, awnings and Venetian blinds. In this

case, internal resistors and heaters were also used. Here all the typical demands are met:

high operational reliability and durability; simple assembly; resistance against oil, grease,

humidity and aggressive environmental conditions as well as simple, reliable electrical con-

nections using a fl exible limb with a ZIF contact. Wiring and solder joints were replaced,

high quality connections applied, and an assembly process for the heating resistors was

avoided.

For another application, a special design and implementation of contacts was created using

a semi-fl exible FR4 PCB with a ZIF contact for use in standard ZIF connectors. This appli-

cation was used in a module for the optical display of temperature and air quality in a sen-

sor for measuring air quality. In order to achieve large bending radii, the single-sided PCB

already had a thickness of 0.3 mm in the contact area, which means that it could be directly

plugged into the ZIF connector without the need for additional stiffeners or extra milling.

Further advantages were that cable wiring to the motherboard was no longer necessary, the

assembly process was simplifi ed and the additional benefi t that a drying process before

soldering was no longer required due to the base material used.

*) Note: ZIF connector – The term ZIF (Zero Insertion Force) originates from the socket tech-

nology of components, mainly CPU’s. In a ZIF socket, contacts are opened prior to place-

ment of the IC, e.g. by a leverage mechanism, allowing for effortless insertion of the con-

tact pins into the socket. The mechanism is then closed, fi xing the contacts to the pins in

the socket, and thus creating the electrical connection.

Particular advantages of fl ex-rigid PCBs

Flex-rigid technology is well-proven, reliable and particularly good in overcoming space and weight issues with spatial degrees of free-dom. Careful consideration of fl ex-rigid solutions and a proper as-sessment of the available options at an early stage in the design phase can return signifi cant benefi ts:

Space requirements can be minimised by applying 3D circuitry.

By removing the need for connectors and cables between the individual rigid parts the board size could be reduced and overall system weight can be brought down.

Less solder joints assure higher reliability.

Handling during assembly is easier when compared with complete fl exible boards.

Otherwise diffi cult connections can be created, thereby simplifying the assembling processes.

Integrated ZIF contacts provide simple modular interfaces to the system environment.

Test conditions are simplifi ed. A complete test prior to installation becomes possible.

Logistical and assembly costs are signifi cantly reduced with fl ex- rigid boards.

It is possible to increase the complexity of mechanical designs, whilst also improving the degree of freedom for optimised housing solutions.

Using fl ex-rigid technology to create ZIF contacts is be-coming more and more widespread, as it offers a number of benefi ts:

savings in joints/components

improved reliability

cost savings in procurement and logistics

reduced installation size

less complexity and expense in design and development

About Würth Elektronik Circuit Board Technology (CBT)

Würth Elektronik is the leading PCB manufacturer in Europe, producing a wide spectrum

of PCBs – from standard technologies through to pioneering system solutions – at manu-

facturing plants in Niedernhall, Rot am See and Schopfheim. The PCB specialist delivers

application specifi c solutions in all technologies and is a driving force behind new techni-

cal innovations, for example, in the fi eld of embedded active and passive components.

The extensive PCB portfolio ranges from double sided PCBs and multilayers in all con-

ventional technologies through to technically demanding PCBs such as HDI, fl ex-rigid and

heatsink technologies.

About the Würth Elektronik Group

Würth Elektronik CBT is – alongside Würth Elektronik ICS (electromechanical and elec-

tronic system solutions), Würth Elektronik eiSos (passive and electromechanical compo-

nents) and Würth Solar (CIS-photovoltaic modules and solar power systems) – a division

of the Würth Elektronik Group, an internationally operating, independent subsidiary of the

Würth Group. Beside their own R&D, Würth Elektronik is also involved in numerous exter-

nal research communities, e.g. GloveNet or TIPS. In 2009 Würth Elektronik employed

around 5,900 personnel and generated a turnover of 374 million Euros.

Further information can be found at www.we-online.com.

DIE

NECK

ARPR

INZE

N 07

10. E

rrors

and

om

issi

ons

exce

pted

.

More informationwww.we-online.com/fl ex-rigid

Würth Elektronik GmbH & Co. KG

Circuit Board Technology

Salzstr. 21 · 74676 Niedernhall · Germany

Tel.+49 (0) 7940 946-0 

Fax +49 (0) 7940 946-55 00 00

info@we-online.de

www.we-online.com

Circuit Board Technology · Tec Report · Issue 08 · July 2010

Figure 7:ZIF contact replaces wiring in a motor control unit for roller shutters and awnings.

Figure 9:By laser cutting the fl exible ZIF contours, precise contact tolerances were achieved and an

ingenious panelisation provided a stable assembly panel.

Flex-rigid technology was also employed in the re-design of an MDE device (mobile data

entry), created for inventory administration. An adapter board with two ZIF contacts enabled

the display to be updated smoothly and securely. Additionally, by laser cutting the fl exible

ZIF contours, precise contact tolerances were achieved and an ingenious panelisation pro-

vided a stable assembly panel. In the fl exible region, the PCBs could be removed by hand,

without the needs for tools or special processing.

TEC REPORTIssue 08 · July 2010