CA1219082A - Surface mounting of devices on both sides of a circuit board - Google Patents
Surface mounting of devices on both sides of a circuit boardInfo
- Publication number
- CA1219082A CA1219082A CA000484186A CA484186A CA1219082A CA 1219082 A CA1219082 A CA 1219082A CA 000484186 A CA000484186 A CA 000484186A CA 484186 A CA484186 A CA 484186A CA 1219082 A CA1219082 A CA 1219082A
- Authority
- CA
- Canada
- Prior art keywords
- devices
- solder
- circuit board
- pads
- contact
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
- H05K3/341—Surface mounted components
- H05K3/3415—Surface mounted components on both sides of the substrate or combined with lead-in-hole components
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/04—Soldering or other types of metallurgic bonding
- H05K2203/043—Reflowing of solder coated conductors, not during connection of components, e.g. reflowing solder paste
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/04—Soldering or other types of metallurgic bonding
- H05K2203/0485—Tacky flux, e.g. for adhering components during mounting
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/14—Related to the order of processing steps
- H05K2203/1476—Same or similar kind of process performed in phases, e.g. coarse patterning followed by fine patterning
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/15—Position of the PCB during processing
- H05K2203/1572—Processing both sides of a PCB by the same process; Providing a similar arrangement of components on both sides; Making interlayer connections from two sides
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
- H05K3/3447—Lead-in-hole components
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Electric Connection Of Electric Components To Printed Circuits (AREA)
Abstract
SURFACE MOUNTING OF DEVICES ON BOTH SIDES OF A CIRCUIT BOARD
Abstract of the Disclosure Surface mounted components or devices on circuit boards can be connected on a first side by reflow soldering and then the circuit board turned over and further devices mounted on the other side and also connected by reflow soldering. The devices connected on the first side are retained in position by the surface tension of a molten solder pad. Solder paste is applied to form a hump and then reflowed to form a solder pad, for example about .010 inches thick. After positioning devices on the board, on the solder pads, they are connected by reflow soldering. On turning the board over, further surface mounting devices can be positioned and connected, or other forms such as leaded components, can be connected, by reflow soldering, without loss of the first connected devices.
-i-
Abstract of the Disclosure Surface mounted components or devices on circuit boards can be connected on a first side by reflow soldering and then the circuit board turned over and further devices mounted on the other side and also connected by reflow soldering. The devices connected on the first side are retained in position by the surface tension of a molten solder pad. Solder paste is applied to form a hump and then reflowed to form a solder pad, for example about .010 inches thick. After positioning devices on the board, on the solder pads, they are connected by reflow soldering. On turning the board over, further surface mounting devices can be positioned and connected, or other forms such as leaded components, can be connected, by reflow soldering, without loss of the first connected devices.
-i-
Description
lZ19(~8Z
SURFACE MOUNTING OF DEVICES ON BOTH SIDES OF A CIRCUIT BOARD
This invention relates to the surface mounting of devices on circuit boards. In particular the invention is concerned with the surface mounting of devices on both sides of a circuit board.
A large proportion of devices, or components, for electronic circuits are surface mounted on circuit boards. Basically, a circuit board is provided with a circuit pattern defined thereon, on both surfaces. The circuit pattern is usually copper which is tinned to ease soldering. The circuit pattern will include contact pads to which contact members or areas on a device will be soldered. Prior to mounting of the devices, solder paste is applied to the contact pads and then the circuit board heated, for example in a vapour, to melt the solder. This is generally referred to as reflow soldering. Contact pads are reflow soldered on both surfaces of the circuit board.
Devices are then applied to one surface, usually by automated apparatus, and then the circuit board is passed through a heated vapour to remelt the solder at the contact pads and solder the devices to the circuit pattern. Conventionally, devices mounted on the other surface are attached by leads extending through holes in the circuit board and then connected by soldering. This can be done at a separate operational step. If surface mounting is required on the other side this is done by hand soldering. Hand soldering is slow and expensive.
The present invention enables surface mountiny devices to be applied on one side or surface of a circuit board and connected by reflow soldering and then the circuit board turned o~er and further 1908;~
surface mounting devices applied to the other side or surface and attached by reflow soldering. Broadly, solder paste is applied, as by screen printing, to the contact pads for surface mounting devices and reflowed so as to build deposits of solder, the amount of solder being related to the size, and particularly the weight, of the related device. After the first attachment of devices on one surface by a further reflow step, the board is turned over and a further series of devices positioned and then attached by reflow soldering to the other surface. During the attachment of the further devices by reflow soldering, the first devices, now on the underside of the circuit board, are held in place by the solder, which will be molten during reflow soldering of the devices on the top surface. By providing the correct amount of solder, the devices are held in position and do not drop off.
A feature of the invention provides for shaping of the contact pads whereby devices are aligned and centralized on contact pads during reflow soldering.
The invention will be readily understood by the following description of certain embodiments, by way of example, in conjunction with the accompanying diagrammatic drawings, in which:-Figure 1 is a plan view of a circuit board; and Figure 2 is a typical cross-section through a circuit board and contact pads, to an enlarged scale.
Illustrated in Figure 1 is a circuit board 10 having a circuit pattern indicated generally at 11, with contact pads 12 for surface mountinS devices. Contact pads for other devices such as leaded devices having leads extending through the circuit board can 1;~19Q8;2 also be provided. The circuit pattern ll and pads 12 are on one surface of the circuit board. On the other surface of the circuit board a further circuit pattern is formed, indicated by dotted lines 13. Contact pads 14 are formed for further surface mounting devices.
The circuit patterns 11 and 13 and contact pads 12 and 14 will normally be very much more closely packed than as illustrated in Figure 1, which is exemplary only.
Figure 2 is a cross-section through a circuit board 10 at a surface mounting device position on each surface. The circuit patterns are indicated at 11 and 13 and the contact pads at 12 and 14.
The circuit patterns 11 and 13 normally comprise a copper pattern which is tin plated to assist in soldering of devices and provide some protection. It is indicated as one layer in Figure 2 for convenience.
The solder for attachment of the devices is applied, in paste form, on to the contact pads in the circuit pattern and then fused on to the contact pads by heating - reflowed. Generally a raised solder pad or lump is formed, as illustrated in Figure 2.
A typical process for surface mounting devices is as follo~s:-1. Deposit solder paste of 63/37 tin lead composition by screening on to contact pad areas; a typical thickness is 0.010 inches with a screen mesh of 90-120; the solder paste has a solid to liquid ratio of about 88/12 and contains a readily activated flux, with a viscosity of about 50 centipoise and a particle mesh size of 200 (particles will pass through a mesh with 200 openings per square inch).
SURFACE MOUNTING OF DEVICES ON BOTH SIDES OF A CIRCUIT BOARD
This invention relates to the surface mounting of devices on circuit boards. In particular the invention is concerned with the surface mounting of devices on both sides of a circuit board.
A large proportion of devices, or components, for electronic circuits are surface mounted on circuit boards. Basically, a circuit board is provided with a circuit pattern defined thereon, on both surfaces. The circuit pattern is usually copper which is tinned to ease soldering. The circuit pattern will include contact pads to which contact members or areas on a device will be soldered. Prior to mounting of the devices, solder paste is applied to the contact pads and then the circuit board heated, for example in a vapour, to melt the solder. This is generally referred to as reflow soldering. Contact pads are reflow soldered on both surfaces of the circuit board.
Devices are then applied to one surface, usually by automated apparatus, and then the circuit board is passed through a heated vapour to remelt the solder at the contact pads and solder the devices to the circuit pattern. Conventionally, devices mounted on the other surface are attached by leads extending through holes in the circuit board and then connected by soldering. This can be done at a separate operational step. If surface mounting is required on the other side this is done by hand soldering. Hand soldering is slow and expensive.
The present invention enables surface mountiny devices to be applied on one side or surface of a circuit board and connected by reflow soldering and then the circuit board turned o~er and further 1908;~
surface mounting devices applied to the other side or surface and attached by reflow soldering. Broadly, solder paste is applied, as by screen printing, to the contact pads for surface mounting devices and reflowed so as to build deposits of solder, the amount of solder being related to the size, and particularly the weight, of the related device. After the first attachment of devices on one surface by a further reflow step, the board is turned over and a further series of devices positioned and then attached by reflow soldering to the other surface. During the attachment of the further devices by reflow soldering, the first devices, now on the underside of the circuit board, are held in place by the solder, which will be molten during reflow soldering of the devices on the top surface. By providing the correct amount of solder, the devices are held in position and do not drop off.
A feature of the invention provides for shaping of the contact pads whereby devices are aligned and centralized on contact pads during reflow soldering.
The invention will be readily understood by the following description of certain embodiments, by way of example, in conjunction with the accompanying diagrammatic drawings, in which:-Figure 1 is a plan view of a circuit board; and Figure 2 is a typical cross-section through a circuit board and contact pads, to an enlarged scale.
Illustrated in Figure 1 is a circuit board 10 having a circuit pattern indicated generally at 11, with contact pads 12 for surface mountinS devices. Contact pads for other devices such as leaded devices having leads extending through the circuit board can 1;~19Q8;2 also be provided. The circuit pattern ll and pads 12 are on one surface of the circuit board. On the other surface of the circuit board a further circuit pattern is formed, indicated by dotted lines 13. Contact pads 14 are formed for further surface mounting devices.
The circuit patterns 11 and 13 and contact pads 12 and 14 will normally be very much more closely packed than as illustrated in Figure 1, which is exemplary only.
Figure 2 is a cross-section through a circuit board 10 at a surface mounting device position on each surface. The circuit patterns are indicated at 11 and 13 and the contact pads at 12 and 14.
The circuit patterns 11 and 13 normally comprise a copper pattern which is tin plated to assist in soldering of devices and provide some protection. It is indicated as one layer in Figure 2 for convenience.
The solder for attachment of the devices is applied, in paste form, on to the contact pads in the circuit pattern and then fused on to the contact pads by heating - reflowed. Generally a raised solder pad or lump is formed, as illustrated in Figure 2.
A typical process for surface mounting devices is as follo~s:-1. Deposit solder paste of 63/37 tin lead composition by screening on to contact pad areas; a typical thickness is 0.010 inches with a screen mesh of 90-120; the solder paste has a solid to liquid ratio of about 88/12 and contains a readily activated flux, with a viscosity of about 50 centipoise and a particle mesh size of 200 (particles will pass through a mesh with 200 openings per square inch).
2. The solder paste is reflowed, for example in FC70 vapour at about 210 - 220C, for approximately 60 seconds, to form lZ1908Z
solder pads.
solder pads.
3. The circuit board is turned over and the steps 1 and 2 repeated,
4. The circuit boards are cleaned to remove any remaining flux and any solder balls which may have formed on the circuit board surface; a Freon type cleaner, such as Freon TES at 80C is typical.
5. The circuit boards are inspected.
6. A flux is applied to the solder pads on one surface;
the flux provides a temporary adhesive to hold the devices in place and also ensures satisfactory soldering of the devices; a high viscosity flux is desired, and a typical flux is Alpha RMA7 high viscosity.
the flux provides a temporary adhesive to hold the devices in place and also ensures satisfactory soldering of the devices; a high viscosity flux is desired, and a typical flux is Alpha RMA7 high viscosity.
7. The devices are then positioned on the one surface, - typical devices being resistors, capacitors and the like; positioning is normally by an automated positioning machine to which the devices are fed on tape.
8. The circuit board is then heated to reflow the solder, at a temperature of about 200 - 220C for about 30 seconds, for example, in the FC70 vapour; the heating is a continuous process, preferably, the circuit boards being fed along on a carrier;
after soldering the circuit boards are allowed to cool, typically for two minutes, and then turned over.
after soldering the circuit boards are allowed to cool, typically for two minutes, and then turned over.
9. The steps 6, 7 and 8 are repeated up to and including the cooling of the boards; the devices positioned may also include leaded devices and chip carriers, as well as resistors and capacitors; while reflow soldering is taking place to solder in position the devices on the now top surface, surface mounted devices on ` 4 :~
~ 1gO8Z
the under surface will be held in place by the surface tension of the molten solder at the solder pads.
The solder pads, as they act to hold devices in place while the solder is molten and on the under surface, have certain parameters. It is convenient to make the solder pads on both surfaces of the circuit board with the same parameters, to avoid having to ensure that a particular side or surface is up and the other down.
However, it is necessary to provide solder pads with such parameters only on that surface which will eventually be underneath and with surface mounted devices positioned on that surface. Conventional solder pads will suffice on the top surface.
It is emphasized that no adhesive is used to hold the surface mounting devices in position when on the underside of the circuit board during soldering. It is solely the molten solder which is holding the devices in place.
The amount of solder provided, as stated, is related to the weight of the device. For a device soldered at each end, two pads retain the device in position. For devices having more connection positions, for example a packaged chip, several pads are provided for soldering of the several contact areas of the packaged chip. Each pad can assist in supporting the device.
The area of the solder pad will affect the thickness of the solder also. A particular feature which can be combined with the self-supporting feature of solder pads, is the ability to form the solder pads to have a shape which aligns and centralizes devices on the solder pads.
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the under surface will be held in place by the surface tension of the molten solder at the solder pads.
The solder pads, as they act to hold devices in place while the solder is molten and on the under surface, have certain parameters. It is convenient to make the solder pads on both surfaces of the circuit board with the same parameters, to avoid having to ensure that a particular side or surface is up and the other down.
However, it is necessary to provide solder pads with such parameters only on that surface which will eventually be underneath and with surface mounted devices positioned on that surface. Conventional solder pads will suffice on the top surface.
It is emphasized that no adhesive is used to hold the surface mounting devices in position when on the underside of the circuit board during soldering. It is solely the molten solder which is holding the devices in place.
The amount of solder provided, as stated, is related to the weight of the device. For a device soldered at each end, two pads retain the device in position. For devices having more connection positions, for example a packaged chip, several pads are provided for soldering of the several contact areas of the packaged chip. Each pad can assist in supporting the device.
The area of the solder pad will affect the thickness of the solder also. A particular feature which can be combined with the self-supporting feature of solder pads, is the ability to form the solder pads to have a shape which aligns and centralizes devices on the solder pads.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of surface mounting devices on both surfaces of a circuit board, comprising:
defining a circuit pattern on each surface of a circuit board, each circuit pattern including contact pads for surface mounting of devices;
depositing a predetermined amount of solder paste on said contact pads on a first surface of the circuit board;
heating the circuit board to melt the solder paste and form raised solder pads at each of said contact pads on said first surface, the amount of solder at each contact pad being related to the weight of a device;
depositing a predetermined amount of solder paste on said contact pads on a second surface of the circuit board;
heating the circuit board to melt the solder paste and form raised solder pads also at each of said contact pads on said second surface, the amount of solder at each contact pad being related to the weight of a device;
positioning said circuit board with one of said first and second surfaces uppermost and positioning devices on the uppermost surface, the devices being in contact with the solder pads;
heating the circuit board to melt said solder pads to connect said devices to said contact pads on said one surface;
turning the circuit board over to position the other of said first and second surfaces uppermost and positioning devices on said other surface, the devices being in contact with the solder pads;
heating the circuit board to melt said solder pads and connect the devices to said contact pads on said other surface;
the devices on said one surface being retained in position by surface tension of molten solder at the contact pads on said one surface.
defining a circuit pattern on each surface of a circuit board, each circuit pattern including contact pads for surface mounting of devices;
depositing a predetermined amount of solder paste on said contact pads on a first surface of the circuit board;
heating the circuit board to melt the solder paste and form raised solder pads at each of said contact pads on said first surface, the amount of solder at each contact pad being related to the weight of a device;
depositing a predetermined amount of solder paste on said contact pads on a second surface of the circuit board;
heating the circuit board to melt the solder paste and form raised solder pads also at each of said contact pads on said second surface, the amount of solder at each contact pad being related to the weight of a device;
positioning said circuit board with one of said first and second surfaces uppermost and positioning devices on the uppermost surface, the devices being in contact with the solder pads;
heating the circuit board to melt said solder pads to connect said devices to said contact pads on said one surface;
turning the circuit board over to position the other of said first and second surfaces uppermost and positioning devices on said other surface, the devices being in contact with the solder pads;
heating the circuit board to melt said solder pads and connect the devices to said contact pads on said other surface;
the devices on said one surface being retained in position by surface tension of molten solder at the contact pads on said one surface.
2. A method as claimed in claim 1, including applying flux to each raised solder pad prior to positioning the devices.
3. A method as claimed in claim 1, including depositing the solder paste to a thickness of about 0.010 inches.
4. A method as claimed in claim 3, the solder paste having a solid to liquid ratio of about 88/12, and a viscosity of about 50 centipoise and a particle size of 200.
5. A method as claimed in claim 1, including heating the circuit board to about 210°-220°C for approximately 60 seconds after each deposition of solder paste to melt the solder paste and form said solder pads.
6. A method as claimed in claim 5, including heating the circuit board to about 200°-220°C for about 30 seconds, after each positioning of devices to reflow the solder pads and connect the devices to the contact pads.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000484186A CA1219082A (en) | 1985-06-17 | 1985-06-17 | Surface mounting of devices on both sides of a circuit board |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000484186A CA1219082A (en) | 1985-06-17 | 1985-06-17 | Surface mounting of devices on both sides of a circuit board |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1219082A true CA1219082A (en) | 1987-03-10 |
Family
ID=4130723
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000484186A Expired CA1219082A (en) | 1985-06-17 | 1985-06-17 | Surface mounting of devices on both sides of a circuit board |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1219082A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1988007317A1 (en) * | 1987-03-19 | 1988-09-22 | Western Digital Corporation | Solder paste replacement method and article |
| EP0303272A2 (en) * | 1987-08-14 | 1989-02-15 | Siemens Aktiengesellschaft | Printed circuits for electronics |
| EP0407685A2 (en) * | 1989-07-14 | 1991-01-16 | Hitachi, Ltd. | Method for inspection of solder joints by x-ray fluoroscopic image and apparatus therefor |
-
1985
- 1985-06-17 CA CA000484186A patent/CA1219082A/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1988007317A1 (en) * | 1987-03-19 | 1988-09-22 | Western Digital Corporation | Solder paste replacement method and article |
| EP0303272A2 (en) * | 1987-08-14 | 1989-02-15 | Siemens Aktiengesellschaft | Printed circuits for electronics |
| EP0303272A3 (en) * | 1987-08-14 | 1990-05-09 | Siemens Aktiengesellschaft | Printed circuits for electronics |
| EP0407685A2 (en) * | 1989-07-14 | 1991-01-16 | Hitachi, Ltd. | Method for inspection of solder joints by x-ray fluoroscopic image and apparatus therefor |
| EP0407685A3 (en) * | 1989-07-14 | 1991-11-06 | Hitachi, Ltd. | Method for inspection of solder joints by x-ray fluoroscopic image, apparatus therefor and mounting construction of electronic parts on board |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |